ELECTRONICS AROUND THE HOUSE - World Radio History

October "80ISSN 0142-6192

55p

SPECIAL ISSUEELECTRONICS AROUND THE HOUSE

Including six DIY projects for the home

WITH THIS ISSUE YOU CAN BUILD:AN INTRUDER ALARM TO PROTECT YOUR VALUBLES

A TUG-OF-WAR GAME TO TEST YOUR STRENGTHA TEMPERTURE CONTROLLED SOLDERING IRON

AN INEXPENSIVE LIGHT DIMMER

and it didn't take very long either. Electronics have evolved faster than anything else. From Marconi's first cracklingmorse transmissions to minichip in a lifetime. But space-age technology poses it's own problems to dealers anywhere.The days you strung your own aerial with a length of copper wire bought just around the corner are over. Nowadays,

if you want the best you'll probably have to go tothe States, or Japan, or Denmark ...

or you can contact us. We're not justaround the corner, but very nearly so.

Located just about an hour fromLondon, near Schiphol airport inHolland we have one ofEurope's largest collections ofaerials, CB equipment, accessories,electronics etc. from all over theworld. Whether it's Danish, Japanese,

American or anything else, we've gotall the top names at bottom prices.So, plug into the mains and contact

WNTJOY 103 High Street,Ltd. Shepperton,

Middlesex TW 17 9BL,England Tel. Walton -

on -Thames (STD09322)48145

Or just simply call us.

TON MILERS ELEKTRONIKAAalsmeerderdijk 349,1436 BH Rijeenhout -Holland, telefoon 010 3.1 2977-2 6611(4 lijnen),telex 15181 tonel nl. ( vlak bij Airport Schiphol).

r

efECTRONICS HAVE GROWN UPWHY DON'T YOU,T00

Wf114 THIS ISSN YOU CAN BUILD:AN INTRUDER ALARM TO PROTECT vOIN IIELUBLES

TUG -OF -HAIR GAME TO TEST vOiJII STRENGTHA TEEPERPARE CONTROLLED SOLDERING NON

AN INEXPENSIVE LIGHT MINIM

A DI Munitive project, see page 33.

Manual to Microchip - see page 43.

daela/e

FEWATCHOOG

Prevent pinching, see page 59.

OCTOBER 1980Vol. 2 No. 12

ABC Member of AuditBureau of Circulation

Editor: Ron Harris B. ScAssistant Editor: Rick MayburyEditorial Assistant: Tina Boylan

Project Editor: Keith BrindleyGroup Art Editor: Paul Wilson -Patterson

Assistant Art Editor: Dee CamilleriDwg. Manager: Paul Edwards

Advertisement Manager: Steve RoweAdvertisement Representative: Roy Perryment

Creative Director: Diego RinconManaging Director: T. J. Connell

KITCHEN TIMERWhat's cooking?TUG O'WARPulling powerLIGHT DIMMERAnother bright ideaFREEZER ALARMFrozen chipsTEMPERATURE CONTROLLED SOLDERING IRONHot stuff!INTRUDER ALARMNicker nabberNOBELL DOORBELLDon't knock it!

13

24

33

40

49

59

67

MONITOR 6News from the world of electronicsINTO DIGITAL ELECTRONICS 17Part 2, down to businessBUILDING SITE 30Pains from the mainsWHAT'S IN A NAME 37The Integrated Circuit StoryHOME ELECTRONICS 43Electronics are everywhere0 LEVELQ&A 53Atoms and power stationsTALKING DESIGN 55Pulse Width Modulation explainedCLEVER DICK 63Answer backBREAKER ONE FOUR 71Open Channel latest

HE Next Month, 11. ETI Next Month, 29. Subscriptions, 42.Hobbyprints 78. PCB foil patterns, 79. Books, 80. Classified Ads 82.

Hobby Electronics is normally published on the second Friday of the month prior to the cover date.Hobby Electronics, 145 Charing Cross Road, London WC2H OEE, 01-437 1002. Published by Modmags Ltd. Distributed by Argus Distribution Ltd,

12-18 Paul St., London EC2A 4JS. Printed by QB Ltd., Colchester.Copyright: All material in this publication is subject to world-wide copyright protection. Permission to reproduce printed circuit board patterns

commercially or marketing of kits of the projects must be sought from the Publisher. All reasonable care is taken in the preparation of the magazine toensure accuracy but Modmags cannot be held responsible for it legally. ©Copyright 1980 Modmags Ltd

Hobby Electronics, October 1980 3

Simply ahead ...POWER AMPLIFIERSILP Power Amplifiers areencapsulated withinheatsinks designed tomeet total heatdissipation needs. Theyare rugged and made tolast a lifetime. Advancedcircuitry ensures theirsuitability for use with thefinest loudspeakers, pickups, tuners, etc. usingdigital or analogue soundsources.

0 10

°05

0 02

0 0

F 1KHzLOAD 80 ON ALLEXCEPT HY400 AT 411

START OF WAVEFORM CLIPPING R

0 5 1 2 5 10 20 50 100OUTPUT POWER -WATTS R M S

ModelOutputPowerR.M.S.

Dis-torsionTypicalat 1 KHz

MinimumSignal/NoiseRatio

PowerSupplyVoltage

Sizein mm

Weightin gms

Price +V.A.T.

HY30 15 W 0.02% 100dB -20 -0 +20 105x50x25 155 £6.34into 8 Sil +95P

H Y50 30 W 0.02% -25 -0- +25 105x50x25 155 £7.24into 8 7 100dB + C 1 09

HY120 60 W 0.01% 100 dB -35 -0- +35 114x50x135 575 £15.20into 8 S2 4 E2 28

HY200 120 W 0.01% 100 dB -45 -0- +45 114x50x85 575 £18.44into 8 S2 + E2 77

HY400 240 W 0.01% dB -45 -0 45 114x 100x85 1 15Kg f27.68into 4 12 100 ., E4 15

ILP PRE -AMPS ARE

COMPATIBLE WITH ALL

ILP POWER AMPS AND PSUs

POWER SUPPLY UNITS

Load impedance - all models 4 CI -Input sensitivity - all models 500 mVInput impedance - all models 100K flFrequency response - all models 10Hz - 45 KHz -3d8

ILP Power Supply Units with transformers made inour own factory are designed specifically for usewith ILP power amplifiers and are in two basicforms - one with circuit panel mounted on con-ventionally styled laminated transformer, for PSU30 and 36 - in the other, for larger PSUs, ILPtoroidal transformers are used which are half thbsize and weight of laminated equivalents, are moreefficient and have greatly reduced radiation.

PSU 30 -± 15V at 100mA to drive up to 1 2xHY6 or6xHY66 £4.50+10.68 VAT

THE FOLLOWING WILL ALSO DRIVE ILP PRE -AMPS

PSU 36 for 1 or 2 HY3Os £8.10+ £1.22PSU 50 with toroidal transformer for 1 and 2

HY5(41 £9.75+£1.46 VATPSU 60 with.toroidal transformer for 1 HY120

£9.75+£1.46 VATPSU 70 with toroidal transformer for 1 or 2

HY120s £13.61+£2.04 VATPSU 90 with toroidal transformer for 1 HY200

£13.61+£2.04 VATPSU 180 with toroidal transformer for 1 HY400 or

2xHY200 £23.02+ £3.45 VAT

AVAILABLE ALSO FROM WATFORD ELECTRONICS, MARSHALLS AND CERTAIN OTHER SELECTED STOCKISTS.

4 Hobby Electronics, October 1980

Simply fill in order coupon with payment orcredit card instructions. Post to address asbelow but do not stamp envelope - we paypostage on all letters sent to us by readers ofthis journal.

ELECTRONICS LTD. 1

Kw 1112FREEPOST 6 Graham Bell House, Roper Close, I

Canterbury, Kent CT2 7EP.Telephone (0227) 54778 Telex 965780

this time with twonew pre - amps

TAPE IN )

TAPEOUTAUX)

RAD

HAG

GND

LTAPE

MONITORSWITCH

VOLUME100K LIN

SOURCESWITCH

SCHEMATIC BLOCK DIAGRAMOF HY6 PRE -AMP, WITHSTEREO CONNECTION SHOWN

I L P POWERSUPPLY UNIT

HY6 mono HY66 stereoWhen ILP add a new design to their audio -module range, there have to be veryspecial reasons for doing so. You expect even better results. We have achievedthis with two new pre -amplifiers - HY6 for mono operation, HY66 Ifor stereo.We have simplified connections, and improved performance figures all round.Our new pre -amps are short-circuit and polarity protected; mounting boardsare available to simplify construction.Sizes - HY6 - 45 x 20 x 40 mm IHY66 90 x 20 x 40 mm Active Tone Controlcircuits provide ± 1 2dEl cut and boost. Inputs Sensitivity - Mag PU - 3mVMic -selectable 1 -12mV All others 10OrnV Tape 0/P - 1 00mVMain 0/P - 500mV: Frequency response -D C to 100KHz - 3dB

HY6,1,5.60

+ VAT 8411

HY66 stereo

10.60+ VAT

Connectors includedB6 Mounting Board78p + 121 VATB66 Mounting Board99p + 151) VAT

III LOW DISTORTION - Typically 0.005%

S/N RATIO - Typically 90 dB (Mag. P.U.- 68 dBI.

II HIGH OVERLOAD FACTOR -38 dB on Mag. P.U.

III LATEST DESIGN HIGH QUALITY CONNECTORS.

II REQUIRE ONLY POTS,SWITCHES, PLUGS AND SOCKETS.

COMPATIBLE WITH ALL ILP POWER AMPS AND PSUa.

El NEEDS ONLY UNREGULATED POWER SUPPLY ±15V to 50V.

* ALL U.K. ORDERS DESPATCHED POST PAIDHOW TO ORDER, USING FREEPOST SYSTEM r

Please supply

Total purchase price

I enclose Cheque PostalOrders E International Money Order

Please debit my Access/Barclaycard Account No.

NO QUIBBLE5 YEAR GUARANTEE

7 DAY DESPATCH ONALL ORDERS

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5Hobby Electronics, October 1980

MonitorShoulder Sounds

You may have heard of the 'BoneFone', it's a kind of flexible stereoradio that hangs around your neck.Well, we've just had the opportunityto try one out. The Bone Fone hasbeen on sale in the USA for a fewmonths now and it's proving verypopular with joggers and skaters.Not having too many joggers orskaters in the HE office our 'fieldtests' have been a little less thanvigorous. Initial reports were lessthan enthusiastic as stereo receptionwas a little noisy, which we dis-covered was due to our reviewmodel having an aerial designed forthe US market. Once outside the of-fice though, things improveddramatically (it must be the bars onthe doors and windows designed tokeep us in). Stereo reception wasquite acceptable and the AM sideworked OK under all conditions.

Only two little niggles, in the first

place the controls are badly sited, it'squite difficult to tune it in by 'feel'only and the stereo indicator lightmight as well have been left out asthere's no way you could ever see itunless you looked at yourself in amirror. The second problem arosewhen gyrating with the music (as isour wont after the odd shandy), thedirectional nature of FM transmis-sions caused a certain amount offading which could be awkward forjoggers unless they jog in straightlines, parallel to the transmissionpath. In all fairness though wesuspect this may be due to the aerialwhich is not really suitable for ourFM service. The US style of 'satura-tion' FM broadcasting dictates that acertain amount of insensitivity bebuilt in. The Bone Fone will beavailable in the next couple ofweeks. Kramer and Co are the peopleto see, take along £39 and the BoneFone will be all yours. Kramer and Colurk at 9 October Place, LondonNW41EJ.

Knight Moves

You guessed it, another chess com-puter, this one is called simply'Intelligent Chess' and comes fromOptim Games Ltd. At around £295 itmust be one of the most expensivechess computers ever but it doeshave an impressive line up offeatures. First away is the built-incassette recorder, it will record up to1,000 different games andlor anaudio commentary on a C90 cassette.The cassette recorder can be usedwith the 'Teacher' cassette (suppliedfree) to help a beginner with thebasic moves, optional extras includea selection of other pre-recorded

cassttes with titles like 'All Karpov'sgames' or 'All named variations'. Thegame is displayed directly on to astandard colour TV set and will playin any one of 13 levels.

Intelligent Chess is the first Britishdesigned chess computer and has animpressive pedigree. Internationalchess master David Levy was respon-sible for the overall design and BarrySavage of 'Softy' fame was responsi-ble for the electronics. The program-mer is one Mike Johnson, winner ofthe first European microprocessorchess tournament in 1978. Withnames like that how can it fail? Thegame will be available in October.Optim Games live at 45 South Street,Bishops Stortford, Hertfordshire.

Tall Boxes

If like the rest of us you keep yourtools and components in a selectionof cardboard boxes then you may bein the market for one of these natty

little toolicomponent recepticles.To give it its full (and rather splen-

did sounding) title, it's a 'Link-Hampson Multiple Services Cabinet',impressed huh? As you can see fromthe photograph the top sectionhouses tools and the lower drawercabinet will happily hold all yourcomponents. To stop them fallingout on the floor a hinged front panelfolds down to allow access to theclear plastic drawers. The outer casecomes in a no-nonsense simulatedleather (at least they're honest aboutit) with a sturdy carrying handle.Link-Hampson assure us that extrastrength is guaranteed by incor-porating reinforced side straps. Allthis can be yours (without the tools)for just £29.95, the cabinet on its ownis only £10. Link-Hampson areawaiting your enquiry at 5 BoneLane, Newbury, Berkshire RG14 5TD.

Just before we went to press wereceived news of another tool box,

this one is called the 'Rolykit'. It'srather unusual in that instead of hav-ing separate drawers or boxes it rollsout from a handy looking hexagonal -shaped carrying case. At first glanceit would appear that this is the idealmethod of jumbling up all your care-fully sorted bits and pieces but someclever design work has taken care ofthat. Each compartment automatic-ally covers the one underneath. Themanufacturers claim it can be drop-ped, thrown about and generallyhandled quite carelessly without anykind of spillage. Rolykit is being laun-ched in the UK in a few weeks andtwo sizes will be available, thesmaller at £12 and the larger at £15.The Rolykit has already been a greatsuccess in Holland, it will be in-teresting to see how it fares overhere. The people to talk to are Co-Ordinated Marketing Services, 21Great Portland Street, LondonW1N 5DB.

Hobby Electronics, Octobe 1980

WATFORD ELECTRONICS35 CARDIFF ROAD, WATFORD, HERTS., ENGLAND

MAIL ORDER, CALLERS WELCOME. Tel. Watford 40588/9

ALL DEVICES BRAND NEW, FULL SPEC. AND FULLY GUARANTEED. ORDERSDESPATCHED BY RETURN OF POST. TERMS OF BUSINESS: CASH/CHEQUE/P.Os OR BANKERS DRAFT WITH ORDER. GOVERNMENT AND EDUCATIONALINSTITUTIONS' OFFICIAL ORDERS ACCEPTED. TRADE AND EXPORT INQUIRYWELCOME. P&P ADD 40p TO ALL ORDERS UNDER E10. OVERSEAS ORDERSPOSTAGE AT COST, AIR /SURFACE. ACCESS ORDERS WELCOME.

VATExport owlets no VAT. Applicable to U.K. Continuos only. Unless waled otherwise. allprices are exclusive of VAT. Please add 15% to ell prices.

We mock thousands more items. It pow to Wet no. We ere Whatnot/ behind Watford Football Ground.Nearest Underground/BR Station: Watford High Street. Open Monday to !Woodsy. Ample Free CarParking space ayeileble.

POLYESTER CAPACITORS: Axial lead type.400N: 1 nE, 1n5. 2n2, 3n3, 4n7, 6n8, 10n, 15n fp; 18n 10p; 22n. 33n 11p; 47n, 68n 14p; 100n 17p;150n, 220n 24p; 330n, 470n 41p; 680n 52p; 1 , F 114p; 242 42p; 447 85p.1110Vi 39,F, 100n. 150n. 220n 11p; 330n. 470n 19p; 680n. 14F 22p; 145, 2,2 32p; 447F 360.1000V: 10nF, 15n 200; 22n 220; 47n 26p; 100n 42p; 470n 53p; 14F 176p.

POLYESTER RADIAL LEAD CAPACITORS: 25011:10n, 15n, 22n. 27n 561; 33n, 47n, 68n, 100n 7p; 150n 10p; 220n,

430n 131IN 47Cn 17p; 680n 1111p; 14F 220; 10530p; 242 34p; 4,760p.

1144 & SMOKE DETECTORSTO 581 2 or 813 4150Socket for above 360

ELECTROLYTIC CAPACITORS: Axial lead type (Values are in y F). 500V: 10 500; 47 78p; 250V:100115p;1136: 0.47, 1.0. 1.5, 2.2, 2 5, 3.3, 4.7, 6.8, 9, 10. 9p; 15, 22, 47, 32, 50 14p; 63. 100. 270;110V; 100,220, 25p; 470, 32p 1000, 800; 40V: 22, 33, 10p; 100, 12p; 2200. 3300. 4700, 1150; 35V: 33,1011; 330. 470. 32p; 21111: 10. 22. 47, 100, 8p; 160, 220, 250, 16p; 470, 250; 640, 1000, 35p; 1500.40p; 21500200,14p; 33 2200.00, 72p; 4700 92p; 16V: 10, 47, 68, 7p; 100, 125, Up; 220, 330, Illp; 470, 20p;1000. , 30p; 36p.TAOAND TYPE: 450V: 1004F 180p; 70V. 4700, 1660; 84V: 3300 911p; 2500 900; EOV: 3300 I35p;2200911p; 401/: 4700130p; 4000920; 30093p; 2500 Sip; 220086p; 2000+2000120p; 30V: 4700

L11091 25V: 15.000195p; 6400120p; 4700100p; 3300 116p; 2200 60p.

TANTALUM BEAD CAPACITORS35V, 0.1s: 0.22: 0.33: 0.47: 0.68,1.04: 2.24; 3.34, 4.7: 25V: 10.20V: 648, 16V: 242: 447. 10. 200.16V: 224, 20p; 47. 100111p: 220 80p.10V: 154, 224. 33. 28p; 100 400474; 68: 10032p; 3V: 10024.

500pF 250p6:1 Ball Once4511/DAF 1460Dial Drive 41036:1/36:1 7760Drum 54min 59p0-1.365pF 326p00-2.365pF 395p

MYLAR FILM CAPACITORS100V: 0001, 0002, 0005, 0-014F Illp0-015. 0-02, 0-04, 0-05, 0-0564F 7p0.14F. tiOV: 0.470F 12p

MINIATURE TYPE TRIMMERS2.5-6pF, 3.10pF, 10-40pF 25p5.25p1 5-45pF. 60pF, 88pF 35p

4.1

CO ION TRIMMERS3-409F, 10-80pF; 25-190pF 330100.500pF 460 I 250pF Sip

POTENTIOMETERS: Rotary, Carbon.Track. 0.25W Log & 0.5W Lin.5000, 1K0 & 2K0 (Linear only) SingleGang 21Ip5K0 -2M0 Single Gang 29p5K0.2M0 Single Gang D/P Switch $Sp5K0 -2M0 Double Gang Sap

SUDER POTENTIOMETERS0-25W log and linear values 60mrn560-500K0 single gang10K0 -500K0 dual gangSelf Stick Graduated Bews

70080033p

PRESET POTENTIOMETERSVertical & Horizontal0.1W 500-5M0 Miniature0-25W 1000 -3.3Mt) horiz.0-25W 2000-4.7M0 yert.

7p10p10p

POLYSTYRENE CAPACITORS:10pF to 1 nF 111p; 1.5nF to 1011F 10p

SILVER MICA (Values in pF) 3-3, 4-7,6.8. 10. 12, 18, 22, 33, 47. 50. 68. 75,82, 85, 100, 120. 150, 180 11p each:220, 250, 270, 300, 330, 360. 390,600. 82018p each: 1000, 1200, 1800,2200 26p each.

CERAMIC CAPACITORS 6011: 0-5oFto 1 OnF 4p; 22n to 47n Sp. 100n. 7p.

EURO HEADBOARD 25.20.

RESISTORS - Carbon Film, HighStability, Low Noise, Miniature Tolerance5%.

RANGE VAL 1-99 100+14W 202-4517 E24 20 1pYiW 202 -4M 7 E12 2p 1p1W 202-10M E12 gp 4p2,SMetal Film 100-1M 6p - 4p1%Metal Film 510.1M Sp Sp100, price applies to Resistors of eachyalue not mined.

s

S -Dec 3600 T -Dec 400pU -Dec 'A 465p U -Dec 'B 699p

VOLTAGE REGULATORS1A T03 A ye -ve5V 7805 145p 7905 220p

12V 7812 146p 7912 2200 '15V 7815 146018V 7818 146pIA 10220 Plastic Casing

, 5V 7805 SOp 790512V 7812 SOp 791215V 7815 809 791518V 7818 11419 791824V 7824 1110p 7924

66p65p65p65045p

We stock pens for mostof the projects in thin

100mA 1092 Plastic Casing5V 78105 110p6V 78L62 30p

79L05 65!

8V 781.82 311012V 78112 30p 7911215V 78115 309 79115 4119 ".CA3085 95p LM323K 6280LM 300H 170p OA 325N 240pLM305H 140p 1M3265 240pLM309K 135p LM327 270pLM317K 350p LM723 39p

TAA550 600T846258 950TDA1412 150p78H05 595p78HG5 550p

JACKSONS VARIABLE CAPACITORSDielectric 0 2 365pF with slow100 / 300pF 2050 motion Once 450p

00 208,176 395p00 208;176 withslowmotion dnve 410pC804-50. 10 15.25. 50pF 250p100, 150pF 335p

34310pF 725p00 3425pF 550p

DENCO COILS'DP' VALVE TYPERange 1 to 5 Ell.,Rd.. TI Wht 101196-7135 Ft 94p1.5 Green 130p'T' type 1 to 5 Bl.Rd. Wht YI 130p89A Valve Holder

35pROT2 120p

RFC 5 chokes 120pRFC 7 (19rnH)

133p13: 14, 15, 16,17

110p18/1.8 116p18/465 132pTOC 1 110pMW5FR 112pMW/ LW SFR 134p

VEROBOARD 0.1 015 0.15(Capper clad) (plain)

71/2 ii 31/4" 66p 699 34P21/2/15" 75p 1199 39P334 x 31/4" 750 750 -31/2.5"

SIP 920 65P255 x 17" - 2020 128p314117" 296p 260p 178041/44 17" 387p ..- 280pPkt of 36pins WE 'DIP' Board 326pSpot face cutter 10/1/ t'0' Board 1449Pin IMWMOn tool 142P g.robwo 4400

OPTOELECTRONICS

111SE4 tier ps1 6711211 Gm. ItTIL212 Yel. 18 -2" Red 15.2" Yet Gm. 18Square LEDs 30ORP12 832N5777 45L0271 40SFH205 98TIL32 58TIL78 707 Segment DisplaysT11321 CA .5" 115TH322 C.0 .5" 115D1704 C Cth .3" 99DL707 C.A..3" 99.3" Green CA 150DL747 C.A..6" 180FND357 120'.MAN3640 17510 Sep Bergraph 225LCD 31/2 Digit 875

SWITCHESMEC. Black body.Red. Gm. Blue,SRL Latching 125SRM Momentary 125TOGGLE. 2A 250VSPST 32DPDT 444 Pole on :off 54SUB -MI5 TOGGLE

magezine SP changeover 59SPST on /off 64DPOT 6 tags 70DPOT c/of 79DPOT Biased 115

SLIDE 25011,1A DPOT 1414E/Pc/off 15hA DPDT 134 pea c/over 24

SWITCHES Miniature Non -LockingPush to Make 16 Push Break 26ROCKER: SPST on/off 104/250V 30ROCKER: Illuminated, lights when on: 3A 240V

5ROTARY: (ADJUSTABLE STOP) 1 pole/2-120way. 2p/2.6 way. 3p/2-4 way, 4p/2-3 way 43ROTARY: Mains 250V AC. 4 Amp 50

ACCESSAwl phone vow orderthrough. We deal withthe nun (but ruin. E10

oteesel.

DIL SOCKETS (Low Profile -T sas) 8 pin 10p:14 pin 12p; 16 pin 13p; 18 pin 14p; 20 pin 22p;24 pin 30p; 28 pin 35p; 40 pin 40p.

DIODES

BA1000512685127CR0330490A470A700A7904810485049004910A950420004202N914N916N4001/25400354004/554006/7N4148N5401/255403/4

4434/1001/34/4001/3A/600V3A/1000V

151212

15846

202018202730

We stock awide selectionof ElectronicBooks andMagazines

ZENERSRange. 2V7 to39V 400mW

Sp sashRange. 3V3 to33V 1 3W

160 mesh

NOISEZ5J 1800

BRIDGERECTIFIERS(plastic case) p14 / 505 2014/100V14/200V14/400V14/600V2A/50V2A/100V24/200V24/400V2A/600V64/100V64/200V6A/400V8Y164VM18 OIL

2225293436444853611

72785504160

SCRsThyristors0 6A, 200V 300.84100V 300.842004 3514100V 4214200V 4714600V 7054300V 3554600V 4384300V 4484500V 588A600V 85124300V 59124500V 92154700V 1962N4444 14061106 150C1060 38TtC44 25TIC45 45

TTL 747400 117401 127402 127403 147404 147405 157406 487407 457408 227409 227410 197411 267412 207413 337414 627416 317417 317420 197421 387422 267423 327425 307426 447427 327428 357430 207432 287433 387437 357438 307440 207441 747442 717443 1207444 1167445 1167446 1327447 997448 997450 207451 207453 207454 207460 207470 417472 317473 407474 347475 567476 417480 557481 1207482 757483 947484 1137485 1217486 337489 2157490 577491 857492 597493 597494 957495 757496 957497 180

,74100 13074104 6274105 6274107 3574109 6074110 5474111 6874112 15074116 19874118 9974119 12574120 10574121 4274122 5874123 95

74125 4574125 5574128 7474132 7074138 6574141 8574142 14574143 35074145 9074147 180,74148 14574150 15074151 7574153 7574154 14074158 8074157 7574159 18574160 9974161 9974182 9474163 9974164 12074165 12074186 15574167 24074170 23074172 42074173 12074174 10574175 8274176 9074177 9074178 14974180 8074181 29074182 8874184 14574186 14574188 29974190 13574191 13574192 13574193 13574194 10574195 19874196 13074197 9074198 196.74221 14074246 19874247 19574248 195

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40741526 48741527 44741528 48741530 24741532 30741542 80741547 85741548 120741S55 70741563 150.741S73 40

741S74 40741575 4$741576 46741583 106741585 106741586 46741590 60741592 76741593 76741595 116741S96 1807415107 467415109 767415112 5074LS113 Si7415114 447415122 707415123 957415124 1$07415125 607415126 507415132 967415136 557418138 707415139 997415145 1207415147 210741S148 1757415151 95741S153 857415155 967415157 7$7415158 55741S160 1207415161 967415162 1107415163 118741S164 1157415165 1557415166 1757415173 1057415174 1477415181 2967415190 1207415191 120741S192 1267415193 1267415195 1267415196 1207415197 1207415221 1207415240 225741S241 2267415242 2327416243 2327413244 2257415245 4607415247 1367415248 1357415249 1357415251 1307415365 907416367 90

CMOS*4000 184001 184002 244006 924007 224008 824009 404010 484011 244012 244013 454014 854015 854016 424017 824018 884019 48

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10501060

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4542


All theseadvantages...

Instant all-weather starting Smoother running Continual peak performance Longer battery & plug life Improved fuel consumption Improved acceleration/top speed Extended energy storage

..in kit formSPARKRITE X5 is a high performance, top quality inductivedischarge electronic ignition system designed for the electronicsD.I.Y. world. It has been tried, tested and proven to be titterlyreliable.Assemblyonly takesl- 2 hours and installatiotieven less due to the patented 'clip on easy toting

The superb technical design of theSpar krite circuit eliminates problems oft hecontact breaker. There is no misfire due tocontact breaker bounce which is el iimilat enelectronically by a pulse suppressioncircuit which prevents the unit firing if thepoints bounce open at high R P MContact breaker burn is eliminated byreducing the current by 95% of the norm . There is also a unique extended dwellcircuit which allows the coil a longerperiod of time to store its energy before tirriodischarging to the plugs The unit incluili.sbuilt in static timing light. systems funannlight, and security changeover switchWill work all rev counters

Fits all 12 v negative -earth vehicleswith coil/distributor ignition up to 8 cylinders.THE KIT COMPRISES EVERYTHING NEEDEDDie pressed case Ready drilled. aluminium extrudedbase and heat sink. coil mounting clips and accessories All kitcomponents are guaranteed for a per iocl of 2 years from date ofpurchase Fully illustrated assembly and installation instructions areincluded

Roger Clark the world famous rally driversays" Spark rite electronic ignition systemsare the best you can buy"

-r r ar rife-etHIGH PERFORMANCEELECTRONIC IGNITION

rilElectronics Design Associates, Dept. HE / 1082 Bath Street, Walsall, WS1 3DE. Phone: 10922) 614791

Name

Address

Phone your order with Access or Barclaycard

Inc V A T and PP QUANTITY REGO

X5 KIT £16.95

LACCESS OR BARCLAY CARD No

8

I enclose chequePU's for

Cheque No.

Send SAE d brochure only 'malted

ICS havehelped thousands

of ambitious peopleto move up into higher paid

more secure jobs in the field ofelectronics - now it can be your turn.

Whether you are a newcomer to the fieldor already working in the industry. ICS can

provide you with the specialised training so essentialto success.

Personal Tuition and Guaranteed Success

The expert and personel guidance by fully qualifiedtutors, backed by the ICS guarantee of tuition untilsuccessful, is the key to our outstanding record in thetechnical training field. You study at the time and pacethat suits you best isnd in your own home. In the wordsof one of our many successful students: "Since startingmy course, my salary has trebled and I am expecting afurther increase when my course is completed."

City and Guilds Certificates

Excellent job Prospects await those who hold one of theserecognised certificates. ICS can coach you for:

Telecommunications TechniciansRadio, T.V. Electronics TechniciansRadio AmateursElectrical Installation Work

Diploma Courses

Colour T.V. ServicingCCTV EngineeringElectronic Engineering & MaintenanceComputer Engineering and ProgrammingRadio, T.V. and Audio, Engineering & ServicingElectrical Engineering, Installations & Contracting

Other Career Courses

A wide range of other technical and professional coursesare available including GCE.

To ICS, Dept. Z263, Intertext House,London SW8 4U tJ

Name

Address

Age

ICSTo ICS, Dept. Z263; Intertext House,London SW8 4UJor telephone 01-622 9911 (all hours)

Hobby Electronics, October 1980

MonitorNews from the Electronics World

Bug Swatter

Stories about phone tapping andbugging seem to be hitting theheadlines with alarming regularity.It's not surprising that companies of-fering anti -bugging services are en-joying a mini -boom at the moment.Here we have an interesting device,it's called the Scanlock Mark V8. It'sbasically a broad band radio receiverthat can 'scan' up and down a rangeof frequencies (10 to 1800 MHz) fourtimes a second. It analyses all thesignals on those frequencies, pickingout any that are significantly strongerthan the others. Once it has lockedonto a likely transmission it tests it byemitting a short tone. All this cantake less than one second. Scanlockwill demodulate any signal, whetherit is AM, FM, or Subcarrier (PhantomModulation). It can also be used todetect 'sleeper' bugs that are ac-tivated automatically by radio con-trol. Once the presence of a bug hasbeen established the Scanlock canlocate it by means of a hand-heldantenna, a continuous tone from theScanlock rises in frequency as theantenna gets closer to the bug.

The Scanlock is completely por-table and can be used in a car. Itcomes with all the accessories,leather carrying case and N i-Cad bat-teries. The price is available on ap-plication from Audiotel Interna-tional Ltd, Saddlers Court, 100Reading Road, Yateley, SurreyGU17 7RX.

Errata

Someone somewhere has really gotit in for use, we even managed to getthe Errata wrong last month. The cor-rection on the overlay diagram forPass The Loop should have said thatIC2 and IC3 numbering was trans-posed, NOT IC1 & IC2. Heads willroll.

The Auto Probe last month had asimilar error on the overlay diagram(Fig.3), LED 1 & LED 2 should beswapped over. Still with the AutoProbe, some people have been ex-periencing difficulty in obtaining thetransistor Q1, this is not a criticalcomponent and almost any generalpurpose PNP type will do (the BC179is ideal).

The Guitar Phaser overlay (Fig.3yet again) shows the connections forQ1 & 2 Drain and Source reversed,the pin out diagram beneath Fig.1 iscorrect.

Last but not least it seems that oneor two people have been experienc-ing instability problems with the CarBooster published in the July issue.We're not sure why but there's a

° possibility that a suspect batch of ICshave been floating around. If you areexperiencing a low 1 Hz click then itcan be cured by putting a 2R2resistor in series with both C7 & C8(on the earthy side) and removing thelink from Pin 7 of IC1. Take thespeaker connection via a flying leadfrom Pin 7 making sure it is well awayfrom IC1.

Book ReviewsYet another pair of books fromBabani Publishing Ltd, both with aworkshop theme. The first is calledElectronic Test Equipment Construc-tion. (F G Rayer, ISBN 0900162 95 3,£1.75). As you might expect it con-tains constructional projects and ad-vice on how to use a wide range of

useful test gear. As anyone who hasbeen faced with a dead project willtell you, fault finding with a wetfinger and a light bulb is no fun.Several of the circuits have full con-structional details though most areleft up to the individual constructor.The designs include an FET Volt-meter, Field Strength Meter, Watt

Meter, Capacitance Bridge and aworthy assortment of RF and AFGenerators. A valuable addition tothe budding faultfinder's library.

Number two is called Power Sup-ply Projects. (R A Penfold, ISBN 0900162 % 1, £1.75). You can't reallygo wrong with this one, it could becalled 'Everything you ever wanted

to know about Power Supplies', itreally is very comprehensive. Pro-jects range from the simplestunregulated, Half -Wave power sup-ply to a 5-15 volt, 3 amp, fully stabilis-ed bench supply. Again construc-tional details are left largely up to theindividual. This book is aimed at themore experienced constructor.

Speaks For Itself!

"Does your watch tell the time?""No, you have to look at it." OK, so itnever was the funniest of jokes. Nowit's not true either. Those wily Orien-tals at Sharp have devised a speakingclock, which is a lot more fun thanthe GPO's version even if it doesn'thave the same cut -glass accent.

At first glance the Sharp CT -660looks like an ordinary multi -functiontravelling alarm clock, with an LCDdisplay. Leave it sitting on your desk,however, and it announces the timeat half-hourly intervals. If youbelieve that clocks should be seenand not heard, this facility can beturned off. Press a button on the topof the clock and it tells you the cur-rent time. All of the other functionsof the clock use the voice too. Whenthe alarm goes off, a short fanfare isfollowed by an announcement of the


time. Just to make sure you're awake,this is followed by a very penetratingrendition of Boccherini's Minuet.The clock reminds you of the timeafter five and ten minutes, tells youto hurry up, and plays the tune again(hope you like Boccherini).

In the timer mode, the elapsedtime is spoken every minute, fiveminutes, or thirty minutes, for up toten hours (depending on setting). Thestopwatch mode is similar, exceptthat the announcements are madeevery ten seconds and lap times andaccumulated times are provided.

All this electronic trickery is pack-ed into a tiny chrome case 114mm by60mm by 22mm, which shows howadvanced electronic speech genera-tion has become. 'Talking Time'should be in the shops about now,and is ideal for gadget freaks or theblind. Wintjoy Ltd have a limitednumber of clocks at the moment foraround £40 each.

Equal OpportunitiesYes, we've all seen car graphicequalisers before, we've even seenthem with booster amplifiers buthere's the catch, how many have youseen for only £25.00?

It sounds too cheap to be true butit's not, this well built booster/equaliser delivers 25 watts per chan-nel with full equalisation over therange of 60 Hz to 15 kHz. It has asturdy metal case with hefty heat -sinks on the side. The quality is e

cellent, worthy of units costingseveral times as much. Connectionto your existing stereo is a simplematter, all the common connectorsockets are fitted and it is smallenough to fit unobtrusively under-neath the dashboard. The HarvardGraphic Equaliser Amplifier is cur-rently being sold for this derisorysum by Minikits Ltd. You can find

them at: 88 HainaultRoad, Leytonstone,

London Eli 1EH.

ON SALEOCTOBER 10th

Thirty Pound Synthesiser

No, not weight, price! That's right, for around thirty quid you can build yourself this highquality, versatile and above all, economical synthesiser. Create outlandish noises, scareyour granny, even play a few tunes. This easy -to -build unit features the latest LSItechnology to reliably generate the sounds.

We're keeping quiet about the technical details, walls have ears and all that. Suffice itto say that this is the design you've been waiting for. You have four weeks, starting fromnow to find your 130. It'll be money well spent, we promise you that.

Electronic Hand Grenade

You'll get a real 'bang' out of this new game. It's the electronic version of that old parlourgame 'musical chairs'. The grenade is passed around a circle of players, the longer it isheld the greater the chance it will go 'off'. The person that has it then leaves. This in-genious little circuit will provide hours of amusement at parties and can be built by eventhe most inexperienced constructor in just a couple of hours.

r

Guitar Sound Shaper

Gasp, shock, horror, you haven't heard of a Guitar Sound Shaper before. Shame on you.How can you ever hold your head up in decent company? People like you give our hobbya bad name, no wonder dogs cross the street when they see you. There's only one thingyou can do, rush out and get next month's copy of HE or forever be a social outcast.

Battery Eliminator

This 35 kilowatt laser is guaranteed to instantly vapourise any battery from a HP7 to aPP9. Batteries are really becoming a nuisance. Stop their takeover right now. The HE bat-tery Eliminator will forever remove the menace of the dry -cell. Just plug it into your localmains socket and laugh as you count all the money you'll save. Actually it's not really a 35kilowatt laser but it will save you a few quid. Look out for it in next month's bigger -than -ever issue.

LL)

Transistor Tester

What can we say? Not a lot really, we don't have to tell you that this is the most advanceddesign ever to measure the collector current of a BC109, you know that already becauseit comes from Hobby Electronics!

Stereo

Now for the first time anywhere this century Hobby Electronics has commissioned thatMaster of the Microcircuit, the Baron of the Breadboard, that well known man of digits,Ian Sinclair (who?) to write the definitive lowdown on Stereo. What is it, how does it do it,what do I do with it? These are just some of the questions that will finally get answerednext month in this exciting top-level feature.

The items mentioned here are those planned, but unforseeen circumstances may affect the actual contents.


* ZERO ADJUSTMENT* 31/4 -DIGIT LCD WITH

200 HRS CONTINUOUSBATTERY LIFE

* AUTO 'BATT'WARNING

* FULL AUTORANGING* AUTO UNIT DISPLAY* CONTINUITY TEST

(6110 and 6100 only)* 10 AMP AC/DC (6110

and 6220 only)

Introducing the latest professional state-of-the-art 31/2 -digit DMM - at really old-fashioned prices! From just an unbelievable £39.95 inc. VAT, plus £I.15 p&p!

6100 6110 6200

RESOloUlION I inV. I OstA, 0 ISt on all models

FULL AUTO RANGING

RANGE HOLD

UNITS OF MEASUREMENT DISPLAYED rnV, V. mA mV. V, mA, A mV. V. mA mV. V. rnA. A

FUNCTIONS DISPLAYED St. KU. AUTO, BATT, ADJ. LO - and AC

MEASURES DC VOLTAGE TO 1000V 1000v 1000V 1000V

MEASURES AC VOLTAGE TO 750V 750V 750V 750v

MEASURES AC DC CURRENT TO 200mA 10A 200mA 10A

ZERO ADJUSTMENT Zeros out minute test -lead resistances for precise measurements

ACCURACY 0 5°0 05°° 0 8°o 0 8=;

LOW POWER OHM RANGES For in -circuit resistance measurements on all models

BUZZER - Continuity Test

BUZZER - Over Range Indicator

COMPLETE WITH Batteries, pair of Test Leads, Spare Fibse, One Year's Guarantee

PRICE ONLY L64.95 ONLY L74.95 ONLY L39.95 ONLY C49.95

P&p £1.15 L1.15 11.15 L1.15

I believe you! Please send me the DMM/s as marked.

6200 @ L41.10 each, inc. VAT, p&p. Total price L.6220 @ LS1.10 each, inc. VAT, p&p. Total price6100 CD E66.10 each, inc. VAT, p&p. Total price E6110 @ E76.10 each, inc. VAT, p&p. Total price E

Total cash/cheque enclosed LCheques payable toMaclin-Zand Electronics Ltd., please

I Available exclusively from the company that givesyou tomorrow's technology today.

LTel.38 Mount Pleasant, London WC i X OAP.

01-278 7369/01-837 1165


Why such a low, low price?Because the A/D converter anddisplay are custom built! This is agenuine top -spec DMM. Checkthese features for unbeatablevalue

- you won't find a hand-heldDMM with these features at theseprices again!

ACCESS orders taken, Please write card no: and signature.

ACCESS NO

Name

Address

Signed

Maclin -ZandMaking state-of-the-art affordable.

To: Maclin-Zand Electronics Ltd., 38 MountPleasant, London WC I X OAP.Despatch by return. For overseas orders, pleaseadd L5 to cost of total order package.

