Training Report

UNIVERSITY OF MORATUWA

Non-GPA module 399: Indu

Field: Electronics and Telecommunication Engineering

Training Establishment

Duration : 1

Date of Submission

UNIVERSITY OF MORATUWA

Faculty of Engineering

GPA module 399: Industrial Training

TRAINING REPORT

Name: B.Ajanthan

Index No: 070013F

: Electronics and Telecommunication Engineering

Training Establishment: Esjay Electronics(Pvt) Ltd.

: 10th February 2010-13th August 2010

Date of Submission: 16th August 2010

trial Training

: Electronics and Telecommunication Engineering

: Esjay Electronics(Pvt) Ltd.

August 2010

Industrial Training Report

Esjsy Electronics (Pvt) Ltd Page i

Preface

The purpose of this report is to present experiences I have got from 10th February 2010 to 13th

August 2010 in Esjay Electronic (Pvt) Ltd.

In my view the industrial training program of industrial training division of University of

Moratuwa is enabled me to get understood about real industry of Sri Lanka and plan my

future carrier accordingly.

During my training period I spent all most all the time at head office of Esjay Electronics

(Pvt) Ltd at Ratmalana Industrial Estate. There I was first assigned to improve their repairing

process of CDMA phone and power supply. Then for last half of the training period I

engaged in coinvalidator design.

This report consists of three chapters.

Chapter one is an introduction to the company. Here I start by giving a brief introduction

about the company and then describe about the corporate information of the company,

product and service of the company, Organizational structure and current projects .then I give

my opinion on current performance, strength and weakness of the company. I terminate the

chapter with my suggestions to improve the performance of the company and my suggestion

on usefulness of the company to the Sri Lankan society.

Chapter two is a brief summary of the work I have done in my twenty four week training. For

ease of presenting I have divided the chapter into four parts according to areas I worked.

Each part first I describe back ground and theoretical perspective of the work then the brief

details about overall process. After that I give details on duties and functions assigned to me

and the problems so far I encountered during the period of I worked on particular area and

solutions. At end of each section I illustrate some special work I have done.

Chapter three is my judgment about training program. Chapter begins with an overview on

training experiences. It continuously gives my point of view on ability of the company to give

training and about training division, department and NAITA. Chapter finishes with my

recommendation on selecting Esjay Electronics as a training place to juniors.

I hope this report gives expected details about works I have done during last 24 weeks to

evaluate my performance on this training program.


Esjsy Electronics (Pvt) Ltd Page ii

Acknowledgement

I hereby take this chance to express my gratitude towards all the peoples who are behind my

successful completion of my industrial Training at Esjay Electronics (Pvt) Ltd from 10

February 2010 to 13 August 2010.

Fist up on all I would like to tell my thanks to director of Industrial Training Division Eng.

N.A. Wijeyewickrame, the senior lecturers of Industrial training division Eng. S.A.S.

Punchihewa and Eng. P. Gunawardena for their support given while arranging this training

Program. Then I would like to express my gratitude towards the officials from National

Apprentice and Industrial Training Authority (NAITA) for their coordination between the

training establishment and training division. Next to that I should thank

Dr.N.W.N.Dayananda,industrial training coordinator of department of electronics and

telecommunication for arranging the Esjay Electronics (Pvt) Ltd as my training

establishment.

it is my pleasure to thanking following peoples from Esjay Electronics(Pvt) Ltd. managing

director Eng.Sirimevan Samarakkody for his decision on taking trainees for this year,

general manager Mr.Jayasiri Danthanarayana for selecting us as trainees, Personnel

Maneger Mr.Stephen for inspecting us daily and other technicians and workers for their

timely help.

Lastly I am thanking all peoples whose names are not mentioned here.

Thank you,

B.Ajanthan

070013F

Department of Electronics and Telecommunication,

University of Moratuwa.


Esjsy Electronics (Pvt) Ltd Page iii

Table of Contents

Preface......................................................................................................................................... i

Acknowledgement ..................................................................................................................... ii

List Of figures ........................................................................................................................... vi

List of tables ............................................................................................................................. vii

List of Equations .................................................................................................................... viii

1 Introduction to Training Establishment .............................................................................. 1

1.1 Introduction to Esjay Electronics (Pvt) Ltd................................................................. 1

1.2 Corporative Information .............................................................................................. 1

1.2.1 Mission ................................................................................................................. 1

1.2.2 ESJAY’S Logo..................................................................................................... 1

1.3 Esjay’s Product and Services ...................................................................................... 2

1.3.1 Magnetic components .......................................................................................... 2

1.3.2 PCB assemblies .................................................................................................... 3

1.3.3 Power electronic product ..................................................................................... 3

1.3.4 Security system .................................................................................................... 3

1.3.5 Services ................................................................................................................ 3

1.4 Esjay Organizational Structure.................................................................................... 3

1.5 Current Projects ........................................................................................................... 4

1.6 Current Performance ................................................................................................... 5

1.7 Strength and Weakness ............................................................................................... 5

1.7.1 Strength ................................................................................................................ 5

1.7.2 Weakness ............................................................................................................. 5

1.8 Profitability.................................................................................................................. 6

1.9 Suggestion to improve the performance...................................................................... 6

1.10 Usefulness to Sri Lankan Society................................................................................ 6

2 Training Experiences .......................................................................................................... 8

2.1 CDMA phone PCB trouble shooting .......................................................................... 8

2.1.1 Introduction .......................................................................................................... 8

2.1.2 CDMA fixed line phone....................................................................................... 9

2.1.3 Repairing process detail ..................................................................................... 10

2.1.4 Duties and function ............................................................................................ 10

2.1.5 Problems and difficulties encountered, solutions .............................................. 12


Esjsy Electronics (Pvt) Ltd Page iv

2.1.6 Progress report ................................................................................................... 14

2.1.7 Inspection sheet .................................................................................................. 16

2.2 Power supply repairing.............................................................................................. 17

2.2.1 Overview ............................................................................................................ 17

2.2.2 Introduction ........................................................................................................ 17

2.2.3 Basic Types of Power Supply ............................................................................ 17

2.2.4 SMPS simple Operation ..................................................................................... 18

2.2.5 Blocks and Description ...................................................................................... 19

2.2.6 Topologies of SMPS .......................................................................................... 20

2.2.6.1 Advantage of SMPS over linear power supply .............................................. 22

2.2.7 Repairing Process............................................................................................... 23

2.2.8 Duties and functions .......................................................................................... 24

2.2.9 Problems Encountered and solution................................................................... 25

2.3 Modifying Payphone Coin Validator. ....................................................................... 25

2.3.1 Introduction ........................................................................................................ 25

2.3.2 Project specification ........................................................................................... 26

2.3.3 Payphone ............................................................................................................ 26

2.3.3.1 Coin Validator ................................................................................................ 26

2.3.4 Methods of coin differentiation ......................................................................... 27

2.3.5 Implementation .................................................................................................. 28

2.3.6 Testing Arrangement ......................................................................................... 29

2.3.7 Problems and solution ........................................................................................ 30

2.4 PCB manufacturing In Esjay electronics .................................................................. 32

2.5 Magnetic Components Manufacturing In Esjay Electronics..................................... 33

2.5.1 Coil winding....................................................................................................... 33

2.5.1.1 Toroidal core winding .................................................................................... 34

2.5.1.2 Transformer manufacturing............................................................................ 34

2.5.2 Inductor assembling ........................................................................................... 34

2.6 Miscellaneous ............................................................................................................ 35

2.6.1 Ballast, Tube light and CFL ............................................................................... 35

2.6.1.1 Introduction .................................................................................................... 35

2.6.1.2 Ballast ............................................................................................................. 36

2.6.1.3 Electronic ballast ............................................................................................ 36


Esjsy Electronics (Pvt) Ltd Page v

2.6.1.4 Additional protection circuits ......................................................................... 37

2.6.1.5 Electronic Ballast Business of Esjay .............................................................. 37

2.6.2 Lightening protection Product-ADSL lightening protection ............................. 38

2.6.3 PLC Programming ............................................................................................. 38

3 Conclusion ........................................................................................................................ 39

3.1 In-Plant Training Of Esjay Electronics (Pvt) Ltd..................................................... 39

3.1.1 Overview ............................................................................................................ 39

