CERTIFICATION

This it to certify that Osisiogu Ukachi Oluwaseun, a student of

Nnamdi Azikiwe University, Awka of the Faculty of Engineering and

Department of Electronic and Computer Engineering with

registration number 2010364149 has successfully completed his

SIWES programme with M & M Electrical/Electronics and

Telecommunications Company, Awka, Anambra State.

Students Signature Date

Industrial Based supervisor’s Signature and stamp Date

1

DEDICATION

To my parents who have been a constant source of support and

encouragement an epitome of godly and loving parents.

To my siblings whose care and affection for me beats my

understanding.

To every teacher who put every effort to see that they produce

students who will one day become better than themselves.

To every upcoming engineer who constantly works hard to help the

world to be a better place.

2

ACKNOWLEDGEMENTS

One of the major lessons I have come to learn in this life is

that “No man is an Island.”

The completion of this industrial training was made possible

because of some special persons who have been helpful in my life.

They include

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To my fellow IT students who have been very motivating to me. I

am grateful to you all.

Also Engr. Abdul Malik, my industrial supervisor whose guidance

has been of immense helps to me.

The co-workers of M & M Electronics, I am also grateful.

I am also grateful to my Parents Prof. and Mrs. Osisiogu, my

siblings and relatives who are always understanding and still

supportive to see that this program was concluded without much

stress.

Finally, to the Omni-potent God for His continuous supply of

wisdom, understanding and knowledge, and a whole lot more. I

forever remain grateful to You.

4

REPORT OVERVIEW

This purpose of this report is to inform the SIWES coordinator of

Nnamdi Azikiwe University. It is also meant to serve as proof

that I actually did undergo the 6 months training required for a

student to do. In this report I will present all I know about the

company, what I learnt in the company, problems I encountered in

the company and as well recommendations for Industrial Trust Fund

and the company of my place of attachment.

5

Table of Contents

Certification 1

Dedication 2

Acknowledgements

3

Report Overview 4

Table of Contents 5

Chapter One: Introduction 7

1.1 Background of SIWES 7

1.2 The Objectives of SIWES 8

6

Chapter Two: Description of Establishment of Attachment

11

(M&M Electrical/Electronics and Telecommunications Company)

2.1 Location and Brief History

11

2.2 Objectives of M & M Electronics

11

2.3 Organisational Structure of M & M Electronics

12

2.4 Various Departments and their Functions

12

Chapter Three: Skills and Knowledge Acquired

14

3.1 Audio Amplifiers 14

3.1.1 Principles of Operation

15

3.1.2 How Sound Amplification Works

16

7

3.1.3 Maintenance and Troubleshooting

18

3.2 The Inverter system 20

3.2.1 Mode of operation 20

3.2.2 Design and Implementation

21

3.2.3 Maintenance and troubleshooting

30

3.2.4 Precautionary measures

31

Chapter Four: Basic Electronics 30

4.1 Construction of Delay circuit using OP-AMP

32

4.2 Regulated power supply circuit

33

4.3 Crossover Circuit 34

Chapter Five: Summary, conclusions and Recommendations

36

8

5.1 Problems encountered during the program

36

5.2 Recommendations 37

5.2.1: For the Industrial Task Fund and SIWES

37

5.2.2: For the Company 38

5.3 Conclusions 39

5.3.1: Benefits I got after the SIWES program

39

5.4 Suggestions to the Improvement of Scheme

40

9

CHAPTER ONE

1.1 BACKGROUND OF SIWES

SIWES was established by ITF in 1973 to solve the problem of lack

of adequate practical skills preparatory for employment in

industries by Nigerian graduates of tertiary institutions.

The Scheme exposes students to industry based skills necessary

for a smooth transition from the classroom to the world of work.

It affords students of tertiary institutions the opportunity of

being familiarized and exposed to the needed experience in

handling machinery and equipment which are usually not available

in the educational institutions.

Participation in Industrial Training is a well-known educational

strategy. Classroom studies are integrated with learning through

hands-on work experiences in a field related to the student’s

academic major and career goals. Successful internships foster an

experiential learning process that not only promotes career

10

preparation but provides opportunities for learners to develop

skills necessary to become leaders in their chosen professions.

One of the primary goals of the SIWES is to help students

integrate leadership development into the experiential learning

process. Students are expected to learn and develop basic non-

profit leadership skills through a mentoring relationship with

innovative non-profit leaders.