1H E

11

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CA3140E 50p SAD10244 1250p

CA3160F 100p SFF96364 11001,

CA316IE 1400 SL490 400p043162E 4500 S0760030 250p

CA3189E 3000 567601374 140p

CA3280 1600 57476013ND 120p

DAC14088 2000 SN76023N 140p

FX209 7SOP SN76023ND 120p

C17106 650p SN76477 175p

C18038 300p SP85 I 5 750p

ICM75551E361LF356PLM10CLM301 ALM 311LM318U319LM324LM339LM 348LM3771M380LM381ANW386W39300709

1509

45p95p

425,30P700

2000225p45p75995p175p

75p1800

95p100036p

144621 275p7134641E411 225p784651 200p16A800 90pTBA810 1000TBA820 900784950 3000TC4210 2500TC4220 350pTC4940 175pTDA1004 3000TD41008 3200TDA1010 225pTDA1022 570pTD41024 120pT041034E1 2509TDA1170 300p

w7 i 0 SOPTD42002V 325p

u44725 3500 TDA2020 320p

04733 1000w 741 180

1M747 70p04748 35pW2917 25001M3900 70pLM3909 70pLM3911 130pLIK3914 225pLM3915 2259

1200114113E 125pLM0MC 1310P 1500MC1458

; MC 1495E 350p

,VOLTAGE REGULATORS

TL071/81 46p11072/82 76011074 130011084 110pT1170 50pU44170 17559

UDN611B 320pUDN6I84 3200ULN2003 1000562206 300pXR2207 400020414 20P254190 226pi

ZN424E 1360ZN425E 400pZN427E 7500

Fined PAN& TO -220 -ve14 +ve

7905 65p5V 7805 800 7912 65012V 7812 80p

7915 70pI155 7815 8007918 700

18V 7818 8007924 700

24V 7824 80p100m% T092 79L05 70p5V 78105 30p 79112 700

12V 78112 300 79115 70015V 78115 300OTHER REOULATORS 78MGKC 8000U8309K 135p 78H05KC 6000LM317T 200p 78MGT2C 135*'191323K 5500 79HGX1 700pU0723 37p 11497 300p

OPTCSFLECTR ONICS255777 45pOCP71 130009912 120p

°PTO -ISOLATORS

011960ORPO 1

T1178

122732120055p

I L074 130p 111111 901191C726 100p 111112 900MC52400 190p 111116 9100

LEDS

11L32 55p 174.220 Red 18p111209 Red 13p 111222 Gr 180771211 Gr 24 111228 Red 22p111.212 Ye 259 Rectangular91216 9ed 18p 11189L G, r 300

DISPLAYS3015F 200p 5085881 5700

01704 1400 171311 800pDL707 Red 140p 111312/3 110p

707 Gr131.747 Red

1400225p

111.321 / 2

T1L33013001400

747 Gr 225p 7750/60 2009F9D357 1213p DRIVERS6,10500 1200 9368 2659FND507 120p 9370 300pMAN3640 175p UDN6118 320pNU914640 200p U 006184 320p

BREADBOARDSEXP350 3 6 sQ 1(Up to 3 5 14 pin ICs)EXP650 3.6 a 2.4(Up to I x 40 pin IC)EXP300 6 x 2.1(Up to 6 x 14 pin ICs)EXP600 6 2.4(Up to 1 x 40 pin DC6

IC TEST CLIPS14 pin use16 pin 2.75

TRANSISTORS6AC126 25pAC127/8 200AC176 25pAC187/8 25pAF116 500AD149 700AD161/2 45pAU107 2000BC107/8 tlpBC109 11pBC117 200BC147/8 9pBC149 10p80157/8 10pBC159 1IpBC169C 12p8C172 12pBC1778 170BC179 18pBC1823 10p8C184 lip8C187 300BC212/3 11080214 12pBC237 15pBC327 169BC337 18pBC338 1898C461 36pBC477/8 30pBC516/7 400BC5478 tiSpBC548C 9pBC549CBC557B

13C5591BCY70BCY71/2BD131/260135/6BD1396014080189BE123280233BD235BD24180242BDY568E200BF244BBF256111

8E257/88F2598F1939

18p16p18p18p22p50054p58080060095975p85p700700

200p32p35p70p32p36p

66640 25pBFR41 25pBFR79 25pBFR80 25pBFR8I 259.BFX29 40pBFX30 340BFX84 / 5 40pBFX86 /7 30pBFX88 30pBRN10 90pBFY50 30pBF95I /2 300BFY56 330BFY90 90086939 45985X19/20 200BU 104 2250

.13U105 1909BU108 250pBU1C9 225pBU205 200pBU 208 200pBU406 145pE300 50pE308 50p6310 50pMJ2501 225pMJ 2955 90pMJ3001 2250MJE340 50pMJE2955 1000MJE3055 700MPF102 45pMPF I 03 / 4 400

MPF105 / 6 400MP86531 50pMPS6534 500MPSA06 30pM PSA I 2 50pMPSA13 50pMPSA20 50pMP5442 500MPSA43 500M PSA56 32pMPSA70 50pMPSUO6 63pMPSUO7 60pMP5U45 909MPSU65 78p0C28 13000C35 1309TIP29A 400TI P 29C 55pTIP304 480TIP3CIC 60p

TW314 56p.TIP31C 620TIP32A 6BpTIP32C 82pTW334 90pTIP33C 114pTIP34A 115pTIP34C 160pTIP35A 225pTIP35C 290pTIP36A 2700TIP36C 3409TIP41A 65pTIP4IC 780TIP42A 700TIP42C 820TIP54 160pTIP120 1200T1P122 1300TIP142 1300TIP147 13001702955 78p7194055 70011843 341111893 309ZTX108 12pZTX300 13pZTX500 15pZTX502 113p

ZTX504 30p204574 260029696 35p2N697 25p28698 4592747088 25p28708 25p20918 45p29930 180291131,236p261613 25p261711 250292102 700262160 35002922194 30p2N2222A 3002923694 25p202484 30p2N2646 45p29290445 30p2029064 30p2029074 30p292926 9P203053 3011203054 650263055 48p203442 14i3p

203553 240p203565 30pZN3584 2505203643/4 411p203702/3 12p293704/5 129203706/7 149203708/9 12p203773 300p2N3819 25p203820 50p293823 70p2N3866 90p2N3902 700p203903/4 lip293905/6 203p294037 85p294058/9 142N4060 12p294061/2 14204123/4 27p204125/6 27p21114401/3 27p21144427 90p204871 60p265087 27p265089 27p205172 27p205179 90p2145191. 90p205194 90p2145245 40p2f45298 55p

205401 50p265457/840p205459 40p205460 64205485 440205875 250p266027 4ftp266052 304206059 325p206107 65p206247 190p208254 13092N6290 85p206292 55p2511172 1513p30128 1213p36140 1213p30141 110p3N201 110p30204 120p40290 250p40360 4440361/2 76p

40364 120040408 70040409 85040410 85p40411 300p40594 120040595 120p40673 75p40841 90p40871/2 1000

10A 4005 100025A 400V 400p

Z BYERS2 7V.33V400nW1W

DIODES89127BYX36-3000A470481068504900A910495042000420210914109161N4148104001/2164003/41144005194006/7105401/3105404 /71S920

12p20p

9p15p15p

9p9p9p9p

100497p405p6p6p7p

14919p

9.P

TRIAGEPLASTIC3A 403V6A 400V6A 503V84 400584 500512A 400V12A 500V16A 400V16A 500V12800D

80p70p88p15995985p

1059110p130p130p

HEAT SINKSFor 10220 Volt-age Rags andTraIlaratOda 22pFor TO5 12p

BRIDGERECTIFIERSIA 505 19p14 100V 213p14 4001/ 2591A 803V 3092A 50V 30p2A 100V 35111

2A 400V 45r,3A 200V 130p3A 6009 72044 100V 95p4A 400V 100p64 50V 80p134 103V 100p6A 400V 1200

THYRISTORS14 50V 70p

3A 40IN 1130pBA 600/ 140p12A 400V 180p164 100V 180p16A 400V 180pBT105 110p1106D 45pMCRIO1 38pTIC44 27p203525 130p204444 140p205060 34p205064 40p

LOUD-SPEAKERSSue21/2 6411 80p252 85 80p2 88 90p11/2 85 100p

MEMORIES21014E MOP210121 120021075 500P21114 300021124 26092114 3000211421 500940271 37504044 700p4116 40005101 51006810 325p740201 350p82516 3250ROM /PROMS71301 700074S188 225p745387 350p740470 650p74S471 650p740571 650p820137 750pCP641600 1200*'1802CE 75002650A 2000*'

750p66502800 550p6802 1100p6809 254313p80804 450p8085A 1100p1988060 1000pZ80 750p280A 9509EPROMS7702A 50002708 450027161+514 EIO

E20SUPPORT DEVICES3242 800P3245 450p6522 6001,6532 90006820 500P6821 37506845 1206850 300p6852 375p8155 1100p8205 320p8212 225p8216 225p8224 275p8226 40008228 525p8251 47598253 1000p8255 450p8257 90098259 950p 280010 60002806910 700p280CIC 600p280ACIC 700pMC14411 1100p __

PROTOSOARD (R) SOLDER LESS BREAD- 16 ICEY K6PADC215 BOARDS Mead SyinchmI

Socket Strips/ Bus Strips/ Binding Pont, mounted UHF ModuMmr 6MHz8310 on %Lady beg, pWR, UHF Moduitor 8MHz

PB6 6 , 14 OIL Ws 66.20 Reed Switches (1 2VA)ECM PB100 10 x 14 OIL Ws E11 SO LOGIC PROBE

P8102 12 x 14 OIL ICs E22.96 SU PERT ESTER 680656.30 PB103 24 x 14 Dft lbs 634.46 MICROTEST 806

PB104 32 x 14 Oft ICs CUSS ' TMK500RN abeam Welds we suitable for all D1L ICs) Pockmoeulltimemm

UARTAY -11015P 400pAY -61013P 400pN6402 504nmS601 1 NC 4003CHARACTERGENERATORS3257ADC 990pRa.3-2513 U.C. 1300pR0-1251311. 700pSN745262AN 610KEYBOARDENCODERAV5-2376 700p

CRYSTALS32.768K m/

250p100KHz 300p200KHz 370p1 OMHz 295p

1 008MHz 350p1 8432MHz

350p2.00MHz 350p245760MHz

350p3.276MHz 303p3.579Mlit 180p4.00MHz 29004 1941MHz POA4 43MHz 126p50MHz 32Sp6 OMHz 325p6.144MHz 325p7 OMHz 325p7 168MHz 325p8 OOMM7 325p13.867MHz 300p1 a00MHz 300p10.7MIQ 300p120MHz 310p1000MHz 360p1B COW: 350p18.432 460019 96861Itt

MAP26.690MHz

300P27145MHz

300P38 6667MHz

350p48 OMHz 300p555MW 35(No1160MHz 350p

LOW PROFILE DR. SOCKETS ofrous

8 pin 9P 18 pin lip 24 0514 pm 10p 20 pin 24 28 pin16 pin 11p 22 pin 24 40 pm

24p301.40p

WIRE WRAP SOCICET5 Tout8 pm 25p 18 pin '60p

14 pin 35p 20 pin 60p16 pin 40P 22 pin Sea

24 pin28 pin40 pin

70pSOp

100p

SUBMINIATURESWITCHESToggleSPST 60pSPOT 85pDPDT 70pDPDT (centre off) 85pPush to make 15pBreak 25pPush latching SPCO

80pSLIDE DPDT 18pROCKER SPST 28pWAFER11/1412W3P/4W411i 3W2P 6W

45945p45p45p

ANTEX SOLDERINGIRONSC -15WCX-17WCCN-15WX25SPARE SITSC/CX/CCNX25SPARE ELEMENTSC/CX/X25CCN

ADCOLA IRONSK1000K2000

41511426p426p440p

50950p

1809200p

550p550p

TRANSFORMERS(pnm 220/240V)6-0-6 100mA 96p9-0-9 75mA 100912-012 500mA 21149-0.9 'Amp 330p15-0-15 14 330p0-12.1520.24-30 14 410p

VEROEOARDSDIP Breadboar4.15 x 6.15 325p(Suitable for 20 5 14 pin or16 x 16 pin DIL 11s) DIP(headboard as above with tracks

for 31 way connector 375p8-0 Boards for ICs 130p(No track cutting)

CONNECTOR PLUGS31 way Plug 120p31 way Socket 120p5100 Busboar 1500p

EDGESOARD CONNECTORS 0.151" PITCH2 s 10 way 350 2 22 way 135p2s 15 way 1001, 2a 25 way 16092 a 18 way 12011

COUNTERS74/925741928ICM721613ICM72174251040E

1TL ECL475p MC40248414* MC4044

22.2°0 1011610231700p

32603259700 '

3600

SPECIAL OFFERS (subject to stocks)555 - 08/100 7805741 E16 / 100 78122114L-3 £4.00 79052708 (450 rIP) £4.25 79122708 (650 ns) £3.75 21141_(450 09) £28 /82716 (plus 5V only) £9.00 2732 £204116 (200 its) E24/8 P&P 4- VAT Extra

0/10£5/10E8/10£8/10

24 pin E4.9040 pin 57.90

450p

E3.75454E0.25

E16.00E33.001E17.00IE22.001

f4.75'

VEROBOARDS0.1

(copper clad)2 55 3 75 65p2 5 x 5 75p3 75 x 3 75 75p3 75 x 5 SOp3 755 17 290p4 75,117 9 3809

Pkt of 100 pinsSpot face cutterPin insertion toolVero Wiring Pen+ 2 wire spools+ combsCombs

50p96p

118p

370p7p

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TECHNOMATIC LTD17 BURNLEY ROAD, LONDON NW10(2 minutes Doll's Hill tube station) (ample street parking)Tel: 01-452 1500/01-450 6597 Telex: 92281 1

KitchenTimerA cheap and simple circuit which is idealfor the newcomer to electronics.

THIS SIMPLE TIMER provides anaudible alarm at the end of a presettiming period, which can be switch -selected in half -minute steps from oneminute to six -and -a -half minutes.Although it's been designed for use inthe kitchen it could of course be used inother applications such as photography.

The circuit uses a minimum ofcomponents and is based on the ever -popular 555 timer IC (what would we dowithout it?). The timer is automaticallytriggered when the unit is switched onand at the end of the chosen period atwo -transistor oscillator is enabled. Thisgenerates an audible tone in a ceramicresonator, a solid-state device whichproduces quite a loud sound with littlepower consumption.

0+9V

OV

0

HE KITCHEN TIMER /721

How it WorksThe circuit is based on a 555 timer (IC1) used inthe monostable mode. R13 and C2 provide anegative trigger pulse to IC1 at switch -on, sothat the timing run automatically commencesand the output at pin 3 goes high. The outputreturns to the low state when the charge on Clreaches the same level as a reference voltage.This voltage can be "trimmed" using RV1, whichis adjusted so that a timing period of one minuteis obtained with SW1 set to the "1 minute" posi-tion, i.e. with C1 charged through R12 only. SW2is used to switch in additional resistors, slowingthe charge rate of C1 and increasing the delaytime by half a minute for each additionalresistor.

Q1 and Q2 are used in a straightforwardastable multivibrator circuit operating at a fre-

quency of a few kilohertz. Initially this is in-operative since the output of IC1 is high, and thetransistors receive no significant supply voltage.At the end of the timing run the output of IC1goes low, and the multivibrator then operatesnormally as it receives virtually the full supplyvoltage.

This produces an audio tone from theceramic resonator which is driven from the col-lectors of Q1 and Q2. A ceramic resonator is nota low impedance device like an ordinaryspeaker, and needs little drive current. It doesrequire a fairly high drive voltage though, andthis is achieved by driving it from the antiphasesignals at the collectors of Q1 and Q2. This ef-fectively doubles the voltage swing across theresonator.

SW1ON/OFF

2 1k 1

SW221/2 R123 TIME 1M5

31/2

44/7

5 51/2 6

NOTE:IC1 IS 55501,2 ARE BC109Tx IS CERAMICRESONATOR

61/2

R1339k

C1

6

ICI

7

RV122k

47uC215n

Figure 1. Circuit diagram of the HE Kitchen Timer.


R14 81582k

8163k9 82k

iDTx

II C32n2

IIC42n2

01 02

R1782k

13

This photograph shows the board and battery fastened to the box withsticky pads, and the controls mounted on the front panel. Note theresistors soldered to SW2.

Time And Time AgainThe timing period of a 555 isdetermined by the values of thecapacitor and resistor connected to pins6 and 7; in fact, the formula used ist=1.1RC, where t is in seconds if R is inohms and C is in Farads. By keeping Cconstant and changing R we can getdifferent periods. In our circuit R isvaried by connecting 11 resistors inseries and using a twelve way switch toselect a point in the chain. Fineadjustment of the timing period (toallow for errors due to componenttolerances) is made with RV1 whichvaries the control voltage on pin 5 ofthe IC. This only needs to be done onone of the ranges.

ConstructionThe timer is built on our standardveroboard size of 10 strips by 24 holes,as shown in Figure 2. Be careful toconnect IC1, Q1, Q2 and C1 the rightway round as wrong connection coulddamage these components. All of thetiming resistors except R12 are mounteddirectly on the terminals of SW2, asshown in the diagram and photograph.Try to solder these to SW2 very quickly,as overheating them could permanentlyalter their resistance and impair theaccuracy of the unit.

Any small plastic box can be used tohouse this project. We fixed theveroboard and the battery inside withdouble -sided sticky pads. HE

BuylinesThe only unusual component is the ceramicresonator type PB2720, and this is availablefrom Ambit International, 200 North ServiceRoad, Brentwood, Essex, CM14 4SG. Satisfac-tory results should be obtained using 5% com-ponents for R1 to R12, but for optimum ac-curacy these should have a tolerance of 2% orbetter. Total cost of all components, excludingthe case, shouldn't be more than £5.

A

B

C

0

E

F

G

H

Kitchen Timer

2 3 4 6 7 9 10 11 12 13 14 15 16 17 18 1 0 21 22 23 24

0

Clo 0 0 0 0 0

020

R170 0 0 0 0

C4C3

0

O

00

O

C2 0 00 0 0 0 0 0 0 0 0 0 0 0 0

Figure 2. (Above) Veroboard layout and interconnection diagram.

J

H

G

F

0

B

A

050000005 5000000000.0000000000000000000otio0oeoo000000000000o0000000000000000oooo000000000000000oo00000oo000000000000000000o0000000000oo000o00000000000000550000000000004sts0Oono00000oooooO0001 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Figure 3. Underside of the Veroboard showing component positionsand track cuts.

Parts ListRESISTORS (All 1/4W, 5% except where stated)R1-11 750k, 5% or betterR12 1M5, 5% or betterR13 39kR14 3k9R15,16,17 82k

POTENTIOMETERSRV1 22k miniature horizontal preset

CAPACITORSC1 47u 16 V tantalumC2 15n ceramicC3,4 2n2 ceramic

+Ve VIASW1

OV

SEMICONDUCTORSIC1 555Q1,2 BC109

MISCELLANEOUSSW1 single -pole, single -throw toggleSW2 12 -way, single -pole rotaryTx ceramic resonator (see

BUYLINES)

Battery and clip10 x 24 hole, 0.1" matrix veroboard.Case to suitKnob.


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Solid state circuitry; D.C. coupled;.....

7 cm. dia. tube; Y input 0.3 v/cm.to-,.------_

S.-.:-..

50 v/cm.; X input 1 volt/cm.; 1v.and , - -T. ---Al10v. cal. signals; response to 1MHz; -

Time base ranges to 80 per cm.; 0 -cl;Size 230 x 130 x 190mm. Wt. 2 Kg. ,i&Operates from 110 volt or 220/240 --lit "'

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£130.00

LK2 DIGITAL MULTIMETERSolid state circuitry with largedigital display. Ranges are up to1000v. D.C. and A.C. and currentD.C. to 100mA. Resistance ranges100K ohms. Battery operated.Size 185 x 110 x 60mm.Digital display : 37 x 16mm

£40.00

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L K3 HOME COMPUTERIdeal simple computer for beginners.Microprocessor has 8 bit data bus and12 bit address bus. Ready programmedROM has 4K bits. RAM of 0.5 x 8kbits fully addressable. 8 digit LEDdisplay. Hexadecimal read out.Hexadecimal keyboard. Re -set switchand single shot facility. Power supplykit included. Provision for cassetteand V.D.U. operation. £190.00

AIiilji..,e, , 11 Ajl' 4»»00 sitc,

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LK4 AUDIO GENERATORCovers 10Hz to 100kHz in fourswitched stages. Variable voltageoutput.Distortion below 0.02%.Sine and square waveoutput. Ideal for HI -Flwork and as signal tracer.

£40.00

4 -li

---., ---.J-

L K5 DIGITAL ELECTRONIC TECHNIQUESExperiments carried out on a P.C. board,size 190 x 150mm covering operationalamplifiers; integrators; basic logic circuits;NAND, NOR gates; Flip -Flops; Multi-vibrators; clock generator; 4 bit camper-itor feed back; analogue switching;building simple digital meter circuits;Timer.Note:- for full benefit with this kit aC.R.O. is desirable although circuits canbe built without one.

L K6 LOGIC DEMONSTRATION PANELBasic introduction to computertechnology; AND and OR gates; NORand NAND; Data line selector; Truthtables; AND and INVERT gate; Half andFull Adder; Latches; Flip -Flops; Shiftregister; Binary coded decimal counter. :,of",--., . .

Over16 experiments are performed .-'... ie--.. .with panel. Battery operated.

l'I'-Ge...

£70.00,

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£35.00

LK7 ANALOGUE TEST METERBasic mufti range test meter kit with20,000 ohm/volt sensitivity. RangesRanges: D.C. and A.C. volts 0-5, 0-25,0-100; 0-500; 2.5 kV.D.C. 0-5mA, 0-500mA, 0-50pAResistance 0-50K; 0-5M. Size 150 x 75x 50mm.

£17.00

.Al

9-40.t e

41.4 ..111t

L K8 SHORT WAVE RECEIVERA simple 3 stage short wave only radioreceiver for the amateur. Very goodselectivity and sensitivity and will givehours of enjoyment. Simple to constructby people of any age.

£25.00 V:-...

To:- LERNAKITS, 4 Cleveland Road, Jersey, Channel Islands. (Est. 40 years)

Please supply Kit at £ add £2 postage U.K. only.£10 postage overseas Air Mail.

BLOCK CAPS PLEASE

NAMEADDRESS

ALL CREDIT CARDS ACCEPTEDName of Card

(Dispatch is normally within 1 week of receipt of order) Signature


No

HE/10/819

Catalogue availableon receipt 12p stamp.

1

J

15

GUITAR PHASER Z085 Sept. '80 £9.60 HOBBYTUNE Z034 Oct. '19 £18.00BENCH POWER SUPPLY UNIT Z087 Sept. '80 £25.00 MULTI OPTION SIREN Z036 Oct. '19 £10.50DEVELOPMENT TIMER Z086 Sept. '80 £8.75 ANALOGUE AUDIOTOUCH SWITCH (on Vero) Z084 Sept. '80 £4.50 FREQUENCY METER ZD35 Oct. '79 £15.00AUTO PROBE ZD83 Sept. '80 £3.00 COMBINATION LOCK Z029 Sept. '79 £12.50REACTION TIMER Z082 Sept. '80 £26.50 *STARBURST Z030 Sept. '19 £14.50MICROMIXER (on Vero) Z081 Sept. '80 £8.50 LAMP DIMMER Z031 Sept. '79 £6.50EQUITONE CAR EQUALISER ZD52 Aug. '80 £13.30 ULTRASONIC SWITCH ZD32 Sept. '79 £21.00GAS DETECTOR Z055 Aug. '80 £22.00 CONSTANT VOLUME AMPLIFIER ZD28 Aug. '79 £11.50PASS THE LOOP GAME Z056 Aug. '80 £12.00 INJECTOR TRACER ZD27 Aug. '79 £4.50RADIO TIMER (on Verol., ZD57 Aug. '80 £5.50 LED TACHOMETER /026 Aug. '79 £14.75MOVEMENT ALARM (on Vero) Z054 Aug. '80 £5.00 BABY ALARM Z025 July '79 £13.50OP. AMP CHECKER (on Vero) Z053 Aug. '80 £4.00 POINTS SWITCH ZD24 July '79 £12.50CAR BOOSTER (no speakers) Z050 July '80 £18.00 LINEAR SCALE OHMMETER Z023 July '79 £14.00HAZARD FLASHER ZD48 July '80 £10.50 SHARK ZD22 July '79 £22.75*PUSH-BUTTON VOLUME G.S.R. MONITOR Z019 June '79 £10.50

CONTROL ZD47 July '80 £19.50 ENVELOPE GENERATOR Z020 June '79 £11.79SOUND FLASH TRIGGER (on Vero) ZD49 July '80 £3.50 DRILL SPEED CONTROLLER Z021 June '79 £7.002 WATT AMPLIFIER (on Vero) Z046 June '80 £3.90 WHITE NOISE EFFECTS UNIT Z018 May '79 £16.85METRONOME (on Vero) Z051 June '80 £3.50 PARKING METER TIMER Z017 May '79 £6.70MICROBE R/C SYSTEM DIGIBELL PROJECT Z016 May '79 £5.00

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Into DigitalElectronics PART TWO

Down to practicalities this month. Ian Sinclair looks at the LS132 NAND gate and some of the

the circuits we can build with it.

CHIP OF THE MONTH, folks, is onewhose full number is SN74LS132; itsfull name is a quad two input SchmittNAND gate. Either way, it's quite amouthful, and we'll refer to it as theLS132. Since this is a strictly practicalseries, we'll start in a practical way byfinding out what this particular ICdoes. (Note: Non 'LS' types are OK).BOARD CONNECTIONS:1A LED ANODE (4)3A LED ANODE (3)5A LED ANODE (2)7A LED ANODE (1)

CATHODE LEADS- ON Y1

1k0 RESISTORS BETWEEN:1A AND 1B3A AND 3B5A AND 5B7A AND 78DIL SWITCH BETWEEN COLUMNS C AND D, LINES 1 TO 8LINKS BETWEEN:

X1 AND X2Y1 AND Y2

Fig.2.1. A reminder of the wiring round the LEDs- this must be completed, along with the switchwiring (shown in previous part) before any furtherwork can be done.

Start by checking the connections ofthe switches and LEDs which you shouldhave from last month. Figure 2.1 is

a reminder, showing where each com-ponent is located and which lines arelinked by wires. Remember to use onlysingle core wire, 0.5mm diameter or so,,because stranded wire will get caughtup in the clips of the Eurobreadboard.If you're using a 41/2 V battery (No.1285) as a power supply, remember toget it the right way round, with + going toX1 (or X2) and - to Y1 (or Y2).

MARKER NOTCH

PIN1

POWER SUPPLY LINKS19B LINK X2 (+)25A LINK Y1

Fig.2.2. How to find Pin 1 of an IC. The links shownare for supplying power to the 74LS132.


Disconnect the battery and find outwhere pin number 1 of the IC is. Figure 2.2shows you how you find the pin 1 of any ICwhich is in this block form (the DILpackage). There's an identifying notch cut atone end of the IC - the end which has pinnumber 1 and also the last pin (14 onthe L5132, 16 on some others we'lluse). Now if you place the IC legsdown as it's shown in the drawing ofFig.2.2 the position of pin 1 is to theleft of the notch. Some manufacturersalso mould a little hollow next to pin 1.Don't be confused if there is whatlooks like a notch at each end - onlythe one which is sunk into the plastic isthe true one!

Now that you've located pin ,1,place the LS132 on the Eurobread-board so that pin 1 is on line A19 andpin 14 is on line B19. You don't need touse tweezers to avoid handling thepins, because these are TTL ICs, notthe CMOS ones which can be so easilydamaged. When you've got the IC cor-rectly placed, push it gently down,rocking it a bit from end to end, so thatthe pins go into the Eurobreadboardholes until the chip is right down on tothe board. Check again that the pinsare in the right holes, because all of thewiring instructions in this part, and allthe following parts, assume that eachIC is in exactly the place we'vespecified.

All You Need Are The RightConnections

We can now start making the connec-tions which create a digital circuit.We're going to use just one of the fouridentical digital circuits which are onthe LS132 chip, and we can make upthe circuit by using just three wirelinks. One useful point about digital ICcircuits is that most of them consist ofjust these links between ICs, with onlya few odd resistors and capacitors to

worry about. The only point to worryabout now is, how do we know whichconnections to make? If you'rebuilding a circuit from scratch, to yourown design, then you have to do it allthe hard way, by tracing which pinsyou need to connect. For this serieswe'll use the easy HE way, using theEurobreadboard line letters andnumbers.

23B LINK 8C (SW1)24B LINK 6CISW2)25B LINK 7B (LED1)

23B 19B

8C

25A

ro 6C246

Fig.2.3. Link diagram (a) and circuit diagram (b) fora gate -test circuit. Only three wire links are need-ed to wire this up, because the switches and LEDsare already in place. This scheme assumes that theIC is in the correct place on the board.

Now there are two ways of showinghow to make these connections, andFig.2.3 shows both. One is a table ofconnections (Fig.2.3a) which showswhich Eurobreadboard lines need tobe linked with wires. The other way,which is a lot more useful, is to writethe Eurobreadboard line numbers ontoa circuit diagram. Why is it moreuseful? Because it gets you used todigital circuit diagrams, that's why.Once this series is finished you're onyoUr own in the big bad world wherethere aren't any tables of Eurobread-board connections, so we're trainingyou to read the circuit diagrams andeventually to be able to fill inEurobreadboard line numbers foryourself.

Fig.2.3(b), then, shows the circuitsymbol for the digital device we're us-ing. It's called a NAND gate, and this

256

76

17

particular example has two inputs andone output. In the circuit shown, theinputs are connected to the switches 1and 2, and the output is connected toLED 1. Since we have only two signallevels to worry about, a switch is all weneed to provide an input. The waywe've wired our switches, up causesthe switch to provide logic 1, downprovides logic 0; and the LED lightswhen the output is at logic 1.

The Truth Is On The Table

Now if this were a linear circuit, like anamplifier, we would probably want tomeasure some quantities like thevoltage gain. We don't have to worryabout such things when we use digitalcircuits, because the only quantitiesthat exist are the two voltage levels 0and 1. We can see what voltage levelswe have at the inputs, because they'reset by the switches, and at the outputthe LED shows whether we have a 1 ora 0. The only thing we need to knowabout a digital IC like this is what com-bination of inputs gives what output.Let's make that a bit clearer. If we hadone input, we would want to knowwhat the output was for a 0 at the in-put, and what the output was for a 1 atthe input. With two inputs, there arefour possible combinations of Os ands which we could have at the inputs,

and it's a bit easier to see what's hap-pening if we write them down in theform of a table (Fig.2.4).

SW1 SW2 LED1

o o

0 1

1 0

1 1

SWITCHES UP FOR 1

DOWN FOR 0

LED LIT FOR 1

UNLIT FOR 0

Fig.2.4. A blank truth table, ready for you to fill in.

We can now try out each combina-tion of signals at the inputs, and findwhat output we get for each line of thetable. This is now a 'truth table' for thedigital IC - it shows what combina-tions of inputs produce 1 and whichcombinations produce 0. Showing thisinformation in the form of a truth tableis neater and simpler than describingwhat happens in words, though not sobrief as the mathematical method call-ed Boolean Algebra.

Come back, don't panic - we're notgoing to do any Boolean Algebra, 1 justmentioned it!

Now how do we go about findingthe truth table for a circuit like the onein Fig.2.3? The obvious place to start iswith both switches at zero (slidersdown). If the LED is lit, then a 1 goes in -

18

0

1

0

LED ON ON ON ON ON ON OFF ON OFF

INPUTA

OUT OF STEP IN STEP

INPUT

74132

Fig.2.5. One possible use for the simple gate cir-cuit.

to the output column on the line whichhas A and B inputs both 0; if the LED isnot lit, then a 0 goes in the output. Thenext step is to try one of the switchesat 1 (slider up), and we usually workfrom the right hand side, making A=0,B=1. Note the output for this one,then set A=1, B = 0 and note the out-put for this, the third line of the truthtable. Finally set both switches up sothat the inputs are A=1, B=1 and seewhat the output is. Fill in this value,and your truth table is complete.

That really does tell you all youneed to know about the way this gateworks. The output is 1 unless both in-puts are 1. When both inputs are 1,then the output is 0. That's all! It'scalled a NAND gate, for reasons we'lllook at later.

Can you think of a use for this? Im-agine that you have two oscillators,one supplying a signal to input A ofthis gate, and the other feeding itssignals to input B. Could you tell whenthe oscillators were exactly in step?Yes, because the LED would be onlydimly lit. When the oscillators are outof step, with one input of the gate highand the other low, the output is high,logic 1, keeping the LED shiningreasonably brightly. When theoscillators are exactly in step, though,the LED is on when both signals are attheir negative peak and off when bothsignals are at their positive peak(Fig.2.5), so that the eye sees theaverage brightness, somewhere bet-ween fully on and fully off.

FROMSIGNALGENERATOR

74132

OUTPUT

Fig.2.6. Using the gate as a signal relay.

Another application? Take a look atFig.2.6. Here one input of the 74L5132is from a switch and the other is from asignal generator. If the switch keeps in-put A at 0, then there is no signal out-put, because the output stays at 1. If

0

0

CITO LED

ON OFF

INPUT A

INPUT B

the switch keeps input at 1, however,the output goes to 0 whenever input Bgoes to 1 (check the truth table to seethat this is so), and the output goes to 1whenever output B goes to 0. This is atypical gating action, opening or shut-ting a gate to let a signal pass or to pre-vent it.

Upside -Down LogicThat brings us to another very usefulaction of this gate. Suppose we usejust one input, and forget about theother one? As it happens, we can't justforget about it, because if a TTL inputis not connected, then it behaves as ifit were connected to logic 1. Figure 2.7shows the Eurobreadboard arrange-ment for trying this out, using switch 1to set the remaining input, and LED 1to indicate what the output is. Thetruth table for this is pretty simple, justtwo lines, one for A = 0, the other forA =1. Try it for yourself, and fill in theoutput values.

19BFROM 8C 23B 74132

25B 7BSWITCH ,

1(m) LINK

LINK24B

(NO CONNECTION)

LINK 8C TO 23B25B TO 7C 25A

A

19B TO X2 0

25B TO Y1

Fig.2.7. Using the gate as a signal inverter -another truth table for you.

Fig.2.8 shows a variation on this.Both of the inputs of the gate are con-nected to the same switch, so that weare using them as a single input. Try itout, and fill in the truth table.

By this time, you should be gettingthe hang of the simple Eurobread-board method of connecting up, andwe're going to use just the diagramsfrom now on. Remember that all theEurobreadboard numbers and lettersshown on one line of a diagram meanthat these Eurobreadboard lines arelinked by wire - that's all there is tobuilding circuits this way.

Back to the digits. The action of thecircuits of Fig.2.7 and Fig.2.8 is called


Into Digital Electronics+VE

19B A 13C

19A21A

INPUT A (SW1)FROM 23B

25B 713

23B020A

SWITCH 1 BC

OUTPUT 0TO LED 22A

258 LED1

248LINK 8C TO 23B T02413

25A 248

258 TO 7819B TO X2

-VE6C

(SW2) 24A25A TO V1 23A

Fig.2.8. Another type of inverter connection.

inversion, and it's not hard to see why.For a 1 at the input, you get 0 at theoutput, and for a 0 at the input you get1 at the output. The output is the in-verse of the input, the other logicsignal. Another name for this action isNOT, because NOT 0 must be 1

(there's nothing else) and NOT 1 mustbe 0 (same reason). A circuit whichdoes this action only is called an in-verter or NOT -gate, and its symbol isshown in Fig.2.9. The little circle at theoutput is what tells you that there is in-version, without the circle, the outputof such a gate would be the same asthe input. The same small circle occursin the NAND gate symbol (Fig.2.8)which tells you that the NAND gate

an inverter. More of thatcontainsshortly.

OA Q

0 O0

Fig.2.9. Inverter symbol and truth table.

Fig.2.11. Another gate circuit. Does this one carry out thesame action as the one in Fig.2.10?

gate as an inverter, we have cancelledthe inverting action inside the NAND -

gate. Yes, that's right, NAND is shortfor NOT -AND.

Something a bit more ambitiousnow - making use of three of the fourgates of the 74LS132. The circuitshown in Fig.2.11, with two gates usedsimply as inverters, but this time at theinputs rather than at the outputs. Doesthis have the same effect as the circuitof Fig.2.10? Try it out, filling in thetruth table so that you can comparethem. Not the same, are they? In factthe truth table of Fig.2.11 shows thatthe output is at 1 if A or B is at one,and it's the truth table of a type of gatecalled the OR gate (Fig.2.12).

Uses? Well just imagine you want acircuit to switch an LED on fromeither of two switches. If that's too sim-ple, imagine this combined with aNAND gate, so that a signal can bestopped or passed using either of twoswitches.

Back to the board. Since we have atotal of four NAND gates in one74LS132, we can use more than one ina circuit.

Strip off all the links which go to the74LS132, leaving only the switches andLEDs as they were. This clears thedecks for the next circuit, and in futurewe'll assume that you've cleared theboard before each circuit. Sometimesyou'll find that the same links are usedagain but until you really get used to itit's always better to start with a clearboard.

Try out the one shown in Fig.2.10.This has the circuit which you usedbefore, with another gate used as an in-verter at the output. Connect up andtry it out, filling in the truth table foryourself. The action of this arrange-ment is on AND -gate, because the out-put is 1 only when both input A and in-put B are at 1. By using the second

+VE

19B

SW1

A 8C

INPUT8

236 218

20B2486CSW2 25A

-VE

A B

0 0 0

0

0

1

19ASC

A

20A

6CB

Nand Nanother NthingAs a grand finale to this part ofthe work, add the last gate of the74LS132, so that you have the circuitof Fig.2.13. ConneCt up, and fill in thetruth table for this lot, which carriesout the action of what we call a NORgate. You should also be able to ex-plain by now why it's called a NORgate!

You should have a fair collection oftruth tables by now, and they are allimportant. We can make AND, OR,NOT, NAND and NOR gates in ICform, and Fig.2.14 shows a reminderof the truth tables for these gates whenonly two inputs are used. We've usedjust one type of gate to make these cir-cuits, though, and that's one of the in-teresting things about digital elec-tronics. A collection of NAND gatescan be used to carry out any action welike, including the action of other typesof gates, so that we could build updigital circuits using only NAND gates,if we liked. We do, in fact, use NANDgates very extensively simply becausethey are so useful; we could equallywell use NOR gates. We couldn't useAND or OR gates for so many usefulpurposes, because they don't invertsignals. We can, for example, producethe action of an AND gate by usingtwo NAND gates (Fig.2.10) but wecould never produce the action of aNAND gate by using any number ofAND gates, unless we could also makeuse of an inverter.

Fig.2.12. The OR -gate truth table.

21A

22A

C---) 24A23A

Fig.2.13. A circuit which makesgates of the 74LS132.

236

78 OUTPUTLED1

Fig.2.10. A circuit using two of the gates on the 74LS132. Constructyour own truth table!

24B

use of all four

I

196

21B258

25A2013

226 76

LED1

A B A B Q A B Q A B a

0 0 0 0 0 0 0 0 0 0

0 0 0 0 0 0 A Q

0 0 0 0 0 0 0

0 0 0

Fig.2 14. Gate types, symbols and truth tablessummarised.


Into Digital Electronics8C

ASW1

19A

B6C

SW2

CSW3 23A

4C

20A

22A

21A

24A

19B

238

24B

25 A

Fig.2.15. Find the truth table for this gate system.

Let's go practical again. Fig.2.15shows a circuit which makes use ofthree NAND gates, and has three in-puts. Now this extra input makes a bigdifference to the truth table, because itmeans eight lines instead of four. Thegeneral rule is that the number of linesof the truth table for a gating circuithas to be equal to 2 multiplied by itselfas many times as we have inputs. Fortwo inputs we need 2x2 lines, for threeinputs we need 2x2x2 (which is eight).Mathematicians write this as 2n (2 tothe power n), where n is the number ofinputs.

A B C --- Q

o o 0

o o 1

o 1 0

o 1 1

1 0 0

1 0 1

1 1 0

1 1 1

Fig.2.16. Blank tru h table to fill in.

The blank truth table is shown inFig.2.16, so you can fill in the outputfor each of the combinations of inputswhich are shown. This one does notform any named type of gate, but itsaction is quite a useful one. Take along hard look at that truth table.Notice that the output is always zero ifB is zero and one or more of the otherinputs is zero, and the output is 1 if Band more of the inputs are at 1. This isa simple form of a 'majority voting' cir-cuit, so called because the output willbe of the same polarity (0 to 1) as themajority of the inputs. It could, for ex-ample, be the basic of a simple voting

19A8C

A SW1

B SW26C

C SW3

20A

4C

> 21A C22A

23A

258 0

78 LED1

E

C

Figure 2.18. Marking out a gate circuit so that you can draw up its truth tablewithout experiment.

machine, but in engineering it is usedfor a much more serious purpose.Some circuits simply are so importantthat no failure must ever happen, evenif the circuit cannot be repaired. Thesimplest way of doing this is to makemany identical circuits, and use a 'ma-jority voting' gate at the output. If allthe circuits are operating perfectly,then all is well, but if some fail, thenthe output will still be decided by themajority. It can be a great comfort ifyou're 250,000 miles away from Earth!

Now for one last bit of practicalwork, try the circuit in Fig.2.17. Thisuses all four gates of the 74LS132, withthree inputs and one output. Becausethere are three inputs, there must beeight lines in the truth table, which youcan complete for yourself by experi-ment. What sort of gate is this?

Gate circuits like this can be used asthe basis for 'combination lock' cir-cuits, which give a 1 at the output onlyfor some particular combination of in-puts. For this reason, the gate circuitsare sometimes known as combina-tional logic - it's the combination ofsignals at the inputs which decide whatwhat the output will be. As it happens,we can make the circuit entirely fromNAND gates if we like. The circuit ofFig.2.17 produces the effect of a three -input AND gate, though we have usedonly two -input NAND gates in the cir-cuit.

How can we find what a gate circuitdoes? One way is to try it out on theEurobreadboard, but another way isjust by writing truth tables. We need atruth table with lots of columns, onefor each input, of course, but also onefor each place where the output of onegate is connected to the input ofanother. Figure 2.18 shows the circuitof Fig.2.17 labelled and a truth tabledrawn up in this way. If we now writein the usual collection of inputs (2n,remember), we can fill in the rest of thecolumns simply because we know the

24B

24A

238

Fig.2.17. Another gate system to investigate - tryit out.

21B

25B

20B

22B a7B

LED1

truth table for the gates we are using.Figures 2.19 to 2.21 show this par-ticular truth table being filled in bit bybit in this way. The final result is theoutput column, which shows the ac-tion of the whole circuit. In this caseit's a 1 when all the inputs are 1, athree -input AND in fact.

A B C D E F Q

o 0 0

o o 1

o 1 0

o 1 1

1 0 0

1 0 1

1 1 0

1 1 1

Figure 2.19. Filling in the ruth able - the firststep. Each possible A,B,C input has been entered.

A B C D E F Q

o 0 0 1 0

o 0 1 1 0

o 1 0 1 0

o 1 1 1 0

1 0 0 1 0

1 0 1 1 0

1 1 0 0 1

1 1 1 0 1

Figu e 2.20. The next step - the E and D columnscan be filled in because you know the truth tablefor the NAND gate and inverter.

A B C D E F Q

0 0 0 1 0 1 0

0 0 1 1 0 1 0

0 1 0 1 0 1 0

0 1 1 1 0 1 0

1 0 0 1 0 1 0

1 0 1 1 0 1 0

1 1 0 0 1 1 0

1 1 1 0 1 0 1

Figure 2.21. The table can now be completed,once again because the truth tables for NANDgate and inverter are known.

The important point is that gate cir-cuits can be designed to give a 1 out-put for any combination of inputs welike. A lot of machinery can be con-trolled just by an ON(1) or OFF(0)signal, so that gate circuits are the oneswe use to make control circuitry. Themore complicated the control actionhas to be, the more suitable digitalgates are to carry it out, becausemechanical switches and relays aresuitable only for comparatively simplecircuits. H E


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nvpr ONLY £7.25152mm 16.0")

All EXP 300 Breadboards mix and match with 600series.