3.1.2 Ability Of Esjay To Give Useful Training ....................................................... 39

3.1.3 Deficiencies In The Esjay Training ................................................................... 39

3.2 Positive Side of University Training ......................................................................... 40

3.3 Negative Side Of University Training Arrangement ................................................ 40

3.4 My Opinion About Training Division & NAITA ..................................................... 40

3.5 My Recommendations About Esjay As A Good Training Place To Juniors ............ 41

4 List of abbreviation ........................................................................................................... 42

5 Reference .......................................................................................................................... 43


Esjsy Electronics (Pvt) Ltd Page vi

List Of figures 1-1 Logo of Esjay Electronics (Pvt) Ltd .................................................................................................. 2

1-2 Logo of Esjay Electromag (Pvt) Ltd ................................................................................................. 2

1-3 Organizational Structure of Esjay .................................................................................................... 4

2-1 Block Diagram of CDMA Phone ...................................................................................................... 9

2-2 Fume Extractor ............................................................................................................................... 13

2-3 CDMA Phone Repairing process summary .................................................................................... 15

2-4 Rejected Phones Rate Over Batch .................................................................................................. 15

2-5 Inspection Sheet Part 1 ................................................................................................................... 16

2-6 Inspection Sheet part 2 ................................................................................................................... 17

2-7 Unregulated linear power supply ................................................................................................... 18

2-8 Block Diagram of SMPS ................................................................................................................. 19

2-9 Topology-Fly back convertor ......................................................................................................... 20

2-10 Topology-Forward Convertor ...................................................................................................... 20

2-11 Circuit Diagram of SMPS ............................................................................................................. 21

2-12 Topology-Half Bridge Convertor ................................................................................................. 22

2-13 Topology-Bipolar Push Pull Convertor ........................................................................................ 22

2-14A Typical Coin Validator ............................................................................................................... 27

2-15 Our Coin Validator Prototype Design .......................................................................................... 29

2-16 Testing Circuit .............................................................................................................................. 30

2-17 Sensor Alignment Problem ........................................................................................................... 30

2-18 Speed Variation Problem .............................................................................................................. 31

2-20 Axial Inductor .............................................................................................................................. 34

2-21 Block Diagram of Ballast ............................................................................................................... 36

2-22 ADSL lightening protection circuit ............................................................................................... 38

2-23 PLC arrangement ......................................................................................................................... 38


Esjsy Electronics (Pvt) Ltd Page vii

List of tables 2-1 Sample Fault Data Collection Table .............................................................................................. 14

2-2 Comparison between incandescent and discharge lamp ................................................................ 36


Esjsy Electronics (Pvt) Ltd Page viii

List of Equations

Equation 1 ................................................................................................................................ 31 Equation 2 ................................................................................................................................ 32 Equation 3 ................................................................................................................................ 32


Esjsy Electronics (Pvt) Ltd Page 1

1 Introduction to Training Establishment

1.1 Introduction to Esjay Electronics (Pvt) Ltd

Esjay Electronics (pvt) Ltd is a Sri Lankan company which has experiences over twenty years

in manufacturing electronic products. It was established with ten workers in a small place in

1982 to wind small coils to equipment manufactured in USA. But coming years it grew as

biggest Sri Lankan company producing magnetic products, wire harness and EMS.

Meanwhile it was a company exporting electronic product in a large scale to countries such

as US, Japan and Europe. Thus the company received prestigious presidential award for

exporting two times

Once the company stabilized in industry they had developed with highly trained technicians,

well facilitated research and development, well equipped production engineering and quality

control with latest instrumentation.

It is a complete manufacturing company which has the capability to meet the manufacturing

demand of the twenty first century.

1.2 Corporative Information

Esjay Electronics (pvt) Ltd is parent company under which there are two subsidiary

companies. One is Esjay Electromag (pvt) Ltd which is to manufacture magnetic product for

export only. And other subsidiary company is Lankaamerica manufacturing Ltd. it is the

company manufacturing other product such as security systems for local market as well as

foreign market

1.2.1 Mission

Esjay’s corporate mission is to use advanced technology to bring to their customers top

quality products at competitive prices

1.2.2 ESJAY’S Logo

Company has two logos which are used in different purposes. First one used under the parent

company and other is used exporting company Esjay Electromag Pvt Ltd.All products have

brand name Esjay and logo of parent company. The name and the logo of the Electromag are

used in documents related to export business.


Esjsy Electronics (Pvt) Ltd

1-1 Logo of Esjay Electronics (Pvt) Ltd

1-2 Logo of Esjay Electromag (Pvt) Ltd

1.3 Esjay’s Product and Services

Esjay has in house facilities to satisfy the customers’ needs by designing, developing and

manufacturing the product customer needed. They have range of products from

manufacturing small toroids to security system. In the case of providing services they are

repairing all kind of CDMA phones, inverters, power supplies and digital clocks. They also

authorized sales dealer for Function Group telecommunication products, Diagnosys p

and tube lights from Wipro and Britania.

1.3.1 Magnetic components

� Line Filters

� Toroidal Common mode

� Toroidal Inductors for RF application

� Power Transformers


Logo of Esjay Electronics (Pvt) Ltd

Logo of Esjay Electromag (Pvt) Ltd

Esjay’s Product and Services



uring small toroids to security system. In the case of providing services they are


authorized sales dealer for Function Group telecommunication products, Diagnosys p

and tube lights from Wipro and Britania.

Magnetic components

Toroidal Common mode chokes for EMI & RFI filtering

l Inductors for RF application

Page 2



uring small toroids to security system. In the case of providing services they are


authorized sales dealer for Function Group telecommunication products, Diagnosys products



� Current Transformers

� Pulse transformers

� Current sensors

� Coil forms

1.3.2 PCB assemblies

� Digital clock

� Fan regulator

1.3.3 Power electronic product

� Electronic ballast

� Power guard

� Stabilizer

� Step-down transformers

� Battery charger

� Battery power inverter

� DC lamp

1.3.4 Security system

� Monitored chain link fence

� CCTV system

� Hand held Metal detector

1.3.5 Services

� Authorized dealers for all types of CDMA/GSM Payphones and Wireless Terminals

from Function Group and service centre.

� Authorized dealers for Diagnosys products

� CDMA phone repairing Contract from SLT

� Authorized dealer for Wipro and Britannia tube lights

1.4 Esjay Organizational Structure

High position of the organization structure is occupied by the founder of the company

managing director Eng.Sirimevan Samarakkody .Under him Administrative director

Mr.Thilakarathne Amunugama administrate both Esjay Electonics (Pvt) Ltd and Esjay

Electromag (Pvt) Ltd. Then each company have different general managers. Mr.Dhammika

Gamage is general manager for Electromag and Mr.Jayasiri Danthanarayana for

electronics. Under each general manager there are professionals as shown in the figure 1-2.



There is a one accounting department for both organization lead by

1-3 Organizational Structure of Esjay

1.5 Current Projects

• CDMA repairing

• Power supply repairing

• Tritel project

• Automatic railway gate design for CGR

general managerelectromag

Mr.Dhammika Gamage

Production manager Mr.susantha

Liyanage

shipping and purchase manager Mr.Lionel Perera

Personnel manager Mr.Stephen

R & D Mr.Nishantha


There is a one accounting department for both organization lead by Mrs.Shamali Bandara

Organizational Structure of Esjay

Power supply repairing

Automatic railway gate design for CGR

managing director Eng.Sirimevan Samarakkody

Administrative director

Mr.Thilakarathne Amunugama

general manager-electromag

Mr.Dhammika Gamage

Production manager Mr.susantha

Liyanage

shipping and purchase manager Mr.Lionel Perera

Personnel manager Mr.Stephen

R & D Mr.Nishantha

general manager -electronics Mr.Jayasiri

Danthanarayana

Personnel Manager Mr.Stephen

R & D

Accountat Mrs.Shamali

Bandara

Page 4

Mrs.Shamali Bandara

Samarakkody

Accountat Mrs.Shamali

Bandara



• Toroid and PCB manufacturing for Orange and Kevilton

• Repairing inverter for SLT

1.6 Current Performance

When I joined with company as trainee they already received three batches of phones to

repair; now they finished the all twelve batches and got a new contract from SLT. Previously

they got only phones which were in level 2(which don’t need too much repairing work than

level 3) but according to the new contract they will receive level 3 phones .this shows their

performance is improved and satisfied the SLT management.

