EMOTIONAL STRESS INDICATOR

JYOTHI ENGINEERING COLLEGECHERUTHURUTHY, THRISSUR 679 531

Mini Project Report

On

EMOTIONAL STRESS INDICATOR

Submitted by

ATHIRA RAJ JYALEEC014MARIA FRAJI FRANCIS JYALEEC036NEETHI KRISHNAN JYALEEC043REMO DAVIS C. JYALEEC050

SIXTH SEMESTER B.TECH(ENGINEERING)

DEPARTMENT OFELECTRONICS & COMMUNICATION ENGINEERING

2014

DEPARTMENT OF ELECTRONICS & COMMUNICATION ENGINEERING

JYOTHI ENGINEERING COLLEGECHERUTHURUTHY, THRISSUR 679 531

CERTIFICATE

This is to certify that the miniproject report entitled EMOTIONAL STRESS INDICA-

TOR is being submitted by REMO DAVIS C (JYALEEC050) in partial fulfilment of the

requirements for the award of Bachelor of Technology degree in Electronics & Communica-

tion Engineering of University of Calicut.

GUIDE

Mr. DIPIN KRISHNAN R. Dr. JOSE P THERATTIL

ASSISTANT PROFESSOR, ECE HEAD OF THE DEPARTMENT

PLACE : CHERUTHURUTHY

DATE : 23/04/2014

ACKNOWLEDGEMENT

First of all we would like to express our sincere thanks to the Almighty God, who empowered us

to complete this project, by showering his abundant grace and mercy.

We would like to express our sincere thanks to Dr. GYLSON THOMAS, our beloved Principal for

his support and encouragement.

We use this occasion to express our thanks to Dr. JOSE P THERATTIL, Head of ECE Department,

for his continuous encouragement and great support to fulfil our project.

We are also thankful to Mr.DIPIN KRISHNAN.R, our project guide for his valuable suggestions

and support in making this project.

We are thankful to Mr. ABRAHAM P.A and Ms. SHINY M.I , our mini-project coordinators for

their inspiration and motivation to develop the project.

We are thankful to all the teaching and non teaching staffs in Electronics and Communication De-

partment for their timely assistance in matters pertaining to project.

We thank our parents and friends for their kind co-operation and suggestions which helped us very

much for the accomplishment of project.

iii

ABSTRACT

All muscles are not created equally strong and the conditions that stretch them vary from

person to person. This equipment consists of two touch pads made of conducting materials into the

fabric that register the mechanical excitation of the muscle fibers that pass the signals to an electronic

analysis system. Muscle tension of people changes with their stress level. The greater the stress, the

more likely the muscles are to produce a synchronous twitching effect. At the same time, skin offers

some resistance to current and voltage. At relaxed state they offer more resistance and at higher stress

they offer less resistance.The basic principle of the circuit is galvanic skin response.It is the measure

of conductivity of electricity in skin. In the circuit,10 LED’s and a buzzer are used to indicate stress

level and IC LM3915 helps to drive these LED’s This circuit is highly sensitive and costless.