By integrating leadership development activities into the

Industrial Training experience, SIWES hopes to encourage students

to actively engage in non-profit management as a professional

career objective. However, the effectiveness of the SIWES

experience will have varying outcomes based upon the individual

student, the work assignment, and the supervisor/mentor

requirements. It is vital that each internship position

description includes specific, written learning objectives to

ensure leadership skill development is incorporated.

Participation in SIWES has become a necessary pre-condition for

11

the award of Diploma and Degree certificates in specific

disciplines in most institutions of higher learning in the

country, in accordance with the education policy of government.

Operators - The ITF, the coordinating agencies (NUC, NCCE, NBTE),

employers of labour and the institutions.

Funding - The Federal Government of Nigeria

Beneficiaries - Undergraduate students of the following:

Agriculture, Engineering, technology, Environmental, Science,

Education, Medical Science, and pure and Applied Sciences.

Duration - Four months for Polytechnics and Colleges of

Education, and six months for the Universities.

1.2 THE OBJECTIVES OF SIWES

The following are some of the objectives of SIWES:

1. SIWES will provide students the opportunity to test their

interest in a particular career before permanent commitments are

made.

2. SIWES students will develop skills in the application of

theory to practical work situations.

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3. SIWES will provide students the opportunity to test their

aptitude for a particular career before permanent commitments are

made.

4. SIWES students will develop skills and techniques directly

applicable to their careers.

5. SIWES will aid students in adjusting from college to full-time

employment.

6. SIWES will provide students the opportunity to develop

attitudes conducive to effective interpersonal relationships.

7. SIWES will increase a student's sense of responsibility.

8. SIWES students will be prepared to enter into full-time

employment in their area of specialization upon graduation.

9. SIWES students will acquire good work habits.

10. SIWES students will develop employment records/references

that will enhance employment opportunities.

11. SIWES will provide students the opportunity to understand

informal organizational interrelationships.

12. SIWES will reduce student dropouts.

13

13. SIWES Students will be able to outline at least five specific

goals with several staff members by comparing performance with

job duties and develop a draft plan with staff to accomplish

performance needs, supervision plan and rewards.

14. SIWES Students will be able to develop a draft agency or

project budget and will be able to identify methods of obtaining

revenue to support the budget.

15. SIWES Students will be able to provide tools to use in

prioritizing tasks of an assigned project and create with staff a

tentative schedule for completion based on these tasks.

16. SIWES Students will be able to develop a model policy that

gives current front-line leaders the permission and expectation

to work with other staff on conflict resolution and explain how

this works to current front line leaders.

17. SIWES Students will be able to describe different skills

leaders can use to

Foster commitment and collaboration with both internal and

external constituents.

14

The 6 months Students Industrial Work Experience Scheme (SIWES)

which is a requirement for the completion of my course of study,

Electronic and Computer Engineering was done at M&M

Electrical/Electronics & Telecommunications Company. It has two

departments. They are experts in the field of sound systems and

inverter designs. The Industrial Training was based on working

with the necessary tools used in an electronics workshop in order

to design, build and implement basic and complex electronic

circuits needed for both home and enterprise users.

These things were being carried out in the company and some of

them form part of my job description.

15

CHAPTER 2

2.0 DESCRIPTION OF ESTABLISHMENT OF

ATTACHMENT

(M & M ELECTRICAL/ELECTRONICS & TELECOMMUNICATIONS COMPANY)

2.1 Location and Brief history of M & M ELECTRICAL/ELECTRONICS &

TELECOMMUNICATIONS COMPANY.

M & M is a young growing company which started its operation as a

company register under Corporate Affairs Commission on the 12th of

July, 2010. Ever since then company has been growing.

She is well interested in seeing that she helps in her own way to

solve the power supply problems in the country by engaging in the

design and building of inverters that could be used with solar

panels.

16

She has her head office at Awka in Anambra State at Odera

Shopping Complex, Shop 67 & 68.

I had the privilege of working in this company which believes in

the training of young minds.

2.2 Objectives of M & M Electrical/Electronics &

Telecommunications Company.

The vision this company runs with is to see that young men and

women are trained in order to live a self-reliant and independent

life i.e. to make a living on their own.

They are also committed to delivering excellent services to

customers.

They are committed to delivering long lasting solutions to the

power problems of the country.

They are committed to excellence and a model of a good servicing

company

2.3 Organisational Structure of M & M Engineering

Company.