Staff from ZTE Corporation, a famous Chinese telecommunication production company,

visited the company recently. The intention of the visit is to inspect the repairing process and

select the company as the authorized service center of ZTE for Sri Lanka. According to the

ZTE staff they will select the company as the service centre soon. This is a greatest

opportunity to the company to put their experience in useful way.

The company is still able to get the market for electromagnetic product from the US

regardless of economic crisis and other problems. The key point helped them to achieve this

is quality of the product. Availability of required tools and experienced workers enabled them

to keep the quality high.

1.7 Strength and Weakness

It is not a matter whether I have enough experience or not, to evaluate the company’s strength

and weakness; because I was there for nearly six month I am eligible here to suggest my own

thoughts. While working there I was able to realize the reasons for company’s success and

failure. The sales manager Mr.Jayasiri Danthanarayana usually talked about these issues very

often and we could get his opinion on past performance of the company.

1.7.1 Strength

• Has enough machinery and infrastructure

• Has enough experiences in manufacturing electronic product

• Attitude of go for new business

• Skilled workers

1.7.2 Weakness

• Lack of strong management

• Hesitance to invest on new projects

• Attitude of workers not to learn new technologies



1.8 Profitability

The main source of their income is export business. They are importing raw materials from

USA for manufacturing the Toroids, assembling them and send back to the same country; this

is just value addition. Other than that a small amount of income they are getting from

subcontracted PCB manufacturing such as Orange fan regulator and digital clock. In addition

to that the CDMA phone repairing is also contribute to their income.

But the overall profitability is affected by the uncontrolled expenses. Still they are running on

lost because of the failure in wire harness business. They have a plan to sell some of the

valuable machinery and invest on new business. They are now working hardly to get a

contract to manufacture wire harness and restore their business.

1.9 Suggestion to improve the performance

It is oblivious with in this open economic market to survive company should think about new

way of businesses that can only be done Sri Lankan companies. Even though the company

had previously substantial amount of local market and export market, now all those

marketing opportunities are taken by others because I think the company did not improve the

product quality as time goes. I had observed some of the manufactured battery charger whose

electronic design was very high standard but the enclosure was made by brittle material and

the dimension also not suitable. When the company engages into production engineering they

should pay attention on all the aspect of the product.

For example the electronic ballast, company has enough experience on manufacturing

electronic ballast. The cost of the product is higher than alternative one that’s available in the

market. But the problem with that ballast is not enough filtering arrangement to filter out the

harmonic noise. In the case of our company’s ballast the safety against the harmonic

pollution is available. Here the missing component is the market doesn’t have that awareness.

The company should advertise these aspects to get the local market

1.10 Usefulness to Sri Lankan Society

Most frequent problem with the economics of the 3rd world countries is the lack of

contribution to GDP by electronics industry. There are some Asian countries runs their

economic by one and only means of electronic industry. Western countries have the raw

materials and discrete electronic components but they need a lot of human recourses to

design, develop, manufacture and market electronic product. But the 3rd world countries like

Sri Lanka have above recourses. Electronic products have a good market all over the world



because in last century electronic industry changed the life style of human being a lot and

created lot of needs related to electronic industries. Therefore it is a vital to Sri Lankan to pay

attention on electronic industry. Esjay is the pioneer company that proved the essential of the

electronic industry to the country.

Esjay like electronic industry is providing employment from Engineers to uneducated normal

workers.

Esjay has enough infrastructures to manufacture a complete product under one roof. They

have over 25 years experience on manufacturing magnetic product, power electronic product,

lighting product and telecommunication product. If we combine both and produce products

for local market then we can reduce large amount of imports from other countries.



2 Training Experiences

Here I rather than presenting my training experiences in the chronological order, present

according to the amount of time each section I have been assigned so far. I have been given

chance to improve the CDMA phone repairing at first. And I have to have work on this all

my training period because I had to observe current process, implement new scheme into the

existing process and get the result of the introduced new scheme. Second most one that

consumed most of the training period is experimental power supply repairing. Then the

modifying the coin validator is the project lastly given to me. And there are some little extra

works I have done whenever I have free time in the training place. In all the projects I and

four of my friends worked together.

I followed a methodology while presenting the training experience, which helped me

organize and present nicely. First I give back ground information of the task such as the

intention and goal of the task and then the theoretical back ground. After that I give small

description of that work if the company already doing that work. Finally I present my duties

and function with problems that I had encountered and my solution in details. Beginning part

of the chapter is devoted for mainly for improving CDMA phone repairing process,

Experimental power supply repairing and modifying coin validator. At last I mention some

miscellaneous works I done as extra.

2.1 CDMA phone PCB trouble shooting

As general manager said on very first day of my training; our first job was to improve the

efficiency of their phone repairing process. They were repairing CDMA fixed line phone for

SLT (Sri Lanka Telecom Ltd) in cannibalizing basis. Their rejection rate was very high; it

was a challenge for them to reduce it below 10 % in order to get the future orders of phone

repairing from SLT. We were given a target to improve the phone repairing process to

reduce the rejection rate below 10% within 2 batches of repairing .they were receiving a

batch of phones which consists of 200 phones per 2 weeks.

2.1.1 Introduction

Finite spectrum and growing amount of customers are the two main factors that lead network

designers to come up with the new technology to efficiently handle these problems. CDMA

(code division multiple access) is the technology uses same spectrum and time for many

communication access link by assigning different code for each channels. CDMA technology

is used in both 2G and 3G networks. CDMA standards for 2G network includes IS-95A and



IS-95B.For 3G network services the CDMA is the foundation technology for which there are

two standards CDMA2000 and WCDMA.

2.1.2 CDMA fixed line phone.

CDMA fixed line phone is the cheapest version of the mobile phone technology which is

affordable by the 3rd world poor peoples. In Sri Lanka the SLT is the pioneer

telecommunication technology and service provider who enables the new telecommunication

technology to reach the rural side peoples through the wireless fixed line technology.SLT

provides the fixed wireless line with CDMA phone. They are importing these wireless phones

from Asian countries such as China and Korea. Fixed wireless line phone sellers or

distributors usually don’t takes the faulty phones for repairing after warranty period is

expired.SLT usually gives those phones to local repairing centers.

Our company was receiving AIJI AP110 phones which were manufactured by Korean based

company called AIJI.

We were able to identify main function block of the phone as MSM (mobile station modem),

memory, RF unit, power management IC and interfacing circuits.

2-1 Block Diagram of CDMA Phone

MSM6025 : it has DSP processor ,CDMA processor, ADC, DAC and interfacing circuits.

Memory

Audio Codec

CDMA

processor

DSP processor

MIC

S

p

e

a

k

e

r Key Pad LCD

Power IC

RF

Transmitter

RF

Receiver

D

u

p

l

e

x

e

r

Antenna



Memory: it contains space to store ringing tones, SMS and phone number and names.

RF unit: RF unit consists of one transmitting IC, a receiving IC, a switch and a dipole antenna

Power management IC: this is the single IC powering all the components. This has capability

to detect overvoltage and low voltage battery.

Interfacing circuits: There are interfacing circuits for keypad, handset, mic, speaker, hook

switch, LCD and RS232 for data communication.

2.1.3 Repairing process detail

Repairing process starts when they receive the new batch of phone and a process of one batch

extends for two weeks. The process can be divided into three sub process according to the job

and people who are involving in these works. First of all the phones are dismantled by normal

workers and the PCB and other parts which cannot be cleaned using water are cleaned using

dust removing brushes. Enclosure is washed by detergent powder. After cleaning they

assembled and given to supervisors. Then the second sub process starts. The supervisors who

are the people going to identify the faults by manual testing and document those faults on

inspection sheet. Inspection sheet they already had consist batch number, model number of

the phone, date of testing, identified fault or faults and name of the inspector. Then final sub

process, the faulty phones are sent to technicians who have more experience and knowledge

on electronics. The job of the technician is to repair the phone in cannibalizing method

according to pre defined methods. Finally all working phones are packed together and other

non repairable rejected phones are documented with details of reasons for rejection.