iv

TABLE OF CONTENTS

ABSTRACT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iv

LIST OF FIGURES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . vi

LIST OF ABBREVIATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . vii

1 INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

2 LITERATURE SURVEY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

3 BLOCK DIAGRAM OF PROPOSED CIRCUIT . . . . . . . . . . . . . . . . . . 5

4 CIRCUIT DIAGRAM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

4.1 OPERATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

4.2 COMPONENTS REQUIRED . . . . . . . . . . . . . . . . . . . . . . . . . 8

4.3 HARDWARE DESCRIPTION . . . . . . . . . . . . . . . . . . . . . . . . . 8

5 IMPLEMENTATION AND RESULT . . . . . . . . . . . . . . . . . . . . . . . . 13

5.1 ARES SOFTWARE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

5.2 PCB MANUFACTURING . . . . . . . . . . . . . . . . . . . . . . . . . . 16

6 CONCLUSION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

BIBLIOGRAPHY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

v

LIST OF FIGURES

2.1 STRESS INDICATOR SAMPLE 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

2.2 STRESS INDICATOR SAMPLE 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

3.1 BLOCK DIAGRAM OF PROPOSED CIRCUIT . . . . . . . . . . . . . . . . . . . 5

4.1 CIRCUIT DIAGRAM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

4.2 PINOUT DIAGRAM OF LM3915 . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

4.3 PINOUT DIAGRAM OF BC548 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

5.1 PCB DESIGN USING ARES SOFTWARE . . . . . . . . . . . . . . . . . . . . . . 16

5.2 PCB IMPLEMENTATION OF ESI . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

vi

LIST OF ABBREVIATIONS

ESI - Emotional Stress Indicator

GSR - Galvanc Skin Response

vii

Emotional Stress Indicator miniproject

1 INTRODUCTION

Emotional Stress indicator is designed for observing stress level.Resistance of skin varies in ac-

cordance with stress. At the stage of high stress, conductivity of electricity through the skin increases.

This small voltage is amplified using signal amplifier. BC 548 is main component of signal amplifier.

LED’s and buzzer are used for indicating the stress levels.IC LM3915 can drive up to 10 LED’s one

by one in the dot/bar mode for each increment of 150mV in the input. LED 1 glows while input of IC

receives 150mV, LED 10 glows when the voltage rises to 1.5V and a piezo buzzer PZ1 beeps when

the stress level is very high.

It helps to find out the level of tension faced by a person , for checking blood pressure, for improv-

ing mental clarity and it can also be used as a lie detector and moisture level monitor. After knowing

the subject is stressed, various exercises can be done like,breathing exercises or yoga to maintain

emotional stress.Rhythmic breathing exercises can help control heart rate.The stress is expected to

diminish subject’s feelings of well-being, balance and enhanced energy will increases.ESI circuit is

very sensitive and shows the response during a sudden moment of stress. This device is ideal to sense

small currents in low input current applications.The circuit is simply and portable. And it is costless

circuit.

Jyothi Engineering College 1 Dept. of ECE


2 LITERATURE SURVEY

Figure 2.1: STRESS INDICATOR SAMPLE 1

Based on Literature survey conducted, we have came across different circuits related to stress

indicators.

This stress meter consists of 16 LEDs in a circle with two touch pads. By placing your fingers

on the touch pads, the circuit started and ran the LEDs in a "chaser" pattern around the display, with

a beep each time a LED was illuminated. The circuit gradually slowed down to a random LED and

the display showed "how stressed you were.Things required to complete this project are:

1: Stress Meter project (Uses 18 LED Display-1 PCB and parts and comes with PIC12F629 chip

pre-programmed with "Stress")

2: Chip Programmer - Model F project.It also requires certain software’s which is very bulky and

costly.It also specifies that the user must have the knowledge of complex programming which is a

tedious task.Certain components of this circuit are not available directly in local market.Since this

needs microprocessor programming,a simple error can delay the working of the circuit.

This circuit is useful to monitor the skin’s response to relaxation techniques. IC CA3140

(IC1) is designed as a resistance-to-voltage converter that outputs varying voltage based on the skin’s

conductivity. It is wired as an inverting amplifier to generate constant current to skin in order to

measure the skin resistance.



Figure 2.2: STRESS INDICATOR SAMPLE 2

IC CA3140 is a 4.5 MHz BiMos operational amplifier with MOSFET inputs and bipolar out-

put. The gate-protected inputs have high impedance and can sense current as low as 10 pA. This

device is ideal to sense small currents in low-input-current applications. The inverting input (pin 2) of

IC1 is connected to ground (through preset VR1) and one of the touch plates, while the non-inverting

input (pin 3) is grounded directly. The output from IC1 passes through current-limiting resistor R1

to the second touch plate. R1 act as a feedback resistor along with the skin when the touch plates

make contact with the skin. So the gain of IC1 depends on the feedback provided by R1 and the

skin. In the inverting mode of IC1, a positive input voltage to its pin 2 through the feedback network

makes its output low. If the skin offers very high resistance in the relaxed state, input voltage to pin