' IANTEX I1943 15 watt quality soldering iron with

bit1947 Replacement element for 19431944 Iron coated bit 3/32" for 19431945 Iron coated bit 1/8" for 19431946 Iron coated bit 3/16" for 19431948 18 watt iron with iron coated bit'1952 Replacement element for 19481949 Iron coated bit 3/32" for 19481950 Iron coated bit 1/8" for 19481951 Iron coated bit 3/16" for 19481931 X25 25 watt iron, ceramic shaft and another

shaft of stainless steel to ensure strength £6.121935 Replacement element for 1931 £2.051932 Iron coated it 1/8" for 1931 £0.581933 Iron coated bit 2/16" for 1931 £0.581934 Iron coated bit 3/32" for 1931 £0.581953 SK 1 soldering Kit contains 15 watt soldering

iron with 3/16" bit plus two spare bits, a reel ofsolder, heat -sink and a booklet 'How toSolder £7.28

1939 51'3 iron stand made from high grade bakelitechrom plated steel spring, suit all models -includes accommodation for six bits and twosponges to keep the iron bits clean £1.89

11724 Model MLX as X25 iron but 12 volts £5.59

CASES AND BOXES

3/32"£5.12£2.33£0.58£0.58£0.58£5.12£2.22£0.58£0.58£0.58

VERO plastic case box. These boss. consist of top andbottom sections which include fixings points for horizontalmounting PC boards/chassis plates, the two sections areheld together by four screws which enter through the baseand are concealed by plastic feet.No. Length Width Height Price170 140mm 4Ornm 205mm £4.35171 140rrun 75mm 205mm £4.85172 140mm 1 1 Ornm 205mm £6.30INSTRUMENT CASES in two sections vinyl covered topend sides, aluminium bottom, front and beck.No. Length Width Height Price155 8in 5; in 2in £1.72156 11in bin Sin £2.92157 bin 4lin llin £1.79158 gin 5:in 211n £2.43ALUMINIUM BOXES made from bright sill, foldedconstruction each box complete with half inch deep lid endscrews.No. Length Width Height Price159 2 lin 11in £0.85160 en 4in 1 ; i n

iC0.85

161 4in 2 lin1'n'

£0.86162 51 -in 4in 1r £0.97163 4in 2iiin 27r: £0.87164 3in 2in tin £0.60165 7in 5in

Pni'£1.43

166 8in 6in [1.83167 6in 4in 2in £1.18SLOPE front aluminium boxes with black vinyl base endsides & aluminium beck, top & front - strong constructioneasily assessable.169 in 5l 2lin 12in nin Bin168 21111 llin 4in 16in 4iin 11in

£5.46£8.21

AUDIO MODULES

AL1OAL20A L30A

AL60

ALSOAL120AL250

AMPLIFIERS3 watt Audio Amplifier Module 22-32v supply5 watt Audio Amplifier Module 22-32v supply7- 10 watt Audio Amplifier Module22-32vsupply15-25 watt Audio Amplifier Module 30-50vsupply35 watt Audio Amplifier Module 40-60v supply50 watt Audio Amplifier Module 50- 70v supply125 wan Audio Amplifier Module 50-80v supply

£3.63£4.11

£4.78

£5.92£9.28

£15.11122.94

STEREO PRE -AMPLIFIERSPA12 Supply voltage 22-32v input sensitivity 300mv

suit: AL10/AL20/AL30PA100 Supply voltage 24-36v inputs,- Tape. Tuner

Mag P U_ Suit iAL60/AL80PA200 Supply voltage 35-70v inputs:- Tape, Tuner.

Mag P.U., Suit :AL80/AL120/AL250

£9.83

£20.30

£20.98

MONO PRE -AMPLIFIERSME4100 Supply voltage 40-65v inputs: Mag, P.U., Tape

Microphone Max. output 500mv £14.29M M1000 Supply voltage 40-65v inputs:2 Guitars.

Microphones Max. output 500my £14.29

POWER SUPPLIESPS12 24v Supply suit 2 AL10,2 AL20.

2 AL30 & PA12/S.450SPM80 33v Stabilised supply -suit 2 AL60.

PA100 to 15 wattsSPM120/45 45v Stabilised supply - suit 2 AL60.

PA100 to 25 wattsSPM120/55 55v Stabilised supply - suit 2 AL80.

PA200SPM120/65 65v Stabilised supply -suit 2 AL120.

PA200, 1 AL250. PA200SG30 15-0-15 Stabilised power supply for

2 GEIOOMKII

£1.90

£5.57

£7.34

£7.34

£7.34

£4.37

MISCELLANEOUSMPA30 Stereo Magnetic Cartridge Pm -Amplifier

input 3.5mv Output 100myS. 450 Stereo FM Tuner Supply Voltage 20-30v

Varicap tunedSTERE030 Complete 7 watt per Channel Stereo

Amplifier Board - includes amps. pre -amp. power supply, front panel, knobsetc - requires 2050 Transformer

BP124 5 watt 12v max. - Siren Alarm ModuleGE100Mk11 10 channel mono -graphic equaliser

complete with sliders and knobsVPS30 Variable regulated stabilised power supply

2-30v 0-2 amps

TRANSFORMERS

2034 1.7 amp 35v suit SPM802035 2 arne 55v2036 750mA 17v suit PS122040 1 5 amp 0 -45v -55v suit SPM12045

SPM120/55v2041 2 amp 0 -55v -65v suit SPM 120/55,

SPM120/65v2050 1 amp 0-20v suit Stereo 301726 150mA 15-0-15v suit SG30

ACCESSORIES

£3.76

£29.39

£24.25£4.43

£26.45

£8.74

P&P£6.21 E 1 21£7.30 E1 47£3.68

£5.98 E 1 21

£7.82 E 1 47£3.74 E0.75£2.04

139 Teak Cabinet suit Stereo 30.320 235 81 mm140 Teak Cabinet suit STA15425 290 95mmFP100 Front Panel for PA100 & PA200BP100 Back Panel for PA 100 & PA200GE100FP Front Panel for one GE100MKII2240 Kit of parts including Teak Cabinet. chassis

sockets. knobs to build 15 watt stereoamlifier (Does not include modules)

£8.05£9.78£2.07£184£2.05

£22.94

SPECIAL OFFERSMINIDRILL 12v hand held battery -operated mini drill. 7,500r.p.m. Collet chuck Ideal for drilling printed circuits or modelmaking. No. 1402. Complete with two drills -1. -15. £6.33TRANSFORMER 240v Primary 0-20v a 2A Secondary. Byremoving 5 turns for each volt from the secondary winding, anyvoltage up to 20v a 2A is obtainable. Ideal for the experimenter.No 2042 £1.50 v 86p. P & PANTEX MLX Soldering Iron. Sturdy 25 watt iron complete with,4; metres of 2 -core cable. Works off a 12 volt batten,. Ideal forCar. Boat. Caravan. No 1724 £5.29

SILICON RECTIFIERS200mA15920 50V15921100V15922 150V1S923 200V15924 300V

1 AmpN4001 50VN4002 100yN4003 200VN4004 400VN4005 600V. -N4006 800VN4007 1000V

1.5 AmpSO 1 5 50V5020 100VS021 200VS023 400VS025 600V5027800V50291000VS031 1200V

Ir7C,51' 50V1570/100 100V1570/200 200V

£0,07£0.0800.09£0.10£0.12

£0.054£0.06£0.07£0.08£0.09£0.10£0.12

£0.10£0.12£0.13£0.15£0.18£0.18£0.23£0.29

£0.86£0.97£1.38

3 AmpN5400 50VN5401 100VN5402 200VN5404 400VN5406 600VN5407 800VN5408 1000V0 Amp

S10150i5OV510/100100VS10/200 200V510/400 400V5101600 600VS10/800 800V510/1000 1000VS10/1200 1200V10 AmpS30/50 50VS30/100 100y530/200 200V530/400 400VS30/600 600V5301300 800V530/1000 1000V530/1200 1200V

1S70/400 400V1570/600 600V1S70/800 800V1570 1000 1000V

£0.1600.17£0.18£0.20£0.24£0.29£0.35

£0,22£0.24£0.26£0.40£0.48£0.59£0.69£0.79

£0.64£0.79£1.07£1.44£2.02£2.33£2.88£3.31

£2.01£2.59£2.88£3.45

THYR STORS600ma TO 18 CaseVolts No. Price

10 THY600/10 £0.1720 THY600/20 £0.1830 THY600/30 £0.2350 THY600/50 £0.25

100 THY600/10 £0.29200 THY600/200 £0.44400 THY600/400 £0.51

1 amp TO 66 CaseVoltsNo. Price50 THY1A/50 £0.30

100 THY 14/100 £0.32200 THY I A/200 £0.37400 THY1A/400 £0.44600 THY I4/600 £0.52800 THY14/800 £0.67

3 amp TO 66 CaseVolts No. Price

50 THY3A/50 £0.32100 THY3A/t00 £0.35200 THY34/200 £0.38400 THY34o400 £0.48600 THY3A/600 £0.58800 THY3A/800 £0.75

5 ampVolts No.50 THY5A/50

100 THY5A/100200 TH954/200400 THY5A/400600 THY5N600800 THY5A/800

TO 66 CasePrice£0 .41£0.52£0.58£0.66£0.79£0.93

5 amp TO 220 CaseVolts No. Price400 THY5A/400P £0.86600 THY5A/600P £0.79800 THY5A/800P £0.93


50 THY7A/50 £0.55100 THY7A/100 £0.59200 THY7A/200 £0.66400 THY7N400 £0.71600 THY7A/600 £0.90800 THY7A/800 £1.06

10 amjs TO 48 CaseVolts Price

50 THY10A/50 £0.59100 THY104/100 £0.66200 THY1ON200 £0.71400 THY10A/400 £0.81600 THY10A/600 £1.14800 THY10A/800 £1.40


50 THY164/50 £0.62100 THY16A,100 £0.67200 THY16A/200 £0.71400 THY 164/400 £0.89600 THY16A1600 £1.04800 THY16A 800 £1.60


50 THY30A 50 £1.38100 TRY30A/100 £1.64200 THY30A/200 £1.87400 THY30A/400 £2.06600 THY30A/600 £4.03

No. PriceEiT101,50OR £0.92BT102/500R £0.92BT106 £1.44BT107 £1.07BT108 £1.13253228 £0.81253525 £0.89BTX30/50L £0.38EITX30,400L £0.530106.4 £0.6987116 £1.73

ZENER DIODES

METAL FOIL CAPACITOR PAKS16204 - Containing 50 metal foil capacitor like Mullard C280series - Mixed values ranging from 01 of - 2 ,2uf. Complete withidentification sheet 71.38

TRIACS2 amp TO5 use 10 ampvolts Na Price volts100 TR12A 100 £0.35 100 TR1104,100200 TR124,200 £0.59 200 TR110A/200400 TR 12A 400 £0.92 400 T51104/400

10 amp6 amp volts

400 781104,400P £149100 TRI6A 100 £0.59200 TR164,200 £0.70 DIACS400 TR16N400 £0.88 85100 £0.23 D32 £0.23

£0.88£1.06£1.29

400 mw 18zy881 D007 Glass encapsulated range of voltagesavailable 1 3v, 2-2v. 2.7v. 3.3v. 3.90.4 3v. 4,7v, 5.1v. 5.6v.6,2v 6,8v 7 5v 8 2v. 9 1 v 10v 11v. 12v 13v. 15v. 16v, 18v,20v 22v 24v 27v 30v 33v 39v. No. 2410p

1w -1.5w Plastic and metal encapsulated. Range of voltagesavailable 1 3v 2.2v 2,7v 3-3v. 390. 4.3v, 4,7v. 5 Iv. 5,6v,6 2v 6.8v 7,5v. 8,2v, 9.1v. 10v, 11v, 12v. 13v. 15v. 16v 18v,20v 22v 24v 27v 30v. 33v 43v. 47v. 51v 68v, 72v, 75v. 82v,91v 100v No. Z13 liplOw Metal stud type S010 case. Range of voltages available.1 3v 2,2v 2 7v. 3 3v 3,9v. 4 3v 4,7v 5,1v 5.6v. 6-2v. 613v.7 5v.B 2v 9,1v, 10v. 11v 12v. 13v. 15v. 16v. 18v, 20v. 22v,24v. 27v 30v. 33v 43v 47v 51v 68v 72v 75v. 82v. 91v,100v No. 210 44p

BRIDGE RECTIFIERSSILICON 1 amp SILICON 2 ampType No. Price Type No. Price

50v HMS BR1 50 £0.23 50, HMS BR2 50 £0.52100v RMS BR1,'100 £0.25 100v RMS BR2 100 £0.55200v RMS 051/200 £0.29 200v RMS BR2 200 03.60400v RMS 951/400 £0.41 400v RMS BR2 400 £0.67

1000v RMS 852 1000E0.78

SILICON 10 amp SILICON 25 ampType No. Price Type No. Price

50v RMS 8510/50 £1.73 50v RMS BR25 50 £2.19200v RMS 13R10,200 £1.98 ?no, RMS BR25 20C £2.53

All prices include VAT: Add _50p post per order-Just quote your Access or Barclaycard number.

Terms: Cash with order, cheques, POs, payable to Bi-Pak at above addressAccess and Barclaycard also accepted

BARCLAYCARD


The premier mail order housespecialising in quality products andsuperior after -sales care.

SEIKO QUARTZLCD MEMORY -BANK CALENDAR WATCH

SPECIAL PRICE ONLY £49.95plus 85p p&p. Usually £89 or over.

Displays hour, minute, second,month, day of the week and date in 12hour indication - or 24 hour at thetouch of a button.

Button touch also displays month andyear and dates for a designatedmonth with Sunday dates flashing.

Stores dates in memory up to 11ahead, flashes 'MEMO' ondesignated dates.

Illuminated time and calendardisplay.

Display flashes when battery nearslife end.

Stainless steel case and wrist strap(adjustable).

In presentation case with instructions.

A LIFETIMEWATCH AT ABARGAIN -OF -A -LIFETIME PRICEFull refund if notcompletely satisfied.

Mitrad, 68-70 High Street,Kettering, Northants.Tel: 0536 522024

To Mitrad, 68-70 High Street, Kettering,Please send me:

I ISeiko Quartz watch(es) at £50.80 inc p&p

LA LM75 watch(es) at £6.80 inc p&pF-1 LM105 watch(es) at £7.80 inc p&p

1 LM40 watch(es) at £10.80 inc p&p

Total value of my order £

LM62 watch(es) at £14.80 inc p&p

LM73 watch(es) at £18.80 inc p&p

I

I LM39 watch(es) at £11.10 inc p&p

Pen watch(es) at £12.00 inc p&p

I enclose cheque/PO or debit my Access/Barclaycard No.

Northants.

1

IE31

orFor complete

for catalogue.or complete product range, ring /

e Credit Card holders may telephone (0536) 522024 24 hours a day stating Card Number for immediate attention. Al orders

Trade price list available fordespatched within 48 hours. Delivery subject to availability. Full refund if not completely satisfied.

bulk orders. L-Mitrad. Registered in England No. 1500613. HE


Name Signature

Address (block letters please)

1

This is a representative selection fromthe collection of guaranteed leadingmake and own brand watches offeredthroug h Mitrad's 48 hour distributionsystem and backed by Mitrad's own /service organisation.

MITRAD UV1105 Five function LCD ladieswatch. Continuous display of hours andminutes with pulsating seconds. Selectablemonth, date, seconds. Auto calendar. Fullyadjustable closely woven stainless steel strap.Case thickness 7mm. In silver only.£6.95 + 85p p&p.

IAITRAD LM73 Gentleman's memory calendar)Iarm chrono. Programmed to year 2009.:ontinuous display of hours, minutes and;econds with optional display modes of hours,ninutes and date, or calendar and month withlashing Sunday flags. Selectable month.\larm mode indicated by flashing bill; settablelnywhere in 24 hour period; activated for full;0 seconds; provided with 10 minute snoozeacility. Chronograph has 12 hour capacityvith split and lap mode facilities: first 30ninutes run as minutes, seconds and 1/100econds, thereafter hours, minutes and


seconds. Back light. Adjustable stainless steelstrap. Case thickness 11mm.£17.95 + 85p p&p.

MITRAD UV140 Four button gentleman's alarm.Continuous display of hours, minutes andseconds plus selectable month, date, day. PMflag. Alarm, settable any -where in 24 hourperiod, is activated for full 60 seconds. Backlight. Closely woven adjustable stainless steelstrap. Case thickness 10mm.£9.95 + 85p p&p.

MITRAD LM75 Five function LCD gentleman'swatch with quality chrono look. Continuousdisplay of hours and minutes plus selectablemonth, date, seconds. Auto calendar. Bocklight. Stainless steel strap. Case thickness 8mm.£5.95 + 85p p&p.

MITRAD LM62 Gentleman's dual time alarmchrono. Incorporates leading made module.Continuous display of hours, minutes and

seconds with a number coded day, AM/PM,alarm setting and the secondary time indica-tion. Chronograph ('running horse') to 1/10sec. Freeze, split and lap modes. Alarm,settable anywhere in 24 hour period, is

activated for full 60 seconds. Dual timingfacility. Fully adjustable closely wovenstainless steel strap. Case thickness 10mm.£13.95 + 85p p&p.

MITRAD LM39 Ladies auto LCD dress watch.Continuous display of hours, minutes and(pulsating) seconds. Month and date with autocalendar. Back light. Integral watch and strapwith sugar frosted finish in gold or silver.Spring clip clasp for comfortable fit. Casethickness 8mm. £10.25 + 85p p&p.

PANTER QUARTZ PEN WATCH Five functionLCD pen watch showing hours, minutes,seconds, month and date. Computerised fouryear date memory. Ball point pen. Stainlesssteel case. £12.00 inc. p&p.

23

Tug aWarGame

Play an old game a new way with this designfrom HE - eliminate sweat, mud and sore palms.The HE Tug O'War is the ideal game for the lessenergetic who only wish to exercise their fingers- a genuine digital circuit in more ways thanone!

HERE AT HE we are basically very lazy(who said 'hear hear?). So we're alwayslooking at ways to turn the physical ex-cesses of the sporting life into gamesthat we can play with one finger, in thecomfort and privacy of our own arm-chairs. Our latest venture into this field(or rather off the field) is the Tug O'Wargame, which does for this sport whatShark did for swimming and the Scalex-tric Lap Counter did for motor racing.

In our version the game is not a trialof strength, (strain gauges are not readi-ly available to the hobbyist!) but rathera contest to see who's finger is fasteston the button. The display consists of aline of LEDs, of which only the centreone is lit at the start of the game. Asingle flashing LED is provided andwhen it comes on the first player topress his button causes the light on thedisplay to move towards him. Themore often a player reacts first, the fur-ther the light moves. The winner is theperson who gets the light to his end ofthe display. All of this is accompaniedby the usual bleeps and buzzes that weknow and love so well.

Our office philosopher once saidthat most electronic games could bereduced to just one, 'Spot the 4017'.You might think that the same is begin-ning to apply to the LM3914 - andwhy not? Like the 4017, it is a veryuseful and versatile chip which can beused for many different applications.Here we use it as a bargraph voltmeterin the 'dot' mode, so that only one LEDin the display is lit up at any one time.

ConstructionWe recommend the use of our PCB.Solder the resistors, capacitors, diodes,transistors, and IC sockets to the board,taking care that polarised componentsare fitted the right way round. Wemounted the display LEDs in clips onthe front panel. The anodes were link-ed together by a length of tinned cop-per wire which was then wired to thePCB, while the individual cathodeswere wired to the corresponding padson the PCB. If you hate interwiring,then it is possible to solder the LEDs

HE

directly in position on the PCB -however you will have to use 0.125"LEDs or the more expensive squaretype as the size we used won't fit.

Wire up the switches, indicator LED,loudspeaker and battery clip and insertthe ICs into their sockets. Now fastenthe PCB inside the case. We simplystuck it to the bottom with double -sided sticky pads. The loudspeaker isglued to the base of the box; but don'tforget to drill a few holes there first orthe sound will be somewhat muted!

How it WorksA player has to push his button first to move thelight on the display towards him - the circuitryaround IC1 detects who is first. A new chance tobeat the other player is provided once a secondwhen IC3a resets IC1. IC3a is connected as anastable (oscillator) operating at one Hertz. Whenits output (pin 9) is high, IC1a and b are reset viaD2 and D4. When pin 9 goes low again IC1a and bare enabled and LED1 lights to indicate this. Thedegree of difficulty of the game can be varied byaltering the mark -space ratio of IC3a (time that itis on and off). This is done by adjustment of RV2.

IC1 contains two D -type flip-flops, or bistables,one for each player. In this type of bistable a pulseon the clock input causes the logic level (high orlow) at the data input (D) to be transferred to theoutput (Q). Clock pulses are generated when aplayer presses his button, and the inclusion of C1and C2 ensures that a player cannot cheat byholding his button down; a new pulse must beprovided every time LED1 turns on. The resetpulse from IC3a forces the outputs of IC1 a and blow and both D pins are held high by R3 and R5,

so the faster player will send his Q output high.Each output is coupled to the reset pin of the

other bistable via D1 and D3. Thus the fasterplayer's high output disables his opponent'sbistable for the remainder of that 'play' period.One of the transistors Q1 or Q2 will be turned onvia R9 or R10, depending on who was first.

IC2, an LED voltmeter, senses the voltage at thejunction of C3 and C4 via RV1. Normally thisjunction is charged to half supply voltage, andRV1 adjusted to light the middle LED of thedisplay. If Q1 turns on, the voltage at the junctionwill rise as C3 discharges and C4 charges. Similar-ly the voltage will fall if Q2 turns on. IC2 respondsby lighting LEDs further up or down the scale.This provides the game display.

IC3b is connected as audio oscillator, normallyoff because its enable pin is grounded (pin 4).When either output of IC1 goes high, IC3b isenabled via D7 or D8 - the pitch depends on thecontrol voltage applied to pin 3 via R20 and R21.The tone shows which player reacted first.


Inside the case, note position of the loudspeaker and battery. Close up of the interwiring of the LEDS. A cable tie keeps things neat.

0

R3150k

CLK

CI10n

R168k

R16120k

RV2IMO

D5

ICla

7 4

SET

R2150k

61522k

RESET

RI7120k

D6

R4150

L14

1u5

13

DI

D2

12103,

9

C610n

LE5605.1

RESET

R5150k

PB2.

IC1b CLK

10

R6150k

C21011

SET

R7 R8150k 68k

IC14

R9lkO

6101k0

R22220k

023100k

C710n

R1112k

R1215k

Figure 1. Circuit diagram of the HE Tug O'War

18F4

17 14

R13C3 1006100u

IC2 14

13

RV1

12 14100k

5 14C4 10100u

7 2 4

4705

NOTEICI IS 4013IC2 IS LM3914IC3 IS 55601,2 ARE BC109Dl -8 ARE 154148LED1-10 ARE 0.2" LEDS(VARIOUS COLOURS)

SW1 '90

j RED

YELLOW

,11015

JYEL. LOW

) RID

1 Ell 10

Buylines

OV

0

There should be no serious problems in obtain-ing the components for this project. Try theusual mail-order companies who advertise withus if you have trouble. Component cost shouldbe about £12, but remember that this price is ex-clusive of case and printed circuit board.

ry


Tug 0' War Game

PB1

RED

LEDS 2-10

RED YELLOW YELLOW REDYELLOW GREEN YELLOW RED

PB2

/////1/1/

LED1

+9V

OV

Parts ListRESISTORS (all 1/4 W 5%) CAPACITORSR1,8 68k C1,2,6,7 10n polyesterR2,3,4,5, C3,4,8 100u 16 V PCB -mounting6,7,19 150k electrolyticR9,10 1k0 C5 1u5 35 V tantalumR11 12kR12R13,23R14

15k100k470R

SEMICONDUCTORSIC1 4013

R15 22k IC2 LM3914

R16,17 120k IC3 556

R18R20R21

560R8k22k2

Q1,2D1-8LED1-10

BC1091N41480.2", various colours

R22 220k

POTENTIOMETERSRV1 100k linear horizontal miniature

presetRV2 1MO linear horizontal miniature

preset

MISCELLANEOUSSW1 Single -pole, single -throw togglePB1,2 Push -to -make non -lockingLS1 Miniature 8R0 speakerPCB, IC sockets, 9 V battery and connector,verocase, clips for LEDs.

26

A

LS1

Figure 2. Overlay and interwiringdiagram for the HE Tug O'Wargame. LED1 and SW1 mount on thefront panel as well but we've drawnthem as separate for clarity

Setting UpDouble check the position of all thecomponents and wiring, then insert aPP3 into the battery connector. Switchon and check that the move indicatorLED is flashing. The ratio of 'on' to 'off'times can be adjusted by RV2 to setthe level of difficulty you require. Nowrotate RV1 until the centre LED is lit.Check that pushing either buttoncauses the light to move in that direc-tion and a tone to sound (different foreach button). If the light moves the op-posite way, swap over the connectionsto the pushbuttons.

If all is well, snap the case togetherand the game is ready for use. All youhave to find is a friend and two arm-chairs. HE


\;or A smIAL c46/2 Lwa-rS -11.4tr wet

Ste, -t -or oeLon/ Si F t.1 %orfoen

CPiPS ! of --41c 11.PASi414.(-1

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Vein.VERO ELECTRONICS LTD RETAIL DEPT.

Industrial Estate, Chandler's Ford,Hampshire S05 3ZR

Tel: (04215) 62829


VCfO

Wiring Accessories

The Vero range of wiringaccessories are all highest quality

`professional' products, carefully selected to easeyour interconnection problems. There's a full rangeof pins and DIP sockets (including low -profile) forsolder or wire wrapping techniques and the popularVerowire prototype wiring system.Add these to our established range of boards, boxes,frames and cases and you've got all you need foryour project. It's all in our catalogue - just send40p. and it's yours by return.

27

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10 0 0 0 0 0 0 0 0 lo t.I. 00006.11.0 P. 11/ 0 I 0 0

ID S NO GO ff

WE HAVE ALL THE NEW ATARI®VIDEO GAME PROGRAM'CARTRIDGES.

AR1111,4"jh

API tr

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II"

GVAT

HI" III

Juno

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RADOFIN DATABASE etc.We keep a full angelSend for cartridge lists stating whichmachine you own

INTELLIVISION MATTEL

£173.87 + VAT

Available August 1980This is the most advanced TVgame in the world.Expandablenext year into a fullmicrocomputer.COLOUR CATALOGUEAVAILABLE WITHDETAILS ON ALL THECARTRIDGES

CHESS

Send for further details.

COMPUTERS

NEW RANGEAVAILABLEAUGUST 1980We specialise incomputer chessmachines &stockover 13 differentmodels from£20 to £300

BRIDGECOMPUTER

* Plays 1/2/3 or 4 Hands* Problem Mode* Audio Feedback* Instant Response* Auto storekeeping

r DRAUGHTSCOMPUTER

Solves ProblemsRejects illegal moves2 level machine£43 + VAT4 level machine£77.78 + VAT

AMAIL ORDER SERVICE - Free postage & PackingTELEPHONE & MAIL ORDERS - accepted on.Access * Barclaycard * American Express * Diners ClubCALLERS WELCOME - at our shop in Welling - Demonstrations dailyOpen from 9am-5pm Mon -Sat (9am-1pm Wed)GUARANTEE - Full 12 months + After Sales Support!We have comprehensive brochures on all products. Please let us know what you areinterested in and we will send you detailed brochures AND our own32 page catalogue covering most games on the market.

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Look out for the November issue -on sale October 3rd.

SPACE INVADERS

In the past few months we've seen all manner of Space In-vaders games - from enormous pub machines to programs,on tape cassette for home computers. We've spent many along hour researching the game in pubs and clubs from Land'sEnd (Watford) to John 0' Groats. Next month we present theETI Space Invaders game for you to build. Plug the lead in-to the back of your telly and sit back with the box of tricks onyour lap. Off you go - blasting aliens out of existence (withfull sound effects, of course). World War III's OK, butthere's nothing like the real thing - ETI Space Invaders - acomputer game with a trick or two up its sleeve, as you'll findout next month.

Photos courtesy of Twentieth Century Fox.

FREE PCB

As we finish printing each issue of ETI with our John Bull set,we're sticking a free, gratis, no -more -to -pay printed circuitboard on the cover. It has a million and one uses - you canprop up a wobbly coffee table, make a shower for the budgie. . OR build the five projects we've designed for your freePCB. There's an RIAA equalised preamp, a 2 W amplifier, atouch doorbell, a light switch and a metronome. We giveyou the PCB; we give you the project designs . . . it couldn'tbe easier.

RADIOACTIVITY

Know your alpha, beta, gammas? If it's all just radiation toyou, you could learn a thing or two from A.S. Lipson's excur-sion into that fantastic, frazzling, phenomenon of modernphysics - Radioactivity. What makes something radioactive?What exactly is radioactivity? All will be revealed next month.

EVEN MORE PROJECTS

Not satisfied with bringing you our amazing Space Invadersgame and FIVE projects for your free board, we've also got adoorbell with a difference (it plays tunes) and a straight-forward, no frills Bench Amplifier for your test bench. It's all inETI November.

AND THAT'S NOT ALLData Sheet puts in an appearance with all you need to knowabout a family of monolithic switched capacitor filter chipsand a speech generator chip (a very clever little block ofplastic). Talking of blocks of plastic, voltage regulators thistime - we look at a very simple discrete component regulatordesign (for when you don't have the necessary chip to handthen and there). We know now that the Space Shuttlelaunch has definitely been postponed until at least next March.Astrologue explains why.

Articles described here are in an advanced state of preparation. However, circumstances may dictate changes to thefinal contents.


BuildingSite

Although the National Grid, courtesyof the Electricity Board, provides us

with a useful source of energy topower our projects, you won't be

surprised to learn that it can also bedangerous if proper care is not taken. Keith Brindley

offers a few suggestions as to how the mains can be safely harnessed.

SOME INTERESTING problems arosewith three of this month's projects - theFreezer Alarm, the Light Dimmer and theTemperature Controlled Soldering Sta-tion, all of which are connected to themains power supply.

Now, nobody can deny 220-240 VAC mains is exceptionally useful as aneasy way of obtaining power for yourprojects and furthermore, running costsare minimal. But the problem still re-mains of the potential shock hazards en-countered with its use. A mains shockwill at best give you a painful jolt, leavingyour arm quite numb for a few minutes.In the worst case, mains voltages arelethal. It all depends on which route thecurrent takes to earth - it willautomatically take the easiest path - soif you are the easiest path - BANG. Forinstance, if your left hand is resting on agood earth point eg. the earthed case ofyour project and you inadvertentlytouch a live point with your right hand,then the easiest current path is up yourright arm, across your chest and downyour left arm. Your heart suffers a bit inthis sort of case, being in direct line withthe current and you may find (or ratherthe first person to come across you afteryour shock may find) that it has stoppedaltogether.

Don't Lose HeartAll joking apart, it cannot be stressedstrongly enough that you should takecare when dealing with mains voltages. Ifyou must probe around inside equip-ment which is connected to the mains,keep one hand in your pocket, notbecause you are mean and want to keep

30

a firm grip on your money but simply toavoid setting up a path through yourheart.

Mains powered projects can bedesigned with certain safety precautionsbuilt in. Take the HE Freezer Alarm forexample, the constructional method isideal for hobbyist purposes as a numberof precautions having been taken. Thefirst is the use of a grommet and someform of cable clip to prevent the mainscable from being pulled out or its insula-tion from being worn. Various forms ofcable clip are available that do the jobsatisfactorily, the type we mostly use is asimple tie -clip. The tie -clips have a non -release ratchet lock action (ie. pull themas tight as you can and simply cut off thelong flying end), which holds the cablesecurely. They are very cheap, around 2or 3 pence each. Tie -clips are also used totie together all the interconnecting wireson the other projects, you may be able tospot them on some of the internalphotographs - this can make a projectlook an awful lot tidier than the usual'bird's -nest' type of arrangement.

Figure 2 shows the use of a very con-venient method of mains connectionknown as European -style chassis con-nectors. None of this month's projectsactually have this sort of plug and socketarrangement fitted but it is such an im-portant method that it is shown here foryour future reference. Connections tothe inside of the circuit can be made us-ing standard 1/4 -inch push -on tab con-nectors or they could simply be solderedon. An advantage of this type of chassisconnector is that you will only need twoor three made-up leads with the cor-responding line plug, as they are readilyinterchangeable.

Another sensible precaution in themains circuit of the Freezer Alarm is thefuse and fuse -holder. A fuse shouldusually be inserted in the live lead to pro-tect the project itself. You should alwaysensure that a correctly rated fuse is used- it is pointless to have a 13 A fuse in acircuit which only draws250 mA. If things gowrong in the projectand more

current is drawn, then it is unlikely thatthe 13 A fuse will blow and your projectmay well suffer irrepairable damage.

A terminal block can be a useful addi-tion to a project because it provides aconvenient way of 'commoning' anynecessary points in the circuit. Thephotograph of the Freezer Alarm showsthe terminal block method in use.

The Light Of Your LifeSpace restriction in the HE Light Dimmerprecludes these connecting methods.Without them the whole unit becomessmall enough to fit into a standard sizedwall box, in place of the existing on/offtype light switch. Once fitted you wouldbe unlikely to take the dimmer out again,so possible hazards are avoided, and it issafe. Nevetheless, we coated the back of

every bit as important. The structure of atransformer is such that it has twomechanically joined coils of wire whichare electrically isolated. This electricalisolation is the key to a project's safety.At no point (usually) is the low voltageside of the transformer joined to the highvoltage mains side, with the possible ex-ception of earth (i.e. zero potential). Thismay or may not be joined depending onthe circuit.

The Light Dimmer and theTemperature Controlled Soldering Sta-tion do not have a mains isolatingtransformer in circuit. So due care mustbetaken - two measures are advised -varnish the copper track side of theboard before use and do not case thedevices in such a way that prying fingerscan get at the insides.

Fig.1. Internal photograph of the mains connection circuitry of the FreezeAlarm, from this you can see the grommet, cable clip, fuse and fuseholder andterminal block.

our printed circuit board (ie. the coppertrack side) with insulating varnish just tobe on the safe side and advise that youdo the same. In fact, it's a good idea to dothat to any PCB which carries mainsvoltages so it may just save a life -yours!

Most mains powered equipment usesa transformer to reduce the high mainsvoltage to a more manageable level(e.g.12 V). It is only pure coincidence thattwo out of this month's three mains pro-jects do not have a transformer in the cir-cuit.

The mains transformer has a secon-dary purpose (pun? what pun?) which is


much hotter), a gas or match flame, or, aswe use, a hot soldering iron held close tobut not touching the sleeving. Picture 1shows such an operation. The sleevedjoint on the left has already been heatedand you can see how the sleeving hasshrunk to tightly cover the joint. The oneon the right is just about to be heated bythe soldering iron. This is a good precau-tion to take on any project, not justmains powered ones, as it protects two ormore close connections from ever shortcircuiting.

Use Your LoafThe important thing to remember if youbuild your own mains powered equip-ment is to take your time. Double checkand triple check everything before you

Fig. 2. A European style chassis connector. Quarter inch tab connectorswere used to make connections.

The Heat Is OnOne precaution that we often take whenbuilding projects in the HE Projects Labis to use Heat Shrink Sleeving. This is avery effective method of covering upand, therefore, insulating any connec-tions which may carry dangerousvoltages. The sleeving is made from apolyolef in material which possesses theremarkable ability to shrink to about halfits original diameter when heated. It's,simple to use, just slip a short length(about 20 mm) over the lead and connec-tion and then heat it up. The heat can beapplied from a proprietary hot air blower(similar to a hand-held hair dryer but

switch on. Use your common sense!From that harmless -looking socket on

the wall you have three leads, colouredgreen/yellow (earth - safe), blue andbrown (neutral and live - DANGER-OUS). When you touch that live connec-tion - if you're lucky, it'll hurt - ifyou're unlucky, you won't feel a thing!

Next month I'm planning to talk toyou about how to make your own PCBs,as quite a few readers have written re-questing more information on the sub-ject. Well, next month you'll see how wedo it and pick up a few hints on how tomake really first class PCBs yourself, sodon't miss it! HE

31

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Make us your No. 1 SUPPLIER OF KITS and COMPONENTS forH E. Projects. We supply carefully selected sets of parts toenable you to construct H.E. projects. Kits include ALL THEEL ECTRONICS AND HARDWARE NEEDED. Printed circuitboards or veroboard are, of course, included as specified in theoriginal article, we even include nuts, screws and I.0 sockets.PRICES INCLUDE CASES unless otherwise stated. BATTERIESARE NOT INCLUDED.If you do not have the Issue of H.E. which includes the project-- you will need to order the Instruction reprint as an extra. 45peach.MICROMIX, Sept. '80 £7.82AUTO PROBE, Sept. '80 £3.67 less caseTOUCH SWITCH, Sept. '80 . . £2.34 less case & contacts

£13.84£11.93£28.94£15.72£27.31

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£29.98 (stereo)FOG HORN, June '80 £5.65EGG TIMER, June '80 £9.99 less case

SPEED CONTROLLER FOR R/C, April '80 £16.39 less caseDIGITAL FREQUENCY METER, April '80HOBBYCOM: TWO WIRE INTERCOM, April '80

£36.17 (Master)£3.38 each

ELECTRONIC IGNITION (CD), April '8025 -WATT MODULE (5080), Mar. '80 £19.98PSU MODULE (5080), Mar. '80

Sub Station

5080 PRE -AMP, May '80 £43.63

£37.73

£21.87

£37.87WIN INDICATOR, Feb. '80 £13.92DIGI-DICE, Jan '80 £10.15BARGRAPH CAR VOLTMETER, Dec. '79 . £7.33 less caseRING MODULATOR, Dec. '79 £12.95GUITAR TUNER, Nov. '79 E11.73TANTRUM STEREO AMPLIFIER, Oct. '79 £85.83HOBBYTUNE, Oct. '79 £28.58ANALOGUE FREQUENCY METER, Oct. '79 £15.52MULTI -OPTION SIREN, Oct. '79 £16.22STARBURST, Sept. '79 £21.72 less caseULTRASONIC SWITCH Sept. '79

£29.85 less 3 pin mains socketHOME SECURITY UNIT Aug '79 £28.56 less sirenSIREN £5.09 less caseLED TACHOMETER, Aug. '79 £18.31INJECTOR /TRACER, Aug. '79 £4.34CONSTANT VOLUME AMPLIFIER, Aug '79 £16.60LINEAR SCALE OHMMETER, July '79 £16.39SHARK, July '79 £26.88GSR MONITOR, June '79 £9.63ENVELOPE GENERATOR, June '79 £15.68PARKING METER TIMER, May '79 £8.79WHITE NOISE EFFECTS UNIT, May '79 £17.74TRANSISTOR GAIN TESTER. April '79 £10.21PHOTOGRAPHIC TIMER, Mar. '79 £18.21("AR ALARM, Feb. '79 £11.47

i.'.RATCHi RUMBLE FILTER, Feb. '79 £26.96 Mono£31.30 Stereo

SINE/SQUARE WAVE GENERATOR, Feb. '79 . £27.05GRAPHIC EQUALISER, Jan. '79 £29.65PUSH BUTTON DICE, Dec. '78 £7.54AUDIO MIXER. Dec. '78 £26.88BEDSIDE RADIO, Nov. '78 £16.99

rEREO AMPLIFIER (HOBIT), Nov. '78 £65.51LATEST KITS: S.A.E. OR 'PHONE FOR PRICES

INTO ELECTRONICS CONSTRUCTIONH E. 6 -part Series. Feb. -80 to July '80. COVERS THE BASICSOF EL ECTRONICS - LOTS OF PRACTICAL WORK. Circuits arebuilt on a plug-in Eurobreadboard REPRINTS AVAILABLE,45p each part. Eurobreadboard and Components for Series£15.63. Components only £9.43.

ELECTRONICS CATALOGUEMagenta's Catalogue has been carefully designed for Electronics Constructors. Productdata and illustrations make the Magenta Catalogue an indispensable guide for theconstructor Catalogue includes ELECTRONIC COMPONENTS. HARDWARE. TOOLS,CASES, TEST EQUIPMENT. Details of advertised items and CIRCUIT IDEAS for you tobuild.No minimum order - all products are stock lines. FIRST-CLASS delivery of FIRST-CLASScomponents.Send for your copy and see how easy our catalogue is to use. WRITE TODAY enclosing 6x 10p stamps.

ADVENTURES WITH ELECTRONICS o scanAn easy to follow book suitable for all ages, ideal for beginners. No Soldering, Usesan S Dec' breadboard. Gives clear Instructions with lots of pictures 16 projects -including three radios. siren, metronome, organ, intercom, timer, etc. Helps youlearn about electronic components and how circuits work Component pack includesan S Dec and the components for the projects.Adventures With Electronics £1.75.Component pack E29.95 less battery.

ADVENTURES WITHMICROELECTRONICS

Same style as above book: 11 projects based on integrated circuits - includes dicetwo-tone doorbell. electronic organ, MW / LW radio, reaction timer, etc Component packincludes a Bimboard 1 plug-in breadboard and the components for the projects.Adventures with Microelectronics £2.35.Component pack £29.95 less battery,

....IIP-

EDUKIT MICROPROCESSOR COURSE1Ideal for beginners - learn the basics of computing from scratch, without spending afortune. Kit is supplied with a comprehensive manual which describes construction,basic theory, initial use, machine code programming, hardware and troubleshooting.An appendix covers soldering and op codes. Kit uses the RCA COSMAC 1802 p P

power supply - can be batteries.EDUKIT, including manual E40.98.

256 bytes of memory, pcb + 20 switch keypad included Requires a 5 or 6V 0.5A

Kit Includes socket for ,. P only - Set of IC sockets for support ICs E2.81 extraPower Supply Kit - simple kit gives 5V 0.5A - includes case and circuit details

hh£7.98. -40AI,

INTO DIGITAL ELECTRONICSCurrent H.E. series. Part 1 in Sept. '80. Covers digital electronics from the basics. Circuitsare built on a plug-in Eurobreadboard. Reprints of back issues available 45p each.Eurobreadboard and components for series £18.95 less battery Components onlyE12.75.

TOWERS INTERNATIONAL TRANSISTORSELECTOR E10.50.ANTEX X25 SOLDERING IRON 25W £4.98.SOLDERING IRON STAND E2.03.SPARE BITS. Small. standard large 65p eachSOLDER. Handy sire 98pEUROBREAD BOARD. £6.20.LOW COST LONG NOSE PLIERS. E1.97.LOW COST CUTTERS. E1.98.SIREN. 12V £15.95.P.C.B. ASSEMBLY JIG. £11.98.P.C.B. ETCHING KIT £4.98.AMFIVI AIRCRAFT BAND PORTABLERADIO. E10.95.WIRE STRIPPERS AND CUTTERS E2.48.P.A. MICROPHONE, coiled lead and switch£4.68.MULTIMETER TYPE 1. 1.000 o p v wishprobes 1" x 31.2" x t" £6.66.MULTIMETER TYPE 2. 20.000 o p v withprobes 5" x 31/2" a 1 %" £11.52.P.M. INDOOR AERIAL. 57p.TELESCOPIC AERIAL. 120 c.m. E2.38.TELEPHONE PICK-UP COIL. 72p.CRYSTAL MICROPHONE INSERT. 58p.SPEAKERS MINIATURE, 8 ohm 87p. 64 ohm98p. PO oho, E1.56.PILLOW SPEAKER, 8 ohm 98p.6" ROUND SPEAKER, 8 ohm 5W E2.28.EARPIECES. Crystal 55p. Magnetic 18p.STETHOSCOPE ATTACHMENT. Fits our earpiece 69p.BUZZER. 6V 32p 12V 35p.MONO HEADPHONES. 7K Padded Superiorsensitive £3.28STEREO HEADPHONES. 8 ohm Padded04.35.DESOLDERING BRAID 69p

HOW TO SOLDER BOOKLET 12pHEAT SINK TWEEZERS 15pSOLDER BOBBIN 30pDESOLDER PUMP E5.98

3 BAND S.W. RADIOSimple T R F Design Covering most ArnateuiBands and Short Wave Bradcast Bands Fivecontrols Bandset. Bandspread ReactionWavechange and Attenuator Coll section is byWavechange Switch. Use with Headphones or aCrystal earpiece Kit contains all the componentsrecurred. incluchng the P C Board and Caseinstructions are included with this kitKIT £18.97. Headphone extra £3.28.