2.1.4 Duties and function

Our main goal was to reduce the rejection rate by introducing new method or improve

existing process. The manager was very careful on new methods or changes that to be

introduced by us not affect the existing process. We were required to introduce new changes

simple and easy to get practice. We were assigned followings as the long term duties

1. Identify the problems with the current repairing process

We divide the task into two parts;

Identifying the problem with fault identification :

First problem with their fault identification process is the non informative inspection sheet. It

is a good practice to keep a well descriptive inspection sheet .Second most important problem



was their inefficient battery selection process(they have to select good batteries from given

batteries).other non important issues are they don't care about electrostatic charges when they

cleaning the PCB, washing the enclosure using detergent water and workers’ lack of

knowledge on PCB.

Identifying the problem with repairing process:

Their technicians were not only dealing with phone repairing but also had other works. Thus

they allocate one day for repairing and that day most probably last day. They were on hurry

that day and reject phones as they don't have time to repair. Other than that they had enough

knowledge and experience.

2. Collect the statics of the fault commonly found in phones

Before collecting the statics on fault we collected all the faults they had encountered in past

and categorized the faults into four main groups. Those are power problems, RF problems,

firmware problems and other hardware problems.

Collect past statics if available:

They didn't have any documented data on faults. They only have the number of total phone

received and rejected phones. We could only get that information.

Collect statics of current batch onward:

We kept a record book for documenting our repairing work. We entered the received phone

ESN number, fault identified and status (rejected or repaired).

3. Explore the available solution to the common faults.

Collect the solutions they already have:

We interviewed both technicians about the common faults and their repairing method. They

also demonstrated some of the repairing techniques.

Come up with any new solution:

We were given 20-30 phones in one batch to repair which consists of phones with new and

un-repairable faults. With the knowledge we got we tried to repair that phone using trial and

error.



We succeeded for some extent and mean while in some of instance our effort made the fault

even worst.

4. Experimenting weather the facilities they have is enough or not for repairing

While we were repairing we were able to realize that the facilities they are providing

regarding repairing is not enough. But rather than requesting management to provide new

tools and equipment and giving them trouble we thought it is better to produce new tool from

old discarded tools and equipment by company or repairing them. They also encouraged us as

this is a cost effective solution to lack of tools. We made fume exhaustion setup and repaired

some old soldering irons.

5. Suggest new method for repairing process.

End of each batch we had to summit a progress report which includes the statistic of repairing

process and suggestion for improvement. After management provided approval to implement

some our suggestion we had to make a document describing the new method in workers’

mother language (Sinhala) and had to explain to them.

6. Get the feedback from the appropriate person and modify the process.

Whenever workers faced little problem when they practicing new method we had to present

there to solve the problems and modify the new method to rectify the new problem. Some

time the workers felt the method was very complex to follow. In such instance we had to

remove some complex things and give that to technicians.

2.1.5 Problems and difficulties encountered, solutions

While we were inspecting the current process we found some management issues such as

poor attendance of the workers, salary issues of the workers, lack of tools and equipment and

lack of workers. As we directly dealing with management peoples we hesitated to tell these

things to them.

As we don’t have previous experience or knowledge on communication devices such as

CDMA phones we required to find the workshop manual for them and CDMA Workshop

which is professional software to troubleshoot variety of firmware faults. But these are only

provided to companies which are authorized by manufacturer. At last we had to deal with out

these requirements.



When we were repairing the faulty phones to identify the possible new solution we

encountered some problems. The fume which comes from soldering iron was not properly

removed from the workplace. As the solution to the above problem we made small fume

exhaustion system using unused pc power supply fans. The soldering irons which are given to

us had small leakage current which may affect the person who is soldering and PCB

components. Usually the soldering irons come with ceramic barrel around the element to

avoid the current leakage. This kind of soldering irons are more expensive and not to be

affordable by our company. As the solution to this problem an earth wire was attached to

soldering iron and the metal barrel around the element and tip was grounded.

2-2 Fume Extractor

It is very important to show our progress to the interested peoples to make them confident on

us. In our case we tried to express our progress through the reject rate of the phone in each

batch, which is not an appropriate way to express the improvement of the repairing process

because there is a correlation between the number of faulty phones, the level of difficulty in

repairing a particular fault and number of rejects. As a solution we prepared a template using

Microsoft Excel which has a table to store collected data and has facility to tabulate the data

in so many different ways.

For some fault we couldn’t find the reason and solution because we had not had a clear idea

about the circuit. Any how we could able to identify the possible components or ICs or part

of circuit responsible for fault. Using that information we were able to re-solder particular IC

or components and get the fault repaired successfully. No dialing and over voltage are such

faults we could repair successfully.

Fume extractor



As we don’t have schematic of the PCB we decided to trace the PCB. But the multilayered

nature of the PCB and the many number of SMD components not allowed us to trace the

circuit successfully.

2.1.6 Progress report

We were required to produce a report on the improvement of the repairing work. The ultimate

goal of this report was to assist the person who is going to submit the application of next

contract on phone repairing with SLT. There was a need to express the company’s ability to

handle and manage the repairing process efficiently.

2-1 Sample Fault Data Collection Table

To simplify the presentation of the statics we need to select a statics model. We decided to

present the data on fault basis because this will give clear idea on the technical or repairing

capability of the company. Fist thing need to be done was the standard naming convention for

Fault Received Repaired

Power Jack 0 0

Antenna Jack 3 3

LED 10 10

Key not working 0 0

Back light 0 0

No display 7 6

Hook switch 1 1

Charging battery 2 2

Over voltage 7 2

Not dialing 8 2

Restart 0 0

Service required 0 0

Divide by zero 0 0

Fatal error 4 0

No signal 0 0

Total 42 26

batch total 200

faulty 42

repaired 26

good after servicing 158

Batch 06



faults which is understandable by an engineer who is going to inspect the contract application

and the normal worker who is going to prepare inspection sheet. We already had the statics

on frequently encountered faults. We named t

describing. At last we produced a spread document

a last one sheet which consists

2-3 CDMA Phone Repairing process summary

2-4 Rejected Phones Rate Over Batch

500

600

200 200

378

521

168 183

batch 01 batch 02 batch 03 batch 04

Process Summary

0

5

10

15

20

25

30

ba

tch

01

ba

tch

02

ba

tch

03

ba

tch

04

ba

tch

05

ba

tch

06

ba

tch

07

Ax

is T

itle

rejection rate %


understandable by an engineer who is going to inspect the contract application


on frequently encountered faults. We named the faults using simple English which is self

describing. At last we produced a spread document which includes a sheet for

ists of overall comparison.

CDMA Phone Repairing process summary

Rejected Phones Rate Over Batch

200 200 200 200 200 200183 190 184 179 179 179

batch 04 batch 05 batch 06 batch 07 batch 08 batch 09 batch 10

Process Summary

Batch Size Total Repaired

ba

tch

07

ba

tch

08

ba

tch

09

ba

tch

10

ba

tch

11

ba

tch

12

rejection rate %

REJECT%

REJECTS

ALLOWABLE

Page 15

understandable by an engineer who is going to inspect the contract application


using simple English which is self

sheet for each batch and

200 200 200179 179 179

batch 10 batch 11 batch 12



2.1.7 Inspection sheet

If fault identification is done effectively prior to repairing it will save the time and speed up

the repairing process. The inspection sheet they were already using was written by hand and

the contents particularly the fault descriptions were written differently by each person; this

may leads to misunderstanding and some time no understanding about the fault.

Therefore we thought it is better to avoid hand written inspection sheet. We decided to

prepare a printed inspection sheet. Our one contains all possible and frequent faults and the

job of the inspector was to tick the cage in front of identified faults. Organization of the

inspection sheet was in such way that It clearly shows the problematic part of the PCB. Back

side of the sheet contains space to document the repairing work of technicians. This

inspection can be helpful when preparing the progress report.

They printed inspection sheet on low cost paper and used for three batch of repair. After that

management decided to stop using new inspection sheet until they will receive the batch of

phone which is beyond the size of 200.because it was not cost effective to use printed

inspection sheet for only 200 phones.

2-5 Inspection Sheet Part 1



2-6 Inspection Sheet part 2

2.2 Power supply repairing

2.2.1 Overview

Our company already had designed and manufactured SMPS for CDMA phones but now the

arrival of low cost power supply from other countries removed their product from the market

and they already gave up the production.