2 reduces and the output remains high. Thus the gain of IC1 varies depending on the current passing

through the skin, which, in turn, depends on the skin response and emotional state.In the standby

state, touch plates are free. As there is no feedback to IC1, it gives a high output (around 6 volts),

which is indicated by shifting of the meter to right side. When the touch plates are shorted by the

skin, the feedback circuit completes and the output voltage reduces to 4 volts or less depending on the

resistance of the skin. Since the feedback network has a fixed resistor (R1) and VR1 is set to a fixed

resistance value, the current flowing through it depends only on the resistance of the skin. The output



from IC1 is displayed on a sensitive moving coil meter (VU meter). By varying preset VR2, you can

adjust the sensitivity of the meter.

For easy visual observation, an LED display is also included. IC LM3915 (IC2) is used to give

a logarithmic display through LED indications. It can sink current from pin 18 to pin 10 with each

increment of 125 mV at its input pin 5.The drawback of this circuit is that touch pad and two IC ’s are

required which will increase the cost of project.

In our circuit we uses a LED diver as in same case and touch pad is replaced by a copper

plate which will drastically reduce the cost of the project and at the same time will have the same re-

sult obtained from the previous circuit mentioned above.Transistor BC548 and copper plate(for touch

pads)are used which will reduce the cost of the project and at the same time will show the same result

as that of the previous one discussed above.



3 BLOCK DIAGRAM OF PROPOSED CIRCUIT

Figure 3.1: BLOCK DIAGRAM OF PROPOSED CIRCUIT

DESCRIPTION OF BLOCK DIAGRAM

1. The touch pads of the stress meter sense the voltage variations across the touch pads.

2. Signal amplifier is used to amplify the signal coming from touch pad.

3. Then it goes to IC 3915.It is a monolithic integrated circuit. It used as dot/bar display that

senses analog voltage level from signal amplifier.

4. LED display is used for visual indication and piezo buzzer is used for a warning beep.

5. IC LM3915 which can drive up to 10 LED’s(with an increment of 125mV each).

6. LED1 flashes when stress level is low(V=150mV) LED5 flashes when stress level is high driv-

ing piezo-buzzer.



4 CIRCUIT DIAGRAM

Figure 4.1: CIRCUIT DIAGRAM

4.1 OPERATION

The gadget is based on the principle that the resistance of the skin varies in accordance with your

emotional states. If the stress level is high the skin offers less resistance, and if the body is relaxed

the skin resistance is high. The low resistance of the skin during high stress is due to an increase in

the blood supply to the skin. This increases the permeability of the skin and hence the conductivity

for electric current.

This property of the skin is used here to measure the stress level. The touch pads(Copper Plates)

of the stress meter sense the voltage variations across the touch pads and convey the same to the cir-

cuit. The circuit is very sensitive and detects even a minute voltage variation across the touch pads.

The circuit comprises signal amplifier and analogue display sections. Voltage variations from

the sensing pads are amplified by transistor BC548 (T1), which is configured as a common-emitter



amplifier. The base of T1 is connected to one of the touch pads through resistor R1 and to the ground

rail through potmeter VR1. By varying VR1, the sensitivity of T1 can be adjusted to the desired level.

Diode D1 maintains proper biasing of T1 and capacitor C1 keeps the voltage from the emitter of T1

steady.

The amplified signal from transistor T1 is given to the input of IC LM3915 (IC1) through VR2.

IC LM3915 is a monolithic integrated circuit that senses analogue voltage levels at its pin 5 and dis-

plays them through LEDs providing a logarithmic analogue display. It can drive up to ten LEDs one

by one in the dot/bar mode for each increment of 125 mV in the input. Here, we have used only five

LEDs connected at pins 14 through 18 of IC1. LED1 glows when input pin 5 of IC1 receives 150 mV.

LED5 glows when the voltage rises to 650 mV and LED5 flashes and piezobuzzer PZ1 beeps when

the stress level is high.

After tying the unit around your wrist (with touch pads in contact with the skin), slowly vary

VR1 until LED1 glows (assuming that you are in relaxed state). Adjust VR2 if the sensitivity of IC1

is very high.