PLUG IN POWER SUPPLY. 6 7 59V d c300mA £4.95.SPRINGS - SMALL. 100 Asstd £1.08.CROC CLIP TEST LEAD SET, t 0 leads with 20i lips E1.15DIMMER SWITCH, 2405 800W £4.48.TRADITIONAL STYLE BELL. 3.8V 70mmchrome gong E1.60.UNDERDOME BELL, 4.10V Smart Doe10rhib f2.48

CONNECTING WIRE PACK_ 5 x 5 yd coils55pVERO SPOT FACE CUTTER. £1.21.VERO PIN INSERTION TOOL. 0 1" £1.66.0 15" F1.67RESISTOR COLOUR CODE CALCULATOR21p.

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ORDER ONLYADD 35p P&P TO ALL ORDERS, ALLPRICES INCLUDE 15% VAT. OFFICIALORDERS FROM SCHOOLS, ETC., WEL-COME.ENQUIRIES MUST INCLUDE S A EOVERSEAS SEND ORDER WITH THREEINTERNATIONAL POSTAL COUPONS WEWC I. QUOTE EXACT PRICE BY AIR MAIL

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51451 NTA gives you FAST DELIVERY BY FIRST-CLASS POST OF QUALITY COMPONENTS ANDKITS. All products are stock lines and are new and full specification We give personal service and qualitypu.d.t Is to all our customers - HAVE YOU TRIED US?


Light DimmerFor those of you who are romantic, this project will let you set the right mood. If you're not,think of the saving on your electricity bill!

LIGHT DIMMERS are always a popularproject. They are cheap, simple, andeasy to build - furthermore they areuseful things to show friends whowonder what on earth electronics isgood for as a hobby. Our design isprobably the simplest and smallestmains lamp dimmer possible - justeight components on a PCB two inchessquare. As we've used an MK blankingplate for the 'front panel' of this projectit's also easy to fit. All you do is removethe existing light switch from the metalwall box and replace it with the HELamp Dimmer, soldering the two mainsleads in position on the board first.

The single active component in thiscircuit is a combined triac and diac(trigger diode) which is cheaper thanusing two components and also takesup less space. Radio frequencyinterference, always a problem with thistype of circuit, is suppressed by L1 andC1. Ll is not a critical coil and can easilyby wound by hand. Details of this aregiven below.

HE LIGHT DIMMER

ConstructionAll of the components, including theswitched pot, are soldered directly tothe PCB. Start by mounting RV1. Theswitch terminals on the back are

4/5 the POWER APPLIED TO THE LOAD

c_

soldered to the PCB and the potterminals connected to thecorresponding pads on the board bymeans of short lengths of insulated wire.Now solder all the other components.The only polarised component is SCR1- make sure you get it the right wayround. Its leads should be bent at right -angles to match the pattern of the PCBpads, so that it lies flat against theboard. Leave a slight gap to allow aircirculation for cooling.

L1 is made by scramble -windingabout 50 turns of 22 SWG enamelledcopper wire on a 3/8 inch former. Thefinished coil should be about one inchlong. Scrape the enamel off the endsand solder it in place. Now the wholeboard can be fastened to the MKblanking plate by means of RV1.

The HE Lamp Dimmer can control aload of about 250 W. We suggest thatfor safety you varnish or lacquer thetrack side of the board before use, andmake sure that no part of the circuit istouching the metal mounting box.

iil 1/5 th POWER APPLIED TO THE LOAD

Figure 1. The waveforms on the left occur when the dimmer is set near maximum brightness, those on the right near minimum brightness.


A view of the completed PCB mounted on the MKblanking plate. This gives you some idea how small itis.

BuylinesWe used an MK blanking plate to mount ourdimmer, this particular variety has a punchthrough hole in its centre allowing insertion ofthe pot spindle. Any good electrical hardwarestore should stock them.

SC R1, the Q4006LT triac with integral diac isavailable from TK ELECTRONICS, who adver-tise with us. As far as we know they are the onlystockists.

None of the other components should causeproblems. Total cost including the blankingplate should be around £4.

L

BULB

SW1a

SW1b

Figure 2. Circuit diagram of the Light Dimmer

NOTE:SCR1 IS TRIAC WITHINTEGRAL DIAC Q4006LTSW1 IS PART OF RV1

How it WorksThe basic block diagram of the HE LIGHT DIM-mer is shown in figure 2. (Figure 2 shows thewaveforms within the circuit when approx-imately 415 power is applied to the load (thelight bulb) and when approximately 115 power isapplied.

A triac is, essentially, a power switch whichcan operate on either the positive or thenegative half cycle of an applied AC waveform(waveform A in figure 1). The triac in the HELIGHT DIMMER is in series with the lamp andso current cannot flow through the lamp untilthe triac is turned on. This is done by an internaltrigger diode (more commonly called a diac)which provides a pulse to the triac gate. This"fires" the triac into conduction (waveform B il-lustrates this). The triac stays on for the re-mainder of the half cycle of applied power, ie.until the voltage across it reaches zero. This is

shown in waveform C. At this point it switchesoff until a further pulse is applied to its gate.

If pulses are applied at the beginning of theAC cycles then the triac is on for the greater partof the time - therefore the bulb has currentflowing through it most of the time (ap-proaching maximum brightness).

If, however, the polies are delayed for a timeafter the beginning of the cycle then the currentonly flows through the bulb for a small amountof the time (approaching minimum brightness).This time delay is provided by R1, RV1 and C2.The use of variable potential divider RV1 makesthe time delay completely variable, allowingcomplete control from minimum to maximumbrightness. RV1 has a built in switch, allowingthe power to the dimmer and the lamp to beswitched off completely.

N

0

VARIABLETIME DELAY

BLOCKS INSIDE DOTTED LINE AREALL PART OF SCR1

DIAC TRIAC

Figure 3. Block diagram of the Light Dimmer

34

C

This photograph shows the PCB with the com-ponents in place ready for mounting on theblanking plate.


Light Dimmer

=Parts ListRESISTORS (1/4W 5%)R1,2 22k

POTENTIOMETERSRV1 100k linear with built-in DPDT

switch

CAPACITORSC1,2 100n 250 V AC polyesterC3 100n polyester

SEMICONDUCTORSSC R1 Q4006LT

MISCELLANEOUSPCB, coil L1 (see text), MK blanking plate, knob.

TO WIRING INLIGHT SOCKET C1

SCR1C2 01

Figure 4. Component overlay of the Light Dimmer

HE

OHIO SCIENTIFIC Superboard 2 Assembled501-4, model E159.95 + 15% VAT post freeColourboard 2 (the new colour version of Superboard21 E215 + 15% VAT

Special offer. If bought with Superboard orColourboard these items are at the reduced *

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styrene capacitors E 12 63V 10 to I 000pf 3p. 1n2 to10n 4p. Ceramic capacitors 50V E6 22p1 to 47n2.5p. Zeners 400mW E24 21,7 to 33v 7p.TV GAMES. AY -3-8550 + kit E8.26. AY3-8600+ kit £12.98. Stunt cycle chip + kit E18.09. Colourgenerator kit £9.95.TRANSFORMERS. 6-0-6V 100ma 80p, 11/2a£2.60. 9-0-9V 75rna 80p. la E2.40, 2a £3.94.12-0-12V 100rna 99p, la E2.90.IC AUDIO AMPS with pcb JC1 2 6W E2.08. JC20lOW E3.54.BATTERY ELIMINATORS. 3 -way type 6/ 71/2 / 9v300ma E3.14. 100rna radio type with press -Muds9v E3.77. 9 + 9 £4.99. Car convertor 12v inputoutput 41/2/6/71/2 /9v 800ma E2.76.BATTERY ELIMINATOR KITS. 100ma radiotypes with press -studs 41/2v £1.49, 6v E1.49, 9vE1.49, 41/2 + 41/2v £1.92, 6 6v £1.82. 9 + 9rE1.92. Stabilized 8 -way types 3 /41/2 /6,171/2 /9 /12/15/18v 10Orna E2.60, I Amp £8.50.Stabilized power kits 218v 10Orna E2.80, 1-30v 10E6.75, 1-30v 2A £12.10. 12v car convertor6. 71/219v IA E1.35.T -DEC AND CSC BREADBOARDS. Sdec £3.79.T dec £4.59, exp4B E2.84. exp300 E6.61, exp350£3.62, exp325 El .84.BI-PAK AUDIO MODULES. s450 £27.90, ALSOE5.62, pa100 E19.24, soma° E5.26, bmt80EGOS, stereo TO E23.94, AL30A £4.53.

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Conquerthe chip.Be it a career, hobby or interest, like it or not the Silicon Chip

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36

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What's In a NameThe Integrated Circuit is probably the most used and least understood of all the semi-conductor devices. Rick Maybury looks at the remarkably short history of the 'chip' and whatit may hold for the future.

FEW INVENTIONS or discoveries everreally change the way we live, thehuman race could continue without thedelights afforded by non-stick fryingpans and sliced bread. Our subject thismonth is altogether in a differentleague, possibly having consequencesas far reaching as the wheel did fivethousand years ago.

The name Integrated Circuit beliesthe importance of a family of electronicdevices first developed some twenty-two years ago. Jack Kilby is the mangenerally reckoned to have producedthe first IC, that was back in 1958 whilsthe was working for Texas Instruments inDallas USA. He perfected a photo-graphic technique that allowed anumber of active semiconductordevices to be built onto a single, minutepiece of semiconductor material.

Photographic TechniqueKilby's research was directly related towork already underway, attempting tofind a way of producing transistors to agiven specification. Early transistorswere made by artificially growing asemiconductor crystal and thecharacteristics of the crystal were un-predictable, to say the least. The methodKilby developed involved depositinglayers of semiconductor material, layerby layer, onto a semiconductor base orsubstrate. After each layer had beenformed it was coated in a photographicresist and exposed to light. A mask bet-ween the light source and semi-conductor layer had a pattern that cor-responded to that part of the circuit,rather like making a multi -layer printedcircuit board. After exposure the un-wanted portions could be washed away.

Computer ChipsDuring the early sixties little was heard ofintegrated circuits, most devices wererelatively crude. The growing computerindustry was the first to benefit. Com-puters are actually very simple devices,most of the circuitry is based upon ourold friend the multivibrator, a basic elec-tronic switch. Even the most basic com-


The infamous 'chip' in close up (left). The layered construction can be clearly seen. The picture onthe right shows the various stages of encapsulation.

puter might need several thousand iden-tical circuits, however, and computermanufacturers turned to the IC for help.

Initially the IC was just a convenientmethod of producing simple circuits ingreat quantity. The need for ever fasteroperation led to smaller and smaller cir-cuits, (even the distances between com-ponents is considered critical thesedays). The decision to make a single typeof device led to problems quite early on.Obviously some circuits would beneeded more than others, typical ex-amples include the AND and NANDgates which were produced in theirmillions. As the photographic methodsimproved, more and more singledevices were put onto 'chips'. Aroundthe late sixties things were getting out ofhand. Literally thousands of separatedevices were available and thedesigners started to look around for a'universal' IC that could fulfill all theircustomers' needs but without having tokeep re -designing their equipment. Theanswer came in 1969 with the nowlegendary microprocessor. It was in ef-fect a programmable IC. Once it left themanufacturer it was up to the customerto program it.

Computer DesignThe development of the integrated cir-cuit is a relatively short story. The basictechniques evolved during the late fiftiesare still in use today and IC manufactureis still a photographic process. Today,the IC manufacturer can put somethinglike 500,000 active devices on a onesquare millimetre chip and this will con-tinue to increase for some time. Thematerials used allow more advanceddevices to be duplicated in greater quan-tity. From the early TTL devices(Transistor -Transistor Logic) to the latestgeneration of LSI CMOS devices (LargeScale Integration, ComplementaryMetal Oxide Semiconductors) marksone of the most dramatic periods in ourhistory. ICs are everywhere, not onlyreplacing old technology but creatingnew sciences that will ultimately dictatethe way we live. Perhaps one of the mostsobering aspects of this new era is thefact that nowadays the designs for newICs are usually made by computer, itselfa collection of ICs. The complexity ofthese devices is such that a mere humancould never hope to do anything morethan instruct the computer. 1984 is onlyfour years away! H E

37

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NORTHAMPTON11 ST. GILES SQUARE, NORTHAMPTON

Tel (0604) 39550

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MAIL ORDERMail Order is a safe and simple way to purchase goods. You arewell protected by the consumer mail order laws and at Metac wecombine a fast service with a genuine 10 -day home approvalscheme You may examine any merchandise purchased throughour mail order division. in your own home for 10 days at no cost toyourself. All postal charges are pre -paid by Metac.For more information on Metac mail order products send for ourfree literature, brochure and watch -care leaflets. toMETAC ELECTRONICS LITERATURE, 47 HIGH STREET,DAVENTRY, NORTHANTS.

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IPOST, PACKING AND VAT INCLUDED IN PRICE.

FreezerAlarmWhen the temperature starts to rise you'll beglad you built the HE Freezer Alarm to protectyour frozen food!

AFTER CENTURIES of complainingabout the daily drudgery of their lives, itseems that women are finally getting abetter deal. Manufacturers are findingmore and more ways of applyingtechnology in the home, from motors inthe can -opener to microprocessors inthe washing machine. One of the mostuseful items for a working woman (orbachelor, come to that) is a freezer. Notonly does it remove the need for dailyshopping trips, but meals can beprepared weeks in advance, in bulk, andsimply heated up when required.

Finding FaultUnfortunately we don't live in a perfectworld and the convenience of a freezercan become a great inconvenienceshould anything go wrong. A failure canbe very difficult to detect as the pilotneon on the front will only tell you thatthe mains is connected. Any other faultmay only become apparent the nexttime you open the door and find amessy heap of defrosted food. Despitethe fact that a freezer is designed tostay cold without power for longperiods (in' case of power cuts), it is not avery good idea to rely on this and hopeyou'll spot something wrong next timeyou use it. It might be too late.

FS1

40

Fault FindingPrevention is better than cure, even ifyou are insured, and the obvious answeris to fit a temperature monitor thatsounds an alarm if the temperatureinside the freezer starts to rise abovenormal, towards the point of no return.This gives you a chance to get thefreezer fixed before the contents areruined.

The HE Freezer Alarm uses anLM3911 temperature controller IC as a

sensor. This is placed inside the freezer,connection to the rest of the circuit ismade by a thin cable. This can passunder the rubber door seal withoutaffecting the insulation. The alarm weused is the now -familiar solid-statebuzzer.

You might think it strange that thecircuit is powered from the mains butthis is OK. It means that you can't forgetto replace the battery, and in any case,as mentioned above, freezers are

How it WorksThe heart of the alarm is the LM3911 - an in-tegrated circuit specifically manufactured foruse in temperature control equipment, althoughwe have adapted its use slightly for this project.The IC itself has three main sections as seen inFigure 1, a zener diode, a temperature sensorand an operational amplifier.

The zener diode is used with R2 in the circuitdiagram to provide a stable reference voltage of6V8 which supplies the temperature sensor andthe internal op amp. The op amp is connected asa voltage comparator - ie. when the voltage atthe non -inverting (+) input rises above that atthe inverting (- ) input, the op amp output goeshigh. The voltage at the inverting input is set bypotential divider chain R3, RV1 and RS. Thevoltage at the non -inverting input is set by theoutput of the temperature sensor - and thisfalls as the temperature increases.

RV1 is adjustable to allow for a temperaturesetting of approximately - 25°C to 0°C. Dif-ferent resistors in the potential divider chain willalter the turnover temperature of the op amp toallow the IC to be used as a room thermostat,say. In fact the LM3911 can be used to measuretemperatures of - 25°C to + 85°C. Power isprovided via mains transformer T1 to isolate thecircuit from mains voltage. BR1 is a bridge rec-tifier which changes the AC from thetransformer to DC and C1 filters the voltage togive a smooth DC supply of about 16 V.

The output of the internal op amp of theLM3911 drives Q2 via R4. As long as thetemperature is below the present level, Q2 isturned on and prevents base current flowing in-to Q1, which is therefore held off. When the opamp swings low, Q2 is turned off and currentcan now flow into Q1 base via R1. Q1 turns onand sounds the alarm.

NOTE.IC1 IS LM391101,2 ARE BC182LBR1 IS 1A 50VALARM IS 12VSOLID STATEBUZZER

TWIN SCREENEDCABLE

IC1SENSOR

2

Figure 1. Circuit diagram of the HE Freezer Alarm


=Parts List__RESISTORS (all 1/4 W, 5%)R1,5 47kR2R3R4

4k733k10k

POTENTIOMETERRV1 22k linear

CAPACITORSC1

C2

2200u 16 V PCB -mountingelectrolytic100n polyester

SEMICONDUCTORSQ1,2 BC109IC1 LM3911B R1 1 A, 50 V bridge rectifier

MISCELLANEOUS9 V, 100mA transformer, fuse (500mA) and fuse -holder, 10 x 24 hole veroboard, twin screenedcable, solid state buzzer, socket for mountingIC (see text).

OUTSIDE CASE OFSPEAKER DIN PLUG

SCREEN 1RED

OV 240V

TRANSFORMER

12V SOLID-STATEBUZZER

Figure 4. (left) Using an ICholder to mount the LM3911

IC SOCKET

designed to cope with power cutsprovided you don't keep opening thedoor.

Construction And Setting UpNothing unusual here apart from themounting of the sensor. We soldered alength of twin miniature screened cableto the pins of an IC socket and encasedthe socket in the plastic cover from aDIN speaker plug. The drawing andphotograph should make this clear. TheLM3911 is then fitted into the socket.We only used a socket to make a tightfit in the plastic cover - if you choosesome other method of constructionthere is no reason why you cannotsolder directly to the pins of the IC(provided you do it quickly).

Take the usual precautions whenbuilding the rest of the circuit, makingsure that transistors and electrolyticcapacitor are the right way round.


BLACK

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

PANELZo,

TO MAINS

TERMINAL BLOCK

16 17 18 19 20 21 22 23 24

Figure 2. (above) Overlay and interwiring diagram.

H

G

D

C

A

GROMMET

0 000000 0 000000000 000000000000000000000000000000000000000000000000000000000000000000000000000 000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000050051 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

CABLECLIP

SCREEN 1

TWINSCREENED

CABLESCREEN 2

Figure 3. Veroboard layout showing component positions and trackcuts.

Please be careful with the mainscircuitry - we would hate to lose anyof you!

To set up the unit, switch the freezerto its highest working temperature andleave the sensor inside to cool down.Adjust RV1 until the buzzer sounds,then back it off slightly to turn thebuzzer off. The alarm is now ready foruse.

BuylinesNothing which will cause any trouble here - allparts should be easily obtainable at your normalcomponent stockist or most of the usual mailorder companies.

All parts (excluding the case) should total ap-proximately £7 - not much to pay to protectthe contents of your freezer. HE

41

Shown here are all of the back issues currently available.Each issue costs just £1,(that includes post and packing).

The latest addition to our stocks is the March issue.Features include:AutomotiveElectronics,PETting it Together and the second part of Ian Sinclair's new seriesInto Electronics Construction.The projects include:The 5080 modular amplifiersystem,PSU module for the 5080,Short Wave Radio and a novel Touch Switch.For details of other issues see our main Index in the January issue.HOBBYPRINTS for this and all back issues are still available.For order codes andinformation on how to use HOBBYPRINTS see the ad.in this issue.

Please send me the following issues.Numbers

I enclose cheque/PO for £Name

Address

BACKNUMBERS DEPARTMENT:HOBBY ELECTRONICS. 145 CharingCross Road,London WC2H OEE.

9A. Marshall (London) Ltd., Kingsgate House,.Knin.ugisogate Place, London NVV6 4TA

sotridael Sales:ol.6 0241

shops 325 Edgware Road, LondonA iso40 Cricklesvood Broadway, London NW? 85 West Regent St Glasgow108A Stokes CrOtt, Bristol.

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0574045 C014 5574955 E055 15 watt CCN £4.20Siemens Ceramic 63v B37448/9 NEW RANGE TMEC CASES 5574055 £0.15 5574965 £0.34x574065

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SINCLAIR INSTRUMENTS100pF to 10.000pFVoltage range up to 6Kv.

catalogue4%" x 3%" x 1%" 0574205 CO 15 55741455 CO 64

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Comprehensive range Siemens BAZELLI INSTRUMENT CASES0574275 E0 19 CO 55S574305 E015 55141545 ft) 90057432IN E017 55741555 C060

PDM35 34.50" DM235 £ 52.50

Layer Polyester Caps: .001 to 5 sizes. 5574375 £0 21 55741575 £0 59 " DM350 £ 72.503.3mF Miscellaneous hardware

0574385 0 21 557416085 CO 705574405 CO 15 5574161AN CO 10 " DM450 £ 99.00

Prices £0.07 to £0.63.See catalogue for details. including .

Vero Board: Superstrips:

St97441AN £0 52 557410285 £0 705574425 £0 40 5514163A5 0705574455 E066 55741645 £080557446AN £0 48 55741655 00 80

Digital Frequency MeterPFM200 £ 49.80

Large range of Mullard/Siemens Vero Breadboard. 55744785 E0 48 55741675coedS57448N CO 45 55741745 Low Power Oscilloscope

Electrolytic Axial/RadialCapacitance values 1.0mF to

Vero boxes (see catalogue forfull

S574505 CO 15 55741755 £0 635574515 E015 55741765 £0740574535 £015 55741775 £11 73

SC110 £139.00

CRIMSON ELEKTRIK HI Fl10,000mFrange). SW4545 El) 15 $IV741805 £0 70

15 6835Voltage ranges 25v: 40v: 63v:MODULES5585714471882155 ,E°1s0,5 774467008N

£036(0

100v:Prices and types as catalogueCE1004Also Mullard C280; SiemensCE1008CI10,-----.--

5574725 ED 24 55741845 Cl 295574738 E025 557418585 Et tO5574745 CO 25 55741865 El 35558577.4776555

cowE031

$585774471.9888.95 £10426

5874805 55747905 CO 74

CE608 Power Amp £18.26" " £21.30" " £23.91

B32231/4 and 832110. All prices Card Frames: Fliptop boxes: 5574815 CO 71 55747915 £0 795574825 E065 55747925 £079 CE1704 " " £30.43

net + VAT and postage/packaging. etc etc. 5574835 £0 60 55741935 CO 79 CE1708 " " £30.435574845 00 95 55741965 E0745574855 E070 58747978 C074557486 5 E025 55741985 E109

CPS1 Power Unit £16.96"TOOLS BAHCO 1980 CATALOGUE

,....'

Side Cutter with Bezel.Side Cutter without Bezel.End Cutter without Bezel.

Vero Metal Shears.

alrNOWSU.K.: 65p post paid jwic=".Europe 85p post paid A V#Rest of World £1.25 -post paid ...,

5574895 C1 66 55741995 nogS57490AN CO 33

CPS3 £20.43CPS6 " £26.09CPR1 Pre Amp £29.57CPR1S Pre Amp £38.70All prices + VAT + postage/

KNOBS & SWITCHESBig selection as catalogueAlso Resistors; Presets; Pots;

Other items as catalogue. . Mail order: 01-624 8582 Opto; Semiconductors etc. packaging


COMPUTERS AUDIO RADIO MUSIC LOGIC TEST GEAR CB GAMES KITS

MPONENTS DEMONSTRATIONS SPECIAL OFFERS MAGAZINES BOOKS

It's all at Breadboard 80This is the exhibition for the electronics enthusiast. FromNovember 26 -30 there is only one place in the universe for theelectronics enthusiast to be - Breadboard '80, at the RoyalHorticultural Hall in London. The majority of leading companies willbe exhibiting, including all the top monthly magazines H the field.There will be demonstrations on most stands and many featurespecial offers that are EXCLUSIVE to Breadboard!All aspects of this fascinating field are catered for, from CB tohome computing, so whether you want to buy a soldering iron or asynthesiser - or just keep up to date with your hobby - don'tmiss Breadboard '80.

Royal Horticultural HallsElverton StreetWestminster London SW1November 26-30 1980 O 6,, .

\26th Nov - WEDNESDAY - 10am-6pm c'\'

27th Nov - THURSDAY - 10am-8pm ........28th Nov - FRIDAY - 10am-6pm29th Nov - SATURDAY - 10am-6pm \,"30th Nov - SUNDAY - 10am-4pm 6' .

THERE WAS A TIME, not so long agowhen home life was a simple matter, fill-ed with simple pleasures and simplemenial tasks. Entertainment consistedmainly of songs sung around the familypiano or the occasional visit to the localMusic Hall. Heating meant lighting acoal fire, and food was cooked on thecoal-fired kitchen range. Cleaning wasdone with a dustpan and brush, and gasand oil lamps needed to be trimmed tokeep them working efficiently. Anyhousehold wishing to eat fresh meatand vegetables, had to buy them dailyfor immediate consumption, as the onlymethods of preservation were stewing,tinning, bottling and salting.

Today electronics are not only mak-ing life easier for the housewife, they arealso making life more interesting andvaried for the rest of us.

Where It All BeganFrom an historical point of view,domestic electrical appliances firstbegan to appear during the 1920s, atime considered 'great' for Britain, justrecovering from the effects of the FirstWorld War. Electricity had originallybeen introduced into the averagehousehold at the turn of the century, atwhich time it was used purely as a lux-ury form of lighting, as gas was then far

44

ElectronicsAre you keeping up with the Joneses or have you been left

Tina Boylan examines the history of the

cheaper - the relatively high price dic-tating that it was not greatly exploiteddomestically.

The first electrical device to appearwas the cooker, and it is safe to say thatthe basic concept of this item haschanged little since those 'roaring' 20s.Later during the 1940s washing ma-chines were being sold for home use,an example of which was manufacturedby Hoover, a company still maintaininga strong grip on the domestic appliancemarket. Their machine consisted of adrum -I ike'washer', impeller driven, witha folding manual wringer on the top.

The switch which controlled the

64,

washing program was motor driven, andthe machine really did nothing morethan wash! The wringer was entirelymanually operated, it was only therebecause it was more convenient to haveit attached to the washer.

During this period the radio was be-ing slowly introduced into Britishhomes, and was finding its place at thecentre of family entertainment. Televi-sion made its debut in Britain in 1935when the BBC was experimenting withit. The Alexander Palace Transmittingstation was opening in 1936, and by1937 when the coronation of KingGeorge VI was televised, though, stillrelatively few people owned televisionsets - it seemed to be just an expensivegimmick as the picture quality was ex-ceptional ly poor.

The Spoils Of WarIt was not until the Second World Warhad ended that electronic devices forthe home really began to make an im-pact. Television transmissions andreceiving apparatus were greatly im-proved thanks to the advances madein radar defence systems used bythe British during the War. Even so,

it was as late as 1953/4 that the BBCopened its Sutton Coldfield

'-""\,, transmitting station and thisheralded the ultimatelyhigh level of television

ownership we knowtoday, it was at lastan indication that

television washere to stay.

111

We Have Lift Off. . .

The next great step forward in elec-tronics was brought about by researchcarried out on the American Space Pro-gram during the late sixties and earlyseventies. The lunar modules used bythe Astronauts had to be computer con-trolled, space was considerably limited,(sorry about the pun!), even transistorswere not small enough, so ultimatelythe Integrated Circuit was developed.When we consider the specialised ap-plication of the IC in its original form, itis quite incredible to consider the extentof the impact it has made on each oneof us. Its invention led to the com-puterisation of many devices, helped in-troduce remote control into the home,and made fuel injection possible inmotor cars, something that was difficultto do by purely mechanical means. To-day even the humble washing machinehas had its chips and is truly program-mable!

In The Homebehind by the developments in the electronic gadget market?labour saver and takes a look into the future.

In 1950 it was again the BBC who ex-perimented with the concept of stereo.It first appeared as a way of demon-strating records in record shops. Ofcourse it was not true stereo, as onlymono recorded discs were available atthe time, but this certainly promptedthe record industry to begin producingstereo discs. Another form of nowpopular entertainment is the taperecorder. These were first introduced in1954 for use as office dictatingmachines. The recordings were madeon a 4" disc and quality was extremelypoor. It wasn't until ferrite tapes were in-troduced around 1960 that recordersfor music were considered a reasonablepossibility. At this time the transistorrevolution was beginning to take effect.Thermionic valves needed huge cases,and the eventual influx of smallJapanese transistor radios broughthome entertainment into the portableage. Miniaturisation was the name ofthe game - far more electroniccapabilities could be included in eachsmall device, many items became moresophisticated; radios, recorders, record

players and televisionsall became smaller andcheaper, indeed the waywas well and truly pavedfor the beginn ing of the

electronic era.

Yesterday, Today, TomorrowJust imagine what the Victorianhousewife would say with herwashboard in one hand and her woodenspoon in the other, as she gazed roundthe treasure trove of 'domestic elec-trical appliances' which can be found inany local department store. Thereseems to be a labour saving device forvirtually everything these days. Theycan cook your toast, boil your kettle,make your coffee, sharpen your knife,heat your water, dry your clothes,preserve your food, clean your teeth,dispense your loo paper dispenseyour loo paper?

Seriously though, amongst theserelatively simple gadgets, one can spotsome of the most sophisticatedmachines which the electronics in-dustry can produce, and all widelyavailable to the general public, if, ofcourse, you have the money in yourpocket, and can decipher the pidgin

English of the instructions.

41,

Electronics In The Home

Common As MuckWashing machines with programs aslong as your arm are capable of turningyour dirty linen into clean, dry itemswithout you having to do more than setthe dial and put in the washing. Thetimers used today are electronicallypulsed, moving to the desired heat andspeed setting, taking in water, washingpowder and pumping it all out againwhen necessary. Never again will arainy Monday mean five days of dripp-ing washing in the bathroom.

Food processors now mean that theaspiring 'Cordon Bleu' cooks can whipup exotic meals at the touch of a button- no more amputated fingers in theGoulash, and no need for muscles like ashot-putter in order to finely dice, grateor whisk your desired recipe into shape.

Cooking the food itself has also beenquite drastically changed by the inven-tion of the Microwave Oven. It mustsurely be the snack enthusiast's dream,as everything is cooked incrediblyquickly, so not too much time elapsesbetween deciding to eat and actuallyeating. You simply put into it whateveryou want to cook, set the timer andstand well back. Of course they're notdangerous, but the concept used toheat the food is certainly revolutionary.

46

The oven works on the principle of pro-ducing an electromagnetic field of veryshort wavelength. This causes rapidmolecular movement which generatesheat cooking the food, but neither heatsthe dish nor browns the food, the latterbeing perhaps a slight disadvantage, ex-cept to the American lady who put herpoodle in it to dry it after a bath. The ef-fect this process has is to cook the foodfrom within, instead of conventionallyheating it on the outside and waiting forthe heat to penetrate the mass.Therefore food is cooked in a fraction ofthe normal time. Among its less obviousadvantages are that it runs cold, is veryclean, and is useful for defrosting andcooking frozen foods quickly. Unfor-tunately if you happen to be one of thepeople who likes his roast chicken tolook like roast chicken, you'll be disap-pointed, though an ordinary electricalheating element may soon be added tothe microwave ovens, although thebrowning process may take up to fourtimes as long as it takes to actually cookthe chicken.

The question now must be 'what dothe Englishmen of the 1980s do in theircastles while their washing is being doneand food prepared?'

. More than likely

they will be listening to their hi-firadio/cassette/record deck, or relaxingin the comfort of an armchair, remotelyswitching on the colour telly, whilekeeping one eye on the quartz controll-ed LED/LCD alarm clock/radio waitingfor the microwave oven to cook the din-ner.

1984 And All ThatSo where does all this leave us. True, it'san easy and effortless life we lead thesedays, but with any luck it could becomeeven easier. The future trends almostcertainly lie in this direction. After all,we know there is no mechanical motionthat can't be controlled electronically,and one step forward from this idealeads to computerisation and controlsystems, which are currently enjoyinggreat popularity with researchers andmanufacturers alike.

From a personal viewpoint I wouldeventually like to see homes complete-ly controlled by a central computer, thetype that will ensure that when I gethome from work I could open the doorto a perfectly clean house, punch outmy instructions on the computerkeyboard, then sit down while the hi-fiselects my favourite record, the robotprepared my meal, the bath was run andthe coffee maker poured my coffee,sheer bliss!

With the way electronics are movingat the moment that might well be adream which will materialise. After ithappens someone will have to developan exercising machine that can keepyou totally fit - preferably in the com-fort of your computerised home. HE


FBrireerinogshtaBm FREEPOST ON ORDERS ACCESSVAT INCLUSIVE PRICES VISA

B19 1BR ADD 30p P&P CHEQUEELECTRONICS 021.233.2400 24 HR PHONE ANSWERING SERVICE

ALL PRICES IN PENCE EACH UNLESS OTHERWISE STATED

C M 0 S Buff LRI.D. LINEAR SEMICONDUCTORS22 11(14044 105 14E74512 Ilts C83046 54 9914 8C182L 12

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22'3 Voltage T841205 88 293904 9 8,85 297E54023 7E14081

Regulators TO41022 713 295457 39 8,50 17

7E14076 3E741387 23 TC1410348 739 295459 35 86051 177(74077 3, 7E14083 80 L5430904181119 T108100 84 40673 138 13710139 507114026 89 7E14080 80 U4723CN 42 TL084CN 156 130107 14 65020 21

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GMT SELL P_ .. .',....t.n-P.A. ECI TCAPACITORSElectrolytic Axial Order Coda Poly Radial Leeds Order Code Electrolytic Radial Laub Order Code-to% to 50% To, Cm 0115 7 1343990 Type. C260/352 Srv. Crop 357 110. 10 50, T0 C.p 03a 02ur v ill 26 40 03 Mould. T.410 nom Pitch Cap 360 ir, V 10 16 25 35 40 60 63

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RESISTORS Order Cods Skeleton Prow* Miniature Order CodeCarbon FIlm, Fixed 0 ,W. 83 I.alun, 10011-114. 1.7, Vertical Mounting 8 Mn Preset V0 2544. (24 Values 100100, 5% Tat 1 non Rn RD'S 0110. 03 000.s. 100610. Ltn norrtOotn Mount 8 ben P 0

1007100 10411107ialual Skeleton Presets. Standard 1/Mae05W. E12 Vetoes 100407, ICI% To, 3 en. Res RON 0.30. 63 Value, 1000407, LA Vero., 140001.19 11 574 new 12

SOP. 030.800.14.4.7000407.1,9.90,190111209011! .1 $1d Prete, MMetal Film. Fixed valuePotentiometer. Rotary05W. E24 Vs.. SRI INS 2% Tot. 8 one R. MR30 0 5, 83 0..,.. , 273 , 39 Ro Pot Lyn2 SW. E12 Wu's, 10127K, 5% Tor 16 ens Rae PR52

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SEND A LARGE S.A.E. FOR OUR`FLOG LIST' & OTHER INFO.

MAINS TRANSFORMERS Order Co01 Plattic &wet - Boss Industrtal MOuldingSsea .,e5Avor tre,onnntert ,n noes or Movie. 11. end Come Cos. E long. 14parallel to Nye err. wrban rangePrin. in 0 220. 24014

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604 Oar. Tv. Consir.roon 235 gun1112 W82 031 90 Cs. 81122003 ORL150 WOO 050 131 Can 8102005 OR

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04 60. 04 50 Secondarres Trans 600 Plastic Box. with Metal Lids0.3v. 060 ec.. T.13.0121,0-12V ABS 8ne. C. Brass Dunn. 10 Oran.0-15V. 0.15120.20v. 0.200 Non tumin.orn Top Penn 7 'Ash. G.80

Order Cod.

20VA Clomp Type Consouctron 360 each t_55 4056029 112 Cale 01,04003 ORs111W71 042 150 Can 13104005 OR

Anarox 16% Peculation I C 70,1148. W46 0161 W96 053 /OS Cm 6104005000.4 50.04 50 Sec..., Trens 20VA Outcast Box.06v 0.61/0.170, 0-170 Orman Bo eno cramped L.10.150, 0150 Aluovnitrrn Box end 1...1 ,r1N ..... 1 irntsb

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0131063 037 124 Coe 6,25003 NA01521082 D50 215 C1.8165005 NA

VERO ELECTRONICS PRODUCTS1,97W113 061 334 Coe 9,25005 NA

SWITCHES25". s' l Man vwobwtd 71 200-2706923.75' 5" I" 9.101 Vm000400 79 200.2107202.5" . 1" I- 8415 Verdbdilrd 151 85,421 200210760

Order CodeM1111416110 Tonle - .0PPVIPP°

3 75' 5" 1" P.P6 Ptpn Board 68 200.7107130 SPOT 67 SW 84 IC- '

582" . 1 9" .1" 8.185 ,40 OIP Board 135 200.2701342 SPOT C.ou 87 SW 8A07'5001 7ece Cutler 107 203.2401340,n Insemon Tool tar 040 0200 DA 147 203210159

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13511.ns P40 11001 4477.0 200.210970 DPDT Crott Ill viti 80100.SS Prns .040 11001 441Pack 200210718Vero.. Kit 1 Inen. 2.0274, 2540011/ 454/K.7 200.213410 Miniature Push -C & KVer.. Conn 1251 109/Peck 200.273394 SP Pusb To Mese. Moments, 83 SW SW0.100.r4 Wtre 171 109/9mo 700.21340E OP Pun To Iliew vc.., 87 SW 8533

RAL TELETEXT KIT ONE APO POwER SLIM, .0JULE 07 , ENE MOS I 0-.U...

ONE AMP POW. SPIPL040ausf KO - swavE 01.1310171101 DECODER REM017 CONTROL SIT

613540 00301. INERTIA CONTROLLER 05 I - NOT RAC. 110-90

PAL ENCODES 0000141051 AT t 2240 ROUT INERTIA CONTROLLER PAR II - TRAIN MANO LENIT, I 2540

COMAE RADAR 4116.4511 9 1440 00511.1911114 CONTROLLER MR Ill - MAIN I0095012 LAPP I. 2540

GEC AM/FM STEREO TUNERAMPLIFIER CHASSIS. Originally de-signed for installation into a music centreSupplied as two separate built and testedunits which are easily wired together.Note: Circuit diagram and interconnec-ting wiring diagrams supplied. RotaryControls: Tuning, on/off volume,balance, treble, bass. Push-button con-trols: Mono, Tape. Disc. AFC, FM (VHF),LW. MW. SW. Power Output: 7 wattsRMS per channel, at better than 2% THDinto 8 ohms. 10 watts speech and music.Frequency Response: 60Hz-20kHzwithin ±-3dELTape Sensitivity: Output- typically 150 MV Input - 300 mV forrated output. Disc Sensitivity: 100mV(ceramic cartridge). Radio: FM (VHF),87.5MHz - 108MHz Long wave145kHz - 108kHz. Medium wave,

520kHz - 1620kHz. Short wave.5.8MHz - 16MHz. Size: Tuner - 21/4in.x 15in. x 71/2 in approx. Power amplifier -2in. x 7Vain. x 41/tin, approx. 240V ACoperation. Supplied complete with fuses,knobs and pushbuttons, and LED stereobeacon indicator. Price £21.50 plus£2.50 postage and packing.

STEREO CASSETTE TAPE DECKASSEMBLY. Comprising of a top panelassembly and tape mechanism coupled toa record/play back printed board assem-bly. For horizontal installation into cabinetor console of own choice. Brand new,ready built and tested. Features: Pausecontrol, auto stop. 3 digit tape counter.illuminated twin VU meters with in-dividual level controls, twin mic, inputsockets, AC erase system, LED recordindicator (Separate power amplifier re-quired) Input Sensitivity: 6 MV (withlevel control set at max.). Input Imped-ance: 47kOhms. Output Level: To bothleft and right-hand channels 150 MV.Output Impedance: < 10K. Signal tonoise ratio: 45 dB nominal. PowerSupply Requirements: 12V AC at300M /A Connections: All connectionsto the unit are via a wander lead termin-ated with nine -pin plug (socket provided).

-

Dimensions: Top panel - 111/2in. x6'/ in. Mechanism fits through a cut out51/4in x 10'/ m. Clearance required undertop panel 21/4in. Supplied complete withcircuit diagram etc. Price £30.50 plus£2.50 postage and packing.

B.K. ELECTRONICS37 Whitehouse Meadows, Eastwood, Leigh -on -Sea, Essex SS9 5TYBARCLAYCARD SAE lit? currant Mtla * 01191.1 orders soaks.. All prices

Include 607 Mil order only * NI items tisclonl (where applocablele special energy absorbing PU loom Callers welcome by priorappennUmat. please leltploann 0702 527572. 514 Wck.xlx 4st.-77

ELECTRONICSA NEW AND EXCITING HOBBY!!

BIG ,WELL ILLUSTRATED BOOKIdeal for beginners - giveslots of general information

explains how to buildlots of projects :

Intercom, Rain Alarm,Radios, Organ, Parki ng

Light etc. All partssupplied and can bere -used on specialdeck provided, soNO SOLDERING is

required. Just neeas41/2V battery.

r1750 inc. VAT & PostAlsoADVENTURES WITH MICROELECTRONICS

- Explore the world of silicon chips -All components & Deck, £27.95 inc VAT & Post,

Component Catalogue & Bargain List 75p

GREENWELD4437 Millbrook Road, Southampton 501 OHX


74097410741?;51314207430743214407442744874737474747514167490749274937496741717412374154741577411274125741957419674783142907436574366

PRIME COMPONENTSLOW PRICES

All our micro chips are at micro prices. Don't be fooled by low prices. We do not offer forsale. surplus, sub -spec or rebranded devices. All our parts are guaranteed new, first quality,factory prime, lull spec devices. It is also our policy to offer you the best of new devices thatbecome available and these are featured regularly. Prices are exclusive of p&p and VAT -please refer to "Ordering Information- before ordering. Official orders from Schools,Colleges, Universities and Gov. Authorities /meowed.

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12500p9500p

19900p

834411 512z 8 40 NS p o.a.93453 11154 40 KS po.a.93451 Utz 8 45 NS p.o.e.

450p 93511 29 al 50 NS p.o.e.