It is a responsible of the company to deliver each phone with a power supply which is in a

good condition.SLT usually supplies same amount of power supplies as phones but only few

amount of power supplies need to be repair. But the management has a plan to receive a batch

(a batch consists of 1000 power supplies) of faulty power supplies and recruit new

technicians to repair. In order to do that they need to know the estimated cost and time to

repair one power supply. They expected us to do investigation and submit a report.

2.2.2 Introduction

The need of AC to DC power converters arises when we want to use DC power appliance and

rechargeable battery with AC power. Generation and transmission of electricity is very

economic in the form of three phase alternating current. Therefore to use the DC power

operated electronic devices we need AC to DC converters.

2.2.3 Basic Types of Power Supply

There are four basic types of AC to DC convertors. Each has its merit and demerit.



1. Unregulated linear power supply

These types of power supplies are very elementary in the world of power supplies.

This consists of circuit to rectify and smooth. Mostly full diode bridges rectify and a

large value electrolyte capacitor is used to smooth the rectified AC.

The design is very simple, low cost and most reliable. It is suitable for low power application.

2. Regulated linear power supply

The difference between previous one and current is later has regulating circuit.

Regulating circuit ensure the constant current or voltage regardless of load changes.

There are ready made ICs available can be used to regulate the output. There should

be a way to remove the heat dissipated by the regulator IC. This is most suitable for

low power applications.

3. Ferro resonant power supply

The difference between unregulated power supply and Ferro resonant power supply is

the Ferro resonant transformer. This transformer gives constant output voltage over a

wide variation of input voltage. But this transformer is very sensitive to frequency

variation in line supply and bulky in size.

4. Switch Mode Power Supply

This is the kind of power supply following paragraphs describes.

2.2.4 SMPS simple Operation

Typical line connected power supply should perform following tasks. voltage conversion

using step down transformer if needed, turning the AC to DC using rectifier ,filtering the

ripple noise using smoothing capacitors, regulating the output voltage independent of

connected load and isolation of the AC part and DC part.

SMPS converts the rectified and smoothed direct AC into required DC applying pulse with

modulation. The regulation is achieved by feedback network. Feedback network samples the

output and control the duty cycle of the PWM to get the output regulated.PWM signal is

2-7 Unregulated linear power supply

Diode Bridge

Smoothing

capacitor



smoothed by a small high frequency transformer called chopper transformer. Isolation

between AC and DC output is done using high frequency transformer and opto-coupler.

There are some safety mechanisms should be taken while implementing the design to

stabilize the operation of the power supply. Such as inrush current protection, EMI noise

filter and filtering the high frequency noise in output.

2.2.5 Blocks and Description

The fuse is connected in series with ac line to protect the power supply from over current.

Momentary rise in current is called surge current and this may be harm to the components.

By connecting a series inductor surge current protection can be achieved.

The purpose of the EMI filter is to filter out the high frequency noises.EMI filter is made by

configuring C-L-C (pi) low pass filter.

Rectification is done using a half or full bridge diode rectifier. And small electrolyte

capacitors are used to smooth the rectified current.

The resulted DC current is converted into pulse waveform using switching mechanism. The

duty cycle of the pulse wave form determines the output value and it can be controlled.

The high frequency fly back transformer has two roles. One is converting pulse wave into

continuous DC wave and other is providing the AC-DC isolation.

Input

connector Fuse

and

surge

protect

ion

EMI

/RFI

Filter

Rectifi

er and

filter

capacit

or

Chopp

er

transfo

rmer

Rectifi

er and

filter

Output

connect

or

Isolated

feedback

circuit

Switching and control

circuit

2-8 Block Diagram of SMPS



The output of the fly back transformer contains high frequency ripple. This noise is removed

by the inductor-capacitor rectifier presents in the output side.

Random variation of the output

output voltage is sampled and pas

coupler inorder to provide AC

grt needed regulation in the output?

2.2.6 Topologies of SMPS

The active element which control the chopper tran

to feedback can be connected to circuit in four different methods. Those are called different

topologies. Fly back, forward, push pull and bridge are those four types of topologies.

Fly back converter

2-9 Topology-Fly back convertor

Forward convertor

2-10 Topology-Forward Convertor


transformer contains high frequency ripple. This noise is removed

capacitor rectifier presents in the output side.

output due to varying load is regulated by feedback

voltage is sampled and passed to switching controller. Which is passed through opto

coupler inorder to provide AC-DC isolation.the swithing controller adjests the duty cycle to

grt needed regulation in the output?

The active element which control the chopper transformer and stabilize the output according



Fly back convertor

Forward Convertor

Page 20

transformer contains high frequency ripple. This noise is removed

feedback mechanism. The

Which is passed through opto-

DC isolation.the swithing controller adjests the duty cycle to

sformer and stabilize the output according





AC wave form Rectified wave pulse width fly back filtered out

Form modulated wave output put

2-11 Circuit Diagram of SMPS



Half bridge convertor

2-12 Topology-Half Bridge Convertor

Bipoler push pull convertor

2-13 Topology-Bipolar Push Pull Convertor

Between these topologies the fly back topologies is most desirable because it has least part

count, only one switching element, no

2.2.6.1 Advantage of SMPS over linear power supply

Since the active element is not operating in a

saturation region and cut off region the power loss is extremely

design to achieve high efficient. There


Half Bridge Convertor

Bipolar Push Pull Convertor


element, no output inductor or fly wheel diode.

Advantage of SMPS over linear power supply

Since the active element is not operating in active region continuously;

saturation region and cut off region the power loss is extremely low. Which

efficient. There are no transformers other than high frequency chopper

Page 22


switching between

low. Which enables this

other than high frequency chopper



which is substantially very small in size, hence the size of the power supply also very small

compared to conventional linear power supplies.

But there is one drawback in SMPS. There is a high frequency noise as a result of switching.

And its design is little complex.

2.2.7 Repairing Process

They had divided the repairing process into two serial processes. First the workers check the

power supply output voltage in normal condition and loaded condition and inspect AC and

DC wires for physical damage .Then they separate faulty power supplies and send to

technicians to repair.

Repairing process starts with replacing the AC and DC wire which have physical damage.

They divide the PCB into two parts. First part consists of components which handle AC

current and second part contains only the components responsible for handling DC current.

The intention for dividing the PCB into two parts is to ease the trouble shooting.

In AC part of the circuit smoothing capacitors .filtering inductors, some resisters and

rectifying diodes mostly fail. There are standard ways to test these components.

Capacitor testing: Remove one lead from the PCB and check the capacitance using multi

meter. Or test whether the resistance of the capacitor is increasing or not when measuring

resistance between two leads.

Inductor Testing: Measure continuity between two leads of the inductor

Resister Testing: Remove one lead from the PCB and test the resistance to rated value.

Diodes: Set the multi meter to diode checking mode and measure the forward voltage drop

for 0.5 voltages and reverse biased voltage infinity.

The DC part of the PCB contains flywheel diode, filter capacitors and inductors, and

feedback MOS-FET. As mentioned above the testing for these components is done.

The components which are connecting both AC part and DC part are Chopper transformer

and opto-coupler. They are checking the continuity of the primary and secondary coils to

identify the fault with chopper transformer. They check the LED site of the opto-coupler to

test the opto-coupler faults.



All the faulty components are replaced with new components and tested with over current

protection circuit.

2.2.8 Duties and functions

1. Understanding the functionality of SMPS in detail.

In order to repair successfully the power supply we need to have clear understanding of the

PCB. Because we don’t have previous experiences on switch mode power supply and

repairing power related PCB have potential electrical hazards as this dealing with high

voltage. We were provided with one book about designing SMPS. We had read the chapters

which needed to us. This gave us introductory theory related to SMPS design, safety issues

and variety of design options.

As I already mentioned our company had previous experiences on manufacturing SMPS. We

asked the technicians about their experiences and got a lot of practical aspect of the SMPS.

2. Finding methods to identifying the faults.

The fault finding process is very simple because the size of the PCB is small and most of the

components are through -hole components. When we inspected their fault finding method we

couldn’t find any problem with their repairing process. As they had previous experiences

their method of trouble shooting was very efficient.

3. Doing repairing for experimental purpose.

We allocated two hours per day to repair power supplies .with in that period only two of us

participated in repairing process. The intention behind this is to estimate the time taken by a

technician to repair one power supply. Initially the time taken to repair one power supply by

us was high but when we repaired more and got experience the time reduced to normal

amount. We were required to submit a SMPS repairing manual .In that we were expected to

document the method of repairing they already had. They are going to train technicians who

will be employed providing them with that manual.