17

M & M has an organizational structure which is expected to be

like an arranged hierarchal manner which starts from the

director, manager of technical services and management,

production manager and installation manager. It also should

include clerical offices such as secretary, cashier and cleaner.

During my stay in M & M electronics I underwent my industrial

work experience scheme under the productions department.

Figure 1 below shows the representation of the company.

2.4 Various Departments and their Functions

1. Technical Services and Management: This department has the

responsibility to make sure that the equipment in the workshop is

functional. They are also the department that repairs all the

faulty systems that a customer brings.

2. Training Department: One of the main visions of M&M

Electronics is to train young men and women who will gain skills

to work in companies of relative fields and also be able to have

their own companies and be self-employed and in turn create jobs

for other people. This department is responsible to make sure

that vision is fulfilled. They train students and they are also

18

responsible for the materials and tools that these students will

use. Courese like basic electronics, power inverter designs,

micro-controller basics and audio amplifiers are taken

3. Production Department: This department ensures that all the

jobs of production are being carried out, they also regulate

quality control. If a customer complains of a product they look

into it. They also make research so they can be able to provide

state of the art services to improve the company’s worth.

Products produces are solar inverters, power inverters, and audio

amplifiers.

4. Installation Department: After the production made by the

production department this department is to ensure proper

installation of equipment, it is possible that the equipment may

not have been produced by the company but they can be called upon

to perform installation services like solar power related

devices, satellite dishes, inverter systems and audio systems.

COMPANY ORGANISATIONAL CHART (Organogram)

19M & M ELECTRICAL/ELECTRONICS & TELECOMMUNICATIONS COMPANY

20

Director

Technical and Services

Management

Production

Manager

Installation

ManagerTraining

Design and production of audio system, automatic voltage regulator, inverter and project design

Repair and Troubleshootin

g of Electrical/Ele

ctronic equipment

Installation of wiring security systems

Clerical Officers

Secretary

Fig. 1: Organisational chart of M & M ELECTRICAL/ELECTRONICS & TELECOMMUNICATIONS

COMPANY

CHAPTER THREE

3.0 SKILLS AND KNOWLEDGE ACQUIRED

During the industrial attachment I was acquainted with a lot of

things which includes

a. Audio power amplifiers

b. The inverter system

c. Basic electronics

3.1 AUDIO POWER AMPLIFIERS

An audio amplifier is an electronic amplifier that amplifies low

power audio signal (signals composed primarily of frequencies

between 20 – 20,000 Hz, the human range of hearing to a level of

suitable for driving loudspeakers and is the final stage in a

typical audio playback chain. The preceding stage in such a chain

are low power audio amplifiers which perform tasks like pre-

amplification, equlisation, tone control, mixing/effects or audio

sources like record player, CD player and cassette players.

Most audio amplifiers require this low-level input to adhere to

line levels. While the input signal to an audio amplifier may

21

measure only a few hundred microwatts, its output may be tens,

hundreds or thousands of watts.

3.1.1 PRINCIPLES OF OPERATION

The audio amplifier works on the principle of magnetic

amplification. The magnetic amplifier is a static device with no

moving parts. It has no wear out mechanism and has a good

tolerance to mechanical shock and vibration. It requires no warm

up time. Multiple isolated signals may be summed by additional

control windings on the magnetic cores. The windings of a magnet

amplifier have a higher tolerance to momentary overloads then

comparable solid state devices. The magnetic amplifier is also

used as a transducer in applications such as current measurement.

22

Figure

Figure 2

A magnet amplifier device may resemble a transformer but the

operating principle is quite different from a transformer

essentially the magnetic saturation of the core, a nonlinear

property of a certain class of transformer cores. For controlled

saturation characteristics, the magnetic amplifier employs core

materials that have been designed to have a specific B-H curve

shape that is highly rectangular in contrast to the slowly

tapering B-H curve of slowly saturating core materials that are

often used in normal transformers. The typical magnetic amplifier

consist of two physically separate but similar transformer

magnetic core, each of which has two windings – a control winding

and an AC winding. A small DC current from a low impedance source

is fed into the series – connected control windings. The AC

windings may be connected either in series or in parallel, the

configurations resulting in different types of magnetic

amplifiers. The amount of control current fed into the control

winding, sets the point in the AC winding wave form at which

either core will saturate. In saturation, the AC winding on the

saturated core will go from a high impedance state into a very

23

Mixer Console

Input Unit

Amplifier Loudspeaker

low impedance state, i.e. current control at which voltage, the

magnetic amplifier switches “on”.