APPLICATIONS

1. It is used for finding stress level of patients

2. It act as lie detector

3. It is used for finding level of tension

4. It helps to find mental state of a person

5. It is used for checking blood pressure

6. It is used by heart patients incase of emergency

ADVANTAGES

1. It sense every small current

2. It is portable

3. It is a low cost device


4. It is easy to handle

5. It consumes low power

6. It is an accurate circuit

4.2 COMPONENTS REQUIRED

4.3 HARDWARE DESCRIPTION

(a) LM3915

The LM3915 is amonolithic integrated circuit that senses analog voltage levels and drives ten

LEDs,LCDs orvacuum fluorescent displays, providing alogarithmic 3 dB/step analog disply.One pin

changes the disply fom a bar graph toa moving dot disply.LED current drive is regulated and pro-

grammable, eliminating the need for current limiting resistors.The whole display system can operate

from a single supply as low as 3V or as high as 25V.

8


The IC contains an adjustable voltage reference and an accurate ten-step voltage divider. The

high-impedance input buffer accepts signals down to ground and up to within 1.5V of the positive

supply. Further, it needs no protection against inputs of Âs35V. The input buffer drives 10 individual

comparators referenced to the precision divider. Accuracy is typically better than 1 dB.

The LM3915 3 dB/step display is suited for signals with wide dynamic range, such as audio

level, power, light intensity or vibration. Audio applications include average or peak level indicators,

power meters and RF signal strength meters. Replacing conventional meters with an LED bar graph

results in a faster responding, more rugged displaywith high visibility that retains the ease of inter-

pretation of ananalog display.

The LM3915 is extremely easy to apply. A 1.2V full-scale meter requires only one resistor

in addition to the ten LEDs. One more resistor programs the full-scale anywhere from 1.2V to 12V

independent of supply voltage. LED brightness is easily controlled with a single pot.

The LM3915 is very versatile. The outputs can drive LCDs, vacuum fluorescents and incan-

descent bulbs as well as LEDs of any color. Multiple devices can be cascaded for a dot or bar mode

display with a range of 60 or 90 dB. LM3915s can also be cascaded with LM3914s for a linear/ log

display or with LM3916s for an extended-range VU meter

(a1) PINOUT DIAGRAM OF LM3915

Figure 4.2: PINOUT DIAGRAM OF LM3915



(a2) LM3915 FEATURES

1. 3 dB/step, 30 dB range.

2. Drives LEDs, LCDs, or vacuum fluorescents.

3. Bar or dot display mode externally selectable by user.

4. Expandable to displays of 90 dB.

5. Internal voltage reference from 1.2V to 12V.

6. Operates with single supply of 3V to 25V.

7. Inputs operate down to ground.

8. Output current programmable from 1 mA to 30 Ma.

9. Input withstands ±35V without damage or false outputs.

10. Outputs are current regulated, open collectors.

11. Directly drives TTL or CMOS.

12. The internal 10-step divider is floating and can be referenced to a wide range of voltages.

(b) BC548

Figure 4.3: PINOUT DIAGRAM OF BC548

1. Breakdown voltage, collector-to-emitter with base open-circuit VCEO = 30 V.

2. Rated continuous collector current IC = 100 mA.

3. Rated total power dissipation P total = 500 mW (some manufacturers may specify 625 mW).



4. Transition frequency (gain-bandwidth product) ft = 150 MHz minimum (300 MHz typical).

5. Noise figure less than 10 db.

6. Belong’s to C gain grouping which are having a gain between 420 and 800.

(c) LEDs

The LED is based on the semiconductor diode. When a diode is forward biased (switched on),

electrons are able to recombine with holes within the device, releasing energy in the form of photons.

This effect is called electroluminescence and the color of the light (corresponding to the energy of the

photon) is determined by the energy gap of the semiconductor.