4. Estimate the cost for repairing one power supply

SLT usually renew their agreement once the year on repairing power supply. Each year they

issue public tender and select the tender according to their criteria. One of the important



criteria they are strongly taking into account is estimated cost for repairing one power supply.

It should be minimum possible price.

2.2.9 Problems Encountered and solution

Repairing power supply usually should be done with enough safety measures to avoid

unwanted accidents. At the beginning we were instructed to make some safety circuits and

tools.

1. After replacing some components in PCB, usually there may be some short circuits or

way to consume more current. This causes burning of components when powering on

the PCB. Connecting an incandescent lamp serially with supply is the standard

protection mechanism used in repairing SMPS. We made a circuit with one three pin

adapter, bulb holder, power indicating LED and socket. Enclosure was made from

wood in order to reduce the cost and electrical shock.

2. There is an opto-coupler to transfer feedback signal from DC output to control IC. On

board testing of opto-coupler was very difficult. As the solution we made a circuit to

test the opto -coupler.the circuit allow a 2 mille-Ampere current to follow through the

LED of the opto-coupler and the working opto-coupler gives 3.4 Volt reading.

3. The smoothing capacitors get charged to nearly 320 Volts when the power is on. After

disconnecting the PCB from the main supply capacitor takes greater than two minutes

to fully discharge. Mean while capacitor is discharging if repairing person accidently

touches the leads of the capacitors he will feel electrical shock. We usually use the tip

of the screw driver to discharge but it is not recommended practice. The best way is to

use high wattage resister connected with high gauge wire to short circuit the leads of

the capacitor.

4. While repairing it was frequent incident touching powered PCB. This could be

avoided wearing safety clothes such as rubber shoes.

2.3 Modifying Payphone Coin Validator.

2.3.1 Introduction

TriTel lanka (Pvt) Ltd is a leading company in deploying coin operated pay phones all around

the country. They have been operating payphones from when Sri Lanka had only PSTN

network. They have lot of phones which are now replaced by CDMA fixed wireless

payphones. The enclosure and other valuable parts of the old payphones is still valuable if we

integrate the CDMA module with existing electronics and hardware. While analyzing the



technical feasibility of integrating CDMA module into old payphones they encountered a

problem with coin validator of the old payphones. That coin validator accepts 1,2 and 5 rupee

coins.1and 2 rupee coins fill the coin box very quickly than five .The coin collector

frequently has to go and collect coins. If we allow the coinvalidator to validate only 5 rupee

coin then we can reduce the coin filling speed. The Tritell Lanka (Pvt) Ltd requested our

company to modify the coin validator of Sondy payphone(old payphone).

2.3.2 Project specification

The new modified coin validator should validate only 5 rupee coin as a genuine coin and

reject rest of the coin as counterfeit coin. Other circuit parts should faction as before without

any change in functionality because of new change.

2.3.3 Payphone

Payphone unit consists of

• Main CPU

• Keyboard

• LCD

• Coinvalidator

• Speaker

• Mic

• Handset

• Power supply

• CDMA module

The functionality of payphone is to allow the user to talk predefined time according to

amount he inserted. To ensure reliable operation and security the whole set is kept in the

metal box.

2.3.3.1 Coin Validator

Coinvalidator is the part of coin operated pay phones which discriminates coins among

different kinds of coins available and detect false coin. As user takes the handset of the

payphone the main CPU sends wakeup signal to the coin validator unit. It is the signal to

indicate arrival of the coin to the coin validator. After coin validator receives that signal it

will energize the coils and observe the changes of some properties due to presence of coin.

Coin validator decides whether the coin is genuine or not and open the door by energizing the



solenoid to direct the coin to coin box or outside. Industrial coin validators use different

method to detect and differentiate the coin.

2.3.4 Methods of coin differentiation

2-14A Typical Coin Validator

1. Coin entry

2. Coin rolling

3. Anvil

4. Coin rolling ramp

5. Optical sensor (a-a’)

Electromagnetic sensors (b-c-d)

6. Acceptation gate

7. Aoin acceptance chute

8. Coin rejection cute



After the customer inserting the coin through coin entry the coin rolls on ramp to remove the

speed variation due to inserting method (gentle push vs. force push).all the sensors on the

ramp way measure some physical properties such as dimension, conductivity, magnetic

permeability and elasticity to take a decision. These measured data are compared with set of

predefine data for each kind of coin and discriminated based on the comparison result. If

more measurements on physical properties are available then the effect of temperature,

noises, sensor accuracy and aging can be avoided. These are the available sensors can be used

in coin discrimination.

1. Optical sensor: light emitting photo diode and phototransistor is used as the barrier when

coin is rolling and the time taken to cross two such barriers can be measured. This time

indirectly tell the width of the coin.

2. Electromagnetic sensors: Conductivity and permeability of the coin can be used to

differentiate the coin. The amplitude, phase and frequency change of the inductive coils due

to the presence of coin corresponds to the conductivity and magneto resistance. magneto

resistance or Hall effect senor can be used to detect the amplitude ,phase and frequency

variations.

3. Acoustic sensors: When the coin is mechanically excited for instance dropped on hard

surface the properties of the resulted sound depends on elasticity, stiffness and dimension of

the coin .The sound can be captured by microphone and analyzed using digital signal

processing techniques.

4. Impact sensors: As in the case of acoustic sensors when the coin is excited the resulting

force on the body on which coin is excited is depends on some properties of the coin. The

resulted force can be measured using pressure sensors or the acceleration of the body can be

measured using acceleration meters.

2.3.5 Implementation

According to our last decision we need to design new external module which can at least

detect only 5 rupee coin and if the inserted coin is other than 5 rupee it should send jamming

signal to inductor coil by means of additional inductor coil in order to reject the coin.

We divided project into two phases, first phase consists of identifying the 5 rupee coin and in

second phase we will be able to send the jamming signal.



As mentioned above there are many ways to differentiate the coin but we have to select a

method which need to be simple (low cost) and has very compact circuitry. There is no space

for mounting sensor unit inside the payphone. So we need to design an external box to mount

the sensor unit on the top of the coin inlet hole. Using optical sensor was a feasible solution

to satisfy our needs.

2-15 Our Coin Validator Prototype Design

We selected light emitting diodes and phototransistor matching pairs to make the optical

barrier. Sensor unit consists of a regulator, comparator, resistors, variable resister, capacitors,

and light emitting photo diode and photo transistor. Sensor unit is separately powered and the

logic unit can disable the sensor unit by off the power when it need not. Comparator

compares the photo transistor output against the predefined voltage which can adjustable

using variable resister.

Logical unit consist a PIC microcontroller. Which generates interrupt as the sensor unit gives

output and starts the timer. Timer count the number of timer resister overflow until sensor

unit give out put logic 0.the count is compared with the range of value corresponding to

genuine 5 rupee coin to make the decision.

The jamming signal generator just consist of a transistor which is operating as a switch which

allow a PWM signal injected into magnetic circuit of existing coin validator.

2.3.6 Testing Arrangement

For testing we made a circuit with sensor unit, microprocessor and array of SSD. When the

inserted coin crosses the beam the timer starts .Every overflow of timer increases the counter



variable by one. At the end when the broken beam is reformed the timer stops and the display

shows the counted value.

2-16 Testing Circuit

2.3.7 Problems and solution

1. First we made an enclosure using polystyrene and mounted the sensor but because of the

sensor was not aligned properly the detector voltage is not enough to trigger the comparator.

We got wrong reading. As a solution for this problem we made a prototype wooden enclosure

and mounted the sensor using epoxy glue. To focus the emitter beam on detector we used an

emitter with lens.

2-17 Sensor Alignment Problem

2. When the coin is dropped into coin inlet from different elevation the speed of the coin

varies. And the reading for the same coin varies as the dropping elevation changes. We found

a solution to that also. The solution is placing two identical sensor detector pairs. The

distance between both pairs should be greater than biggest width of the coin (2 Rs) in order to

avoid crossing both sensors simultaneously.