KEYBOARD ENCODER

795p

1011 SPECIAL OFFER! 4K CMOS RAM (1K x 4) 450 NSONLY £6.95! (8 for £45)

The TC 5514P from Toshiba, CMOS equivalent of the 2114!I ow Power Dissipation

' 10pV11/ BIT (TYP) @ 3 OV (STANDBY)' tOuVol z BIT (TIP) (g) 5 OV (OPERATING)' Data Retention Voltage IV to 5 50' Single 5V Power Supply

18 PIN Plastic PackageFull Static OperationThree State Output

' Input /Output TTL Compatible' Fast Access Time 450N S

Toshiba s TC5514P (industry type 6514) is a full static read write memory organised as 1024 words by 4 toots using CMOS technologyUltra low power dissipation means it can be used as battery -operated portable memory system and also as a non-volatile memory withbattery back-up Operates frorn a single 5V power supply with static operation, hence no refresh periods and a much simplified powersupply circuit design Three state outputs simplify memory expansion for minimum data retention voltage is 2V, the battery back-upsystems needs only simple circuit Toshiba s original CZMUS technology also means wide operating and noise margins The TC5514PIs moulded in a dual in line 18 pin plastic package 0 3 inch in width

OVISTEREO! S100 SOUND COMPUTER BOARD!At last an S100 Board that unleashes the full power of two unbelievable General Instruments AY -3-8910 NMOS Computer sound ICsAllows you under total computer control to generate an infinite number of special sound effects for games or any other program Soundscan be called In BASIC. ASSEMBLY LANGUAGE etc.

KIT FEATURES'Two GI Sound computer ICs (403-8910)'Four parallel I/O ports on Board'Uses on Board audio Amps or your STEREO'On Board proto typing area'All sockets, pans and hardware are Included'PC Board is soldermasked. silk screened with gold contacts'Easy. quick and fun to build, with full instructions'Uses Programmed I/O for maximum system flexibility'Both BASIC and ASSEMBLY language programming examples are included

COMPLETE KIT ... ONLY £59.86. includes 60 page data ManualBARE BOARD ... ONLY E25.00, includes 60 page data ManualAY -3-0910 chip special price with purchase of BARE BOARD (2 chips) E15.

SOFTWARESCL is now available! Our Sound Command Language makes writing Sound Effects programs a SNAP! SCL also includes routines forRegister -Examine -Modify. Memory -Examine -Modify and Play -Memory. SCL is available on CP /M compatible diskette or 2708/ 2716.Diskette - £19.95. 2708 - E14.95, 2716 - E24.95. Diskette includes the source. EPR 0 Ms are 0 RG at E000 H.

SE 01 Sound EffectsKitThe SE-Ol Ts a complete kit t h aContains all

F017711-01 0/0 leverted Bus the parts to2905p build a pro- WA

101791 801 0/0 Mewled Boo gramrnable4995p sound effects

101792 B-01 313 marled Ow generator3495p Designed

101793 601 0 Tree IQ around the5495p new Texas

101194 301 30 Trve Bus Instruments3495p SN76477

101795 B 313 Needed Bus. Sound Chip,ode staiscl 5995p the board

101791 II 0 0 True Bin providesode select 5995p banks of

MINI DIPswitches andpots to pro-gram thevarious com-binations ofthe SLFOscillator.VCO. Noise,One Shotand Envelope Controls A Quad Op AmpIC is used to implement an AdjustablePulse Generator. Level Comparator andMultiplex Oscillator for even more ver-satility The 3'4" x 3" PC Board features aprototype area to allow for user addedcircuitry Easily programmed to duplicateExplosion, Pluser Guns, Steam Trains,or almost an infinite number of othersounds. The unit has a multiple of applications The low price includes all partsassembly manual programming chartsand detailed 76477 chip specifications II

runs on a 9V battery (not included) Onboard 100MW amp will drive a smallspeaker directly or the unit can be con-nected to your stereo with incredibleresults, (Speaker not included

COMPLETE KIT ONLY £14.99P&P 67o VAT

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74C74C2074E7614C65/4C9774E9814C10)140160140161/4C16774C16374C19214019374[19474C195' 1C903

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145p125p125p100p110p145p145p145p175p175p175p175p45p

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BOOKSPlease cider books by reference no and title, and add 50p post & packing for each book ordered.21168 Active Filter Cookbook21440 Aviation Electronics 3rd Ed.21558 Audio IC Op Amp Applications 2nd Ed.21524 The Cheap Video Cookbook21398 CMOS Cookbook21539 Design of Active Filters with Experiments21537 Design of Op Amp Circuits with experiments21545 The Design of Phased -Locked Loop Circuits with Experiments21686 Design of VMOS Circuits with Experiments NEW!21616 Electronic Telephone Projects21127 How to Read Schematic Diagrams 3rd Ed.21613 How to Use Integrated Circuits Logic Elements 3rd Ed21527 IC Converter Cookbook21695 IC Op Amp Cookbook 2nd Ed.21416 IC Timer Cookbook21601 Instrumentation: Transducers and Applications21452 Learn Electronics Thru' Troubleshooting 2nd Ed.21694 LC Circuits21542 Logic and Memory Experiments Using TTL Integrated Circuits - Book 121543 Logic and Memory Experiments Using TTL Integrated Circuits - Book 221568 linear IC Principles, Experiments and Projects 2nd Ed21612 Oscilloscope Applications & Experiments21635 99 Practical Electronics Projects 2nd Ed21599 Practical Low -Cost IC Protects 2nd Ed.21557 Practical RF Communication Data for Engineers and Technicians21482 Regulated Power Supplies 2nd Ed.21419 Security Electronics 2nd Ed.21621 Solar Heating21035 TTL Cookbook21103 Troubleshooting with the Oscilloscope 3rd Ed.21313 TV Typewriter Cookbook21339 Video Security Systems21521 Video Tape Recorders

£10.95£6.75£5.95£4.50£7.75E5.95E5.95E6.75£5.95E4.95£4.25E4.50

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UNIVERSAL SCRC106D 400V 54 Sale 30p

sEINt AY -3.8910a4 Ding

/weeTHE NEW GI

COMPUTER SOUND CHIPin, amazing AY -3-8910 is a fantasticatlypowerful sound and music generator perfectfor use with any &bit microprocessor Contains3 tone channels noise generator 3 channels ofamplitude controls 16 -bit envelope periodcontrol 7 parallel 4'0 3D A conveners plusmuch more All in 40 pin DIP Super easy tointerface to the 5.100 mother BussesOnly 1E5.50 + VAT, including FREE reprint ofBYTE 79 article) Also add E2 25 for 60pagedata manual

Perhaps the nest tarn°. composer will notdirect a 150 piece orchestre but rather a trio ofmicrocomputers controlling a bank of AY 38910s BYTE July 79

TUNES SYNTHESISER

The AY11350 Is a MOS wicreceemoler syelhesizer al pregregrammed Nees lerapdheettess tetras manic Noes eel low domes The steidere Inns has a set el25 lillereel pawnor and Genteel Isles le eilitie there ere 3 [biome males atotal 51251.ms

FEATURES

exgreel cepeseetsNtemetic srancloet1 sip.) led el Nee lot power sari.,

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3 -DIGIT LIQUID CRYSTAL DISPLAYwith 'Low bat' Indicator

High Contrast Rabe a 4.1.80.B ; Wide Viewing Angle 0.5 in. Digit Height ULTRA Low Power ConsumptionLCD106 £6.45.

LED BAR GRAPH ANDANALOG METER DRIVER

New Sc,,,a5onal 1M3914 Drives 10 LEDdirectly for making bar graphs audio powermeters analog meters LED Oscillators etcUnits can be stacked for more LEDs A superversatile and truly remarkable ICSpecial price Only £2.2511 page data 25pMatching red bar display MV57164 E2.25Data 25o

ov,40' THE NEW ULN-2232A INTEGRATED MOTION DETECTOR

.400° The most SOPHISTICATED MOTION DETECTOR available!Automatic rimed Reset I 00n6Ad Aodio Output

' I 20 Hz RejectionTwo Sound Patterns

' \nsible or Infra red Response

'14 -pin Dual In -line Clear Plastic Package

Long Range Operation

Combining 121 and Bipolar circuitry. the ULN-2232A Motion Detector is a complex optolinear IC which Includes a"on -chip photodiode high -gain logarithmic and Itnearamps extensive digital circuitry for sound generation and timingand high -current output drivers Add on live small capacitors a speaker and power source and you turn thisstatepl.the-an device into a complete Motion Detector sensitive to small changes in light level as a function of timeDETAILED DEVICE DESCRIPTION AND APPLICATIONS INFORMATION INCLUDED WITH EVERY ULN-2232AONLY ET6011

Ordering information Unless otherwiseslated. for orders under E50 add 50p p&p.Add 15% VAT to total (no VAT on books). Alldevices are brand new, factory prime and fullspec and subject to prior sales andavailability Prices subject to change withoutnonce

MUSIC FOR YOUR EARSBullet 5 Electronic Music Maher TM Kit has e smote 29 pin Microprocessor Chip with ROM thal has been

programmed It play the last 6 lo 10 Isles al the 25 popular tunes toted below. Each nine tan easily be addressedindividually or played sequentially al the push al s button. The 3 chime sequences are activated al any time by separateswlich closure, sa when used as a doorbell one door can play songs while two others will play dillerent chimes. The unithos a 5watt audio Amp and will run on either 12 VAC or 12 ROC. Construction is very simple works with anyB or 16 ohm speakeer or hell speaker Mot included). Tunes can be remotely programmed using a single rotary switchMot included!. it desired. Complete Kit £9.95 740 V Translonner optional.

Minimum telephone orderusing ACCESS is £10 Ifordering by post withACCESS, include name

address and card nowrit-ten clearly Please allow4;6 weeks delivery onbooks

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NEW FROM EXARThe XR2266 Decoder/Sense & Drive Chip for toycars that DRIVE LIKE REAL! ONLY £5.451

This versatile 18 -pin dual in -line IC combines both the decoder and the senseand drive functions to cut remote control car circuitry by at Mast a factor of two'Steering, lights indicators speed control - all from the new XR2266 at only£5.45!

MicroCircuits

Dept. HE2, 4 Meeting Street,Appledore, Nr. Bideford, North De-von EX39 1 RY. Tel. Bideford(02372) 79507. Telex. 8953084.

TemperatureControlledSolderingIronTame your soldering iron with this ingenious temperature controlledsoldering station

A MAJOR FACTOR in the art ofsoldering concerns the ability ofyour soldering iron to do its job. Forinstance, if the iron is a high wat-tage type, say 100 watt, it obviouslyshouldn't be used to soldersensitive ICs into circuit (you mayeven find it lifts the track from theboard because of the intense heat- never mind damaging the ICs!).Likewise, if the iron is only a 15 wattjob, then it won't have thenecessary power to solder com-ponents on to a hefty earth bus.

There are two ways in which anefficient level of soldering can beobtained - either use a specificiron for a corresponding job (whichmeans you need a selection of threeor four irons) or use a temperaturecontroller which heats the iron tothe correct temperature for anychosen use. It is a well documentedfact that good control over solder-ing tip temperature not only im-proves the quality and integrity ofsoldered connections but also great-ly increases efficiency and extendstip life, whilst reducing troublesomeoxide buildup on the tip.

Now, all this sounds great, all youhave to do is rush out and buyyourselves one of these tremendousgadgets and then you can solderaway to your heart's content,whatever the job. But here's whereyou will hit a slight problem. A corn -


plete soldering systemwill cost youquite a few weeks' pocket money.

One simple alternative to holdingup the local High St. bank is the HETEMPERATURE CONTROLLEDSOLDERING STATION, which willenable you to convert any 15-100 Wsoldering iron to a fully controllediron, capable of intermittent hobbyuse to full time production use, aswell as providing a convenientsoldering stand. (If you have achoice most electronic soldering ap-plications are best handled using a40 watt to 60 watt iron with thiscontroller).

The 4000 series CMOS ICs wereselected for their cheapness andversatility and to give the elec-tronics enthusiast some insight intojust how versatile these ICs are. Thedesign has incorporated zerovoltage switching which eliminatesradio frequency interference (RFI)caused by phase control of linevoltage and the potentially destruc-tive spikes created by ther-mostatically or 'magnetically' con-trolled soldering irons. The solder-ing iron temperature can be variedfrom full off to full on whilst theiron is in use. A visual indication ofcontroller operation is also provid-ed.

The output waveform consists ofcontrolled burst of pulsating DCand is, therefore, suitable for

resistive element soldering irons on-ly. (Soldering irons or guns that usetransformers cannot be used withthe project). This waveform wasselected to simplify power supplydesign, reduce internal power bydissipation and eliminates costly,sensitive gate triacs which would berequired for direct interface withCMOS logic.

ConstructionConstruction is reasonablystraightforward - start with thePCB. Nothing special here, justremember to mount R1 and 2 (alongwith Rx if used) about three or fourmm from the board, to help heatdissipation.

Remember that IC1 and 2 areCMOS and we advise the use of ICholders (not essential but helpful).Next, mount the spring and holdingbolt, neon and RV1 on the frontpanel and follow the wiring diagramof figure 3 to connect up yoursoldering station.

The cable ties at the mains inputand iron output grommets arenecessary to avoid strain on thecable connections. The PCB simplyslides into one of the grooved slotsin the case eliminating the use ofspecial fixing procedures. Finally,make sure that the earth connectionon the front panel is a good one.

49

Testing and Setting UpPlug the controller into 220-250VAC mains. Advance the temperaturecontrol clockwise until the powerswitch clicks on. Advance the con-trol further clockwise until the neonlamp just begins to flash. This is thelowest temperature setting of thecontroller. At this setting the solder-ing iron tip will be barely warm tothe touch. Advance the control fur-ther clockwise. You will note thatthe on -off ratio of the neon lampwill slowly change as the control isadvanced fully clockwise.Whenever the neon lamp is lit,power is being applied to theheating element. At the maximumclockwise position of thetemperature control the neon lampwill remain on continuously and thesoldering iron will produce full out-put.

The controller takes advantage ofthe 'thermal mass' of the solderingiron in maintaining a reasonablyconstant temperature at the tip (thelarger the iron, the better the regula-tion). Any fluctuations in tiptemperature due to increased ordecreased loading can be easilycompensated by adjusting thetemperature control as required. Ifthe neon lamp comes on at full in-tensity at the full counter -clockwiseposition and does not flash on andoff, the wires to the 100 k poten-tiometer (R3) are probably reversed.

The incoming mains voltage is switched viaSW1 which is integral with the temperaturecontrol RV1. The mains voltage is then fullwave rectified by D1 -D4. The resultingpulsating DC (illustrated in waveform 'A') candeliver the same heating power to a resistiveelement as 220-240V AC mains. The pulsatingDC will heat the soldering iron element and il-luminate the neon whenever the silicon con-trolled rectifier SCR1 is gated on by the com-bined logic of IC1 (1 hertz variable duty cyclemultivibrator) and IC2 (zero voltage cross-over detection and SCR gate driver). Withoutgate drive SCR1 will cease to conduct eachtime the pulsating DC returns to OV.

The mains potential pulsating DC is drop-ped via R1 and R2 and clamped to a pulsating+15V via ZD1. Waveform 'B' which is pro-duced by the clamping action of ZD1 alsopre -regulates the supply voltage for the in-tegrated circuits. 05 prevents the power sup-ply filter capacitor C1 from filtering out thesync pulses.

IC1 and the associated components form avariable duty cycle astable multivibratorwith a frequency of 1 Hz.

At the fully counter -clockwise position ofRV1, the output of this astable is low (logic 0)for 99% of the 1 second period. At the fullyclockwise or maximum setting of the RV1, theastable output is high (logic 1) for 99% of the

Figure 1. Circuit diagram of the HE SolderingStation.

FRONT PANEL

GRN/YELLOW /477

MAINS

BROWN

BLUE

1a

(PART OF RV1)

NOTESICI IS 4001IC2 IS 4011ZD1 IS 15V 400,11WD1-4 ARE 1N4004D5-8 ARE 1N4148SCR1 IS C1060

R510M

RI68k

AVVI141R268k

IStE TEXT)

0 .Vcc

R6IMO

7 CW

1101 0D7

D6

RV1500k

lin

0CCN

2

3

T122u26V

How it WorksMEASURED BETWEEN COMMON

& POINTS INDICATED.WARNING COMMON IS AT MAINSPOTENTIAL ABOVE EARTH.

-- 220V R M S

5mS

- - 311V PEAK

15V] ZENER POTENT IA Li

-OV

+ 15V

OV+15V

- + 7 V5

f-OV-.15V

10m5 10mS

RV1 -MIN

1 HERTZ

-OV

RV1- MAX

R810k

ZD1

Cl220616V

R9100k

O5

1

IRON NEON

.Vcc 40-0

R10470k

8

4

11

12

I9

C310n CO

I10T

R710k

1° ICld 8

9

12

0 -Vcc

VccSCR1

14

IC2c

7

0-Vcc

R1110k

period. Waveforms 'F' show these twomodes. Mid -positions of RV1 produce out-puts which vary between these two extremes.In summary, the setting of RV1 will vary theratio between the logic '1' state and the logic'0' state (duty cycle) without appreciablyaltering the period of the complete cycle.

The line synchronisation signal illustratedin waveform 'B' is coupled to the input ofIC2a via voltage divider R8 and R9 which pro-tects IC2a from the sync signal which is slight-ly higher in potential from 1C2's operatingsupply. IC2a inverts the line sync signalshown in waveform C and improves the transi-tion between the logic levels. IC2b, c and dserve as a logic AND gate i.e. only when itstwo inputs (pins 5 AND 6) are at logic 1, willthe output (pins 10 and 11) be at logic 1.

Therefore, whenever the line sync pulse isat OV (logic 0 inverted to logic 1 by IC2a) andthe output of the proportionally controlledastable is at logic 1, a pulse is applied to thegate of the SCR. This applies power to thesoldering iron element in fully controlledbursts.

The combination of all sections describedabove results in SCR1 being gated on onlynear zero crossings of the mains voltage. Thiseliminates RFI. The on -off ratio and thereforethe soldering iron temperature is propor-tional to the setting of the temperature con-trol RV1.


1.1411.11411.11=111111.111.11.rn

Temperature Controlled Soldering IronNOTE:

Rx - Install an additional 68k1 Watt resistor if the mainsvoltage in your area fallsbelow 220 Volts

1 1

- 117 I 1

R1 R2

Figure 2. Overlay diagram for the SolderingIron controller.

LIVE (BROWN)

NEUTRAL (BLUE)

GROMMET

EARTH (GREEN/YELLOW)

PRINTED CIRCUITBOARD

Figure 3. (Above) Wiring and interconnectiondiagram. To ensure safe operation you mustfollow this diagram closely. Remember, mainsvoltages are lethal!

ALL MOUNTED ON FRONT PANEL

NEON (WITHINTEGRAL RESISTOR)

SOLDERING IRONCOIL STAND

EARTH (GREEN/YELLOW)

CABLE TIE

LIVE(BROWN)

GROMMET

4,6

-:1.5

WarningThe circuit described here does notuse an isolation transformer andtherefore all sections of the circuitmust be considered dangerous.

It is advisable not to operate thedevice without its case.

=Parts List=.RESISTORS (All 1/4 W, 5%, except wherestated)R1, 2, x 68k 1 wattR3, 5 10MR4, 6 1M0R7, 8, 11 10kR9 100kR10 470k

POTENTIOMETERSRV1 500k lin with double -pole,

single -throw switch

CAPACITORSC1

C2C3, 4

220u 16 V printed circuitmounting electrolytic2u2 16 V tantalum10n ceramic

SEMICONDUCTORSIC1IC2ZD1D1-4D5-8SCR1

4001 quad NOR gate4011 quad NAND gate15V 400 mW zener diode1N 40041N 4148C106D

MISCELLANEOUSSpring mount for soldering ironNeon with integral resistorKnob for potentiometerCase to suitGrommets and cable clipsHeavy weight (for bottom of case)

BuylinesA complete kit for this project (including PCB,all PCB mounted components, a silk-screenedcase and all case components) is available fromCompu-Tech Systems for £11.95, all inclusive.All you have to find is the mains plug andsoldering iron. Compu-Tech will also supplythe copyrighted PCB separately.Compu-Tech SystemsGaymers WayLaundry Loke Industrial EstateNorth WalshamNorfolk

HE


O Level 12 & ANick Walton, our tame teacher now looks at some of the units and quantities we shall be usingthroughout this series.

THIS MONTH we will take a look atsome of the basic concepts of electrici-ty. Once these have been established(or you have been thoroughly con-fused!) we will relax and consider theenergy sources that help to make elec-tricity and how that electricity gets tous by means of the National Grid.

The little beast around which it allcentres is the electron, one of the threemost important particles that make upthe atom. The other two are theneutron and the proton and they live inthe centre of the atom, called thenucleus. Everything and everybodyaround us is made up of atoms andthere are slightly over one hundred dif-ferent stable varieties; hydrogen, oxy-gen, copper and silicon to name butfour. Of course most substances con-tain combinations of many differentelements. Atoms are so small that ap-proximately five million would fitacross the full stop at the end of thissentence. Atoms have been thoughtabout of since ancient times but it wasnot till a bright New Zealander, LordRutherford, arrived in 1911 that theycame to be regarded at tiny "solarsystems" with electrons (which carrynegative charge) buzzing in their orbit-als round a central part called thenucleus, rather like our planets movein their orbits round the Sun.

Big and SmallThe nucleus, which is about a tenthousandth the diameter of the atom,contains protons which carry a positivecharge and neutrons which do notcarry any charge at all, together withvarious other subatomic particles weneed not worry about. So, for example,the carbon atom illustrated in Figure 1has six electrons round the nucleuswhich itself contains six protons(whose six positive charges balance thenegative charges of the six electrons)tucked together with six neutrons.

Relative sizes when playing withatoms can sometimes be a bit mind -bending. For instance, if we look at itthe other way round and magnify ournucleus up to the size of a full stop,then the atom will be five metresacross, (i.e. about ten thousand fullstop diameters) and our original fullstop, which if you remember was fivemillion atoms across, will now have

grown to a blob twenty five millionmetres across; this is twenty five thou-sand kilometres across, or approx-imately twice the diameter of the earthand rather a lot of printing ink!

The CoulombIn fact for electrical purposes all weare concerned with is the electron andthe negative charge it carries. Charge ismeasured in units called coulombs(named after a French scientist) andone coulomb is the charge of about sixmillion million million electrons. Thiscan be written as 6x1018 electrons.When electrons start to flow in an elec-trical circuit we get a current. It is

measured in amps or amperes (namedafter another French scientist, Mon-sieur Ampere, the architypal absent-minded professor. He once forgot adinner date with the EmperorNapoleon - and got away with it; hisfather was guillotined during theFrench Revolution).

If those units are too big you can al-ways subdivide amps into thousandthsand call them milliamps (nothing to dowith Ampere's daughter) or mA forshort. If you could sit in the wire andwatch the electrons going past, then acoulomb's worth of electrons (i.e.6x1018 of them) passing you everysecond would constitute a current ofone amp.

The VoltOur next problem is to consider what ispushing this charge round the circuit.Whatever it is that causes this to flowis measured in volts (named afterVolta, an Italian scientist). If it is a bat-tery then the term electromotive forcecan be used (though strictly it is not aforce in the purely scientific sense). Wemight for instance talk of a batteryhaving an electromotive force (or EMFfor short) of 9 volts, this being the totalvoltage it can offer. Note that avoltage can be present even whenthere is no flow of charge - a batteryhas an EMF of 9 volts even when it isnot connected to a circuit. As thevoltage is potentially available to pushcharge around, the word "potential"has come to mean voltage, and we canrefer to the difference in voltage bet-ween parts of the circuit as a "poten-tial difference".

Volts pushing charge round a circuitimplies that the charge has been givensome energy. Energy is measured injoules (named after an English scientistthis time: a Manchester brewer in factwho is reputed to have spent hishoneymoon, well some of it, measur-ing the temperature difference be-tween the water at the top and thebottom of waterfalls in Switzerland).The more joules you supply to yourcoulombs of electricity (or they supplyto you) the greater the voltage, or inother words the greater the quantity ofjoules per coulomb. Incidentally theunits of your electricity bill (which arein fact kilowatt-hours) are no more andno less than units of energy - lumpsof 3,600,000 joules at a time.

While on the subject of British scien-tists, we should not forget our Scottishfriend James Watt who did great thingswith steam engines. He gave his nameto the unit of power which is the rateat which energy is being used up orprovided. Thus a watt refers to onejoule being used every second (1 jouleper second).

SummaryIf all that was new to you and you gotit first time, you're either a genius oryou're kidding yourself. Anyway, let'ssummarise it.Units of electric charge are coulombs.1 coulomb is the charge of about6x1018 electrons.Units of current are amperes, amps ormilliamps. 1 amp is the flow of 1

coulomb of electric charge per se-cond.Units of voltage are volts (Surprise!) 1volt is 1 joule per coulomb.Units of energy are joules (or kilowatt-hours. 1 kWh= 3,600,000 joules).Units of power are joules per second. 1watt is 1 joule per second.Battery voltage (total) can be describ-ed as.electromotive force (EMF).Voltage between two points can bedescribed as potential difference (PD).

ACIDCHaving now established the idea of asteady voltage driving a steady cur-rent, we need to be aware of the ex-istence of a commonly occurring formof voltage that is by no means steady.This is called alternating voltage (giv-


Multitester20,000 opvAC volts,- 0 - 10 - 50 - 100 - 250 - 500 - 1000DC volts,- 0 - 0.5 - 5 - 25 - 125 - 250 - 500 --

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- 20 to +63 dbDims,- 127 x 90 x 32 mm

Please add 30p P.P. per unit order as MT 7

HeadphonesHigh velocity mylar diaphragms. Coiled lead.Finished in a combination of bright aluminium,

Impedence -Frequency response -Weight -

8 ohms15 - 22000 HZ350 gms

Please add 30p P.P. per unitorder as PH 12

TWO ORBITALS CONTAINING A TOTALOF SIX (NEGATIVELY CHARGED) ELECTRONS

NUCLEUS, WHICH IF MAGNIFIED, WOULD BESEEN TO CONTAIN THIS:

SIX PROTONS EACH WITH A POSITIVE CHARGEAND SIX NEUTRONS (NO CHARGE)

Figure 1. Simplified structure of a carbon atomshowing the positions of the electron orbitalsand nucleus.

ing rise to alternating current or AC)and we have all met it in the form ofour 240 volt mains supply (not literallyI hope!) This rises smoothly from zeroto a peak of about 340 volts and thendrops again to zero and goes on drop-ping till it reaches - 340 volts at whichpoint it smoothly turns round andcomes back to zero. This cycle is

repeated fifty times every secondwhich is why we talk about mains fre-quency being 50 cycles per second, or50 Hertz or Hz (a German scientist thistime, who discovered radio waves). Allthis to and fro motion gives out thesame amount of energy as we wouldget from 240 volts direct which is

where the figure of 240 comes from.

Power ProblemsOur coal resources are not going tolast forever - I have seen estimateswhich range from 100 to 300 years and

oil is going to run out during thelifetimes of most of us. Estimatesrange from 15 years if you are apessimist to about 30 if you are an op-timist. Whatever your personal feelingsabout nuclear power, the fact is that itis the only form of energy capable offulfilling our expanding needs. Thetechnology exists and so do the risksand unless a series of 'governmentstake active steps to fund research intoalternative sources at a scale that canmeet our needs, the more certain it willbecome that you will be poweringyour HE project or home computerfrom electricity generated by energyunlocked from that little nucleus I

mentioned at the beginning.Other forms are interesting and pro-

mising. Solar energy in its present formcan help us reduce our hot water billsbut no sane person in this countryseriously reckons it can do more thanmake a small contribution. Then againthere is wind power; windmill sails orrather propellers could well enjoy acomeback and waves and tidal energymay help too. Areas in Italy, Icelandand New Zealand are fortunate in be-ing able to tap energy from naturallyoccurring steam, but these are just not

Multitesters 1043,000 opvAC volts:- 0 - 5 - 10 - 250 - 1000DCvolts, 0 05 25 10 50 250 - 1000DCcurrent,- 0- 10ua - 25ua - 500ua -0 - 5 ma -50 ma

-500 ma - 10 ampAC current- 10 ampResistance,- 0 - 20 ohms - 200 ohms - 5 K ohms - 200 K

ohms - 50 K ohms - 200 K ohms - 5 meg ohms- 50 meg ohms

As a transistor testerHFE:- 0 - 5 (NPN) - PNP)IC0,- 0 - 5 ua (NPN - PNP)Dims:- 178x 140 x 70 mmPlease add 30p P.P. per unit order as MT 20

Multitester1,000 opvAC volts:- 0 -5 - 150 - 500 - 1000DC volts:- 0 - 15 - 150 - 500 - 1000DC current:- 0 - 1 ma - 150 maResistance:- 0 -.25 K ohms - 100K ohms

90 x 61 x 30 mmPlease add 30p P.P. per unit order as MT

13'50

RROW UDIO ENTRE20 NORTH BAR BANBURY OXON 0X16 OTF.TELEPHONE BANBURY (0295)3677TERMS: CHEQUE/PO WITH ORDER. CALLERS WELCOME

capable of supplying energy in the re-quired quantities.

Supposing we do solve our energyproblems we will still need power sta-tions and the huge network of pylonsto distribute all the power they pro-duce. This network is known at the Na-tional Grid and it carries electricity atvery high voltages (132,000 volts, i.e.132 kV is typical). The reason for thehigh voltage is that the electricalpower is multiplied by the current. Soa high voltage allows you to get awaywith having a small current, and it is

the size of the current which deter-mines how much power is wasted inheating up the transmission lines. Ac-tually the power wasted depends onthe square of the current, so for in-stance, if you could reduce the currentto a third of its original value youwould have reduced the wasted powerto a ninth.

So much for the difficult stuff; butdon't forget it as we shall be needing itover and over again. Next month it willbe resistors and capacitors and meterswhich hopefully will bring us a littlenearer to the real world of HE projects.Meanwhile happy soldering and keepthinking! HE

TILL 10th OCT., '80SAFGAN ST -45

Single Trace Oscilloscope

at £127 + VAT P&P Free10MV - 5MHz - 4" CRT

*,10mv/div -5v /div* 200ns/div - 250ms/div* Trigger level ± slope* 0.5div int, 100mv ext* H215mm WI 65mm S280mmOrders to:SAFGAN ELECTRONICS LTD.56 Bishops WoodWoking, SurreyTel: Woking 66836 or 69560 ST -45

AERIALSPLITTERS

AERIALAMPLIFIERS

2 -UHF Televisions from one aerial. Price£2.70 each.10 -Moulded Co -ax Plugs £1.20.Low loss Co -ax Cable, white, 15p permetre.

100-MULLARD C280 /C281CAPACITORS

Values from .01u1 to 1.5uf 250V /W. Ourchoice. Good mixed selection. Price per100 U.

Aerial Amplifiers can produce remarkableimprovement on the picture and sound infringe or difficult areas.B45 - For Mono or Colour this is tunableover complete UHF television band.811 - For Stereo or Standard VHF/FMRadio.B12 - For VHF Television Band 1 & 3All Amplifiers are complete and readyto use.Battery type PP3 or 8v to 18v dc, next tothe set type fitting. Prices £6.70 each.

SIGNAL INJECTORS with (Pre-set) variable AF, which emits RF Harmonics into theUHF band. Protected up to 300 volts dc. Complete with leads, £5.70 each.

All prices include VAT at 15% P&P per order 30p. S.A.E. for Leaflets, Access Cardsaccepted.

ELECTRONIC MAILORDER LTD.62 Bridge Street, Ramsbottom, via Bury, Lanes. BLO 9AGH

Tel. Ramsbottom 3036


AND THERE'S MORE WHERE THIS CAME FROMIt's a long time since one of our adverts was presented in list' form - but simply because we do not try to squeeze this lot in every timedoesn't mean that it's not available. Our new style price list (now some 40 pages long) includes all this and more, including quantity pricesand a brief description. The kits, modules and specialized RF components - such as TOKO coils, filters etc. are covered in the general pricelist - so send now for a free copy (with an SAE please). Part 4 of the catalogue is due out now (incorporating a revised version of pt.1).

TRANSISTORS CAPACITORSAll 5nam or less spacing

LINEAR ICs - NUMERIC LISTINGS TTL N and LSN

TBA1205 1.00 084413 1.95

L200 1.95 KI34417 1.80 7400N 0.13

023711 1.28 TIA4420 2.25 741500 0.20

U2478 1.28 0844208 1.09 7401N 0.13

025711 1.28 KB4423 2.30 741501 0.20

U267B 1.28 KB4424 1.65 7402N 0.14

1/4301/1 0.67 084431 1.95 741.002 0.20

1243015 0.30 084432 1.95 7403N 0.14

U41081 -I 0.96 084433 1.52 741503 0.20

1213089 0.65 I034436 2.53 7404N 0.14

1M339N 0.66 684437 1.75 741504 0.24

LM348N 1.86 0134438 2.22 7405N 0.18

LE351N 0.38 0114441 1.35 741505 0.261F353N 0.76 1034445 1.29 7406N 0.28

LM374N 3.75 084446 2.75 7407N 0.38

LM380N-14 1.00 K84448 1.65 7408N 0.17

LM380N-8 1.00 NE5044N 2.26 741508 0.24

LM381N 1.81 NE5532/J 1.85 7409N 0.17

ZN419CE 1.95 586000 3.75 741509 0.24

NE544N 1.80 SL6270 2.03 7410N 0.15

NE555N 0.30 SL6310 2.03 741510 0.24

NE556N 0.50 SL6600 3.75 7411N 0.20

NE560N 3.50 0L6640 2.75 74LS11 0.24

NE562N 4.05 SL6690 3.20 7412) 0.17

NE564N 4.29 516700 2.35 74114 0.30

NE565N 1.00 ICL8038CC 4.50 7414N 0.51

NE566N 1.60 MSL9362 1.75 741515 0.24

NE570N 3.85 MSL9363 1.75 7416N 0.30

SL624 3.28 HA11211 1.95 7417N 0.30

TBA651 1.81 HA11223 2.15 7420N 0.16

uh709FIC 0.64 HA11225 1.45 741520 0.24

uA709PC 0.36 HA12002 1.45 7421N 0.29

uA710HC 0.65 HA12017 0.80 741521 0.24

uA710PC 0.59 RA12402 1.95 7423N 0.27

uA741CH 0.66 HA12411 1.20 7425N 0.27

uA74104 0.27 HAI2412 1.55 7427N 0.27

uA747CN 0.70 1813741 0.33 74LS27 0.44

uA748CN 0.36 SN76660N 0.80 7428N 0.35

uA753 2.44 741.528 0.32

FREQUENCY DISPLAYuA758 2.35 7430N 0.17

TBABlOAS 1.09 & SYNTHESISER ICs 741,030 0.24

TBA820M 0.75 7432N 0.25

TCA940E 1.80 SAA1056 3.75 74LS32 0.24

T041028 2.11 SAA1058 3.35 7437N 0.40

T041029 2.11 SAA1059 3.35 7438N 0.33

2E41054 1.45 11C900C 14.00 741538 0.24

T041062 1.95 11,0232 19.00 7440N 0.17

TIA1072 2.69 191242 19.00 741.040 0.24

TD41074A 5.04 MSL2318 3.84 7441N 0.74TEA1083 1.95 MSM5523 11.30 7442N 0.70T[A1090 3.05 MSM5524 11.30 74LS42 0.99HA1137 1.20 MSM5525 7.85HA1196 2.00 M0M5526 7.85HA1197 1.00 M345527 9.75 4043 0.85

TIA1220 1.40 MSM55271 9.75 4044 0.80

LM1303 0.99 ICM7106CP 9.55 4046 1.30

1M1307 1.55 ICM7107CP 9.55 4047 0.99

MC1310P 1.90 ICM721613 19.254049 0.52

MC1330 1.20 ICM7217A 9.50 4050 0.55

MC1350 1.20 008629 3.85 4051 0.65

HA1370 1.90 S08647 6.00 4052 0.65

HA1388 2.75 951190PC 6.00 4053 0.65

T1141490 1.86 111)10551 2.45 4063 1.09

MC1496P 1.25 H144015 4.45 4066 0.56

SL1610P 1.60 HL12009 6.00 4068 0.25

SL1611P 1.60 H144752 8.00 4069 0.20

SL1612PSLI613P

1.601.89

40704071

0.200.20

SL1620P 2.17 CMOS 4000 SERIES 4072 0.20

01.16210 2.17 4073 0.20

SL1623P 2.24 4001 0.17 4075 0.20

SL624C 3.28 4000 0.17 4076 0.90

SL1625P 2.17 4002 0.23 4077 0.20

5116268 2.44 4008 0.80 4078 0.20

SL1630P 1.62 4009 0.58 4082 0.20SL1640P 1.89 40108 0.58 4093 0.78

S11641P 1.89 4011AF 0.20 4175 0.95TUA2002 1.25 401111 0.20 4503 0.69

TU42020 3.00 4012 0.55 4506 0.51

ULN2242A 3.05 4011 0.55 4510 0.997L1422838 1.00 4015 0.95 4511 1.49

CA3080E 0.70 4016 0.52 4512 0.98

CA3089E 1.84 4017 0.80 4514 2.55CA3090A0 3.35 4019 0.60 4518 1.03

CA3123E 1.40 402011 0.93 4520 1.09

CA3130E 0.80 4021 0.82 4521 2.36

CA3130T 0.90 4022 0.90 4522 1.49

CA3140E 0.46 4u2( 0.17 4529 1.41

CA3189E 2.20 4024 0.76 4519 1.10

MC3357P 2.35 4025 0.17 4 549 3.50

1M3900N 0.60 4026 1.80 4554 1.53

1439099 0.68 4328 0.72 4560 2.18

I/43914N 2.80 4029 1.00 4566 1.59

1113915N 2.80 4010 0.58 4568 2.18

kb4400 0.80 4035 1.20 4569 3.03

0114406 0.60 4040 0.83 4572 0.30

E84412 1.95 4042 0.85 4585 1.10

7443N7444N7445N7446N741547

7448N7415487415497451N741,051

7453N7454N7415547415557460N7415637470N7472N

7473N7415737474N7415747475N7476N741576

741.578

7480N7481N

7482N7485N74158574LS867489N7490N741590

7491N74LS917492N7415927493N741593

7494N7495N7415957496N74LS967497N

1.151.120.94

0.940.89

0.560.990.990.17

0.240.17

0.17

0.240.24

0.17

1.240.280.28

0.320.380.270.28

0.380.37

0.380.38

0.480.86

0.691.040.990.402.050.330.900.761.100.380.780.320.99

0.780.651.140.581.201.85

7410107 0.3874109N 0.637415109 0.7074110N 0.547411113 0.68

7415112 0.387415113 0.387415114 0.38

74118N 0.8374120N 1.1574121N 0.42

74122N 0.46

74123N 0.737415124 1.7574125N 0.3874L5125 0.4474126N 0.57

7415126 0.4474128N 0.7474132) 0.73

7415132 0.787415136 0.407415138 0.6074141N 0.56

7414214 2.65

74143N 3.12

74144N 3.12

74LS145 0.97

74147N 1.75

74148N 1.097415148 1.1974150N 0.99

74151N 0.557415151 0.8474153N 0.64

7415153 0.5474154N 0.9674155N 0.54

7415155 1.1074156N 0.8074157N 0.67

7415157 0.5574LS158 0.6074159N 2.10

74160N 0.827415160 1.3074161N 0.927415161 0.787415162 1.3074163N 0.927415163 0.7874164N 1.047415164 1.3074165N 1.057415165 1.0474167N 2.50

VOLTAGE REGULATORS

78series 0.9579series 1.00

78Mseries 0.6578Lseries 0.3579105 0.8578MGT2C 1.75

79MGT2C 1.75723CN 0.65L200 1.95TD11412 0.75NE5553N 1.251M317M0 1.481M337MP 1.48

MICROMARK ET

8080A/28212821482168224

82518255

6800P6810682068506852

MC270821144027

2102211225111144716811.097

7.502.303.501.953.50

6.255.40

7.50

5.957.454.904.85

7.506.505.78

1.703.40

7.544.501.25

7415I6974170N74181707411017474175N741517574176N74177N74181N

7415181741518374184N74185N74L519074192N

741519274193N741519374194N74196N7415196741019774198N74199N741524774LS257741526074L527974152837415293741,0365

7415366741S36774153687410374741537774153797415393

2.002.30

VARICAPTUNING DIODES

2.00 BA102 0.30

1.20 8Al2) 0.300.87 11'7210 0.30

1.10 8820413 0.36

0.75 8B1058 0.360.78 136109 0.271.65 MVM125 1.053.50 BB212 1.952.10 KV1210 2.451.35 KV1211 1.751.34 KV1226 1.950.92 KV1225 2.751.05 KV1215 2.551.80 KV1225 2.751.05 SWITCHING AND1.80 PIN DIODES1.05 SHOTTKY DIODES0.99 196263 0.621.10

BA182 0.191.10

0A244 0.171.501.60

84379 0.35

0.93T1141061 0.95

SIGNAL DIODES1.08

1.53 & RECTIFIERS

0.52 1N4148 0.06

1.20 194001 0.06

0.95 194002 0.07

0.49 1145402 0.15

0.49 0491 0.07

0.43 AA112 0.25

0.49 BRIDGES:

1.80 1A/50V 0.351.95 6A/200V 0.751.301.40

TOKO COILS AND FILTERSSEE THE EXTENSIVE SECTIONIN OUR NEW PRICE LISTS ANDCATALOGUE

LF/HF FIXED INDUCTORS-FULL E12 RANGE711A series 1111-1-1m44 0.16

8143 series100uH-33mH 0.19lORB series33m8 -120m11 0.33

1081313 series

120m11-1.51-1 0.55

PIEZO SOUNDERPB2720 0.44

CRYSTAL FILTER PRODUCTS LEDs

10.7MHZ 2 POLE TOTS:10M15A 15KHZ BW 2.4910.7MHZ 8 POLE TYPES:1011481 15kHz EW 14.50H4402 7.5KHZ 1314 15.501011220 2.4KHZ SSB 17.20HF FIRST FILTER:834F8A 34.5MHz HF 32.00

RADIO CONTROL CRYSTALS

(No splits available)AM TX: -

3rd OT 30pF 8I0251/ 1.65

AM/FM RX: -

3rd CT 30pF I-C25U 1.65

FM TX :-

Fund 20p8 HC25UPairs FM

Pairs AM

1.853.25

3.10

CRYSTALS32.768 kHz 2.70100kHZ 3.85

455kHZ 5.001.0M5z 3.00

3.2768MHz 2.70

4.000MHz 2.004.19439MHz 2.306.5536MHz 2.1010.0MHz 2.5010.6985MHz 2.5010.7015111z 2.50

10.2454Hz 2.5010.7MHz 3.00

11.52MHz 2.50

100MHz 3.00

Please send anSAE with allenquiries.Access/Bard aycd(min £5 please)Callers welcome

PRICES EXCLUDE VAT - PLEASE ADD 15%.Postage 35p per order. CWO please. ('UK only) it

IN 1INAL ea

5MM RED 0.123MM RED CLEAR 0.153MM RED 0.15

2.5 X 5M14 RED 0.175MM GREEN 0.153MM GN CLEAR 0.16

3MM GREEN 0.162.5 X 5MM (33 0.20

5MM YELLOW 0.153MM YELLOW CL 0.163MM YELLO4 0.18

2.5 X 5M4 YE 0.205MM OPANGERED 0.205MM CRA CL 0.293MM ORANGERED 0.192.5 X 5MM ORA 0.245MM INFRA RED 0.56BPW41 IR DET 1.51IR OPT CPLR 1.445MM CLIP 0.04

Lah3.5 digit

4 digit5 digit

9.458.958.95

SCHOPIKY DIODE WI.MIXERS (013L1=MD108)SBL1 1-500MHz 4.25

S8L1-8 .1-200MHz 4.55

SBL1-X 10-1000MHZ 5.75SRA1 .5-500MHz 8.45

SRA1-1 .1-500MHz 9.25

SRA1H .5-500MHz 13.35SHA3 .025-200MHz 10.25

AUDIO DEVICES80237BC238812 39

81307BC308

BC3098041381,414

BC415

6112416

BC546BC556

BC550BC56080639

BC640

0.080.080.08

0.080.08

0.08

0.100.110.07

0.080.120.120.120.120.22

0.23

2SC1775 0.182SA872A 0.1420D666A 0.30258646A 0.3025D668A 0.40258648A 0.40200760 0.45

258720 0.4525C2546 0.192S41084 0.202SC2547 0.192541085 0.20

AUDIO POWERDEVICES208753

2087232SK133253 48

2SK134251(135

251 50811535

811536

80377

BD378BD165BD166

SMALL

2.34

2.34

3.003.00

3.103.753.75

0.520.520.33

0.330.300.31

SIGNALRF DEVICES

FRAMP 50v202,11.3,41/7,6P%

802, 101',150,180. .0.04

221',170,33P,47P160,680,82P,1000.0.051500,2201',2700530p,390P,470P 0.0551N0,2N2,3N3,4N7 0.06ION (0.01uF) 0.05

22N,47N 0 06100N,220N 0 09

MONOLITHIC CERAMIC10N,100N 0 16

FEEDIMIC

1NO SOLDER IN 0.09

POLYESTER (SIEMENS)

10mm LEAD SPACING

109,2213,3313 0 1747N,68N,100N 0 19

22013,4709 0 22

luE 0 29

POLYESTER (GENERAL)

10mm 11:111) SPACING

10N,15N,22N,33N 0.0647N,68N,10011 0 08220N 0 11

20mm LEAD SPACING22014,3305,47011-0.18

MYLARSow LEAD SPACINGLN0,10N,22N,33N..0.08100N 0 09

20mm LEAD SPACING22019,47013 0.17

POLYSTYRENE10P,15P,18P,22P,27P,47P,56P,68P..0.08100P,180P,220P,270P,330P,390P...0.09470P,680P,820P...0.10IN0,1N2,1N5,1N8..0.112N2,2N7,3N3,3N9..0.124117,5116,6118,1013..0.13

8E194 0.188E195 0.18

8E224 0.2288241 0.18

TANTALUM BEAD CAPS16v: 0.22,0.33,0.68,1 0 0 1816v: 2.2,4.7,10..0.19

BF274 0.18 6v3: 22,47 0 308E440 0.21 10v: 22,100 0 358F441 0.21

BF362 0.49 ALUMIN ELECTROLYTICS8E395 0.18 RADIAL (VERT. MOUNT)8E479 0.66 (uP/voltage)BF679S 0.55 1/63,2.2/50,4.7/35BET191 1.33

10/16,15/16,22/10BFW92 0.60

33/6.3 0 088E195 0.99EFY90 0.90

22/16,33/10,47/10 09

40238 0.8510/61,22/50,33/

500

RF POWER 47/16,100/16 0 10DEVICESVN66AF 0.95

177/06/::1300/25,220/16

0 12213866 0.85 100/63,470/16,

rFLEilT:A=1E-T 1000/10

0 181000/16,470/63...0.231000/63,2200/16..0 303300/25 0 691000/100 0 8810000/70

AXIAL (HORIZ. MOUNT)00

10%4.7/16,6.4/250

33/16)08

4.7/63,22/10,22/109

1000/16

47/25,100/180

10

100/255

2200/16,1000/25.1 111000/35,4700/16..0 45

1000/50 0 58

8E256 0.3825K55 0.28

2SK168 0.35J310 0.69

J176 0.6540823 0.6540673 39K5130645 0.493SK51 0.543SK60 0.58MEM680 0.75130961 0.70BF960 1.24

30648 1.64

LCD Module

CM161.Miniature clock,

12/24 hr., alarm,

day, date,

backlight

All for 9.95

RESISTORS0.25W, 54 112 LAMMlohm-104 0 020.25W 14 012 METAL FILM1.1ohm-IM 0 05

HORN CARBON PRESETSlOnyi TYPE100ohms-2M5 0 12

HORIZ CEHMET PRESETSlk, 10k 0 27

CWO PLEASE Commercial MA terms on applicationGoods are offered subject to availability, prices subject

to change - so please phone and check if in doubt.