(d) RESISTORS

A resistor is a two-terminal electronic component that produces a voltage across its terminals

that is proportional to the electric current passing through it in accordance with Ohm’s law.Resistors

are elements of electrical networks and electronic circuits and are ubiquitous in most electronic equip-

ment. Practical resistors can be made of various compounds and films, as well as resistance wire (wire

madeof a high-resistivity alloy, such as nickel/chrome).

(e) CAPACITORS

A capacitor (formerly known as condenser) is a passive electronic component consisting of a

pair of conductors separated by a dielectric (insulator).When there is a potential difference (voltage)

across the conductors a static electric field develops in the dielectric that stores energy and produces a

mechanical force between the conductors.Capacitors are widely used in electronic circuits for block-

ing direct current while allowing alternating current to pass, in filter networks, for smoothing the

output of power supplies, in the resonant circuits that tune radios to particular frequencies and for

many other purposes.



(f) POTENTIOMETER

A potentiometer is a three-terminal resistor with a sliding contact that forms an adjustable volt-

age divider.If only two terminals are used (one side and the wiper), it acts as a variable resistor or

rheostat.Potentiometers are commonly used to control electrical devices such as volume controls on

audio equipment. Potentiometers operated by a mechanism can be used as position transducers.



5 IMPLEMENTATION AND RESULT

The circuit was implemented and designed and was ready to use.The steps used are described

as below.The circuit is assembled as a small piece on a printed circuit board(PCB).The PCB can be

implemented using ARES software.

5.1 ARES SOFTWARE

ARES (Advanced Routing and Editing Software) forms the PCB layout module of the Proteus

Design Suite and offers net list based PCB design complete with a suite of high performance design

automation tools.

Major features of ARES Professional include:

1. 32 bit high-precision database giving a linear resolution of 10nm, an angular resolution of 0.1◦

and a maximum board size of +/- 10m. ARES supports 16 copper layers, two silk screens, four

mechanical layers plus solder resist and paste mask layers.

2. Accelerated display using the power of your graphics to improve speed andprovide true layer

transparency.

3. Of the art ergonomic user interface with modeless selection, selection and activityindicators

and localised functionality via context menus.

4. Based integration with ISIS schematic capture, including the ability to specify routing informa-

tion on the schematic.

5. Automatic Back-Annotation of component renumbering, pin-swap and gate-swap changes.

6. Physical Design Rule Checker and integrated Connectivity Rule Check reports.Powerful route

editing features including topological route editing, auto track necking and curved trace support.



7. Class adaptive shape based autorouter capable of achieving completion on even the most com-

plex of boards.

8. Technology Data scheme allows for flexible re-use of board outlines and design constraints.

9. Drawing with Symbol Library.

10. package libraries for both through hole and surface mount parts including SM782 and IPC7351

standard SMT footprints.

11. Pad/Trace/Via Styles.Full metric and SMT support. This includes all dialogue form fields as

well as the coordinate display and grid settings.

12. Output to a wide range of printers and plotters including the Valor ODB++ format and tradi-

tional Gerber/Excellon. Also output in DXF, PDF, EPS, WMF and BMP graphics formats - to

file or clipboard where appropriate.

13. Built in Gerber Viewer - this enables you to check your Gerber output files before spending

money on bureau fees or board manufacture.

14. Board Visualisation with solidworks compatible STL output and 3D DXF and 3DS output.

5.1.1 MAIN THINGS TO BE CONSIDERED IN ARES SOFTWARE:

The largest area of the screen is called the Editing Window, and it acts as a window on the drawing

- this is where you will place and track the board. The smaller area at the top left of the screen is

called the Overview Window. In normal use the Overview Window displays, as its name suggests,

an overview of the entire drawing - the blue box shows the edge of the current sheet and the green

box the area of the sheet currently displayed in the Editing Window. However, when a new object is

selected from the Object Selector the Overview Window is used to preview the selected object.

There are different tools and menus for efficient completion of PCB design.



The control bar at the bottom of the application is different from what we have seen in the ISIS

application and essentially splits into four sections:

1. Layout Selector

2. Selection Filter

3. Status Bar

4. DRC Status and Mouse coordinates

Common steps to be followed:

1. Run the ISIS professional program by clicking the icon on the desktop, then this splash screen

will appear.