A relatively small DC current on the control winding is able tocontrol or switch large AC currents on the AC windings. Thisresults to current amplification.

3.1.2 HOW SOUND AMPLIFICATION WORKS.

In the amplification of sound, you need not just the audio

amplifier but also the presence of the audio speakers and the

microphones in conjunction with an audio mixer. In order to give

more illustrations we will use the block diagram.

Figure 3.1: Block diagram of sound amplification

Here, the input unit can be a microphone depending on the mode of

application. This device converts sound to electrical signals.

This signal is fed to the mixer console where the effects of the

sound can be modified and made better and then this signal is fed

to an amplifier which may be inside the mixer console or through

the use of a power amplifier as discussed above. Then the signal

produced by the amplifier is then fed into the loudspeaker to24

drive it. When this is done this signal is then converted form

electrical signal to sound.

3.1.3 Maintenance and troubleshooting

In the maintenance of an audio speaker it normally requires that

you observe the sound waveform produced through the use of an

oscilloscope especially when it is running at a maximum output.

A good example of this type of maintenance is the adjustment of

the bias of the final amplifier tubes in an amplifier. Using a

sine wave test signal as input to the amplifier tubes in an

amplifier, the output tube bias may be adjusted is that the

output signal has no crossover distortion.

In any event where the audio power amplifier is not coming on, we

troubleshoot to ascertain the fault with a bit to fixing it.

These are the things we were told to check.

When we plug it and the amplifier does not come on at all,

we check for the fuse.

We check for the fuse in the external plug if it is bad, we

replace it.

25

If it is not that we check the fuse in the amplifier.

We also have signs to check if it actually a power problem.

For example if there is a power surge when it is being

plugged then we can infer that one of the components of the

power supply like the transformer or even the rectifier

diode is damaged.

If we check the above and they are still alright, then we

check the power transistors. This is most likely to be the

problem with almost all the panels we worked on. So when

this occurs we test for the damaged one and then replace it.

If the issues still persist we check for other components

like the capacitors to make sure they are connected to the

printed circuit board (PCB)

We also check the relay which is used for switching

There are even times when most or all the components in a

panel get burnt to much voltage being initially supplied to

it. In that case we have to design and construct a new

panel. This time around we can even produce a better one

26

that will suit the conditions of power supply in this

country.

By the time we are sure that the solution is perfect we then

test the equipment and make sure it is working properly.

Some other issues may also come up. The ones listed above

were amongst the common ones I encountered in the workshop.

3.2 The Inverter System

The inverter system is an electronics device that converts direct

current (DC) to alternating current (AC); the converted AC can be

at any required voltage and frequency with the use of appropriate

transformers, switching, and control circuits.

Solid-state inverters have no moving parts and are used in a wide

range of applications, from small switching power supplies in

computers, to large electric utility high-voltage direct current

applications that transport bulk power. Inverters are commonly

used to supply AC power from DC sources such as solar panels or

batteries. There are two main types of inverter. The output of a

modified sine wave inverter is similar to a square wave output

except that the output goes to zero volts for a time before27

switching positive or negative. It is simple and low cost and is

compatible with most electronic devices, except for sensitive or

specialized equipment, for example certain laser printers. A pure

sine wave inverter produces a nearly perfect sine wave output

(<3% total harmonic distortion) that is essentially the same as

utility-supplied grid power.

Thus it is compatible with all AC electronic devices. This is the

type used in grid-tie inverters. Its design is more complex, and

costs 5 or 10 times more per unit power. The electrical inverter

is a high-power electronic oscillator. It is so named inverter

because early mechanical AC to DC converters was made to work in

reverse, and thus was "inverted", to convert DC to AC. The

inverter performs the opposite function of a rectifier

We have three types of square wave inverter when we classify them

under the type of waveforms they produce

1. Square wave inverter: Square wave inverters were the first

invented inverter. Square wave inverter has odd number of

harmonics and can hardly be used on AC appliances except some

lights and fans. This kind of inverter eventually reduces the

28

life span of the appliances they power. This is also the cheapest

form of inverter.