-

200 north Service Road, Brentwood, EssexTELEPHONE (STD 0277) 230909 TELEX 995194 AMBIT 6 POSTCODE CM14 4S6

CATALOGUES2 & 3 60p ea4 75p

14 inc. rev. ofpart 1)

ALL PARTS:£1.75

Talking DesignPulse Width Modulation is a phrase you'll be hearing more and more. This important controltechnique looks set to revolutionise digital electronics.

THIS MONTH we are going to delve in-to the realms of digital control. The par-ticular technique involved is pulsewidth modulation. This technique is

likely to become more and more com-mon in audio amplification and poWersupplies, especially now that high speedswitching devices are becoming widelyavailable.

To understand the principle, look atthe simple circuit of Fig. 1 d. Here a tran-sistor, used in the common emittermode, has a square wave of equal markspace ratio as an input. The transistor isin saturation or cut off for equalperiods, so the average voltage at thecollector, as measured with amultimeter will be half the supplyvoltage (Fig. 1 a). If the mark to spaceratio is increased as in Fig. 1 b then theaverage voltage will rise. Conversly ifthe mark to space ratio is decreased(Fig. 1 c) then the output voltage wil I fall.Taken to extremes the transistor wouldbe either in saturation or cut off for thewhole time and the output voltagewould either be zero or supply voltage.

Well, you say, so what? The simpleanswer is that, unlike an analoguedesign, a current can be delivered to aload with hardly any power loss ordissipation in the driving device. For in-stance, look back to the circuit of Fig. 1and assume that we have a supplyvoltage of 9 V and a collector resistanceRc of 100R. To maintain a voltage of4.5V across this resistor there must be acurrent flow of 45 mA. The powerdissipated in the transistor and theresistor is found by multiplying thevoltage drop by the current flowing. Inthis case 4.5 V x 4.5 x 10-2A, = 0.2025 W.In the switching circuit a 1:1 markspace ratio square wave would be usedto set the required voltage across theresistor. Ideally the voltage drop acrossthe transistor would be zero when it wasin saturation, and the current throughRc is then 9 V 100R = 90 mA. So thepower dissipated would be V x I, i.e. 0 Vx 90 mA, zero! When the transistor is cutoff the full supply voltage would appearacross it and the power dissipationwould again be equal to V x I, 9 V x 0

+Vcc

AVERAGEVOLTAGE

OV

INPUT

VccAVERAGEVOLTAGE

OV

INPUT

+Vcc

a)

AVERAGEVOLTAGE

OV

b)

INPUT -

d

INPUT

Vcc

C)

VAVE RAGE

mA, again zero! In reality there willalways be a small saturation voltageacross the transistor of a few hundredmillivolts, and even when the transistoris cut off there will still be a smallleakage current flowing, although thiswill only be in the order of a fewmicroamps.

Although transistors are imperfectdevices, you can see that the squarewave circuit is many times more effi-cient than an analogue one.

Square WavesBefore the idea can be used practically,a means must be found of generating asquare wave with an easily adjustablemark space ratio. A simple method ofdoing this is to feed a triangle wave of

Figure 1. (a) 1:1 mark -space ratio. (b). In-creasing the mark -space ratio increases theaverage voltage. (c) Reducing the mark -space ratio reduces the average Voltage. (d)Using an NPN transistor to demonstrate theprinciple of Pulse Width Modulation.

known amplitude into one input of acomparator, and a control voltage intothe other. For those unfamiliar withcomparators, a quick description is pro-bably in order. A comparator has two in-puts, an inverting and a non -inverting,like an op amp. It also has a high voltagegain but unlike an op amp is operatedwithout negative feedback. It functionsas a switch - the output is at zeropotential when the non -inverting inputis more negative than the invertingwhile the output is fully positive whenthe non -inverting input is more positivethan the inverting one. Because the gainof the comparator is very high a voltagedifference of a few millivolts at the in-puts will be sufficient to ensure swit-ching. Comparators, as the name im-


V0

V0

COMPARATOR

plies, are used for detecting and com-paring voltage levels. If one input is fedwith a triangle wave and the other with avariable voltage level the output con-sists of a square wave whose markspace ratio depends upon the voltage atthe input. Figure 2 should make thisclear.

PracticalitiesThe practical application is shown inFig. 3, a pulse width modulator that willdeliver in excess of one amp to a load(such as a motor or lamp) that can besimply adjusted by a control voltage.

The circuit is an excellent power sav-ing device with an efficiency of 90%and is ideally suited to battery operatedequipment.

To keep the circuit simple whilst pro-viding maximum flexibility, a low costquad op amp is used as the activedevice. The type chosen, the LM324,contains four op amps that are similarto the good old 741 but with the advan-tage that the output can go down toground even when operated from asingle supply voltage.

IC1 a is used as an astablemultivibrator that produces a 1:1 markspace square wave at its output. Theseare input to an integrator, which con-verts the square wave into a lineartriangle wave suitable for the pulsewidth modulator, IC1 c. IC1c is used as a

NOTE01 IS TIP4SAIC1 IS LM32401 IS 1N4001

Figure 2. (left) Using a comparator to produce square wave from a triangle wave and avariable DC level.

Figure 3. (above) A practical circuit using Pulse Width Modulation to control a motor.

comparator with the triangle wave atone input and the control voltage at theother. The resulting square waves at theoutput of IC1c are used to drive the out-put transistor, a TIP41A which is used inthe common emitter mode.

Having outlined the circuit we canconsider its operation in more detail.

How It WorksThe non -inverting input of IC1a is con-nected to the junction of R1,R2 and R3.IC1 a is being used as a comparator andits output must either be high or low.

When power is first applied C1 isdischarged. Thus the voltage at the in-verting input is held lower than that ofthe non -inverting input, and the outputof the op amp is at supply voltage. C1starts to charge up via R4 and when thevoltage at the inverting input exceedsthat at non -inverting input the output ofthe op amp goes down to 0 V. Now C1discharges through R4 and the op amp'soutput stage.

The non -inverting output is held at apotential that depends on the values ofR1,2 and 3. When the output is high R1and R3 are effectively in parallel whilstwhen the output is low R2 and R3 are inparallel. Since R3 is connected from theoutput to the non -inverting input apositive feedback loop is obtained. Inpractice this ensures that the output ofthe op amp changes from high to lowstate and vice versa very rapidly. If allthree are made equal in value then thepotential at the non -inverting input willoscillate between 1/3rd and 2/3rds ofthe supply voltage.

The frequency at which the circuitruns is determined by the values of R4and C1 and can be calculated from theformula

f= 1

1 . 4 R4 C1

To operate small motors and lampsfrom the pulse width modulator the ac-tual frequency employed is not critical.The lower limit for reliable operationseems to be 100Hz. At the upper endthis particular circuit is limited by therate at which the output of the op ampcan change. This is known as the slewrate and you will find it quoted on opamp data sheets. For the LM324 theslew rate is 0.5 V/microsecond. Anothermeasure of this same effect is the fullpower bandwidth, also quoted in datasheets. For the 324 this is 6kHz. Withinthese limits the values of R4 and C1 canbe whatever happens to be at hand. Inthe prototype an operating frequencyof 1kHz was chosen. A 10n capacitorwas available for C1 and so the equa-tion was rearranged thus

R4 = 1 = 1 ÷ 4x103x10-11 -4fC1

68k is the nearest value.Our square wave must now be con-

verted into a triangle wave by a circuitknown as an integrator. The output ofthis circuit is directly proportional to theintegral of the input. The integral of asquare wave is a linear triangle wave. Apositive voltage level at the integrator'sinput produces a negative ramp at theoutput. If a negative voltage level is in-put, a positive -going ramp comes out.Since our square wave consists of alter-nate high and low levels the trianglewave at the output will resemble thatshown as V2 in Fig. 2. To calculate thevalues that we require for R5 and C2 weuse the following formula,

vo Vcc4RCf

Again a large range of values can beemployed arid by simply rearrangingthe equation one can easily calculatethe required values. An example of theprocedure follows. To get a large adjust -


Talking Design1 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

0 0 0 0 0 0 0 0 0 0 0 0 0 0

R9 i

0 0 0 0EtO 0 0

0

00

0

0

TOLOADleg. MOTOR)

CONTROLVOLTAGE

Figure 4. Veroboard layout for the circuit in Figure 3.

ment range a fairly large signal swing isrequired. Assuming that the circuit willbe employed over a range of supplyvoltages it is necessary to ensure that anundistorted and unclipped signal is

available. For this reason a peak -to -peakvoltage of 7 V was chosen and the re-quired component values werecalculated as follows. Choose an ar-bitary value for C2, say 100nF. The valueof R5 can be calculated by rearrangingthe above equation thus:

R = Vcc4VoCf

9 = 3.2x1054 x 7 x 10-7x103

The nearest value is 330k.

O

A

0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0O 0 0 0 0 0 0 0 0 0 0 0 0 40 0 0 0 0 0 0 00 O0 0 0 0 o 0 0 0 0 0 c) o 0000000000000O 0 0 0 0 0 0. 0 0 0 0 0 0 0 0 0 0 0 0O 0 0, 0 055000500000000550 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0000000000000000000 0 1 0 0 0 0 0 0 0 0 0 (D 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Note that 9 V was taken for the supp-ly voltage. This calculation does notneed to be repeated for other voltagesas the amplitude of the triangle wavewill be in direct proportion to the supplyvoltage used.

The last part of the circuit is builtaround ICI c. This is the pulse widthmodulator proper and its function hasalready been described. The outputsquare wave drives the power transistor,a TIP41A. Base current is limited by R9.

D1 is included to protect Q1. When acurrent is fed into an inductive load, forinstance, a motor winding, energy isstored in the magnetic field that buildsup around the wire. When the supply isinterrupted the field collapses and as itdoes so the magnetic flux produces a

large reverse polarity voltage spike.This spike can have sufficient

amplitude to destroy the driving tran-sistor. The diode will short any suchspikes to the positive rail thus protec-ting the transistor. If you glance throughany projects in HE where transistors areused to drive relays, for example, youwill notice this feature has been inclu-ded.

LayoutA simple stripboard layout for the cir-cuit is given in Fig. 4. The TIP41A doesnot require a heats ink. As it stands thecircuit has many applications. A typicalapplication would be a model trainspeed controller. HE

TRIACS

\\.

3A 49p 16A 95p8A 58p 25A 190p

12A 85p 80p6A with trigger 65p8A isolated tab 18p

Diac

400V Plastic Case (Texas)

MINITRANSFORMERS

Standard mainsprimaries 240V a c100mA secondaries6-0-6V 80p9-0-9V 85p

12.0-12V 90p

LEDs

LEDS0.1" Red 9p0.1" Green 12p0 1" Yellow 12p0.2" Red 9p0.2" Green 12p0.2" Yellow 12p0.2" clips 3pRectangular Red 18pRectangular Green 20pRectangular Yellow 21p

MINI KITS

These kits form useful subsystems which may beincorporated into larger designs or used alone. Kitsinclude PCB. short instructions and all cowponentsMK 1 TEMPERATURE CONTROLLER/THERMOSTATUses LM3911 IC to sense temperature (90'Cmax) and troc to switch heater

1 KW E4.00MK2 SOLID STATE RELAYIdeal for switching motors, lights. heaters, etcfrom logic Optodsolated with zo voltageswitching Supplied without trtacer Select therequired triac from our range. E2.80MK3 SAR /00T DISPLAYDisplays an analogue voltage one linear 10.element LED display as a bar or single dot. Ideal forthermometers level indicators, etc May bestacked to obtain 20 to 100 element displays.Requires 5-200 supply £4.75MK4 PROPORTIONAL TEMPERATURECONTROLLERBased on the TDA1024 Zero voltage switch thiskit may be wired to form a burst fire powercontroller or a proportional temperaturecontroller enabling the temperature of an enc losure to be maintained to within 0.5 C

3KW E5.55MK5 MAINS TIMERBased on the ZN 1034E Timer IC this kit will switcha mains load on for off) for a preset time from 20minutes to 35 hours Longer or shorter periodsmay be realised by minor component changesMaximum load I KW. E4.50

D.Y.M. THERMOMETER KIT

Based on the ICL 7106. Thiskit contains a PCB, resistors,presets capacitors. diodes, ICand 0.5" liquid crystal display.Components are also includedto enable the basic DVM kit tobe modified to a Digital Ther-mometer using a single diodeas the sensor. Requires a 3mA9V supply (PP3 battery).

£20.75

TK's SPECIAL OFFERS OF THEMONTH

Orders must be received by 31.10.80

SPECIAL OFFERSAY5-1224 Clock IC . .

LM3915 Bari Dot Driver . .

2 x DL304 0 3" cc Display2 x DL307 0.3" ca Display2 x 2N3442. 10 off each 0 2" LEDsRed, Green, Yellow

E2.20E2.10E1.35E1.35£1.80£2.90

INTEGRATED CIRCUITS111111W 555 Timer 21p

741 Op Amp 19pAY -5-1224 Clock £2.60

AY -5.1230/ 2 Clock /Timer £4.50AY -3.1270 Thermometer £8.20ICL7106 DVM (LCD drive) £7.00LM377 Dual 2 W Amp E1.45LM379S Dual 6W Amp E3.50LM380 2W Audio Amp 80pLM382 Dual/low noise Preamp E1.00LM386 250rnW low voltage Amp 75pLM 1830 Fluid Level Detector El .50L M2907 1.v Converter (8 pin) E1.40LM2917 hy Converter (14 pin) E1.60L M3909 LED Flasher /Oscillator 60pLM39 i 1 Thermometer £1.20LM3914 Dot/ Bar Driver E2.10MM74C911 4 digit display controller E8.50MM74C91 5 7 segmentBCD converter 96pMM74C926 4 digit counter with 7 seg 0 /Il £4.50S5660 TouchdirnmerS9263 Touchswitch 16 -waySN76477 Complex Sound GeneratorTBA800 5W Audio Amp.TBA810AS 7W Audio Amp.TDA1024 Zero Voltage SwitchTDA2020 20W Audio Amp.ZN 1034E TimerAll ICs supplied with data sheetsData Sheets only 10p each device.

E2.50£4.85E2.52

68pE1.00E1.20E2.65E1.80

AND NOW A DIMMERTHAT MAKES TOUCH DIMMERS OBSOLETE

lwii,earcab,,, thccromcsfroni-heflatotichcbminer kit the T 0300K wluch made knot/controlled dunmers obsolete This was

0 o e :

, elrnenh11 great SsICCPSS Plat Malty

to you) hatol

magerinns and morn iotrolein 4,0,1aMflfiCall similar flaslans ,f1) V.OTHERS MAY r111 OW I havedesigned s too I, donntor kit with en',Ara alai affrokfle. tialf01 enablinpV011 la switch and co notenghtnese 01 tour affm

Onchat of your filo, rau air lee well as menurolly by touching the boob:dearnr traftlalny the TOPIC miens..., kin I.As with all our kits these units come complete with ell Components

'including RE, suppresewn. frontplete. e neon to help you hod Me switch inhe dark and a neat hos for the transmitter the blebe honarlete ht.. no metal

Pads to touch ensuring complete safety and enabling the oleo to becovered with decorative finish to blend .

with your room decor

REMOTE CONTROLCOMPONENTS

VPRIS Ilnla PV1,00010,1 aff tellola 101114. (.0111101

dimmen. -All InFlaa fMifTE)711,3017, NOW coo ior, El 30 ri

the dfmniar Mil (4 70 tic the If IMSOMIr". f`l Val of still

Asallalfla At re 60 4P,1,110 IDE at [2.00DON 1 f MICA T to add 40p P&P end I c,.VAT10 Salla total purchase

RC500K KIT

10271 IR Emitting Diode 38pSFH205 Photothode Detector 95pSL480 IC Pulse Amp E1.70SL490 32 command encoder; transmitter E2.40M L 922 10 channel receiver +3 analogue outputs

E4.20ML926 16 channel receiver 4 momentary binary

E1.40ML928 16 channel receiver 4 latched binary o /p

E1.40ML929 16 channel recewer 4 latched binary o --p

£1.40Data Sheets per device 10pThese ICs can be used with infra red. ultrasonic orradio links, depending on range, cost and speed ofoperation

II you do not require a sophisticated multi -channelremote control, we have developed a simplesingle -channel on /off infra red transmitter andreCelVel kit. The transmitter unit comes completewith a hand-held box and requires a PP3 (9V)battery. The receiver includes a mac capable ofswitching up to 500W at 240V a c and comprises'a pre -amplifier bistable latch and a mains powersupply. making the unit completely self contained.The small size of the receiver enables the unit to be

built into all kinds of equipment from lamps Intape recorders. Range approximately 20ft

£12.50

ALL COMPONENTS ARE BRAND NEW AND TO SPECIFICATION. ADD VAT ATCURRENT RATE TO ABOVE PRICES. iltlp P&P MAIL ORDER - CALLERS WELCOMEBY APPOINTMENT

TK Electronics(H.E.), 106 STUDLEY GRANGE ROAD

LONDON W7 2LX. TEL. 01-579 9794


BARGAINCORNER

Show us that you could have purchased forless within one month of your purchase andwe will refund the difference!

CAR AUDIO New 7 Channel Stereo Grapic Equaliser/Booster Amplifier. 17 watts R.M.S. per chan-nel frequency response 20Hz to 30,000Hz12 D6 cut/boost on each channel, completewith fitting kit. You would pay £45 elsewhere.For a limited period we offer the unit for theincredible price of £26 (-I- £1.20 post). Suitable Speakers for above. Adjustableangle, shelf-mour,ting, power handling 30 wattsmax. £16 (+ Et .20 post)

Model Stereo Cassette/Radio. M.W.,stereo FM and stereo cassette player, 8 wattsper channel, fast foreard and autostop, includesfitting kit and FREE SPEAKERS. Sold elsewherefor up to )85 (believe it or not). Our price £45 +£1.50 post. (For negative earth cars only).

MULTIMETERS

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Induction BalanceModel. Highly sensitivemodel with speaker andmeter, 7 -inch search headand telescopic stem. Usuallysold for £39.95. Our price£24.50 + E1.20 post. Yet another stock clear-ance bargain: A remarkablelittle BFO detector which willdetect a coin in 6 -inches ofsoil. A perfect machine to seeif you really have the patienceto take the hobby upseriously. £10 (+90 pencepost).All goods guaranteed one year. 10 day moneyback offer on all undamaged goods. Goodsex -stock at time of going to press. Send S.A.E.for details

DT 1314 Asuperb 38range meter.Special featuresinclude 50K0 /VDC move-ment, 10 ampDC Scale, res-istance up to100 MO, 2'ranges for tes-ting batteries,long extraflexleads, batteriesincluded.Usually sold for£35. FORLIMITEDPERIOD £25 +75p post.

DT1004 20KO /VDC move-ment, 16 rangesand off position,mirror scale, pro-tected move-ment, battery in-cluded. Usuallysold for £16, ourprice £12 +50p post.

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Is

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ALARM CHRONOGRAPHA superbly styled analogue watch only 7.5mm thick (approx.) with a multifunctionaldigital display.

ANALOGUEIndependent. hours, minutes and sweep second hand.

DIGITALTime: Independent, 6-digit,display of hours, minutes and seconds, with a.m./ p.m.indication (12 -hour system) or 24 -hour readout.Calendar: Alpha day and date with automatic adjustment.Alarm: The 24 -hour alarm sounds for 60 seconds. 12- or 24 -hour readout withalarm set symbol continuously displayed.Chimes: The hourly signal, with symbol, can be switched on or off.Stopwatch: Measures net times from 1 / 100 second to 1 hour.Dual time, count down and accumulation function availability. Stainless steelcase and bracelet. Hardlex glass, shock and water resistant. Anti -magnetic. Approx.2 -year battery life.

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Interval countdown alarm timer.Weekly programmable alarm.

Comprehensive display of hours, minutes. seconds, day.date and month. The 24 -hour alarm can be programmed toring on any day or days of the week. The hourly chimes canbe switched on or off. The interval alarm timer can be set for aperiod of time up to 16 hours and is repetitive until switchedoff.The stopwatch measures net, lap and 1st and 2nd placetimes from 1/100 second to 20 minutes, then in seconds to12 hours, the upper display indicating lap times and thelower display total time. Stainless steel case and bracelet.Hardlex glass. Approximately 7 -year battery life. 6 solarpanels. 12 month world-wide guarantee.

Water resistant case with-stands, splashing, etc.

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IntruderAlarmBanish burglars, vanquish villains andthwart thieves! The HE Watchdog isa steal at only £10.

CONVENTIONAL BURGLAR alarmcircuits show up in electronicsmagazines with disturbing regularity -we say disturbing because it's a sadreflection on the state of society thatsuch projects are made popular bynecessity. Generally these circuitsinvolve concealed switches in doors andwindows which can be connected inone of two ways - all of them wired inseries and normally closed, so thatopening one switch breaks a circuit andsounds the alarm, or all of them wired inparallel and normally open, so thatclosing one switch completes a circuitand sounds the alarm. It is also possibleto mix the two systems, for example youcould have normally -closed switches onthe doors and windows combined withnormally -open switches in the form ofpressure mats under the carpets.

The problem with such systems isthat, although they will deter (or trap)the amateur housebreaker or the kidslooking for cash and kicks, aprofessional burglar is quite anothermatter. The normally -closed switchsystem can be disabled by shorting thewires, and the normally -open by cuttingthem. A professional could have theknowledge and experience to make aguess about your system and risktampering with it. Three courses ofaction are possible. You can make itimpossible for anyone to get at thewires by burying them in the plaster orrunning them under the floorboards -this requires lots of hard work andextensive redecoration. Or you can optfor a different system altogether, usinginfra -red beams or ultrasonic movementdetectors, but these are more expensiveand more complex, and complexburglar alarms have a nasty habit ofgiving a high proportion of false alarms.

II/wire-shortdoorM ndow on

open

HEWATCHDOG

The third possibility is to devise a circuitin which the wires are tamper -proof.This is the approach we have used inour latest design.

This burglar alarm is based on awindow comparator. Note that this isnot a device that compares openwindows with closed ones! In its basicform a window comparator is a devicewhose output is in one logic state unlessthe voltage it is monitoring movesoutside certain limits (the 'window'), inwhich case its output changes state. Thewindow comparator in our circuit isslightly more complex than this, as weneed to indicate whether the inputvoltage is above or below the 'window'in the event of an alarm.

The external wiring of the alarm ismade as follows. Each protected pointhas a concealed switch fitted which isnormally closed, and each switch has aresistor soldered in series. Each of theseswitch/resistor combinations is thenwired in parallel with the others. Figure1 should make this clear. The totalresistance of this chain is thereforeequal to the parallel sum of theindividual resistors, and this value isused in one arm of a potential dividerthat is monitored by the windowcomparator. Any change in the value ofthis resistor chain will trigger thewindow comparator and set off thealarm.

This solves the problem oftampering with the wiring. If a door orwindow is opened the correspondingresistor is taken out of circuit and thealarm sounds, as it will if the wires arecut, or a short or resistance of any valueconnected between them. This meansthe wiring can be run anywhere incomplete safety, even along the outsidewall of the building if you want. It also

allows you some flexibility in use -since the threshold can be adjusted witha potentiometer, you can leave aprotected window open (on a hot nightfor example) and alter the setting toallow for the changed circuit resistance.An 'alarm' LED is included in the circuitso that you can make these setting -upadjustments without the bell or sirengoing off - this avoids the need toassist several large members of theconstabulary with their enquiries.

Burglar alarms should always bebattery -powered, as power cuts providegood cover for those with nastyintentions towards your belongings, sowe've used a new CMOS op amp, theICL7611. This only draws 10 microampsquiescent current, less than that throughthe resistor chain, so your PP3 shouldlast for months. The external alarmshould also be battery powered,preferably a high -capacity, heavy-dutytype. A mechanical bell is probably stillthe best choice for an alarm - beingresonant it can produce vast quantitiesof decibels with only a small currentdrain. You might consider making thebell circuit self -latching, so it rings for along time even if the PP3 gets drainedby the relay. This is left as an exercisefor the reader!

ConstructionNothing unusual here; the controls andthe LEDs fit on the front panel andeverything else fits on the printed circuitboard. Use sockets for the ICs and don'ttouch the pins of any of them wheninserting them - the op amps areCMOS and therefore static -sensitive too.If you can't find a relay whose pins fitthe PCB, just mount it off the board andwire it to the pads. We made theexternal connection via a jackplug and


socket, as shown in Fig. 3, but if you'reworried about the plug being pulled outyou can make a direct solderconnection to the board.

It is possible to use microswitches inthe alarm circuit but we aren't that keenon them - they are prone to give falsealarms if the door vibrates in a strongwind or if the woodwork warps. Reedswitches are a better bet, mounted inthe doorframe with the magnet let intothe door.

The resistors associated with theswitches should be of equal values -the correct value depends on thenumber of switches and is chosen togive a total parallel resistance of about50k. For example, if you have 12switches each resistor must be about12 x 50k i.e. 600k. The nearest preferredvalue is 620k. Solder the resistor closeto one of the switch terminals. It mightbe an idea to sheath it in heat shrinksleeving for protection (see this month'sBuilding Site for details).

To set up, close all the doors andwindows that you want closed, disablethe relay, switch on the unit and adjustRV1 until the alarm LED stays off whenthe reset button is pushed. Then switchthe relay back in.

Some final points about protectionagainst theft; a burglar alarm is nosubstitute for proper locks on yourdoors and windows, nor for forgetting tolock up when you 'just pop round thecorner!

Figure 1. This drawing shows how the resistorsand alarm switches are wired in the externalcircuit, one pair for each protected door and

window. You can use any convenient twin -core cable (e.g. speaker cable) and loop itfrom one installation to the next. We have

shown the switches as microswitches (easier todraw!) but reed switches and magnets are

probably more reliable. Resistors RA to Rnshould all have the same value; see text for

details of how to calculate the values.

How it WorksIC1 and IC2 are two op amps with no feedbackconnection between output and input i.e. theyfunction as comparators (for more informationon comparators, see this month's 'TalkingDesign' feature). In this circuit the two com-parators are connected together to form a win-dow comparator, one to monitor the upper limitof the window and one for the lower limit.

The reference voltages for IC1 and IC2 are ap-plied to pin 3 (non -inverting input) and are set byresistors R1, R2 and R3. R1 and R3 are equal andhave large values compared to R2 so thereference voltages are approximately at half thesupply level. R2 sets the reference voltage forIC1 and IC2 slightly above and slightly belowhalf -supply voltage respectively. The monitoredvoltage is fed to pin 2 of the two ICs.

This input voltage is taken from point XA 01 adivider chain consisting of RV1 and the resistorsassociated with the door and window switches(see Fig. 1). When all the switches are closed, theresistors are connected in parallel and the totalresistance is therefore given by R = RAIn wheren is the number of resistors and RA is the value ofeach resistor in Fig. 1 (all equal). If RV1 is nowadjusted to equal this resistance, the voltage atpoint XX will be half the supply voltage (i.e. in-side the window). Hence the output of IC1 willbe high and the output of IC2 will be low.

The outputs of the two comparators are takendirectly to the inputs of NAND gate IC3a, and tothe inputs of IC3b, another NAND gate, via in-verters IC4a, IC4b. Both NAND gates have one

input high and the other low, so both their out-puts are high. This holds LEDs 1 and 2 off.

Suppose a door or window switch is nowopened or the alarm wiring cut. The correspon-ding resistor will now be out of circuit and thetotal resistance of the external chain increases.This causes the voltage at point XX to dropbelow the lower window threshold and the out-put of IC2 goes high. This has no effect on thestate of IC3b since its inputs will both be low,maintaining its high output. However, both in-puts of IC3a will be high and its output switcheslow, turning on LED1 to indicate an open door.

However, if the external wiring is shorted atany point, the voltage at point XX is taken abovethe upper threshold and IC1 output goes low.IC3a is now unaffected (both inputs low) butIC3b will have both its inputs high. Its outputgoes low and turns on LE D2, indicating a short.

The two remaining NAND gates IC3c andIC3d are connected as a set -reset latch. Normal-ly its 'set' input is held high by R6. If either IC3aor IC3b goes low, the associated diode (D1 orD2) pulls this input low and sets the latch (pin 11goes high). The outputs of the inverters IC4c-IC4f go low and turn on LED3 (alarm indicator)and the relay. The inverters are connected inparallel to increase their drive capability. Press-ing PB1 resets the latch and turns off the alarm.

The relay contacts may be used to operateany external bell, siren etc. SW1 is included todisable the external alarm while setting up thethreshold control. D3 prevents any voltagespikes from the relay damaging LED3.

TO POINTS X AND XXON THE CIRCUIT BOARD

NOTE.SWw. 8 etc can be any normally open switch, erg. micro reed,which is closed when the door or window is closed.

TO DOOR ANDWINDOW SWITCHES

l.1r.n`a

Al

IMP

3

CI

+

IC3a

C b

LED

LED2

R5160

0

RE

150k

R71506

C415

11

9 6

C4

SWi

R8160

LE 03

SW2 09y

RELAY.2006

IC3c1

la81RESET

IC3c10

NOTE'IC1.2 ARE ICL 7611IC3 IS 4011IC4 IS 40490123 ARE 154148LED1-3 ARE 0.2" RED LED

O

Figure 2. Circuit diagram of the Intruder Alarm showing the components contained in the main control box. Points X and XX are connected to the door andwindow switches as shown in Figure 1.


Intruder Alarm

BuylinesThe components for this project, excluding caseand PCB will amount to around £10. The win-dow and door switches will cost extra and theirtotal price will depend upon how many andwhat types you use - we estimate that micro -switches should be available for about £1 each,reed switches and magnets should be somewhatcheaper - shop around, you will probably finda great deal of difference from one place toanother.

The only hard -to -come -by components maybe IC1 and 2. They are from a new family of in-tegrated circuits and at the moment may beslightly difficult to find. Any of the mail-ordercompanies will, no doubt, advise you if youhave trouble.

SOCKET CONNECTIONTO DOOR/WINDOW

SWITCHES

Photograph showing the internal layout of the Intruder Alarm control box. Follow theinterwiring diagram (Figure 3) and you should have no problems. Cable ties keep the wiringneat and tidy.

/////////////////////////7/////74,4%/77////////////// /// '// 7///////:////////////////////// /

LED2 LED1 -WIRE-SHORT DOOR/WINDOW SW2

RV1 OPEN ON/OFFTHRESHOLD

RELAY

,./

wLED3 PB1

ALARM RESET SW1ALARM

DISABLE

Figure 3. Component overlay and interwiring diagram for the main control box, showing the controlsfixed to the front panel and the input jack socket on the back panel. If you think a jack plug might getpulled out, you can leave it out and solder the wires from the alarm switches directly to the printedcircuit board.


=Parts List,RESISTORS (all 1/4W, 5%)R1,3 IMOR2 22kR4,5,8 1k0R6,7 150kRA-Rn see text

POTENTIOMETERSRV1 100k linear

CAPACITORSC1 4u7 35 V tantalum

SEMICONDUCTORSIC1,2 IC L7611IC3 4011IC4 4049D1-3 1N4148LED1-3 0.2" red LED

MISCELLANEOUSPB1 Push switch (non -locking)SW1,2 Single -pole single -throw toggleRelay Coil >200RPC B

IC socketsCase9 V battery and connector.

HE

61

STEVENSONREGULATORS

7905 85p7912 85p7915 85p

78L0578L1278L15780578127815

TIC246 16A 400V Teas 115PC106D 4A 400V 50 SCR 45p

33p33p33p70p70p70p

POTENTIOMETERSPreset ver, or her. . Bp

Rotary 5K -1M Log or Lin . . 33pRotary 5K -1M stereo 110pSlide 60mm travel 5K -500K log

or Lin, single . 65pSuitable knobs for above with colouredcaps in red, blue, green, grey, yellowand black. Rotary 16p. Slide 12p each.

SPEAKERS64mm 811 110p64mm 64 11 110p70mm 80. 1400

56mm 8 11 100p 70mm 8011 170p

Pair of ultrasonic transducers 380pMagnetic earphone 3.5rnm plug 17pCrystal earphone u 3 5mrn plug 489

CONNECTORS

DIN2 pin3 pinSpin 180JACK2.5mm3.5rnmstd.Stereo

Plug9P

12p13pPlug10p11p17p25P

ChassisSocket8P

10p11p

Scr. plug16p18p300390

LineSocket12p12p16pSocket

9p9p

22p250

ANSISTORS

AC127AC128AD161AD162BC107BC108BC109BC1478C178BC182BC182LBC184BC184LBC2128C212LBC214BC214L

25p25p40p40p10p10p10p

9p16p10p10p10p10P10p10p10p10p

BC 547BCY71BD131BD13280139BD140BF X29BF X84BF Y50BFY51MJ2955TIP29C

8p18935p35035p35p25P26p23p23P98p60p

TIP3OCTIP 2955TIP3055ZTX107ZTX108ZTX109ZT X300ZT X5002N30532N30552N37022N37032N37042N38192N39052N5777

70p65p60P12p12p12014p15p25p55p

9P9P9P

22P10p50p

DIODES1N914 4p 1N4148 3p1N4001 4p 1N40021N4006 7p 1N5401 14p8ZY88 series Bp each.

MISC. 8mm strandedconn. cable .

Min. mains cable per metre .PP3 battery clips . .

Crocodile clipsAA rechargeable cells .

PP3 rechargeable cells .

Red or black terminals3 lead TO18 socketRed or amber neon indicatorSubminiature SPST toggleStandard SPST toggle .

Miniature slide switches .

IP12W rotary switchesPush to make switches .

30P TO5 heatsinks25p 20rnm panel fuseholders

6p ORP12 LDR6p 3.75 x 5 0.1 veroboard

145p 2,5 x 1 0.1 veroboard495p 3 x 2 x 1 aluminium box

30P 6 x 4 x 2 aluminium box15p Miniature 606, 909 transformer42p TI L111 optoisolator65p 4 self adhesive feet .

40p SRB Soldering iron .

16p Desoldering tool .

52p16p12p22P70p99P21p82P990

110P80p202

430p550p

LINEAR741 18p747 70p748 40p7106 850PGA3046 70pCA3080 75pCA3130 100pCA3140 60PLF347 170pLF351 45pLF353 90pLF356 95PLM301A 30pLM318 85p

LM324 52pLM339 550LM348 100PLM377 170pLM378 230pLM380 80pLM381 140pLM382 120pL M386 90pLM387 1200LM1458 400LM1830 180pLM3900 60PLM3909 72pLM3911 1209LM3914 320pLM3915320P

511

MM57160 650pNE531 140pNE555 23pNE556 60PNE567 120pRC4136 100pSN76477 230pTBA800 80PTBA810 110pTDA1022 630PTL081 45pTL082 85pTL084 1259XR2206 390pZN414 80pZN425E 475p

CMOS

40014002400640074011401340154016401740184020402240234024

25p25p95025030p45p85p48p80p90p

110p100P

25p60p

402540264027402840294040404240464048404940504052406040664068406940704071

25p150p

50p90P

110P110p

85p110P60P50p50P80p

120963p25p25p25p25p

4072408140824085409340954510451145184520452745284532454345834585

25p30p30p85p809

110P900

100P90p

110p165P100p125P170P

80P115P

SKIS8 pin14pin16pin18pin20Pin

Low ProfileTexas

9p 22pin 20911p 24pin 22P12p 28pin 26p16p 40Pin 38p18p

Our new catalogue is now available. It contains 100 illustratedPages detailing over 3000 line items. Send 5013 for your copy,Y-iu will recieve. A reply paid envelope. A Mail Orderform to facilitate rapid despatch. A 500 Discount voucher,All prices include VAT.Please add 50p carriage on all orders below E15.00.

21\.. Srtem

NSA

:1) -Access & Barclaycard welcomeimNek"..Sales office 01464 5770. Fie, '--

Road,76 College Road, Bromley, Kent BR111DE.

PACKS

opTO0.125in. 0.2in.

Red TIL209 TIL220 10p4).));, Green TIL211 TIL221 16p

-21 Yellow TIL213 TIL223 16PClips 3p 3pDL704 0.3in CC 130pDL707 0.3in CA 130pFND500 0.5in CC 100p

CAPACITORS TANTALUM BEAD

0.1, 0.15, 0.22. 0.33, 0.47, 0.68, 1and 2.2u F @ 35V4.7, 6.8, 10uF @ 25V22@ 16V, 47@ 6V, 100 @ 3VPOLYESTER (Mullard C280 series)0.01,0.015, 0.022, 0.033, 0.047, 0.10.15, 0.220.33, 0.47RADIAL LEAD ELECTROLYTICS

12p20p26p

6p8P

12P

63V 0.47 1.0 2.2 4.7 10 7p22 33 47 9p

25V 10 22 33 47 7p100

470

Specially designed packs intend-ed for development work at aconsiderable saving.

)).w resistors. 10 of each value 4.7ohm to 1 Mohm.a total of 650 resistors. 530p each.)4w resistors. 10 of each value 4.7ohin to 1 Mohr,a total of 650 resistors. 875p each.Presets. Pack of 5 of each value from 100ohms to1 Megohrn. a total of 65 presets. 390p each.LED's. Pack containing 10 of each colour LED0.2 size. Total of 30 Led's clips. 450p each.Zeners. Pack of 5 of each value from 2V7 to 33VA total of 130 zeners 880p each. 1000

9P20032p

Recommended for: Civil De -

DANGER from RADIATION Bere

WITHURppared O RADIATION DETECTOR fence, Fire, Police, Hospital

& Medical use

General Information:Pocket dosimeters provide an accurate, reliable

and immediate method of measuring the integrateddose of radiation received by those exposed toionising radiation. The dose may be read at any timeand in any place, providing a source of light isavailable.

Principle:The dosimeter is an ionisation chamber type using

a quartz fibre electroscope as the indicating element.'A microscope is used to project the image of themoving quartz fibre element on to a graticule scale.The quartz fibre is mounted on a wire electrode, whichin turn is supported by a high quality insulator. Whenthe instrument is charged, positive charges distributethemselves over the wire electrode and quartz fibrecausing the fibre to bend away from the electrode. Thefibre will take up a position depending on the amountof charge on the system.

When the surrounding air in the ionisationchamber is ionised negative ions will be attracted tothe positively charged electrode thereby reducing itscharge. The resulting fibre movement will be relateddirectly to the quantity of radiation producing theionisation. The fibre movement can thus be calibrateddirectly in roentgen units and the rate of movement ofthe fibre will be proportional to the roentgens receivedper unit time

Construction:The microscope electroscope and ionisation

chamber are housed in an outer skin which may be ofbrass or aluminium At one end of the tubular case isfixed a charging assembly. and at the other aneye -piece window These two assemblies are solderedinto the outer case to ensure a hermetic seal.

Each dosimeter is provided with protective end captranslucent window so that the cap need not beremoved for reading.