2. Next, a work space with interface buttons for designing circuit will appear.

3. Note that there is a blue rectangular line in the workspace; make sure that whole circuit is

designed inside the rectangular space.

4. Next step is selecting the components to our required circuit.

5. Select the components from library. In menu bar library > pick device/ symbol.There is another

way to select the components. In work space left side there is a tool bar. In that tool bar click

the component mode button or pick from library.

6. Components are added to devices list. Click on the device and change the angle of the device

by using rotate buttons. Then click in the work space then the selected component is placed in

work space.

7. Place all the devices in work space and put the cursor at the component pin end then draw the

connections with that pen symbol. Connect all the components according to circuit then that

designed circuit is show in below image.



8. If any modifications want to do to the component place the mouse point and click on right

button then option window will open.

9. After completion of designing save with some mane and debug it. This is virtual simulation

means without making circuit we can see the result in virtually through this software and we

can design the PCB layout to our required circuit with this software.

Figure 5.1: PCB DESIGN USING ARES SOFTWARE

5.2 PCB MANUFACTURING

5.2.1 DESIGN OF PCB

The miniaturization in electronic equipment design has introduced a new technique known as

Printed Circuit Board. Printed circuit board is used to interconnect various electronic circuit printed

on it and is provided with holes to accommodate various electronic components. Printed circuit board

(PCB) consists of an insulating base substrate, which is rigid, with metallic circuitry photo chemi-

cally formed up on the substrate. Interconnections between components are achieved by means of

conducting paths (thin Cu film) running on or through the substrate called tracks.The width of the

tracks depends on the amount of current it has to carry. The tracks meet components to which they

are to be connected by means of Land or pads which takes form of larger area of Cu. The lands may

be of different shapes and sizes and have holes drilled through them.These holes can either accommo-

date component leads or via-holes. The via -holes also known as plated through holes (PTH) provide



connections through the substrate to other track areas. These aroused in case of double sided and

multilayer PCBs only.

Once PCB is designed and fabricated, the circuit can be assembled easily by mounting and sol-

dering the component in the holes provided for them.

Figure 5.2: PCB IMPLEMENTATION OF ESI

There are three types of PCB’s :

1. Single sided PCB

2. Double sided PCB

3. Multi layered PCB

4. Flexible PCB

Besides the complete outlines and interconnections, the layout should include information on:

a. Component hole diameter

b. Conductor width

c. Minimum spacing to be provided between the tracks.

Finally take the print out of the pattern layout on a normal A4 size paper. Also make sure that it

is the correct size; Check the layout carefully. This printout is called as positive film.



5.2.2 Making of Printed Circuit Boards-

Various steps involved in the making of PCB are:

1. Preprocessing

2. Photo-lithography

3. Etching

4. Stripping

5. Tin plating

6. Drilling

7. Testing

8. Loading of components

9. Soldering

(1) Preprocessing

As its name, this step involves all the initial preparation to be made before actual processing of

copper clad laminate starts, such as

a. Collect the printout of the layout from the CAD lab.

b. Cut the copper clad laminate to the required size using a cutter.

c. Clean the board by scrubbing with steel wool or very fine wet sand paper.

d. Dry the board thoroughly.

e. Make sure that the board is clean and free from fingerprints or any traces of contamination.

d. Drill tooling mounting holes.

(2) Photo Lithography

Photo-lithography is typically the transfer of the copper track and land pattern from the negative

film to a photo sensitive material by selective exposure to a radiation source such as UV light. It

includes the following steps:



a. Pattern transfer:

Apply photo resist. Coat the Cu surface of the Cu clad laminate with a photosensitive material

in a dip coating machine. In lithography, the photosensitive material used is typically a photo resist

(also called resist). Both positive and negative photo resist can be used, but the negative photo resist

which become insoluble on exposure with UV light is almost universally used. Now place the photo

resist- coated board in the oven for 10 minutes to dry the photo resist. Exposure to UV light: Remove

the board from the oven and place it in ultraviolet exposure machine with the photo resist side facing

up. Now place the mask (i.e. the negative film) over the board and correctly align it with the board’s

geometry. Masking tapes can also be used to keep the negative film in position. Switch on the UV

exposure machine for 3 minutes. The UV light falls on the photo resist only through the lighter or

transparent part of the mask. Thus the photo resist changes its properties only where exposed to radi-

ation. Take out the board from the UV enclosure by holding it from the edges (using forceps).

b. Development

After exposure, the image of the pattern transferred on the photo-resist needs to be developed.