2. Modified sine wave inverter: Modified sine wave is more like

the square wave which possesses less harmonic distortion compared

to square wave. The harsh corners from the square wave were

eliminated to transform it to a modified sine wave. This type of

inverter is the most seen in today’s market. Although it is less

harmful to devices compared to the square wave, it still heats up

the coil in filer due to large amount of harmonic distortion and

dissipates power.

3. Pure sine wave inverter: Unlike square wave and modified sine

wave, pure sine wave inverters maintain the best quality due to

the least number of harmonic distortions present in it. Usually

sine wave inverter is the more expensive of the two.

The advantage it has over the others is that it allows us to use

all AC appliances and reduces the humming noise of inductive

loads like fans. The figure below shows the output of a pure sine

wave form.

29

Before we go into the design of an inverter we must firstunderstand the basics.

So I will start with a block diagram

30

Oscillator

Circuit

Amplifier

Circuit

Switching

Circuit

Transformer

AC Output

AC MainsChange Over

Circuit

Output Socket

Battery Charger Battery

Sensing Unit

Figure 3.2: Waveforms of Square, modified and pure sine

3.2.1 Mode of operation

The power inverter I learnt during my IT operated in the

following way:

The DC voltage from a battery is fed to an oscillator which

produces signals that may be pure sine wave, modulated sine wave

or square sine wave. These signals can then be amplified by an

amplifier circuit which then increases the strength of the signal

in question. It should be noted that the amplifier section is not

compulsory. The switching circuit is made up of transistors

especially Metallic Oxide Semiconductor Transistors (MOSFETS) and

is connected in such a way that the output of the oscillator

switches them on and off at the frequency of the oscillator. The

transformer steps up the resultant AC from the switching circuit

to a value that can drive the required load.

The change over circuit enables the battery to connect to the

oscillator which in turn feeds the amplifier. The amplifier feeds

31

Fig. 3.3: Detailed block diagram of

the switching circuit while the switching circuit feeds this

signal produced to the transformer to get the required AC voltage

output for the inverter. The AC from the mains supply is also

connected to the changeover circuit so that it will feed the

output socket when there is power from the public AC mains. When

there is supply from the AC mains, the oscillator circuit will be

switched off to switch off the inverter. The AC main also feeds

the battery charger through the changeover circuit in order to

charge the battery. The sensing unit senses a number of

conditions like low battery, full battery and overload.

3.2.2 Design & Implementation of Inverter System

In the implementation of the above mentioned design, we are going

to be looking at the following components.

a. The required power transformer

b. The regulator circuit

c. The Oscillator circuit

d. The signal amplification circuit

e. The switching circuit

f. The battery charger32

g. The charge controller

3.2.2.1 THE POWER TRANSFORMER

In order to obtain the required specification needed to

construct we are going to perform some calculations.

Using the formula:

Where P = perimeter of bobbin

V = voltage

T = number of turns

Applying this formula we can therefore calculate the transformer

windings for both secondary and primary windings.

During my industrial training we were faced with the task of

producing a 5KVA inverter, with primary winding voltage of 48V,

secondary winding voltage of 220V and the inverting voltage to

be 290V.

33

The perimeter of the transformer bobbin was given as 27cm2

For the primary voltage we have that V = 48V, therefore the

number of turns needed is given as

For the secondary voltage winding at 220V

Therefore,

For the inverting voltage winding at 290V

It should also be noted that in getting the correct wire gauge

to be used for the inverter we must know the current that will

pass through the coil and use an approved chart to get the

appropriate wire gauge to use.

3.2.2.2 THE REGULATOR CIRCUIT

The regulator gives the oscillator its reference voltage and

determines the amount of power that drives the system. The

34

amplitude of the oscillator or timer is determined by the voltage

output of the oscillator and the current of the regulator

determines the stability of the oscillator. The zener diode D1

determines the regulating voltage ranging from zero to the

maximum applied voltage since to clips and clamps the base

voltage of the transistor Q1.

The transistor Q1 determines the regulator output current and the

maximum applicable voltage the regulator can regulate whiles the

resistor R1 gives a feedback between the input and regulating

reference voltage.

3.2.2.3 The Oscillator circuit

During my industrial training we used the SG3524 integrated

circuit (IC). This was used to generate a modified sine wave. The

figure below shows the IC pin-out

35

Fig 3.4: The regulator circuit

3.2.2.4 The signal amplification circuit36

Fig 3.5: The pin out of SG3524

Fig 3.6: A schematic diagram of the

The signal from the oscillator is fed to a dual input class AB

push pull amplifier to produce an alternating output with the

same waveform but with higher power, powerful enough to drive the

switching circuit.