Dosimeters meet vibration, drop, salt sprayhumidity, water immersion and temperature tests.

Features:

These units will read automaticallythe amount of radiation in the air

This instrument is only a little largerthan a fountain pen

Clips on to your top pocket

Weight less than 3 oz.

Contains three lenses

Fully charged, tested and guaran-teed, Refurbished by us

British design and manufacture,rugged construction

Manufacturer's list price of similarmodel is over £25

Buy now whilst stocks available.Delivery by return post

BE PREPARED, EVERY HOME SHOULD HAVE ONE

SECTIONAL DRAWING I -

Protective cap

Marker sleeve

Pocket clip

Microscope body

Ionisation chamber

Capacitor

Protective cap(Captive)

t.

ACTUAL SIZE. 115 x 14mmWindow

Eve tens

Graticule

Field lens

Case tube

Objective lens

Ouartz fibre

Electrode

1/ri

ALL YOURS FORONLY

£10.95Incl, post paid

Charging belle,

TWOFREE

RE -CHARGE

VOUCHERSWITH EVERYDETECTOR

Manufacturer s current list price similar model is over £25

DONDENE LTD. r- ;.

Phone (01) 723 1008/9404 Edgware Road, London W2, England I.E.D. -- -4

Supplied complete withData and Information onradiation and detectors.

All units are checked and tested justprior to despatch by first-class mail inproper protective packing.

VIEWTHRULENS


Clever DickWorried about hard -to -get servicemanuals, troubled by ultrasonic recordplayers? Your worries are over asClever Dick attempts to answer someof your weird and wonderful questions.

OUR FIRST LETTER this month comesfrom a Welsh Flasher. Mystified? Wellread on:

Dear Seedy,A few questions:

1. Will the Flash Trigger project (Julyissue) work on the external trigger socketof the motor drive unit of my Nikon FE?2. Could you design a Time -Lapsephotography project? The Nikon Inter-valometer is rather prohibitive at f325.3. How about a slide projector dissolveunit?4. And a tape/slide synchroniser to workwith the dissolve unit.Thank you for reading/publishing thisletter and also for the excellent mag.P.S. Thanks also for the Binder.

P K RobertsNew Quay, Wales

Seedy?? Well, it's original. Now, aboutyour Nikon, I've checked the officeBrownie only to discover it doesn't havea motor drive. We're not rich enough toafford a Nikon so at a guess I'll have tosay no. The Flash Trigger was designedto operate an electronic flash gun. I

assume you want the camera to wind onafter each exposure. This may or maynot involve mucking about with themotor drive unit's innards so unless youwant to take a chance on ruining it I'dleave it well alone. If anyone else hassome thoughts on this matter we wouldbe pleased to hear from them.

Your idea for a time-lapse unit soundsmost interesting, it has been passed onto the project department. The slideprojector dissolve unit is easy, howabout a large tub of very strong Sul-phuric acid, no? OK that was just a littlejoke (very little), that idea and your sug-gestion for the synchroniser have allbeen passed on. One last point, youmust be extremely rich to own a Nikonso you can buy your own Binder, thecheek of this man!

David Clark starts his letter in a muchmore promising manner, a definite can-didate for the Binder of the month.

Dear Richard -The -Intellectual,I am planning to build the Car Booster

and Equitone but as my cassette playerhas a rather insensitive volume control Iam wondering if I could modify thebooster with a pot in series with R1, if sowhat value would you suggest?

A quick point concerning the CBmonitor offer in the August issue, I seemto remember that it was illegal tomonitor transmissions on 27 MHz, if thisis not the case how about a circuit for aconverter?

David CarleStrathaven

Your problem with the insensitivevolume control should disappear withthe Booster in circuit. You could put apot in series with R1 but I suspect thatyou won't need to. The CB monitor istechnically illegal if if is used to monitorillicit transmissions, listening to Policebroadcasts also comes under thisheading. If you use it to monitor RadioControl or foreign CB you should beOK.We have actually got a circuit for a CBmonitor but the parts alone wouldcome to more than £11.50!

Do you remember Adrian Hallas's letterin the August CD? He wanted to know ifultrasonics could be used to replace themechanical stylus on a record player.We asked for comments, here's onefrom Paul Fletch.

Dear CD,Concerning Adrian Hallas's letter

about playing records by ultrasonics, I'msorry to put the damper on it but theresolution of a system using normalultrasonic sound would be far too low,for the following reasons:

Say 100 kHz (and that's rather high)and the speed of sound around 300metres per second.

Now:velocity = frequency x wavelength.

So wavelength mm3000

The resolution of a wave system (eg lightin an optical microscope) is always less

than the wavelength. So the smallestdistance that can be judged is larger than3 mm - which is far too large. A higherresolution can only be obtained with im-practically higher frequencies, sorry.

Paul FletchWatford

That sounds like fairly logical reasoning,we have heard of ultrasonic micro-scopes though the frequency is into themegahertz and gigahertz region. itlooks as though the Ultrasonic RecordPlayer idea is doomed to failure.

As you can imagine we get hundreds ofletters each month, and many goodones have to go unanswered. We'llfinish off with some abbreviated ver-sions of the more urgent questions butplease try to keep your letters as shortand to the point as possible.

Where do you get those 'chunky' PP3battery clips?

Steven Turner.Gwynedd

Any of the larger mail-order companies,Watford, Mapl in, Stevenson etc.

Where can I get a service handbook foraSingle Beam Oscilloscope Model MSB100?

Jim McMahonManchester

Try Austrec Ltd, 76 Church Street,Larkhall, Lanarkshire ML91 EH. Send anSAE for their list.

Where can I get a 1R106 thyristor orequivalent?

Robert EwingCoventry

The I Rstands for International Rectifier,any 106 device will do, eg. C106 etc,these are obtainable from any of themail order companies previously men-tioned.

That's it again for another month,thanks for your letters, see you in fourweeks. HE


THREE FOR FREEFROM CS

EXPERIMENTOR BREADBOARDSNo soldering modular breadboards, simply plugcomponents in and out of letter number identifiednickel -silver contact holes. Start small and simplysnap -lock boards together to build a breadboard ofany size.All EXP Breadboards have two bus -bars as an integralpart of the board, if you need more than 2 busessimply snap on 4 more bus -bars with the aid of an EXP4B

EXP 325 £1.60 The ideal breadboardfor 1 chip circuits. Accepts 8, 14, 16 andup to 22 pin ICs. Has 130 contact pointsincluding two 10 point bus -bars.

EXP 350 E3.15 Specially designedfor working with up to 40 pin ICsperfect for 3 Et 14 pin !Cs.Has 270 contact points including ,two 20 point bus -bars.

it

11::111

EXP 300 E5.75T hemost widely boughtbread -board in the UK.With 550 contactpoints, two 40 pointbus -bars, the EXP 300 will accept any size IC and upto 6 x 14 pin DIPS Use this breadboard withAdventures in Microelectronics.

EXP 600 £6.30 MostMICROPROCESSORprojects in magazinesand educational booksare built on the EXP 600.

1

EXP 650 E3.60 Has .6"centre '''''spacing so is perfect for °MICROPROCESSOR applications.

EXP 4B E2.30 Fourmore bus -bars in"snap -on" unit

The above prices are exclusive of PEW and 15

THE CSC 24 HOUR SERVICETELEPHONE (0799) 21682

With your Access, American Express,Barclaycard number and your

order will be in the post immediately

CONTINENTAL SPECIALTIES CORPORATION=0C.S.C. (UK) LTD Dept. 14PPUnit 1, Shire Hill Industrial Estate,Saffron Walden, Essex CB1 1 3AQ.Tel: Saffron Walden 10799) 21682 Telex: 81 7 4 7 7

Available from selected stockists

ELECTRONICS BY NUMBERSNo. 7 DIGITAL DICERoll the dice - the electronic way! Thedigital dice gives you an instant scorerandomly chosen from 1 to 6, every timeyou press the button. No losing this underthe table!No. 8 QUIZ MASTERPlay your own 'Sale of the Century'! Up tofour contestants pit their wits; the first oneto get the answer lights up his 'win' light,and stops anybody else from having a go.No. 9 MOVING TARGET GAMETest your reactions! A moving 'line of light'travels along from left to right, over andover again. You've got to 'fire' at just theright moment to score a hit. Fun for all thefamily!Want to get started on building excitingprojects, but don't know how? Now usingEXPERIMENTOR BREADBOARDS andfollowing the instructions in our FREE'Electronics By Numbers' leaflets,ANYBODY can build electronic projects.For example, take one of our earlierprojects, a L.E.D. Bar Graph;[114.1.Th'P., r 0

111

I:', '?O ": '1./

it:5.413CIZ/ -01211.

DIRplayUP

You will need; One EXP 300 or EXP 350breadboard, 15 silicon diodes,6 resistors, 6 Light Emitting Diodes.Just look at the diagram, Select R 1, plug itinto the lettered and numbered holes on theEXPERIMENTOR BREADBOARD, do thesame with all the other components,connect to the battery, and your project'sfinished. All you have to do is follow thelarge, clear layouts on the 'Electronics byNumbers' leaflets, and ANYBODY can builda perfect working project.

betss -

oectronIcNi

Nuni No

proiects °

For full detailed instructions and layouts ofProjects, 7, 8 and 9, simply take the couponto your nearest CSC stockist, or send directto us, and you will receive the latest'ELECTRONICS BY NUMBERS' leaflet.

If you missed projects, 1, 2 and 3, or 4, 5and 6, please tick the appropriate box in thecoupon.

PROTO-BOARDSThe ultimate in breadboards for the minimum of cost.Two easily assembled kits.

PB6 Kit, 630 contacts, four 5 -way binding postsaccepts up to six 14 -pin Dips.PROTO-BOARD 6 KIT E9.20

PB 100 Kit complete with 760 contacts accepts up toten 14 -pin Dips, with two binding posts and sturdybase. Large capacity with Kit economy.PROTO-BOARD 100 KIT 01.80- - - I T' S EASY WITH C.S.C.

TO RECEIVE YOUR FREE COPY OF PROJECTS 7, 8 and 9I Just clip the coupon For immediate action

The C.S.C. 24 hour, 5 day a week service.Telephone 0799 21682 and give us your Access,American Express or Barclaycard number and yourorder will be in the post immediatley

Give us your name and full postal address lin block

I capitals). Enclose cheque, postal order or credit cardnumber and expiry date, indicating in the appropriateboxlesl the breadboarells) you require.

I

III

II

I

EXPERIMENTORBREADBOARDS CONTACT

IC CAPACITY14 PIN DIP

UNIT PRICE INCP&P Et 15% VAT

Otyreo

EXP 325 130 1 f 2.70EXP 360 270 3 E 4.48

EXP 300 550 6 E 7.76

EXP 600 f 8.39

EXP 660 270

use won0 6 Pact,

Dps StpoBus Bar

f 5.00

EXP 48Four 40 Point

Bus Bars.f 3.50

PROTO BOARDS

P88 630 6 01.73P8100 76() 10 04.72

ADDRESS

I enclose cheque/P.O. for EDebit my Barclaycard, Access,

American Express card No.

Expiry date

If you missed project No's1, 2, 3, 4, 5, and 6, tick box.For Free catalogue tick box

C.S.C. 1UKI Ltd. Dept.14PP, Shire Hill Industrial Estate Unit 1, Saffron Walden, Essex CB11 3AQL Tel: Saffron Walden 107991 21682 Telex: 817477

1II

NAME

III

II

I


COMPUTER WAREHOUSSCOOP PRINTER PURCHASE

PROFESSIONAL EQUIPMENT AT HOBBYIST PRICESSO LOW EVEN OUR COMPETITORS GASP!

TELETYPE ASR33I/O TERMINALS

ICL TERMIPRINTER300 BAUD TERMINALS

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Fully fledged industry standard ASR33 data ter-minal. Many features including: ASCII keyboardand printer for data I /0, auto data detect circuitry,RS232 serial interface, 110 baud, 8 bit paper tapepunch and ready for off line data preparation andridiculously cheap and reliable data storage. Sup-plied in good condition and in working order.Options: Floor stand E12.50 + VAT

Sound proof enclosure E25.00 * VAT

THE CHIPS ARE DOWN

MOSTEK, INTEL, NEC, MOTOROLA

I.C. PRICES SLASHED!

A massive purchase of brand new"state of the art" data processingequipment enables us to offer thefollowing chips at never, and we mean

never to be repeated prices.8085A Central Processor E11.998155C 256x8 Static Ram E11.95

8253C Programmable Interval Timer 8.958255A Programmable Peripheral Interface E9.958259A-8 Programmable Interrupt Control £4.758755A 2Kx8 Eprom 16 1 /0 Lines 34.50MC6850P ACAI £3.752652 MPCC Comms. Controller £24.002102 1K Static 650ns Rams 8 for £5.251 702 256x8 Eprom E3.755101L-1 256x4 Static Ram 450ns £4.95

And Remember All Chip Prices Include V.A.T.

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P C137s [proms supplied washed.

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Made under licence from the world famous GE Co.The ICL Termiprinter is a small attractive unit withso many features it is impossible to list them in thespace available! Brief spec. as follows; RS232serial interface, switchable baud rates 110, 150,300, 130 cps), upper and lower case correspond-ence type face, standard paper, almost silent run.ning, form feed, electronic tab settings, suited forword processor applications plus many morefeatures. Supplied in good condition and in working order. Limited quantity.

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7486 34p 74LSt64 110p7400 10p 7420 17p 74LS86 35p 74166 120p74S00 25p 74S20 18p 7490 28p 74170 235p74LSOO 15p 74LS20 19p 7493 28p 74172 445p7401 12p 74H21 20p 7495 65p 74173 110p7402 12p 7425 30p 7496 60p 74174 85p74S02 14p 7427 34p 7497 175p 74LS174 105p74LS02 15p 7428 35p 74107 32p 74175 80p7403 14p 7430 17p 74109 50p 74180 92p74503 16p 74LS30 20p 74S112 90p 74181 150p7404 14p 7432 28p 74S114 45p 74LS182 90p74H04 16p 74LS32 28p 74116 195p 74190 85p74LSO4 15p 7438 35p 74118 75p 74191 85p7405 18p 74LS38 35p 74121 28p 74193 85p7406 32p 7440 17p 74122 41p 74LS193 95p7407 32p 74S40 19p 74123 45p 74194 85p7408 17p 7441 65p 74LS123 60p 74197 75p74LS08 22p 7442 55p 74125 53p 74198 140p7410 15p 7447 45p 74128 72p 74LS266 95p74H10 17p 7450 17p 74132 68p 74283 155p74LS10 19p 74LS51 22p 74148 103p 74284 400p74LS11 38p 7454 17p 74150 98p 74285 400p7413 30p 74LS54 23p 74151 60p 74298 180p7414 50p 7470 33p 74LS151 100p 74366 95p7416 27p 7472 28p 74153 65p 74393 195p

* RAM AND EPROM STAR OFFERS *2716 Single 5v rail EPROMS £10.252716 Three rail EPROMS £ 8.502708 EPROMS £ 4.95411616k x 1200 n s RAMS 8 for £28.50

32K x 8 DYNAMIC/STATIC RAM CARDSA masterpiece of electronic engineering and our own advantageousbuying enables us to bring you a complete memory system at a give-away price. Originally made for a large processor the RAM card hasmany features, including on board refresh, internal parity generationand checking. Standard TTL inputs/outputs, + 5, + 12, -15vsupply rails and its effective STATIC capability make it useable withmany CPU's. A fast cycle time of approximately 400ns make this asnip at only £90.00+ £3p & p. Supplied complete with circuits.

Amazing value mixed semiconductors, includetransistors, digital, linear I.C.'s, triacs, diodes, bridgerats. etc. etc. All devices guaranteed brand new, fullspec. with manufacturers markings, fully guaranteed

50 + BAG E2.95 100 BAGS £5.15

MUFFIN FANSKeep your equipment Cool and Reliable with our tested ex equipmentMuffin Fans' almost sileni running and easily mounted. Available in

two voltages. 110 V.A.C. 5.05. pp 05p OR 240v A.C.06.15 pp65p DIMENSIONS 4i a 4E

ELECTRONICCOMPONENTS

EQUIPMENT 66%DISCOUNT

Due to our massive bulk purchasing programmewhich enables us to bring you the best possiblebargains, we have thousands of I.C.'s, Transistors,Relays, Cap's., P.C.B.'s, Sub -assemblies, Switches,etc. etc. surplus to our requirements. Because wedon't have sufficient stocks of any one item toinclude in our ads., we are packing all these itemsinto the "BARGAIN PARCEL OF A LIFETIME"Thousands of components at giveaway prices!Guaranteed to be worth at least 3 times what youpay plus we always include something from our ads.for unbeatable value!! Sold by weight

2.5kis £ 4.75+pp £1.25 Skis f 6.75+pp £1.8110kIs £11.75+pp £2.25 20 kis f19.99+pp £4.75

* SHUGART SA800 *8" Floppy Disk Drives

as new £225.00 + VAT

DISPLAY I C ANDTRANSISTOR BARGAINSNEVER CHEAPER

All I. C s and Transistors bywell known manufacturers and fullyguaranteed. No fall outs. Comprehensivedata on I. C 's 15p per type.2N4351 N channel MOS FET2N4352 P channel MOS FET60p each El .00 per pairHIGH VOLTAGE NPN POWERSWITCHING transistors BVcbo 600vBVceo 500v BVebo 15v lc 5 ampsPc 125 watts HFE 60 typ ft 2.5 mhzideal invertors, etc TO3 El 60 each4 for E5.40.BF258 NPN 250v @ 200ma 45p each3 for El .08.I.R. BSB01 2.5 amp 100v bridge rec.P C. mount long leads 35p each 4 forEl 08.IN4998 4 amp 100v P.C. mount diodeslong leads 14p each 10 for f 1 10LM309K + 5v 1.2 amp regulator El 10each 6 for E5.35AGFACIOcomputergradecassettescom-pietewithlibrarycases68peach,10forE5.50IN4004 SD4 1 amp 400v diodes ipeach 18 for f 1 00I.R. 12 amp BRIDGE RECS. 400 voltf I 25 each

POWER DARLINGTON SCOOP.kV 000 NPN 60v 90w 8 amps T03 95p each2M63135 NPN so, 100w 10 amps TO3 f 1 25 each144.14030 11501 60v 150w 16 amps 103 02 25 each

S.C.R.'s2143001 30r 350 ma T018 22p each 6 for f 1.002115061 60v 8U0ma TO18 27p each 4 for f 1 00

2111441 50,13 amps 10220 45p each 10 for f 4 00C10601 400r 5 amps T0202 55p each 10 for f5 00

TRIALSG.E. 12 amp 600v 1022048 95p each 10 for fB 75

III amp 400v made mounted on 2} I 21heatsink f 101 each 4 for I] 75

LOW PROFILE I.C. SOCKETS8D.I.L.10p each 12 for fl 00

14 0 I 14p each B for f 10016 0.1 L Gold Plated mil grade 22p each 6 lot22011.2Ip each 5 forf 1 0024 0 It 35p each 3 for LI 0040611.80p each 2 for f1.00

OTHER GOODIES2113055 (RC A r 65p each2115943 RI output 40 volt. I wan up to MAWT.0.5 550 each Al for MOO

254304 WN720 F I T transistor 37p each 3 for f 1 00

LM3SOWSL5051 14 0 I L 2 watt A F amp BOp

each 8 far f6 00CA30288 OC 120 MHZ differential cascade ampft 00 each 3 for 0250CA3011 20 MHZ wideband amp 7099 case 65peach 2 for 01 0041114S3114 OVAL MOS 128 Oil static shift reg DC25 MHZ f 150 each I10, f 4 25

6E421 zero voltage switch. !riot SCR relay dower705 can f 1 10 each / for f6 50

1.91384 5 Watt audio I.C.s 01.50 each 10 for 011.00

FP133125 4 NPN 50v 500ma transistors in la: L pack /Op each 2 for II 00

BARGAINS GALORE!In our walk round Warehouse

NOW open Monday to Saturday 9.30-5.30

ELECTRONICSDept. H.E. 64-66Melfort Rd., Thornton Heath, Surrey MAIL ORDER

Telephone 01-689 7702 or 01-689 6800 INFORMATIONUnless otherwise stated all prices inclusive of VAT. Cash with order Minimumorder value E2.00 Prices and Postage quoted for UK only. Where post andpacking not indicated please add 40p per order. Bona Fide account ordersminimum E10.00. Export and trade enquiries welcome. Orders despatchedsomeday where possible. Access and Barclaycard Visa welcome.

SUPERVALUE P.C.B. SPECIAL

Another great buy. Board contentsinclude 62 Digital I.C.'s all located in 14pin D.I.L. sockets. Original cost over £90,our price only £4.95 + pp 65p

POWER SUPPLY UNITSBuilding a system? Then your P.S.U. require-ments stop here) Removed from brand new firedamaged front end processors originally costingseveral thousands of pounds each, these sup-plies feature 1980's technology includingswitching regulators. Fully smoothed and regu-lated continuous outputs of: + 5v @ 15 amps,+ 12v @ 3 amps, and -12v @ 3 amps all on a

P.C. B/heatsink measuring only 12- x 7.5- x 2.5Supplied complete with circuit, transformer andeasily removed smoke marks! £34.95 + £2.50 car.

KEYBOARDS* LOW PRICE CHASSIS *

al1a 11111111111111111110111111111MIla 4-

o special bulk purchase enables us to offer the above keyboard at a

lowest ever price 49 coded keys encoded into a direct TTL compatible7 bit output. Features such as delayed strobe 5 volt 0 C single railoperation and rollover protection make this an absolute must for theMPU constructor, Supplied complete with connection diagram and edgeconnector. at a secondhand

"no time to test" f2 0.00 + P.P. £1 .60price of only

SUPER CASED VERSION Same as above spec but housed in attractivetwo tone moulded free standing case. Unit also includes an all TTL parallelto serial convertor inn details/ etc

1E27.50 + P.P. £1.85

TOROIDAL TRANSFORMERS

PR 240v ph sec 15 0 15 @ 2 amps dimensions 3 s 2i fl 95.p p 99pTM 240v 110v pit sec 15 0 15 Bv4 dimensions 2} 1 fl 95.p p 30p

All voltages measured off load

Plugs, Sockets ft Connectors Cannon "D" Range

Ways9

152537 E2.35 £4.1450 £2.90 £5.46

25 way ex -equip. plug or socket E1.25

Edge connectors, gold plated0.1 DS 85 way £3.990.1 'DS 45 way £2.450.15 DS 56 way E3.250.1 56DS 36 way £2.00

All connectors easily cut to size1000's of other connectors ex stock

Plug SocketE1.03 E1.26£1.17 £2.01£1.72 £2.58

9UPeR153NE.NIV

ar9.Top of all systems

tested by independentnational authority

July -r9

C300 I ES200high performance electronic ignition,to add power,economy, reliability, sustained smooth peak perfor-mance, instant all weather starting, to your car.Surefire has sold in its thousands in ready made form from bigname accessory firms, but 'Os now available in quality kit form to fit allvehicles with coil ignition up to 8 cylinders.

ES200. A high performance inductive discharge ignition incorporatinga power integrated circuit (special selection): electronic variable dwellcircuit (maximises spark energy at all speeds): pulse processorlovercomes contact breaker problems). Coil governor (protects coil).Long burn output. Negative earth only. Compatible with all rev counters

C300. In it's ready built form (C30001 it came top of all systems testedby an independent national authority July' 79. A high energycapacitive discharge ignition incorporating a high output short circuitproof inverter, top grade Swedish output capacitor, pulse processorcircuit, transcient overload protection. Fast rise bidirectional outputideal for fuel injection, sports carburation, oily engines. Compatible willmost rev. counters. (Low cost adaptors available for rare cases.Application list enclosed with each kit. Note: Vehicles with Smiths.Jaeger rev. counters code RVI on dial will require adaptor type ICI).

What's in the kits. Suref ire's own precision anodised aluminiumextruded case. P.C. mounted security changeover switch, staticliming light. Special selection Motorola semi -conductors. Capacitors,resistors etc selected after 5 years experience. Glass fibre pcb, soldercomplete down to last washer.Fully illustrated comprehensive instructionsand full technical back up service.

Suretron Systems (UK) Ltd. Dept. HE7

Bayer Buildings, Lower Bristol Road, Bath, BA2 3EF. Tel. Bath (0225)332317

Address

PI, Me' order with Aeer.n Bdtt duiVAT P & P int

Quantityre,111Ired

ES200: Neg 4: £13-94 01.95C300: Pus -1-1.- £L2'95 £15.95

C300: Neg 1 f11-95 f15.95

Tacho Adapt. TC1 f 3.90

/ VIICIUSC

chi,/ PO

Ch,/ Nu

First the EuroBreadBoardNow the EuroSolderBoard

a'0oat

, \Ne

ok-c3oe

lndispensiblefor the professional

9is

4,1', Ideal

for the beginner

Design on a EuroBreadBoard - Instal on a EuroSolderBoard

First the EuroBreadBoardWill accept 0.3" and 0.6" pitch DIL IC's, Capacitors, Resistors,LED's, Transistors and components with up to .85mm dia leads.500 individual connections PLUS 4 integral Power Bus Strips alongall edges for minimum inter -connection lengths.All rows and columns numbered or lettered for exact locationindexing (ideal for educational projects)Long life, low resistance (<10m ohms) nickel silver contacts£6.20 each or £11.70 for 2

Now the EuroSolderBoardNew 100mm square, 1.6mm thick printed circuit board with pre -tinned tracks identically laid out, numbered and lettered to Euro-BreadBoard pattern.Four 2.5mm dia fixing holes.£2.00 for set of three ESB's

And don't forget the EuroSolderSuckerIdeal for tidying up messy solder joints or freeing multi -pin IC's, this195mm long, all metal, high suction desoldering tool has replaceableTeflon tip and enables removal of molten solder from all sizes ofpcb pads and track. Primed and released by thumb, it costs only£7.25 including VAT & PP

Snip out and post to David George Sales,Unit 7, Higgs Industrial Estate, 2 Herne Hill Road, London SE24 OAUNowa immaima =mammas ation IIIIMMMEIMII =IMP

David George Sales, HE10Unit 7, Higgs Ind. Est., 2 Herne Hill Rd., London SE24 OAU.Please send me: -

1 EuroBreadBoardor 2 EuroBreadBoardsor 3 EuroSolderBoardsor 1 EuroSolderSucker

@ 6.20@ £11.70@ E 2.00@ £ 7.25

00 Please

0 Tick0

All prices are applicable from Jan. 1st 1980 and include VATand PP but add 15% for overseas orders.

Name

CompanyAddress

Tel. NoPlease make cheques/P.O. payable to David George Salesand allow 10 days for cheque clearance and order processing


HE NOBELL

. . .

0

Nobel!DoorbellRing in the changes with this revolutionary design that faithfully reproduces the noise ofthose old time door knockers.

GLANCE THROUGH THE newspapersand it seems that almost every dayanother field of human activity hasbeen taken over by the relentless marchof the microprocessor. It's obvious thatthere's no limit to man's ingenuity forcomputerising anything and everything,no matter how trivial. Not even thehumble doorbell has escaped, and youcan now have the arrival of a visitorbrought to your attention with a blastof almost any popular tune you fancy.

Knock Knock ...

Although we at HE don't exactly disap-prove of this electronic takeover bid (itkeeps us employed), we feel a bitnostalgic for the good old days whenyou made your presence known to ahouseholder by banging away on ahuge brass knocker. So we've combin-ed the past and the present in the formof the HE Nobell, an electronicdoorknocker. The Nobell's a prize-winning design that won't leave you inpeace (OK, don't turn over the page, wepromise not to do it again).

The audio generator is built arounda single transistor oscillator. When itreceives a trigger pulse it produces a'boing' noise which can be tailored toresemble a knocking sound. Othersounds are possible as detailed in thesetting -up procedure below. The soundis amplified by a standard LM380 audiopower amp IC, a chip which should befamiliar to regular readers of HE.

The rest of the circuit is there toprovide a set of five triggering pulses

for the audio generator from the singlepulse caused by pressing the pushswitch on the front door. This is doneby a tone burst generator, a fairly stan-dard electronic circuit. Two 555 -typetimer/oscillators are connectedtogether, one wired as a monostable(i.e. it produces only one output pulseof fixed length) and the other as anastable (it produces pulses as long as itis turned on). The push switch turns onthe monostable which then turns onthe astable. This results in a burst ofpulses at the output. Normally the fre-quency of the tone is in the audiorange and it is used for testingamplifiers and loudspeakers. In thisproject we use a very low frequency togenerate our set of knocks.

Power can be obtained from anyAC or DC supply in the 6 V to 12 Vrange. If a DC supply is used it may beconnected either way round becauseof the steering action of the bridge rec-tifier D3 - D6.

ConstructionConstruction of this project isstraightforward, especially if you useour printed circuit board. Make theusual careful checks to ensure that theICs, electrolytic capacitors and the tran-sistor are soldered in the right wayround. How you case the project islargely up to you. As the photographsand overlay show, we mounted thePCB and loudspeaker in a verobox andconnected the input leads to aminiature jack socket. The wires fromthe push switch were terminated in a

matching jack plug. Connect up thepower and you're ready to set up thecircuit. If you are using this project toreplace your existing doorbell then youcan make use of the existing belltransformer and push switch.

Setting Up and CustomisingRV1 is adjusted to set the correctoperating point for the Q1 oscillator,and should be turned until oscillationsoccur only when a trigger pulse isreceived. However,the exact position.depends on your own personal taste.The sound can be varied from a short,sharp tick, through a sound resemblinga knock, to an extremely good imper-sonation of a bongo drum.

Further alterations can be made bychanging component values. Asalready mentioned, the number ofknocks depends on the time period ofthe monostable and the frequency ofthe astable. In our circuit, these are setat half a second and ten Hertz respec-tively, so there will be five knocks. Themonostable period is set by R3 and C2and increasing either of them lengthensthe time of operation. The astable fre-quency is set by R5, R6 and C5 and ifone or more of them is decreased the'knocks' will come faster.

If you decide to use the bongosound, then you can vary the pitch byaltering the values of C7, C8 and C9 inthe twin -T filter. The same approximateratios between the capacitors shouldbe maintained - for example if youhalve their values (to 4n7, 4n7 and 10n)then the pitch of the bongos will bedoubled.


Internal view of the Nobell, note position of the speaker.

When the push switch on the door is pressed,the brief pulse that is generated must be stretch-ed out to operate the rest of the circuit. This isdone by one half of IC1, a dual 555 -typetimerloscillator. This half (pins 1-6) is connectedas a monostable multivibrator i.e. a pulse of fix-ed length appears at the output (pin 5) whenevera trigger pulse from the push switch is receivedat the input (pin 6). The length of the outputpulse is determined by the values of C2 and R3.

The other half of IC1 (pins 8-13) is wired as anastable multivibrator, or oscillator. It producesa square wave at pin 9 whenever the output

How it Workspulse from the monostable forces pin 10 (enableinput) high. The frequency of the square wave isdetermined by the values of R5, R6 and C5. Thesquare wave passes to the sound generator viaC6 and D2.

The sound generator circuitry is a 'twin -T'type sine -wave oscillator. Q1 is an amplifierwith a twin -T filter in its feedback loop (R9, R10and C9 form one 'T' and C7, C8 and RV1 formthe other). If the loop gain of this circuit isgreater than one, oscillation occurs at the reso-nant frequency of the filter. RV1 is adjusted sothat Q1 is just on the verge of oscillation - a

=Parts List=RESISTORS (all 1/4W, 5%)R1,2 8k2R3 2M7R4 10kR5,6 680kR7,11 15kR8 22kR9,10 47kR12 2R7POTENTIOMETERSRV1 100k linear horizontal miniature

presetCAPACITORSC1,7,8 10n polyesterC2 220n polyesterC3,4,5,10,11,12 100n polyesterC6,9 22n polyesterC13 47u 25V PCB -mounting

electrolyticC14 1000u 25V PCB -mounting

electrolyticC15 100u 25V axial electrolyticSEMICONDUCTORSIC1 556IC2 LM380D1,2 1N4148D3-6 1N4001Q1 BC109MISCELLANEOUSPCB, push switch, loudspeaker (.?_- 8 ohms),Verocase.

pulse via D2 will force the oscillations to startbut they quickly die away. This makes a 'bong'type of sound.

The signal is amplified by audio amplifierIC2, and LM380, and fed to the loudspeaker.

The power supply is not at all critical. An ACsupply rectified by diodes D3 - D6 and thesesame diodes mean that a DC supply can be con-nected either way round. The supply is smooth-ed by capacitor C14 and additional decouplingof the supply to IC2 is provided by C12 and C13.

DI

lOn

2M7

C2220n

IC1

10 11

13

9

C3100n

Figure 1. Circuit diagram of the HE Nobell

68

C4112/On

°SOF

R6680k

C5100n

C6

1122

RV1100k

C922n

C10100n

00n

C141000,,

NOTE:ICI IS 556IC2 IS LM380151,2 ARE 194148D3 -5 ARE 19400101 IS BC109

SPKRAIR

gr:, a12 VOLTSAC


Nobel! Doorbell

TO PUSHSWITCH

es ese

RIF' Girl(4.1"AND

RV1

...........

III= .7=1:MNI,)

JACKSOCKET

JACK PLUG

OBELL PUSH

Figure 2. Component overlay and wiring diagram.

R11

b

C11

O

C12

C13

E 1111

53

TO 8R0LOUDSPEAKER

FROM BELLTRANSFORMER

BuylinesNo problems are foreseen in obtaining any ofthe specified components at your neighbour-hood electronic supermarket. An approxima-tion of the cost of components (with the usualexception of case and PCB) comes to £7.50.

HE

[i PETITEMINIATURE DRILLS AND ACCESSORIESfor all your modelling needs

-a=

A choice of three powerdrills that fit snugly in thehand, so light they enableyou to carry out the mostintricate tasks - drilling,shaping, cutting, polishing,etc., in the minimum oftime.There are two types of drillstand, plus all the necessaryaccessories in a range thatfills every need.Send 9" x 4" S.A.E. for fulldetails.

See them on STAND No. 87,MODEL ENGINEER EXHIBITION,Wembley, Jan. 1 to 10, 1981.

Sole UK Distributors PRECISION PETITE LTD., Dept. H.E.

119a HIGH ST. TEDDINGTON, MDX.Tel: 01-977 0878


* POWERFET AMPLIFIERS *Conservatively rated, high quality

designs with substantialheatsink / mounting bracket

CA3080E 70pCA3140E 45pMC3401 30p71081 29pTL082 56p2102 110p2114 34.0p40018 17p40118 17p40138 40p40168 40p555 26p709 15p710 2Sp733 50p741 11078105 211p78L12 29p

J. W.

A80w into 80THD<0.008%.S/N 120dB.Kit 01.95Built £13.95.

POWERPETS8D512 (60, 172A, Echlin l 656.80522 (60v. Nchan ) SOpVN67AF (60v, 2A, Nchan 75p25J49 (140v, 100w. Pchan I 340p256134 (140v, 100w. Nchan ) 340p

HI -Fl ON TWO CHIPSHA12017 (Preamp 0.001% distor-tion 83dB S.N in phono application)99pHA1370 (Powerarnp 20 watts in80. 0.02% distortion Itypl 1915pBoth with a and circuits.

ME

A 11 20w into 80THD <0.005%.S/N 120dB.Kit £19.85

.Built C21.85.

SCOPE TRACE DOUBLER P.C.B.Built C W shift, chap. select, cho-prate controls and instructions. use-ful display from DC to 10MHz. Runsfrom 9V battery £9.95CAR AMP I.C. HA 1 388 Bridge ampdelivers 18w 196p.Heafsink for above 40p.

VCA High quality design offers at-tenuation from 0dB to 90d8. S N90dB. THD 0.01%, B.W. DC to100KHz. Complete components setand circuit £2.50

, ,i, ,,., ,,,... tr, 146. 'IT PP, .0(pooi L25

"...' 428 7651ROC 6667

PARNDON ELECTRONICS LTD.44 Paddock Mead. Harlow. Essex. CM18 7RR. Tel: 0279 32700 (Dept. No. 221

RESISTORS: I/a Watt Carbon Film E24 range ± 5°/.i tolerance. High quality resistorsmade under strictly controlled conditions by automatic machines. Bandolieredand colour coded.£1.00 per hundred mixed (Min 10 per value)£8.50 per thousand mixed (Min 50 per value)

Special stock pack 60 values. 10 off each £5,,,

DIODES: 1N4148 3p each. Min order quantity - 15 itemsET60 per hundred

DIL SWITCHES: Gold plated contact in fully sealed base - solve thoseprogramming problems.4 Way 86p each. 6 Way f1.00 each. 8 Way £1.20 each.

DIL SOCKETS: High quality. low profile sockets.8 pin - lop. 14 pin - 13p. If, pin - 15p. 18 pin - 19p. 20 pin - 25p.22 pin - 29p. 24 pin - 35p. 28 pin - 39p. 40 pin 57p.

ALL PRICES INCLUDE V.A.T. & POST & PACKING - NO EXTRASMIN. ORDER - U.K El .00. OVERSEAS ES CASH WITH ORDER PLEASE

CBH-5

CASPTRONICSIMPORTER AND DISTRIBUTOR

OF MURA PRODUCTS FORU.K & IRELAND CBS -44

MP -100/101£65

The MP.I00/101 is packed with outstandingfeatures that include An effective rangeof 900 feet A remote that operates up to12 hours on its built-in rechargeable nicadbanery 2 or 3 party intercom and pagingcapabilities Telephone privacy control Automatic line release if MURAPHONE isleft 'off hook.'

A MURAPHONE MP.I00/101 Systemconsists of (I) The MP -I00. A rechargablebattery powered portable unit whichoperates up to 12 hours on a single charge.This portable phone is rugged. lightweightonly 10 oz) and compact. It can be clippedonto your belt or slipped irito a pocket

CBM-10Dual -Function CB Meter

The two functionsmost critical for tuningand checking CB an-tennas are combined inthis one -low cost unit,

The CBMI0measures StandingWave Ratio (SWR) andField Strength IFS) onan easy -to -read meterwith D'arsonval precisionmovement. The CBM.I0is provided with its ownantenna for relativefield strength measure

ant.The unit cn he left in a coax line

permanently with no appreciable signal loss.comes with detailed instructions for use, andis covered by Mure's 3.month limitedwarranty.SPECEFICATIONS-SWR Seale: 1:1.1:3VSWR FS Seale: 0-5 salads. male

Frequency Range: 3.5-150 MHz Ito.dews: 52 Obese Antenna: 5-esedentelmeopk Dimension.: 6" " ".

COM- 30 Twin -Scale Meter

This meter is provided with separatepower and SWR scales. allowing forsimultaneous monitoring of SWR and RFoutput power functions.

The wide. easy -to -read scales arematched with precision -built D'arsonvalmovement for accurate readings of bothfunctions.

The CBM-30 is provided with a 2 -foot

connecting cable permanently attached foreasy installation. The unit comes with adetailed instruction booklet.

3.month limited warranty.

SPECIFICATIONS-SWR Seak: -1011YSWIL + 5% Power Soaks 0-100 Watts+20% Ftespene, Range: 3.5-55 MHz Impedance: 52 Ohms Dhoensleas:

MP -300/301HERE IT IS! THE BEST SELLING, BESTVALUE CORDLESS TELEPHONE SYSTEM

IN AMERICA.

Range depends on conditions

(2) The MP -I01. An AC powered basestation. The base unit is easily attached (doit yourself) to the phone system throughstandard phone jacks. The standard tele-phone instrument may be connected to thephone system through the MURAPHONEbase station. In addition to the intercomcontrol. the base station has a line releasebutton which can be used to disconnect theportable unit to assure telephone privacy.(31 A battery re -charging cord and a

complete, easyto.follow owner's manual.The system is handsomely finished in

aocoabrown and wood grain with brushed

luminum accents. Packaged in an eye.catching. self: display carton.

CBM-20 3 -Function Meter

The versatile CBM20 measure,transceiver RF output power on two scales,as well as measuring SWR and relative heldstrength.

The unit is equipped with a telescopicantenna for field strength measurement andcan be left permanently in coal line withnegligible signal loss.

A highly useful feature of the CBM20 is aswitchable impedance sening for testingtwin antennas.

The CBM-20 is provided with 2.footconnecting cable permanently attached.complete instructions, and Mures 3 -monthlimited warranty.

SPEC61CATIONS--SW1 Seale: 1.1-3:1VSWR Power Scaled. M1-10; 0-100 Watts FS Scale. 1-10 relative scale FregoeneyRange: 1.5-55 !Mb Impedance.: 52. 75Glees Antenna: 2-seetlro telessemk Dizneneloue: 6 s2'

CBTSAM Antenna ...once Matcher

Ease of operation, convenience andaccuracy distinguish the CBT.15. anantenna impedance matcher with a buillinSWR meter.

Since the SWR meter is an integral partof the unit. everything necessary for precisetuning of the antenna system is in onecompact cabinet.

Like the CBT.8. the CBT.15 incorporates awide impedance.matching range. facilitaring accurate adjustment under allconditions and for all channels. For night-time use, the SWR meter scale is backlit-a Niue innovation. A 2.foot connectingcable is prewired to the unit.

SPECIFICATIONS: Impedance MatchingRange. 25.140 Ohm. SWR mole: 1VSWR Dhnemion.1 5" a1/4".21/:".

This deluxe system rot a tees affordableprice) permits the used to both receivephone calls and originate phone calls fromanywhere within its 900 h range.The MP.300 30I's stylish beige and

wood grain finish and outstanding featuresare sure to capture the attention of therapidly expanding cordless phone marketthat MURAPHONE has been so instil,mental in eremitic.

MP -300.301 individual features andcontrols include: The MP100 RemoteUnit Operates 12.15 hours on a recharge.able nicad battery Slide type volumecontrol A great convenience is theautomatic 'last number recall' memory. Bysimply pressing a button the MP -300automatically radials the last number

citestwo Poo, antenna Ina...ince Mat< he

Incorporating all the features of the CBT-8and COT -IS, the CBT.25. in addition, offersan RF power scale for measuring transcieveroutput power.

The RF power scale enables the user toachieve the lowest possible SWR whilemaintaining optimal transciever output.

Other features of the CBT.25 include abacklit meter scale for each night-timeviewing. and a 2 -foot connecting cablepre wired tome unit.SPECIFICATIONS: Lepodasee MatchingRange: 25.140 Olma. SWR Seale: I:1-3:1VSWR Power Seek: 0.10, 0-100 Watt Dimessione: 5" 2 " z2

dialed II The rernine weighs 14 or andeasily slips into a picket or slips onto belt.The MP -301 Base Station Incorporates a 3LED display (yellow. red. green) to indicate'Charging. -Poser' and 'In Use' modes Builtin remote charger A 'Line Release'button to assure telephone pecans and an'Intercom' button for paging the remotesnit.

The system is smartly styled to comple.mem any home or office decor. Attaches tothe phone lines and AC poser.

Owner's Manual that completely- andclearly describes installation and operatingprocedures.

The MP.300 301 system is compatiblewith either rotary- dial or touch buttontelephone systems.

Beautifully packaged.