Emitter

Lense

Detector

Top view



Meaning of symbols

D-width of coin under test

h -distance between both sensor pairs

u -speed of the coin when crossing first barrier

v -speed of the coin when crossing second barrier

T1 -time taken to coin cross the first barrier

T2 -time taken to coin travel the distance between both sensors

T3 -time taken to coin travel the distance second barrier

� � ��

�------------------------------------------------------------------- (1)

� ��

�------------------------------------------------------------------- Equation 1

2-18 Speed Variation Problem

U m/s

V m/s

h

T2

T1

T3

Emitter1

Emitter2

Detector 1

Detector 2

d



� ��

�------------------------------------------------------------------- Equation 2

(1), (2) =>� � ��

�� 1 ��

�

� ��

� ��

��-------------------------------------------------------- Equation 3

According to above design the microprocessor takes the reading T1 and T2, and at the end it

calculates (Equation 3) the coin width d and compares it with standard value. Comparison

result helps to differentiate the coins.

3. In order to calculate the coin width the microcontroller should do complex calculation

according to our design. The processing power of the microcontroller is not enough to handle

this complex calculation. But the microcontroller has only few jobs to do then wasting

processing power on complex calculation is not a problem. Thus we did not think about the

solution.

4. The noises presents in input to the microcontroller triggered the timer randomly. To avoid

these noises we have placed a capacitor to ground the noises and we used shield wires.

2.4 PCB manufacturing In Esjay electronics

The PCB manufacturing was demonstrated to us when we visited the factory at Meegoda.

They explained the method and we got understood the difficulties and constrains they are

facing in the process. They only manufacturing small amount of PCB for electronic ballast,

fan-regulator and digital clock. Followings are steps they are using in PCB manufacturing.

2-19 Solution to False Triggering Problem

Microcontroller

GND

Sensor



1. Screen printing: The designed circuit is printed on UV sensitive membrane using UV light.

The membrane is placed on the top of copper board and the screen printing ink is applied on

the membrane. The membrane only allows ink to propagate through transparent part. The

aligning is done manually. They also have capable of doing double side PCB.

2. Etching: For etching they are using FeCl3 solution. The concentration of the solution is

determined by them using previous experience. The screen printed PCB is placed into the

container which consists etching solution. When the container is heated and applied air

bubbles inside the container the etching process more activated than usual.

3. Drilling: They have CNC drilling machine but now it is not working. They are doing

drilling manually.

4. Removing screen printing: When etching the most part of the printing marks are removed.

If some part of the printing marks remaining then they use screen wash to remove them.

5. Tin plating: They have a simple tin coating machine. The machine has a pot of melted tin

the PCB is send on the top of the tin pot using a roller.

6. Solder mask printing: After Tin plating if there is a need to apply solder mask; using same

techniques as screen printing the solder mask ink is printed on the PCB.

7. Cutting etches: Cutting the PCB is done using die press.

8. Inspecting for faults: There is a device which emit fluorescent light .When the PCB is placed on the top of the light the broken connections can be easily identified and remake the connection by soldering a wire.

9. Method of making through hole connection: they don’t have facilities to do through hole

plating. They just fill the hole with solder and make connection between top and bottom layer

of the PCB.

2.5 Magnetic Components Manufacturing In Esjay Electronics

Manufacturing magnetic components is the real strength of the Esjay Electronics. Their

manufacturing process can be divided into following two categories. Coil winding and

inductor assembling. For all the process the raw materials such as coil, coil forms, Leads and

ferrite core are imported from various country all around the world. Primarily their current

final magnetic product are axial inductors, radial inductors, chopper transformers and toroids.

2.5.1 Coil winding

Under the category of coil winding troids and chopper transformers are coming. They have

machineries for winding toroidal core and transformer core for mass production. But due to

some reasons the production rate had been now reduced.



2.5.1.1 Toroidal core winding

Toroid coil winding is done using coil winding machines available there. The operation of the

machine is semi-automatic. An operator first enters the required number of turns according to

their experience or pre calculated value. The machine pull required length of wire to wind the

specified number of turns .Then the operator place the ferrite core in to appropriate place and

the machine starts to wind .At the end the operator checks the inductance of the toroid using

digital LC meter and adjust the number of turns according to the required tolerance in

inductance value.

2.5.1.2 Transformer manufacturing

Currently they are manufacturing chopper transformer for their ballast circuits. The coil and

the ferrite core are imported from foreign countries. But the bobbin for place the coil winding

and ferrite core is manufactured by them.

2.5.1.2.1 Bobbin manufacturing

They have three plastic molding machines which are used to accomplish the needs of plastic

works arise during various manufacturing process. One such instance is plastic bobbin

manufacturing for chopper transformer. There is a custom made mould to manufacture the

bobbin. They fix this mould to the one of the machine and put feed the machine with plastic

grains. The machine melts the plastic grains and injects the liquid plastic inside the mould.

After cooling the bobbin is removed from the mould and the support is broken manually by

hand.

2.5.1.2.2 Transformer Coil winding

the coil wire for transformer also is wound on the bobbin using the transformer coil winding

machine .the operation of the transformer coil winding machine also same as toroid winding

machine. Here the required tolerance in inductance of the core is adjusted changing the air

gab between the ferrite core.

Finally manufactured chopper transformers are tested by fixing it on a ballast circuit.

2.5.2 Inductor assembling

Lead

Inductor Coil

2-20 Axial Inductor

Coil form



All parts needs to manufacture a inductor are imported from other countries. Here only the

assembling part is done. The lead is inserted into coil form and glued using Epoxy. Epoxy is

inserted in to small hole by compressed air. Then the inductor is placed in to an oven and

heated four five hours. At last the inductors which pass the tensile test are packed for

shipping.

2.6 Miscellaneous

During my training period there were some instances I was not occupied by any works. Such

that time I was encaged with some work the technicians already doing. I learned new

techniques and helped them.

2.6.1 Ballast, Tube light and CFL

As I mentioned already Esjay is manufacturing electronic ballast and selling imported

fluorescent lights. Before three years Esjay was manufacturing ballast successfully. I referred

the past documents and got the idea about the circuit diagram of the ballast and

manufacturing process. And I also able to realize how they modified the circuit according to

market requirement from the history of circuit diagram changes. The technicians explained

how they lost the market because of low cost imported ballast that is now available more in

the market.

2.6.1.1 Introduction

Incandescent and gas discharge tube lights are the two types of electric light source available.

Under the type of gas discharge tube fluorescent, mercury vapor, metal halide, high-pressure

sodium (HPS) and low-pressure sodium (LPS) are sub categories. Both convert the electric

energy into use full light energy according to different mechanisms. Incandescent lamp uses

Joule heating process. Here the high resistance Tungsten filament is heated to high

temperature to emit photons. But in the gas discharge tubes first the electrical energy is

converted into kinetic energy and then to electromagnetic radiation.

When we select electrical light from above categories we have to consider some properties of

those products. Such as luminous efficacy, life time of the lamp, lumen depreciation and

color rendering. Here luminous efficacy means amount of luminous per one watt power

consumption, life time of the lamp is related to failure rate of the lamp and lumen

depreciation and problems in color rendering are the results of aging of lamp. Following table

compare above properties for incandescent lamp and discharge tube.



Properties Incandescent lamp Discharge tube

Efficacy 10 % 20-30%

Life 1100 hours 20000 hours

lumen depreciation 10-15% 60-80%

2-2 Comparison between incandescent and discharge lamp

It is clear from the above table hat it is better to go for discharge tube to set up most

economic lighting system.

2.6.1.2 Ballast

Gas discharge tube needs an auxiliary part to ignite the discharging process and limit the

current through the discharging tube. The resistance of the tube has negative incremental

coefficient against current. The large drop in the resistance of the tube during operation

allows large current to follow and make damage. In order to limit the current there should be

a load. Most probably inductive impedance in the case of AC operated tubes.

Magnetic ballast and electronic ballast are the two available means of current limiting

auxiliary parts for discharge tube. The electronic ballast is preferred now over magnetic

ballast because magnetic ballast is bulky in size, generate audible hum, visible flicker and has

no cost effective way to regulate the power.

2.6.1.3 Electronic ballast

The functionality of the electronic ballast is to provide inductive load while operating at high

frequency. It takes the AC line as a input, rectify and smooth to get DC voltage which is

again converted to high frequency AC voltage using half bridge inverter. Half bridge inverter

has two transistors acting as a switch which are opened alternatively to create PWM signal.