The development stage involves removal of less soluble unexposed area of resist in case of negative

resist and exposed areas in case of positive resist. Here, we are using a negative photo resist. Method:

Take a tray and put sufficient developer solution in it such that the board can be completely dipped

in it. Developer solution is prepared by mixing liquid photo-resist developer concentrate with 1 part

developer to 9 part of water.

Place the board into the white developer solution. The board should be handled at its corners

with the help of forceps. Now lift the tray on each side in rotation so that the liquid developer is

flowed over and back on the board. This id continued throughout the developing time (1 min). During

development, the developer solution etches away the unexposed region of the negative photo resist

showing copper and the PCB layout will be revealed. After the development is over, lift the board and

wash it in stop bath. This will effectively stop the development action.



c. Fixing

To fix the pattern on the board, mix 1 cap of fixer (blue die solution) in 1 glass of water in tray.

Place the board in the solution for at least 0.5 min. Remove the board from the fixer bath and wash it

under running water.

(3) Etching

This process is used for removal of PCBâAZs copper surface, which is not protected by the photo

resist. Thus final Cu pattern is formed on the board after etching.

The board obtained after photolithography is dipped in an etching solution and gitated for 6-10 min.

At 400◦C,the solution etches and dissolves away the exposed or undesired copper areas, leaving the

desired copper pattern on the board. The different types of etching solution used are:

a. Ferric Chloride (FeCl3)

b. Chromatic Chloride

c. Cupric Chloride (CuCl2)

d. Alkaline Ammonia

Out of these four, ferric chloride is the most commonly used etchant.

(4) Stripping

After etching, the negative photo resist coating left on the copper pattern can be removed using a

tube of photo resist stripper and the PCB is washed clean under tap water and dried using tissue paper.

(5) Tin plating

This is done to provide a fine finish and to protect the copper from oxidation. Also soldering will

appear neater and will flow better. For this, pour a solution made up of fine tin powder mixed with

water into a basin. Place the board in the solution for 10 minutes. The board should then have a silver

finish.



(6) Drilling

Drilling is used to create the component lead holes and through holes in a PCB. These holes pass

through the land areas and should be positioned correctly. The drilling process can be performed

by using manually operated drilling machines or by using CNC drilling machines. For a particular

PCB, a wide range of drill holes may be required e.g. smaller holes are required for component leads

whereas larger diameter holes are required for bolting heat sinks, connectors etc.



6 CONCLUSION

Stress meter has different applications like skin response, to find out the level of stress , to find

out the level of pain and can be used as tension meter. Stress meter is based on the concept of varying

skin resistance according to emotional states.That is the resistance of skin is inversely proportional

to the stress level.When the stress level is high, an increase in blood supply occurs which result in

high permeability and hence an increase in conductivity of electric current.It gives visual indication

through LED display along with warning beep.Relaxed state is indicated by green LEDs, intermediate

stress by yellow LED’s, high level stress is indicated by red LED’s.



BIBLIOGRAPHY

1. Electronic Devices and Circuits, by T.f.bogart, J.S.beasley, G.Raco.

2. Engineering Circuit Analysis, by William Hayt, Jack E Kemmerly, Mc Graw Hill.

3. Operational Amplifier and Linear Integrated Circuits, by R.F.Coughlin and Fredrick, F.Driscoll.

4. Wikipedia for information about skin and skin resistance, muscle and muscle strength.

5. IEEE papers referred to myieee.org.

6. D.Mohen kumar, Stressmeter

www.electronicsforu.com/electronicsforu/circuitarchives/view article/stressmeter


EMOTIONAL STRESS INDICATOR

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