3.2.2.5 The switching circuit

After the amplification is done this signal is then fed into the

switching circuit. This circuit is made up of MOSFETs of which

the gates are all connected together and the signal from the

oscillator is fed in.

Also the drain of all the MOSFETs are all connected together and

then connected to the transformer, while the source are also

connected together and then connected to ground.

The frequency of the oscillation produced by the oscillator

switches, these transistors on and off at that same frequency

thereby generating the AC signal which then fed to the

transformer, the transformer steps up this AC signal to the

required voltage which can now be fed to the load.

37

3.2.2.5 Change over circuit

In order to avoid the frustration caused by power outages, which

make some equipment to restart. An automatic changeover has been

designed to tackle the issue.

By a proper configuration of D.C relays the load, the inverter

and the mains is being designed to direct all loads to the mains

38

Fig 3.7: A schematic diagram for a MOSFET switching circuit.

and redirect the load automatically to the power inverter when

the mains fail.

While operating in this mode, the switching system also turns the

inverter circuit on automatically. The selection of relay for

this system is carefully selected based on the stability and the

reliability when it is putted under unfavorable conditions like

low voltage and unstable power supply.

3.2.2.6 Operation and Description

39

Fig. 3.8: A schematic diagram for the change over circuit.

When grid power is on, the transformer T1 is energized which

triggers all the switches to “ON” mode. At this mode the loads

automatically connects to the grid power and DC supply to the

regulator is cut off to stop the inverters from operating.

When the grid power goes “OFF” the switches are released and the

load automatically connects itself to the inverter and at the

same time power is released to the regulator circuit which causes

the inverter circuit to start operation. No capacitor is used to

filter or smoothing the rectified power from the bridge diode

because the introduction of a capacitor to a relays power supply

increases the tendency for a delay in switching the relays to

either “ON” or “OFF” mode.

3.2.2.7 Charging System

The charging system for this system is in a hybrid mode (internal

and external) meaning that at time the mains or the grid power is

available the internal charging system would partially recharge

the battery when its voltage is below 12.5. An external source

like the Solar Cells or the

40

Wind turbine can also be connected to replace the internal

charger when the system is being used at a place where grid power

is not available. The internal charging circuit uses a

transformer less battery charging system instead of the normal

transformer type because the transformers produces great amount

of heat when the batteries are highly discharged which sometimes

eventually causes it to burn.

3.2.2.7 Battery Charger

When 220 volts AC is connected in series to a capacitor making

the AC tire which passes through the capacitor to make behave

like a pulse which created when the capacitor charges and

discharge. Since power cannot pass through the charger but only

store electrical power. The output from the capacitor is series

to the rectifier, changes the power to D.C ripples near zero

hertz making it conductive for battery charging. The diode only

used power stored in the capacitor. This procedure continues

until capacitor charges to full charge or the mains are

disconnected.

41

3.2.2.8 Charge Controller

The charge controller is a circuit tuned to either close or open

circuit for charging the battery when it is low and cut charging

when the battery is fully charged.

The minimum voltage is set to 9V and the maximum is left to the

digression of the installer since ever battery has a different

charging voltage.

42

Fig 3.9: A schematic diagram of the battery charger

3.2.3 Maintenance & Troubleshooting

During the course of my industrial training we did not only

produce the power inverters we also did some maintenance and some

trouble shooting. Also due to the fact that we are core

manufacturers, customers always come to us in order to repair the

faulty components.

One of the major problems we faced in the workshop was the

overheating of transformers. To tackle that issue we always had

to trace the fault by recoiling the power transformer, sometimes

the transformer had a bridge inside it or the transformer gets

burnt when any of these happened we recoiled the transformer.

43

Fig 3.10: A schematic diagram of a charge controller

Another problem we faced also was when the MOSFETs started to

overheat once the inverter was turned on so we just had to trace

the fault to the connection of these MOSFETs to their drain,

source and gates that were connected once the wrong connection

was rectified it would work perfectly.

Lastly, when the other circuits involved in the inverter circuit

seems to be faulty, problems may come from damaged transistors,

damaged relay, and any other damaged circuit. The needed action

to take was simply the replacement of such component and then

test for its functionality.

3.2.4 Precautionary measures

During my industrial training I was made to understand some

precautions that were needed to be taken. They are

1. Do not overload the inverter system so as to avoid blowing

up the inverter system.