That signal is fed Into a LC resonator circuit which has tube as a part of the circuit. And the

inductor of the resonator circuit gives necessary load to the current following through the

tube.

AC

rectifier

EMI filter Half bridge

inverter

T

u

b

e

AC

input

2-21 Block Diagram of Ballast



2.6.1.4 Additional protection circuits

In addition to elementary circuit there are many safety circuit arrangements should be made

in order to increase the quality of the product

Inrush current protection: To reduce the damages to the components because of inrush

current a fuse should be connected serially. In addition a varister can be connected between

live and nutral to ground the high current. varister is a discrete electronic component whose

resistance is reduce as the current following through it increasing.

EMI filter: The intention of placing EMI filter is to avoid high frequency noise generated

within the ballast propagates into the AC network. The noise affects frequency sensitive

equipments.

Power factor correction: For rectify the AC in ballast usually it is a common practice to use

diode rectifier as it is low cost. However, it has very poor line side Power Factor (PF) and

large Total Harmonic Distortion (THD).the low power factor increases the amount of reactive

power and increases THD. There are two types of power factor correction circuits. Active

power factor correcting circuit uses boost converter while passive power factor correcting

circuit uses LC filter.

2.6.1.5 Electronic Ballast Business of Esjay

Following are the reasons for unsuccessful ballast business of Esjay as I identified.

1. When I looked the electronic design it had all the circuitry additional safety

arrangement. But the PCB and soldering was very low quality, the PCB was not rigid

and the heat sink of the transistor not mounted properly. The PCB manufacturing

techniques was not updated today technology.

2. The enclosure was not a custom made but the current enclosure is suitable for local

market.

3. Lack of advertisement to the local market about the quality of the product.

However the management has now started a smart business on ballast. Now they are

importing fluorescent lamp from India, fixing their ballast and selling it back to the local

market. In my view this decision looks as a smart one because it is the only available first

step toward restoring their previous business



2.6.2 Lightening protection Product-ADSL lightening protection

Esjay has designs for various kind of lightening protection products and the manufactured

for local market; that was a good business because lightening problem is a very serious

problem in Sri Lanka in rainy season. From those I have got chance to get to know about

their ADSL lightening protection circuit.

2.6.3 PLC Programming

Esjay has got a project from SRC to design automatic railway gate control. in this project

they are going to use a PLC as a main control device. in order to do the project they first have

plan to learn about PLC design. I have gone through the documentation and wrote simple

program .I also tested written program real-time .I made arrangement like shown in the figure

2-22 and tested successfully.

2-22 ADSL lightening protection circuit

To line

To

equipment Resistor

Inductor

Gas discharge t tube

Avalanched

diode 18V Avalanched

diode 7.5V

GND

250mA Fuse

Push buttons

Input

Ladder LOGIC

Out put

Power AC

230V

Power supply

DC

24V PLC

Light

2-23 PLC arrangement



3 Conclusion

3.1 In-Plant Training Of Esjay Electronics (Pvt) Ltd.

3.1.1 Overview

At very first day of my training when I was given a CDMA phone to repair after introduction

given by general manager, I was in shock as I expected systematic Engineering training. I

could realize this type of training is suitable to a technician. But after two day I could change

my attitude we can learn even from repairing. There are some faults even the technicians

could not find the solution yet, I challenged myself to find the solution. It was a good

challenge for me because there were no repairing manuals and there were no datasheet for all

the ICs because those are custom made ICs. Only available equipment was multimetre I

could only measure the voltage and continuity. But at last I was able to find solution for some

faults.

Even though there are lots of advanced technologies I should have learnt but as electronics

engineering undergraduate student I got a chance to learn very basic skills like soldering and

PCB debugging. I believe this type of unbalanced training compare to my colleagues will not

affect my feature carrier and studies.

3.1.2 Ability Of Esjay To Give Useful Training

Esjay has necessary sources to give a satisfactory training to electronic engineering

undergraduate. But it depends on the time of the training program. Some time they do not

receive any project just they do repairing. That kind of time is not suitable for training.

During such time the undergraduate should have to ensure that he is getting all aspect of

industrial training by tired less effort.

3.1.3 Deficiencies In The Esjay Training

Esjay’s management peoples first should understand the training program. I could understand

their attitude on training on the very first day when they asked like this question “Are you

going to do research here?”; As they already said they have not had engineering back ground,

they expected to some work done by us, which could not be done by their technicians and

learning from these works is responsible of trainee. These are some deficiencies I identified

regarding the training I got from Esjay.

• They don’t have any training program, schedule and responsible person

• Don’t have attitude in providing necessary sources quickly



• Don’t provide safety arrangement

• No supervisors when dealing with high potential sources.

• Technicians and workers didn’t speak in English difficult for Tamils.

It is not suitable here giving suggestion on improving training program of Esjay. Because

they have lot of other necessary problems to be solved in order to survive in industry in

future. I also participated with my full potential in their efforts in restoring their industry back

as possible as soon. I think these kind of contribution is only can be provided by Engineers

and that’s Esjay’s expectation from us and future trainees.

3.2 Positive Side of University Training

The training program is an essential part of every undergraduate’s carrier because it fills the

gap between the theory and practical. It helps a lot to trainees to get the understanding of

industry before their graduatation. And adjust their carrier planning suitable to current

industrial trends.

3.3 Negative Side of University Training Arrangement

There are some problems with training arrangement of university. Before sending students to

training establishments they should analysis the eligibility of the training establishment to

provide the useful training. This cannot be evaluated through the past report of trainees. Even

one week is enough to a company to fall into lost. And we can’t expect all undergraduates

express their true opinion in the report.

Another problem is their assessment in training places. It is good to staff come and evaluate

the performance of the trainees but the time they are coming is not suitable. They are coming

at the end of the training and giving feedback on trainees’ performance but no time to correct

trainees’ mistakes according to their feedback. I recommend one month after start of the

training is a suitable time to visit staff from university.

3.4 My Opinion about Training Division & NAITA

In my view training division and NAITA are doing good job for undergraduate students as

well as country. The guides given by training division staffs were useful for me and those

were suitable advices for me. When the training division staffs visited us they thoroughly

understood our feeling on training and gave valuable advices.



Dr.Pasqual and his group from our department also visited. We had a good discussion with

him about our company and ways to improve its performance think these types of discussions

are very necessary and frequently should be done

3.5 My Recommendations about Esjay As A Good Training Place To Juniors

I agree on Ejay has enough experiences and infrastructure to provide the training to

Engineering undergraduates. But they don’t have necessary amount of human resources to

provide the training .they can’t assign their consultant engineer to training program. Because

he don’t have time and it costs more.

Any how they expect something from engineering students to come out from the past lost of

them. We also have responsibility to help them because they provided good training for our

seniors in past and when I saw the works our seniors done; I could realize how much ESJAY

dedicated in order to give good internship to our seniors.

Therefore I recommend the Esjay Electronic (Pvt) Ltd as a training place to my juniors who

have interest and previous experiences in electronics.



4 List of abbreviation

Here is the list of abbreviation I used throughout the report

AC-Alternating Current

DC-Direct Current

CDMA-Code Division Multiple Access

SLT-Sri Lanka Telecom Ltd

SMPS-Switch Mode Power Supply

MSM-Mobile Station Modem

LPS-Low Pressure Sodium

HPS-High Pressure Sodium

PF-Power Factor

THD-Total Harmonic Distortion

SRC-Sri Lanka Railway Corporation

ADSL-Asynchronous Digital Subscriber Loop

PLC-Programmable Logic Controller



5 Reference

1. http://www.esjay.com

2. Datasheet of MSM6025 IC

3. Datasheet of Vipro19

4. Micro C manual

5. Datasheet of PIC16F877A

6. J. Echapare, “A coin handling apparatus”, European Patent EP0246993,

Azkoyen Industrial, S.A., Priority: 21.05.1986; Filing: 19.05.1987; Publication:

16.12.1992

7. Kazimierczuk, M.K. and Szaraniec, W., “Electronic ballast for fluorescent lamps,” IEEE

Transactions on Power Electronics, Volume: 8, Issue: 4, Oct. 1993 pp. 386-395

Training Report

Documents

training period

training experiences

training place

week training

esjsy electronics pvt

esjay electronic pvt

esjay electronicspvt

f department of electronics