011135Oua1Scale Meter Antenna Impedance Mitch,

This deluxe unit feature separate scales forsimultaneous measurement of SWR and RFpower. Used in conjunction with the antennatuning controls. the twin meters allow agreater degree of tuning precision. A newfeature of this model is a % Voice Mod.!Mien Scale. This scale is located on theSWR meter face.

Like CBT.15 and CET.25. this model isequipped with backlit meter scales a 2.footcoaxial connector. An additional feature ofthe CBT.35 is a special mounting bracketsupplied with the unit for easy attachmentabove or beneath the transceiver.SPECIFICATIONS: Impedance MatchingRange. 20.140 Ohns. SWR Seale i 111-0.1VSWR Power Seek. 0.10, 0.100 Weds DI101111011: " 121/4"121/4".

CBC-24Required to connect CO transceivers to

test equipment.This 24 inchcoaxial cable is fitted with

standard PL.2S9 connectors.

FIGURE I input slain) before amp-lification: no asymmetry

and sharp peak..

FIGURE

MURAPHONE MP.100REMOTE I RECHARGER

An cora MP:100 remoteenables the owner of an. MURAPHONE System to hate availableat all times a fully chargedremote. No more down timewaiting for remote to charge.The system is now operational24 hours a day.

Completely compatible with allMURAPHONE Systems. thoughit cannot be used to dial out overthe MP:301 full function baseunit.

Individually- packaged withrecharger

90 days limited warrants.

£25MI-KV/IONE MP.300

REMOTE & RECHARGERCompatible wilt any MURA.

PHONE System. the MP.300remote permits aroundtherolockoperation in the system becausea fully charged remote is alwayses ailable. The addition ofMP -300 remote to an MP.I00an101 system will not upgrade thatsystem by giving it a 'call out'

capability. Dial capability re.& es both the MP.300 remoteand the MP -30I base.

Individually packaged withrecharger. 00 -net's manual and90 dot brined warranty.

£45

P05-100 Vas -sable GaelPower Mocrophone

With eat PR/4 - Unlike test instruments thatgenerate the clean audio signals known as sinewaves. the human voice. when transformed by ainicrophone cartridge into electrical energy.produces a signal that is asyrnmetical - that is.a signal with sharp excursions (peaks) a onlyone direction. This type of signal preventsuniform amplification. since the peaks willexceed the clipping point training audio dis-tortion) while the less -modulated areas of thesignal are just reaching audible levels. OrdinaryCO microphones do nothing to correct tilts signal

WirnIthb.laPRM"' - Mora engtneers tackled theproblem by developing a way to electroorottly

dunroute the peak portions of the signal tole modulated are.. This peakredistributionmodulation (PR.) effect u made possible

by

Procmms. delaying peak components for minute amountsof time before being passed on to the amplifierstage of the transceiver. Thu process effectivelycreates symmetry in the signal rod lessens theaverage energy levels of th e peaks. The evenlydistributed input signal cro now be amplified tom.imurn (preclipping level with a simnficentlygreater portion of the signal at close to tntalmodulation. Result- a tremendous increase in

+ modulated power - more than Pince doe tall1 Y. powers of ronvennonal equipment. with foe less

distortion (since clipping ts not required toproduce high overell modulation).

FIGURE 3 Amplified PILM-procemed The Omni product - Sin of the finest CB mikessignal, wino more of signal ever made. Including three old favourites and

et higher energy koala. three brood new additions to the line.

same slain( alter PRM

114t, t,

1 \13 1

PIM 100 E22.95CBM 10 113.95LIIM 20 011550CBM 30 £20.95CRT 15 t23.50CDT 25 E25.95CM 35 029.95CRC 24 £2.95OM 5 £6.95CBS 44 £6.95PL 259 .65QDK le 13.95WINS 49 45.All prices heeled. VAT

SPEOAL OFFER ON HI -GAINANTE/MU AM 'FM, CB SOTSSPUTTER BOX DISGUISE £20.95570 TRUNK OR ROOF MOUNT DEB

All prices bode VAT.Post and Parkhas phone ud mamma £1 .50

meters and eperhar. £1.Mall odaer lame .50

CASPTRONICSCATHEDRAL ROAD,

ARMAGH,NORTHERN IRELAND,TEL: 0861 523914.Trade and retell enquiries woloomis.

Selected Kenos available base More awlSpan, Donegal Pro, Bedessa.

Phones and W0.15 49 not liceeeable In UK.


BreakerOneFour

Send any news, comments or information you have to:Breaker One Four, Hobby Electronics, 145 Charing CrossRoad, London WC2H OEE

Now that the Open Channel Green Paper has finallyappeared we have a chance to air our views. RickMaybury reports on the latest happenings on theCB scene.

TWO OUT OF THREE, that's our rating. The GovernmentGreen Paper published on the 5th of August made in-teresting reading. We wholeheartedly agree with the sug-gestion that 40 channels would be needed. Even the in-ference that 25 watts would be the optimum power levelsounds reasonable, it was the choice of frequency thatspoilt an otherwise interesting document.

Looking at it rationally 928 MHz is a strange figure,how on earth did they decide upon it? (We reckon it wasscientifically chosen with a sharp pin and a shakey hand). Insetting out their arguments the Government have madetwo serious errors of judgement. The first is the mood ofcurrent CBers. When asked what would the Governmentdo about the thousands of illegal operators Timothy RaisonMP replied 'Well, they'll just have to stop doing it ...' Op-timism in Government employees must be at an all timehigh. Not one single Breaker is going to dump his rig in hisdustbin and wait for the glorious day when he can spend anunspecified amount of money on equipment that might ormight not work as well as cheap and readily available gearwill.

Their second mistake is the choice of 928MHz, overand over again tests have proved that high frequencies arenot suitable for short range urban communication, evenless so for open country where a leaf on a tree is an effectivebarrier to any RF signal above 700 MHz.

Do Something About ItAs soon as the document was published we had dozens ofphone calls from people complaining that 928 MHz was nogood and asking what we were going to do about it. Thesimple answer is we can't do much, but you can. The GreenPaper is meant to promote discussion and comment, in factit invites it. Every single one of you has the opportunity to

HOME OFFICE

OpenChannel

a discussiondocument

Has this got anything to do with CB?

tell the Government exactly what you think about it. If youhaven't already seen a copy then you can obtain one bywriting to:The Officer in Charge, Home Office, Supply andTransport Branch, Royston Road, Caxton, Cambridge CB28PN (natty post code!) and ask for 'Open Channel - aDiscussion Document'. Read it carefully then send yourcomments no later than the 30th November to: RadioRegulatory Department, Home Office, Waterloo BridgeHouse, Waterloo Road, London SE1 8UA. We won't tellyou what to write but we will say that if enough peoplemake a fuss something may be done about it. Don't moan,do it.


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£20,000 worth of equipment constantly in stock, unlikesome others!!

THE BIG EARS PROMISETo all our customers producing this ad., any piece of equipmentbought from us you find cheaper elsewhere, we refund thedifference.S.W.R. METERS from £10 Ariels from £6


Big EarsEarlier this month we took the M1 north to meet the famousBig Ears, CB accessory dealer extraordinaire. The journeyitself was something of an advertisement for CB, the almostperpetual roadworks and numerous accidents took somethree hours to negotiate. Even when we arrived the rathervague directions had us looking everywhere but the rightplace. Eventually we found the shop, where Terry (Big Ears)assured us that a day earlier you couldn't move for stock,we could hardly get in that day so you can guess what sortof trade he has. 1 ust about every conceivable accessorywas on show and prices were as good as (and in some casescheaper than) any we've seen. After a diabolically hot curryTerry showed us around Leicester, it turned out to be aneventful journey as you'll see from the picture. A youngpolice constable tailed us for some five miles before pull-ing the Big Ears van over. One of the Big Ears employees isseen here telling the constable his rights (more of that later).After some 20 minutes he actually managed to persuadethe Constable to give up. That man could talk the hind legsoff a donkey, (and then convince the donkey it didn't needthem in the first place). The next day we heard from BigEars, apparently the shop had another visit just after weleft, this time from the Home Office and Customs & Excise.Again they found nothing.

Your RightsThe question of right of entry by police, Post Office, HomeOffice etc. is an old one. Recently a document came intoour possession. It is a general guide to the authorities onhow to handle a situation involving use of antransmitter. It starts off with an interview. The questions arefairly straightforward:

'Are you the owner of this equipment'?'Where did you get it?''What call -sign do you use?'

This is interposed by the usual cautions, 'You are not oblig-ed to say anything ...' etc and details of test transmissionsmade giving frequency (isn't that it legal?) and channels. Thesecond part of the document goes on to tell the interviewerwhat the law allows. The most interesting part comes at theend of the second page:

'It is emphasised that there is no power under the WirelessTelegraphy Acts for the Police, Post Office or Customs & Ex-cise to detain apparatus for evidential or any other purpose.Apparatus may only be removed with the owner's consent'.Before you get too smug, the Police may detain the equip-ment under the Customs and Excise Management Act but

He got away with it too!

The Big Ears Shop

this must be with prior agreement from the C& E. In practicethis can be almost impossible to do. So now you know yourrights but try arguing that with half -a -dozen burlypolicemen!

Club SceneIt didn't take long for a new club to be born from the dis-quiet generated by the Green Paper. In fact as we go topress no less than four organisations are about to or arealready looking for members. The first one we have anyfirm details of is the Campaign for British Citizens Band

14th of lastmonth. For further details of the club's activities contactour old friend Keith Townsend at:CBCB Glasgow CB Club,1163 Yardley Wood Road, President Ian Patterson,Birmingham, B14 4LE 147 Trassachs Road,(Love the postcode Keith!) Rutherglen,

Telford CB Radio Club Glasgow.

Chairman: P. McGuiness, (Phone 041-647-6923)

192 Bishopdale,Brookside,Telford.

South Birmingham CB Club (SBCBC)Secretary: R.A. Smith,14 Del reme Road,Solihull,West Midlands B90 2H H.

South Coast Area Breakers,Telephone Worthing 62929.

Circle City Breakers (CCB)Leeds: (Call Breaker Channel for details)

The South Birmingham Club have been very active duringtheir relatively short existence, already they boast over 100members and a regular monthly meeting. Whilst we're onthe subject of well organised clubs the North Birminghamgroup have also been doing well. Already they are printinga well thought out newsletter with masses of local informa-tion for their members. We would like to see any newslet-ters from any of the other clubs, we might even print the bitsthat are of national interest.

Thanks too to all those of you that have sent innewspaper clippings, again we would like to see any reportsof CB in your local papers especially if it is out of the or-dinary, emergencies, stolen cars, dramatic busts, etc.


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CALLERS WELCOMEHobby Electronics, October 1980

CB VIPTERRY (BIG EARS) NEWELL

Big Ears is our CBVIP this month, as you'll see he has had a very full andinteresting life. We asked him for his views on Open Channel, we think he'snot alone with some of his observations! By the way, he asked us not topublish his picture, the gentleman on the right is a good friend of Terry's.

BOF. OK Terry, tell us your life story.TERRY. I was born at a very early age, in 1948 to be precise.B. What were you doing before you got involved with C B?T. I was heavily involved with the Rock and Roll business as a

'Rodent' for some years.B. Rodent, what's that?T. I was a go-getter.B. How long did you do that?T. Fourteen years.B. That's a long time, were you involved with any big bands?T. Yeah, Black Sabbath, PFM, Magma, Pretty Things.B. You must have travelled quite a bit then?T. Four countries in as many days, and that was taking it easy!B. So when did you first come across CB?T. In the States, I was a truck driver for a while.B. How long?T. Not long, New York to LA and you know all about it, 3000 miles

non-stop. I've had white line fever, you can stop the truck andthe road is still moving.

B. So when did you come back to the UK?T. I never really left.B. No, I mean when did Big Ears and you start, was it when you

returned?T. Big Ears as a company began on the 1st of January this year, I

was involved in the CB scene for the past two years though.B. I hear you've got a shop in Wales.T. That's right, and maybe one in London soon.B. What are your printable interests?T. Horse riding, radio control modelling, I've got a Stock car at the

moment that I race.(The rest of Terry's interests are most certainly not printable butare common to most red-blooded males)

B. Do you race seriously?T. Oh yes.B. Are you any good?T. Not yet.B. Do you get any interference from CB?T. Believe it or not, no.B. So how do you see the future?T. The number of 27 MHz rigs in this country is grossly

underestimated, I've got reliable figures that show at least250,000 rigs in operation. The Government have left it too late.All the people I've spoken to are not prepared to accept theOpen Channel system with all its limitations and probable cost.

B. What are you going to do about it?T. Well, we've formed the National Association for the Legalisation

of 27 MHz and we'll be starting our campaign of action verysoon.

C-13easties7r-c.D. LEQSUITION IS LIKE A 'SAnirna

KRQSslAni Ciass-rr kLco&c_k --roo MOW .1.

B.T.B.T.

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Would you like to tell us exactly what you'll be doing?No Comment, you'll see soon enough.Is this organisation backed by any big names?No, just the people who matter, the Breakers, but it's not aBreakers' organisation as such. We want to totally divorceourselves from the UBA, UKCBC and all the other publicity-seeking organisations. We're not interested in getting our faceson TV, just getting CB legalised and preferably on 27 MHz.I can see your point but what will you say to those who claim 27MHz CB interferes with other electronic equipment?The evidence is pretty slim, I do accept that aero modellers cansuffer but the recent announcement by the Home Office thatR/C is to get another channel should take care of that.How about hospital paging systems, I hear that the BreakerChannel in Leicester is 19, isn't that because of a paging systemon 14?Exactly, it interferes with CB, not vice -versa. There are 39 otherchannels, there is no need to use 14. There are several reasons theGovernment do not want CB to exist in this country. For instance,and I want you to print this, the situation at Grunwick could havebeen far worse if only half a dozen stewards had CB sets, and thesame applies to the recent Steel dispute. The Government seesCB as a social/political menace, all forms of communication, ex-cept word of mouth, are controlled by the Government. OpenChannel is a con, they are putting it into a prohibitive pricebracket and limiting the number of sets, if it ever happens. Thewhole point is that 27 MHz is available, it works, people like itand want it, we can have it now. The constitution is surelyGovernment for the people by the people. The people say theywant 27 MHz so the people should have 27 MHz. If enough peo-ple get together then they will have to do something about it. Thebenefits are well known, if you were on a motorway and you hadfive miles warning of an accident you could do something aboutit.That's right, we could have got here an hour earlier.Right, if you had a CB in the car you might have avoided takingan hour to find my shop, you could have put out a 'Break' and Iwould have helped you straight away. A three minute call dialledon your own rig costs nothing.So what do you think will happen?The Government have got one thing working for them, apathy. Ifenough people get off their backsides we can do somethingabout it, everyone must make their views known.Thank you very much and good luck with the campaign.


T.V.E.S.12/13 GREENPARK ROADBRAY, CO. WICKLOWS. IRELANDTel. No.(0001) 868727(0001) 860077Telex No. 31539

( avant-.1111111i,

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Clearly plays each major type of CB interferenceand tells how to eliminate them.

GC ELECTRONICSt:tf ViStON of HYDROVIC TA SWS-FOI poctuoftft ,t,tmols U.S S 611, 4)

The CB Trouble Tape available from Wintjoy Ltd - see Odds and Endsbelow.

National Directory of HandlesAt last, the Directory is ready. Problems with distributionare forcing us to offer the Directory on a mail-order onlybasis. Each handbook -sized issue contains thousands ofregistered handles all with an individual number and loca-tion, all the addresses of the national and local clubs, hun-dreds of hints and tips to make your life easier and thechance for you to register your handle in the second editionthat, hopefully, will be appearing on a regular basis. Fulldetails next month.

Odds and EndsTwo items of interest from the accessory dealers thismonth. The first comes from Big Ears and is an automaticantenna matching unit. This motor -driven device willautomatically SWR the antenna every time the channel ischanged. There are only three connections, the rig plugs in-to one side, the antenna into the other and a connection ismade to positive 12 volts. Installation is kept to an absoluteminimum as the unit is held in place with a hefty magnet, aquick twiddle to set it up and your antenna will forever re-main perfectly SWRed. Big Ears has a limited supply ofthese devices, they're called Sylvania Automatch and canbe yours for £45.00.

Our second item this month comes from Glyn Hall atWintjoy, it's called 'CB Trouble Tape'. Basically it is anAmerican cassette with recordings -of all of the most com-mon types of interference. There are sections on identifyingthe cause of the trouble and eliminating them, all easy tounderstand. Wintjoy are currently offering them for arounda fiver, a mite pricey, but then how valuable is your time?


Missing ChildCast your minds back to the beginning of last month. Youmay remember the story of the two year -old child ElizabethPeck who decided to have a stroll around a forest near herhome for a couple of days. Happily she was found, none theworse for her ordeal. The news reports at the time said thatlocal radio amateurs were helping with communication tothe search parties. What the media failed to report was thehelp given by some 60 local Breakers who turned up inresponse to a plea from the local Fire Brigade. They set upan impressive communications network complete withmobiles and base station, under the supervision of the localconstabulary. The Police are now (understandably) reluc-tant to acknowledge the help given by the CBers. Aspokesman from the club said:

'Our main concern was to help find Elizabeth, not topublicise CB, but the authorities' flat denial of ourassistance prompted us to make the truth known'.

We would like to thank publicly Moonraker, Wallaby,Green Turtle, The Mole and all the other members of theSouth Coast Area Breakers for their prompt and selflesshelp.

NATCOLCIBAROur last item this month concerns the latest meeting ofthe Technical Sub -Committee of the National Committee

. for the Legalisation of Citizens Band Radio.As you mayor may not know BOF' has been attending these meetingsfor the past six months. The meeting on the 22nd of Augustwas held to discuss the Green Paper and finalise thealternative specifications that NATCOLCIBAR hope theGovernment will adopt. To cut a long story short theNational Committee have investigated all the possibilitiesand deduced that an area around 42 MHz is sufficientlyfree, (remember cheap equipment is available for thisfrequency).

Their final comment was: the Government Green Paperhas absolutely nothing to do with CB. That just about sumsit up really! Stay Lucky and see you next month.

The Sylvania 'Auto SWR' in position HE

77

HOBBYPRINTS

If you have never used HOBBYPRINTS before,then you don't know what you've been missing.HOBBYPRINTS are an etch -resistant rub -downtransfer. Just place the appropriate HOBBY -PRINT over a clean piece of copper clad PCBmaterial and rub. It's as simple as that. Oncethe design has been transferred, immerse theboard into the Ferric Chloride. 15 minutes lateryou will be rewarded with a perfect PCBprepared from our original artwork, so you canhave no worries about making a mistake. Bythe way, HOBBYPRINTS are ideal for makingPCBs by Ultra -Violet exposure.

HOBBYPRINTSHEETS AREAVAILABLE FORISSUES FROMNOV. 78 RIGHT UPTO THIS ONE.ALL SHEETS COST0.20 ALLINCLUSIVE OFPOST ANDPACKING ANDVAT.ORDER BY SHEETLETTER ANDISSUE MONTH(SEE BELOW).

ISSUESHEET REF.

ISSUESHEET REF.

Nov. 78 A Sept. 79 KDec. 78 B Oct. 79 LJan. 79 C Nov. 79 MFeb. 79 D Dec. 79 NMar. 79 E Jan. 80 0Apr. 79 F Feb. 80 PMay 79 G Mar. 80 QJun. 79 H Apr. 80 RJul. 79 I May 80 SAug. 79 J Jun. 80 T

IFor your HOBBYPRINT refer to the chart aboveand send your cheque or postal order to:HOBBYPRINTS,Modmags Sales Office,Hobby Electronics,145 Charing Cross Road,London WC2H OEE.


PCB Foil Patterns

3

"CTSTEMP.

CON0 TROL00

TUG


0 WAR

HEWATCHDOG

8

ctl+w000m

*--kLIGHT

DMMERBWO

8

orPmmOfto

.411107,7111077

Books from the HE Book Service28 Tested Transistor Project

£1.55Richard Torrens. The projectscan be split down into simplebuilding blocks which can berecombined for ideas of yourown.

Electronic Projects for Be-ginners £1.65F. G. Rayer. Divided into 'NoSoldering Projects,' Radio andAudio Frequency, Power Sup-plies and Miscellaneous.

Practical Electronic Calcula-tions and Formulae . £2.55F. A. Wilson. A valuablereference for the home andlaboratory, containing all themost frequently used, andsome of the less well-knownelectronic formulae and calcu-lations.

Popular Electronic Projects£1.75

R. A. Penfold. A collection ofthe most popular types ofcircuits and projects usingmodern, inexpensive and freelyavailable components.

POPULAR ELECTRONICSBOOKSSinclair, I. R., IntroducingElectronic Systems . . £1.95Sinclair, I. R., IntroducingAmateur Electronics . . £1.65Sinclair, I. R., Electronic FaultDiagnosis £3.55Sinclair, I. R., Repairing PocketTransistor Radios . . . £2.60Sinclair, I. R., Oscilloscope InUse £3.10Sinclair, I. R., UnderstandingElectronic Components £4.20Sinclair, I. R., UnderstandingElectronic Circuits . . . £4.20Kitchen, H. T., Handtools ForElectronic Workshop . £2.95Kitchen, H. T., Electronic TestEquipment £5.20Capel, V., How To Build Elec-tronic Kits £2.35Darr, J., How to test almosteverything electronic . £3.70Brown, R. M., How to readelectronic circuit diagrams

£5.60

AUDIOEarl, J., Audio TechniciansBench Manual £3.70Earl, J., Pickups and LoudSpeakers £3.70Earl. J., Tuners and Amplifiers

£3.20Earl. J., Cassette TapeRecorders £5.40Earl. J., ABC of Hi-Fi £4.35Capel, V., Microphones In Ac-tion £3.15

Digital IC Equivalents andPin Connections . . . £2.85Adrian Michaels. Covers mostpopular types and gives detailsof packaging, families, func-tions, country of origin andmanufacturer.

Radio Stations Guide £1.75B. Babani and M. Jay. An inva-luable aid to everyone with aradio receiver helping them toobtain maximum entertain-ment, value and enjoymentfrom their set.

IC 555 Project £2.05,E. A. Parr. Circuits are given forthe car, model railways, alarmsand noise makers. Also coversthe related devices 556, 558and 559.

Second Book of CMOS ICProjects £1.80R. A. Penfold. Following in thesuccess of the original CMOSprojects book we present thesecond volume covering allaspects of CMOS technologyfrom multivibrators to trig-gering devices.

Electronic Security Devices£1.75

R. A. Penfold. Full of construc-tional circuits covering the mostbasic security systems to theUltrasonic and Doppler Shiftsystems

How To Build Your OwnSolid State Oscilloscope

£1.80F. G. Rayer. The book containsconcise practical instructions sothat even an inexperiencedhobbyist can construct a fairlysophisticated instrument withthe minimum of difficulty andexpense.

50 FET (Field Effect Transis-tor) Project £1.55F. G. Rayer. Contains some-thing of interest for every classof enthusiast. Short Wave Lis-tener, Radio Amateur, Experi-menter or audio devotee.

Linear IC Equivalents andPin Connections ... £3.10Adrian Michaels. Gives mostessential data for popular de-vices.

Essential Theory for theElectronics Hobbyist £1.55G. T. Rubaroe gives the hob-byist a background knowledgetailored to meet his specificneeds.

Beginners Guide to BuildingElectronic Projects . £1.55R. A. Penfold. Covers com-ponent identification, tools,soldering, constructionalmethods and examples ofsimple projects are given.

50 Projects using IC CA3130£1.25

R. A. Penfold. Describes audioprojects, RF project, TestEquipment, Household andmiscellaneous circuits.

50 Circuits Using 7400Series ICs £1.65R. N. Soar. The author hasmanaged to compile no lessthan 50 interesting and usefulcircuits using this range of de-vices, covering many differentaspects of electronics.

Capel, V., Improving Your Hi-Fi£3.65

Capel, V., Creative Tape Record-ing £4.20Hellyer, H. W., Tape Recorders

£4.45Sinclair, I. R., Audio AmplifiersFor Home Construction £2.85

RADIO CONTROLDrake, J., Radio ControlledHelicopter Models .. . £4.20Jeffries, C. R., Radio ControlFor Model Yachts .. . £3.85Safford, E. L., Radio ControlManual £2.60

COOKBOOKSTracton, K., BASIC Cookbook

£4.10Lancaster, D., TTL Cookbook

£7.00Lancaster, D., RTL Cookbook

£4.65Lancaster, D., CMOS Cookbook

£8.20Jong, W., IC Op Amp Cook-book £10.00Lancaster, D., T.V. TypewriterCookbook £7.75Lancaster, D., Cheap VideoCookbook £7.00Jong, W., IC Timer Cookbook

£7.50Lancaster, D., Incredible SecretMoney Machine (a how to cookbook for setting up your com-puter or technical business)

£4.95

QUESTIONS AND ANSWERSSIMPLE AND CONCISEANSWERS TO MANY QUES-TIONS WHICH PUZZLE THEBEGINNER.Coker, A. J., Q & A On ElectricMotors £1.90Hellyer, H., Q & A On Radiosand T.V. £1.90Hibberd, R., Q & A On Inte-grated Circuits £1.90Jackson, K., Q & A On Elec-tricity £1.90Brown, C., Q & A On Hi-Fi

£1.90Brown, C., Q & A On Transis-tors £1.90Brown, C., Q & A On Elec-tronics £1.90Reddihough, J., Q & A On Col-our T.V. £1.90Miller, H., Q & A On ElectricWiring £1.90

CONSTRUCTOR GUIDESGraham, P., Simple CircuitBuilding £2.70Colwell, M., Electronic Dia-grams £2.70Colwell, M., Electronic Com-ponents £2.70Colwell, M., Printed CircuitAssembly £2.70Ainslee, A., Practical ElectronicProject Building . . . . £2.70Colwell, M., Project Planningand Building £2.70

BEGINNER'S GUIDESinclair, I. R.. Beginner's GuideTo Tape Recording £3.45

Sinclair, I. R., Beginner's GuideTo Integrated Circuits . £3.45Sinclair, I. R., Beginner's GuideTo Audio £3.45King, G. J., Beginner's GuideTo Radio £3.45King, G. J., Beginner's GuideTo Television £3.45King, G. J., Beginner's GuideTo Colour T.V. £3.45Guilou, F., Beginner's Guide ToElectric Wiring £3.45

PROJECT BOOKSMarston, R.M., 110 CosmosDigital IC Projects For TheHome Constructor . . £3.95Marston, R. M., 110 WaveForm Projects For The HomeConstructor £3.95Marston, R. M., 110 Op AmpProjects For The Home Con-structor £3.95Marston, R. M., 110 Semicon-ductor Projects For The HomeConstructor £3.95Marston, R. M., 110Thyristor/ SCR Projects For TheHome Constructor . . . £3.95Marston, R. M., 110 ElectronicAlarm Projects For The HomeConstructor £3.95Marston, R. M., 110 IntegratedCircuits Projects For The HomeConstructor £3.95Marston, R. M., 20 Solid StateProjects For The Car andGarage £3.20Marston, R. M., 20 Solid StateProjects For The Home £3.20

Note that all prices include postage and packing. Please make cheques, etc. payable to Hobby Electronics Book Service (in sterling onlyplease) and send to.Hobby Electronics Book ServiceModmags Ltd * Prices may be subject to change without notice.145 Charing Cross RoadLondon WC2H OEE


IMLICOM-2

Stock

n £335+ VAT

Full after salesservice

MICRO-COMPUTERFREE 16k BRAM BoardFREE POWERSUPPLY

MICROPROCESSOR BOARD (NASCOM 2)4MHz Z80 CPU; TV or Video + 1200 baudKansas City + Serial RS 232 printerInterfaces; Keyboard; 128 character ASCIIplus 128 Graphics in 2 x 2K ROM; free18 -way parallel port; 8K BASIC; NAS SYSoperating monitor. £280 built and tested.Firmware Et MOS ICsZeep Assembler 14, 11(x8 EPROMS) £50Mae Pen text editor (2, 1Kx8 EPROMS) £30Expansion boards (in kit form)16K RAM £127.50 32K RAM £175.0048K RAM £220.00High Resolution Programmable Graphics £90Colour Board Kit £140High Resolution Colour add on £37.60

STEREO CASSETTE TAM MEAS.111.1 polity rep1ewel Nr. 111.1.0 marl/replayNag Iaclet/216taws purls, auk Mc/= m1 2pa161 E325

auk Ilitunl/Play Na Impaimma1.4.011

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DIASWINNIma Tape Rawls I TrackW ENN E2.25SOT 111116.4.1 fawn f2.511MIT rah 15.1.1.1 scrum E2_51)

116 Erin Mud 115p

11/101/31.6ara/Play tnekISMS

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LP1171 & LP1179 MODULES

by MULLARD

LP1157 & LP1186LP1 I 71 and LP1179 tuning heart andIF modules which form the basis of aquality AM /FM tuner. Full mediumlong wave and VHF coverage. May beused as the basis of a quality portableor tuner. Supply 6V so 15mA output70mV at 20KPair E6.76

SUPPLIED COMPLETE WITH DATA

LP1 1 57 Medium & Long Wave tonermodule -heart E2.150

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COMPUTER KEYBOARDS

heybrairi

STAR DEVICES MK III 71 keytouch sensitive key-board. With numeric pad. All ASCII charactersincluding control keys. Auto key repeat. Paralleloutput with strobe. Shift lock with indicator LED.Built in 'beeper' with level control. 5V DC at 300mA15" x 7" x 1.25". Grey case with white keys on blue.48.50 plus VATCARTER 57 key ASCII keyboard. Conventional keyboard. 128 ASCII characters including control keys.Parallel output with strobe. Shift lock. + 5 V and-12 V DC. 12" x 5.5" x 1.5". Black keys with whiteledgends.311.34 + VAT.FERRANTI - "SIZE 14 x 5 x 3" SLOPING FRONT55 Key ASCII Coded in steel case. Complete .withPlug and Cable with circuit to convert to T.T.L.levels.In good condition at only E25 + VAT, P/P E2.50

CENTRONICS QUICK PRINTER

40/ tp,,,IMIIWOURPRICEplusVAT

EXCLUSIVE TO HENRY'S E 1 9550% OFF MAKER'S PRICE

for: Software selectable 20, 40 and 80TANDY, ?column using Ommlminium-

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perroll supplied.minute.

NASCOMKNeonscotromnibsTapandr:I etlel cdate interface for

240 volt mains Input. ASCII character setPaper feed, and on/off select switches'BELL' signal Weight 101beSize: 13" x 101 x ith"

New, boxed and fully guaranteedPOST PAID Price £195.00 + VAT

See COMPUTING TODAY RecommendationsMARCH/MAY ISSUES

Ad mg isog.rd /gam MIS plua VATTY INS kajewd WAWA ...mann Nyand NI iffiz(6--mERviiNNON cab nimcler. CANN /WINN et E20.00

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W. i.e. NAN.. . im-rick nolicli accepts LONDON STOCKISTSlial" " TMa " w " "*"l """ M' t 65 Kit, Incl. VATNOT psi Rai X NN M. main I. ro.y v. NI 1 cro a n £79.35r"a I'll"k1T"'"`"`"'" '''''''''. " Microtan 65 Assembled,Om yam mil -whim IMerNminatanl Ilk £90.85

E43.56 Mos VAT

SEND FOR COMPLETE BROCHURE TO ADDRESS BELOW

Tama pap. camI AN- lot VAT E4111.45

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amity Grnakia het I.I.VAT £7.5020 NI Erman IN . VAT EII.50MtwatiMor leant ha VAT E1.65Complete Tangerine ramp avallMa

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El .50 P.P. 25p10 for E12.50

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iy r BELT DRIVENw%' TURNTABLE

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LIST PRICE OVER £50J.V.C. Turntable supplied com-plete with Audio Technica ATIOstereo magnetic cartridge.' BELT DRIVEN

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AT ONLYLIMICKSTED

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Size 6x5x5mmPostage 50p each

Price£0.151 A. 1 3/4

£1.160E2.115E2.50E2.50E2.50£2.50

GECHIGH

QUALITY STEREO10+10 watt AMPLIFIERWITH AM/FM STEREO TUNER

IDEAL FOR THE HOMEA cancelled export orderbrings you this offer

AM, FIN Memo Tuner AmplifierReady swill Comprising of a tuner pre amp board and

separate power supply power amp board willwiring diagram

Rotary Controls: Tuning on off volume balancevale bass Stereo Beacon indicator

Push-button Controls. Mono Tape. Disc. A f CM INWI LW. MW SW

Power Output 7 wens MS per WAHL al betterthan 2'. TWO into 13 ohms 10 watts speech andMUSIC

Frequency Response. 60112200Hr within 308Tape Senotivity. Output - typically 150 my Input -

SOO my for riled outputDisc Sensitivity. 100 my (ceramic cartridge)Radio. FM IVHFIR75M14 1013MIltlong Wale 1451OP 265100Mediums Wan 520.6, 1620A111Short Ware 5 NIN IVANSite Tuner - 2' ,in 115in 07 .in Power Amp - 2in

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5 +5 Watt Car Stereo AmplifierWITH pre amplifier and Al 5 Long wave assemblySupplied as two Swill and lotted milts

a R.I. Bed 1.1 stereo preamplifier and radio1 ri 2 a l"* 5+5 watt Mares amplgtor 12,14 von 4 it 20 I"a Complete with circuit data and connection diagrams* tooled &ant& meltable ex stock

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Peal Slip

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NENRy'sPhone (01) 7231008/9404 Edgware Road, London W2, England I.E.D.

PRO 125 Professional capacitor boom -arm microphone by Eagle.A gracelui 60 cm boom urn capacitor studio microphone uncap a cardioid capsule *highstandard of lirush lm infusion use and yet robus1 enough to withiland met periods betweenmaintenance Supplied complete will I red and I elate windshield and 6 metres or limnscreened cable terminating al the microphone end in an SLR connector.

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Cable: 6 metres Iwo conductor shielded Connector' MLR 7-I IC Battery type: 11P7

LIST PRICE131 40

OUR PRICE£19.95

11( VATPOST 11 50


RATES

1-3 insertions £5 per scc4-11 insertions £4.50 per scc12 insertions £4 per scc18p per word (Min. 1 5 words)Box No on application

IIFIEDAll advertisements in this section must bepre -paidClosing Date:- 1st Fri month precedingpublication

Advertisements are accepted subject to the termsand conditions printed on the advertisement ratecard (available on request).

SEND TO. HE CLASSIFIED, 145, CHARING CROSS ROAD, LONDON WC2H OEE. TEL: 01-437 1002 Ext. 26

50Hz SUPERBOARDSBRITISH MODEL

NOW FROM £159.95+ VAT + P&P

Fully built, set up and tested mikAccessories, software metal cases, etc.11111

AUTHORISED dealer back-upC.T.S.(HE), 1 Higher Calderbrook

ip Littleborough, Lancs.Tel. Littleborough 79332

anytime

OSCILLOSCOPE £12. Easy build converterplugs into TV aerial socket and converts tolarge screen oscilloscope (Components costunder £12). Circuit and plans £3. - Kerr, 27Coles Road, Milton, Cambridge CB4 4BL.(Callers by appointment).

MAGICIAN REQUIRES electronic en-thusiast to build a radio controlled device toelevate and retract a small prop from a box.01-749 2999.

TECHNICALLY ORIENTATED? Variedjob, small scientific company. ElectronicWiring Mechanical Assembly Simply DesignWork. Also some office and field work. Suitsemi -retired or young person with drive to dowell. Must have initiative. Full or part-time.£2 p/hr. plus bonuses. - R. A. Scientific atEarls Court. Tel: 01-373 6933.

PRINTEDCIRCUITS

HARDWARE

Comprehensive range Constructors Hardwareand accessories

Selected range of popular componentsFull range of HE printed circuit boardsnormally ex -stock same day despatch atcompetitive pricesP C Boards to individual designsResist -coated epoxy glass laminate for thed y man with full processing instructions tnounusual chemicals required)

Alfac range of etch resiSi transfers and otherdrawing materials for p c boards

Send 15p for catalogue.

RAMAR CONSTRUCTORSERVICES

MASON'S ROADSTRATFORD-ON-AVONWARWICKS. Tel. 4879

CENTURIONALARMS

BURGLAR ALARM EQUIPMENTAT UNBEATABLE VALUE

JUST LOOK!Order No100 ALARM TRIGGER MODULE. 100% Solid State Batte4yoperation Pos B Neg Rings N / C for 4.wire contacts N 0 forMats etc. One Arno Switching Capacity Only E9.95210 Quality White Flush letting 4 -woe MAGNETIC REEDCONTACT.malchng magnet £1.10220 Surface 4 -wire MAGNETIC REED CONTACT £1.50240 PRESSURE MAT, Standard eze 4/wire 30", 15" E2.20250 PRESSURE MAT. Starr sae 23",6'h" E1.73260 VIBRATION DETECTOR. Pendulum type to Ivory Case withcontacted Lid +-self /adhesive backing. Ad fustable sensitrytty £3.50360 SIX INCH UNDER DOME BELL £9.95390 BEST QUALITY BELL HOUSING. PVC coated metal not tobe confused wrth the cheaper decoy covers Fully egnwritten wothour Centurion Insignia E9.50400 DECOY P.V.C. BELL COVER C6.60Note. All equipment operates on 12 Volts DC.710 SCOOP Offer SMOKE ALARMS. Solf /coma med IonisationType 11 5'S obscuratron1 with low battery warning at theUNREPEATABLE PRICE of only E8.75 While Stock Lest!!!Term Add 15% VAT to Pnces L- 40p Postage 5 Packing

No Minimum Order_Access telephone orderswelcome on.0 4 8 4-35 52 7 or sendSAE for Full list to

CENTURION ALARMS & ELECTRONICSALES, Dept. HE, 265 Wakefield Road,Huddersfield, W. Yorks HI35 98E.

UK. AIR BAND FREQUENCIES LIST.Approach, Tower, ATC, Radar, Weather,Rescue, Emergencies, etc., £1. SendCheques/ P.O.s to PLH Electronics. 20Vallis Road, Frome, Somerset BA1 1 3EH

ALL MIXED. 200 components £4. 50 tran-sistors 95p. 100 diodes 85p. 10 switches95p Lists 15p - Sole Electronics (HE), 37Stanley Street, Ormskirk, Lancs. L39 2DH.

RECHARGEABLE NICO BATTERIES forsale due to bulk purchase. 1.25v 1.2A cells£1.55; 2.5v 1-2A racks £3. Carriage extra. -Birchley 0452-855312.

SUPER BARGAINS. 100 mixed Resistors80p, 300 mixed Capacitors £2.50; 200mixed Components £2. S.A.E. for furtherprice lists.-E.R.S. Components, 62 Thomp-son Hill, High Green, Sheffield S30 4JU.

BACK ISSUES! Hobby and Electronicsmagazines. Bought /sold /exchanged. Staterequirements and request quotation. De-nstone Educational Publications, 1 WaterfootAvenue, Southport PR8 3TE.

ZX80 GAMES. Mastercode (Number Mas-termind). Runs on Basic ZX80, extra memorynot necessary, on cassette. Send £2.50 orS.A.E. details/list. - Bobker, 29 ChaddertonDrive, Unsworth, Bury, Lancs.

DIGITAL WATCH BATTERYREPLACEMENT KIT

These watches all require battery(power cell) replacement at regularintervals. This kit provides themeans. We supply eyeglass, non-magnetic tweezers, watch screw-driver, case knife and screwbackcase opener. Also one doz. assort,push -pieces, full instructions andbattery identification chart. Wethen supply replacement batteries-- you fit them. Begin now. SendE9 for complete kit and get into a

-M. fast-growing business. Promptdespatch.

4/ NIBOLSTER INSTRUMENT CO. HEIO11 Percy Avenue, Ashford, Middx. TW15 2PB

LARGEST STOCKS ANYWHERESHEETS AND MANUALS. Service sheetsonly £1 s.a.e. Sole suppliers of the famousT.V. Repair Systems. Complete Diagramcollection Mono T.V. /Washing Machines/Col. T.V. /etc. in huge binders, only £13.50each. S.A.E. brings newsletter, bargainsoffers, quotes. - G.T., 76 Church St., Lark -hall, Lanarkshire (0698 883334).

AD INDEX

AHLERS ELECTRONICA 2AMBIT INTERNATIONAL 52ARROW AUDIO CENTRE 54BIG EARS LTD. 72BI -PAN SEMICONDUCTORS 21BK ELECTRONICS 47

381115CASPTRONICS 70CSC 64DAVID GEORGE SALES 66DISPLAY ELECTRONICS 6500NOENE LTD. 62EDA 8ELECTRONI-KIT 36ELECTRONIC MAIL ORDER 54ELECTRO VALUE 74GMT 47GREENWELD 47HENRY'S RADIO 81ICS 8ILP 4 & 5MACLIN-2AND 11MAGENTA ELECTRONICS 32MARSHALLS 42METAC 38 & 39MICRO CIRCUITS 48MINIKITS 58MITRAD 22 6 23VICTOR MORRIS 74NIC MODELS 74PARNDON 69T POWELL 16PRECISION PETITE 69J. W. SIMMER 69SAFGAN ELECTRONICS 54SILICA SHOP 28SKYWAVE 74C. N. STEVENSON 62SURETRON 66SWANLEY 35TECHOMATIC 12TECHNOMATIC 12TEMPUS 58TK ELECTRONICS 57T.V.E.S. 76VERO 27WEST HYDE DEVELOPMENTS 36WHEELS OF DOVER 72WINTJOY 72


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Recorder Kit)

Space InvadersFight the space invaders, be a polaris captain or a spaceshipcommander. Full colour action on your own TV set and over

450 games to play.Basic console with Combat cartridge (ACOOA) £99.50 + £2.50 carriageAll cartridges available including:

Space Invaders (AC26DI . £29.95 Adventure (AC22Y) £23.95Indy 500 (AC24B I £34.50 Skydiver (AC13P) (16.95Chess (Sieve's) IAC28F I £34.50 Breakout (A CO5F I £16.95Golf (9 holes) (AC181.1) f16.95 Slot Racers (AC19V) £16.95Air Sea Battle (AC0113) £16.95 Programming (AC27E) £34.50Space War (ACO2C) £16.95 Olympics (AC04E) £16.95Brain Games IAC16S1 £16.95 Street Racer (AC14Q) £16.95Outlaw (ACO3D I £16.95 Keyboards per pair (AC29G I £11.95

All prices include VAT and carriage except where shown.

Post this coupon now for your copy of our 1979-80 Catalogue price 70pPlease send me a copy of your 280 page catalogue. I enclose 70pplus 46 p&p). If I am not completely satisfied I may return

the catalogue to you and have my money refunded. If you liveoutside the U.K. send f 1.35 or ten International Reply .Coupons.I enclose 11.16.

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ByonpurnMaplin Electronic Supplies LtdAll mail to:- P.O. Box 3, Rayleigh, Essex SS6 8LR.Telephone: Southend (0702) 554155.

Shop:'284 London Road, Westcliff-on-Sea,Essex. (Closed on Monday)Telephone: Southend (0702) 554000

Catalogue now available in all branches of WHSMITH iti Price f1.00

ELECTRONICS AROUND THE HOUSE - World Radio History

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Transcript of ELECTRONICS AROUND THE HOUSE - World Radio History