2. Ensure that the polarity of the inverter system is not

reversed or bridged or else a hazard may occur.

44

3. Make sure that the battery being used is an original so that

it can serve you for longer hours.

CHAPTER FOUR

4.0 Basic Electronics

a. Delay Circuit using Operational Amplifiers

b. Power Supply Circuit.

c. Crossover circuit for Audio Speaker

45

4.1 Construction of a delay circuit using operationalamplifiers

The circuit uses RC circuit in combination with an Op-Amp

Comparator to accomplish the delay characteristic of a timer. In

the above diagram a voltage is applied across the R3-C1

combination. The input for the Op-Amp is tapped at the point

where R3 and C1 meet. This is the point where the positive

terminal of the capacitor gradually charges to the value of the

power supply. As the capacitor C1 reaches the Op-Amp's reference

voltage, the Op-Amp's output pin turns from High to Low, allowing

current to flow through the transistor, Q1, current enters the

base of the transistor and flows to the collector which acts as a

switch to turn the relay on. When the relay is on, current then46

Fig 4.1: A delay circuit with the

passes through the LED (causing the LED to glow). The time delay

can be controlled by changing the values or R3 or C1 or by

adjusting the value of the R1 and R2. For a new timer cycle to

occur, you must discharge capacitor, C1. 

4.2 Regulated Power Supply Circuit

During my industrial training I also learnt how to build a power

supply circuit.

First I had to understand the basics using a block diagram

From the diagram we can infer that the AC voltage is fed into a

transformer which steps it down to a value defined by the voltage

specifications of the transformer. The output of the transformer

is then fed into a rectifier.

The rectifier converts the AC to DC. There are three kinds of

rectification which are the half wave reactivation, full wave47

AC Mains FilterRectifierTransformer

Regulated DC

output

Fig 4.2: A detailed block diagram of a power supply circuit

rectification (with the use of two diodes) and also the full wave

rectification with use of four diodes. The one that I constructed

was full rectification with four diodes. The output from the

rectifier is then being fed to the filter circuit in order to

reduce the ripple effect.

The filter circuit is of 3 types we can just connect the

capacitor in parallel to the rectifier or use the pi and T method

but this time we use an inductor.

Finally the output from the filter circuit is then fed into the

regulator which can be an IC or through the use of a zener diode.

It

should also be noted that we can also provide a variable

regulated power supply or a constant regulated power supply.

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Fig 4.3: A schematic diagram of a dual rail regulated power supply circuit

Fig 4.4: A schematic diagram of a single rail regulated power supply circuit

Also the power supply can be a single rail power supply (can only

give an output of one polarity) or a dual rail power supply (can

give an output of both polarities).

It is important to note that in constructing a dual power rail we

must

use

a

center tapped transformer.

4.3 Crossover circuit

For certain loudspeakers that has both a woofer (bass) and a

tweeter a crossover circuit is being used because the balance

that the speaker gives depends on the amount of frequency the

sound produces.

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The tweeter speaker is used for higher sound frequencies so it

will be connected to a high pass filter circuit, while the bass

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Fig 4.5: Picture of a crossover circuit

Fig 4.6: Schematic diagram of a crossover circuit with a tweeter and to bass speakers

speaker is connected to the low pass filter in order for the

correct amount of frequency to pass through. Figure 3.16 shows a

picture of a crossover circuit, while figure 3.17 shows the

schematic diagram of a crossover circuit.

CHAPTER FIVE

5.0 SUMMARY, RECOMMENDATIONS AND CONCLUSIONS

5.1 PROBLEMS ENCOUNTERD DURING THE PROGRAM

I enjoyed my industrial training at M & M Electrical/Electronics

And Telecommunications Company but I was not left without

challenges.

1. No allowance

During my training I was not given any allowance to help

with the expenses that I had to take during the course of my

training like the transportation, feeding and then the

purchase of some needed equipment for work.

2. Distractions

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During the course of training the colleague of my industrial

supervisor had many friends who came around. Sometimes they

would chat for a long time and this distracted us the

trainees. They would even ask us to go get something for

them in the midst of our learning. This did not help us to

learn very well.

3. Inefficient transfer of knowledge

I did learn a few things but I believe I would have learnt

more if we did not just only rely on “on the job training”

because we were not even given much jobs to do. Sometimes

the industrial based supervisor did not have enough time to

teach us some things. So there was transfer of knowledge but

it was not so satisfactory.

4. Lack of seriousness

Some of my colleagues were not even so serious. Some would

come in late and then some would not even come at all. So

whenever they were not around I was told to do things that

were not even related to my field of study.

5.2 Recommendations

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SIWES is a very important programme in the life of any student

especially for those who would want to practice engineering.

SIWES has gone a long way to bridge the gap between what is done

in the university and what is done in the industry.

5.2.1 For the Industrial Task Fund and SIWES

I strongly recommend that ITF should keep visiting the students

on a regular basis i.e. at least 3 times in the space of the 6

months of the training so that these who are not serious will be

more dedicated to their place of work.

I also want to recommend that ITF should always liaise with many

companies to ensure that IT students do not have a hard time

finding a place of attachment.

I also want to recommend that in order for ITF to fulfill its

objectives in the career of students they should always ensure

that companies with the facilities to train engineering students

should be willing to accept a larger number of students than they

are doing now. This will go a long way to minimize the search

many students undergo before they find a place for attachment.

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5.2.2 FOR THE COMPANY

I actually learned some useful things during my stay in M & M

Electronics. During my stay I observed a few things and I want to

recommend the following.

1. One of the things the company lack is a good marketer. There

are lot of persons in Anambra State and probably other

states who may need the services you provide but they need

someone to encourage or push them to buy it. A good marketer

with good skills can make you get more jobs and more money

so that you can even pay the trainees that come to the

company to work. One of the challenges I faced during my

training was lack of allowances during my stay there. So

doing this can be of good help in future.

2. The environment where the company is hidden. You provide

good services yet you are not well known in Awka. I will

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advise that you either get another place or you make banners

or posters that will advertise your products and attract

much more customers. One of the challenges I also faced as

regards the venue was the fact that it was not conducive

enough for learning because of the level of noise and some

other distractions.

3. The customer relationship was not so wonderful, I am

actually trying to say that the way some customers get

disappointed because of a delayed job or a job not well done

that causes them to come back again over a short period of

time can continue to degenerate customer relationship. So I

recommend that they treat customers well so that in the long

run they would not lose many other customers.

4. In the world of business collecting loans to improve one’s

business is not that bad. I know you have a lot of things in

mind but then you need more packaging and packaging is going

to cost money. You have the capacity to become one of the

leading electronic schools in Awka but you have not provided

room for that. So I recommend that you get loans or apply

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for programs that can fetch such loans in order to get more

money. One of the challenges I faced was that most of the

learning I did was always on the job training. It was only a

few times we sat down and learnt a few things. This did not

cause efficient transfer of knowledge. So I recommend that a

training school be set up so that the trainees can benefit

well and even be willing to pay.

5.3 Conclusion

In conclusion this industrial training has afforded me the basic

practical and theoretical knowledge that I may not have gotten

from the lecture room. It also gave me the opportunity to have a

feel of what it would be like after graduation when I start

working. It has also helped me to have knowledge of the

electronics industry.

5.3.1 Benefits I got after the SIWES program

More Confidence

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During my training I developed confidence in constructing any

electronic circuit, because I was told to do that a lot. I can

even solder better than I used to.

With that to I can be able to analyse most electronic circuits.

Knowledge

During my SIWES program I was used to seeing many things on

electronics especially the components used in making a circuit. I

have an in depth knowledge of audio systems and how they operate

and also the inverter system.

Working Ethics

During this program I was learnt how to handle customers, and

also involved myself into many jobs that had to do with teamwork.

Exposure

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I was exposed to many things like how to solder in a special

way, how to respond to faulty equipment and also how to respond

to customers anytime.

Networking

During my industrial attachment I made new friends in my field of

study, people I can be able to look up to and also seek their

help any time I have challenges whether it is during ny stay here

or beyond.

5.4 Suggestions to the improvement of Scheme

In order to make this scheme more interesting awareness needs to

be made corporate bodies on how industrial attachment students

should be treated. Any company that can train students that has

not yet started accepting students can collaborate with ITF and

see the best way they can start taking industrial attachment

students.

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SIWES supervisors should be visiting us more often than they are

doing so that we can be encouraged to be very serious with this

programme.

SIWES should increase the pay and also pay the first half at the

beginning of the training and then pay the remaining at the end

of the training so that those who may encounter financial

problems can be able to cope.

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