SAROJ MOHAN INSTITUTE OF TECHNOLOGY

GUPTIPARA, HOOGHLY

Electronics & Tele-Communication Engg.

ProjectOn

_PULSE WIDTH MODULATION_

Academic Year: 2008-2011

CERTIFICATE OF APPROVAL

This is to certify that the project report on

“PULSE WIDTH MODULATION”

Is submitted by

GROUP - G

FROM,

Department of“Electronics and Tele-Communication

Engineering”

“Saroj Mohan Institute of Technology”

has been successfully designed, tested and implemented in the department laboratory

towards the fulfillment of6th semester,

Diploma division for the academic year 2008-2011.

-----------------------------------------

( Mr. Mainak Mukherjee ) PRINCIPAL OF SAROJ MOHAN

INSTITUTE OF TECNOLOGY DIPLOMA DIVISION

CERTIFICATE OF APPROVAL

This is to certify that the project report on

“PULSE WIDTH MODULATION”

Is submitted by

GROUP - G

FROM

Department of“Electronics and Tele-Communication

Engineering”

“Saroj Mohan Institute of Technology”

has been successfully designed, tested and implemented in the department laboratory

towards the fulfillment of 6th semester,

Diploma division for the academic year

2007-2010.

---------------------------------------- -----------------------------------------

Mr.Moloy Ghata Mr. Mainak Mukherjee Lecturer & Project Guide Head of the Department Department of E.T.C.E Department of E.T.C.E

Acknowledgements

Acknowledgement is not only a ritual but, also an expression of indebtedness to all those who help the process of development of this term report. One of the most pleasant aspects in collecting the necessary information compiling it is the opportunity to think of those who actively contributed to it. I wish to express my heartfelt thanks to all those who assisted me during this project.

I also wish to express my sincere thanks and profound gratitude to our project guide sir MALAY GHATA for his persistent and able support, guidance and inspiration that helped

us to pursue the project entitled " PULSE WIDTH MODULATION”. His valuable knowledge and much needed assistance helped us to unearth the deepest intricacies involved in the pursuance of such a project. His patience and comforting attitude helped us to make this project a success and have inspired us to carry it forward.

We also take this opportunity to express our heartfelt gratitude to the Director, the faculty

members and the teaching staff of our college "Saroj Mohan Institute of Technology", who provided us with innumerable suggestions regarding this project time and again.

We also take this opportunity to express our heartfelt gratitude to the Director, the faculty members and the teaching staff of our college "Saroj Mohan Institute of Technology", who provided us with innumerable suggestions regarding this project time and again.

COMMENT ON PROJECT OF PROJECT TEACHER

This year I get an electronics batch for project. Almost everyone in my group is laborious and talented .So I thought to do some new project and express my thought to my group. They enjoying accepted my thought and after some day they decide to do the project “PULSE WIDTH MODULATION” and shown me. It was an excellent project so I enjoying granted it. Through the year almost all the group member work very hardly at their label best and at the end of the year they finish the project it was very pleasant experience for me.

Thanks,

…………………….. (SIGNATURE) MALAY GHATA TEACHER IN CHARGE (GROUP A)

MEMBER OF THE PROJECT GROUP

SATYAJIT MONDALROLL: D136054005 NO: 17774

SHAMS TANWEERROLL: D136054005 NO: 17776

SOUMI KUNDUROLL: D136054005 NO: 05251

SUMAN GHOSHROLL: D136054005 NO: 05244

“We build up this project . I entered in this matter from top to bottom and worked in this project very sincerely and consciously. According to theory and circuit diagram it is manufactured.”

“I am always innovative and wanted to do this project. I have completed this project with the help of other group members & assisted by project head”

“Interested in this project for self experience in pulse amplitude modulation techn. I also gather practical experience through this project which will help me in future.

“Through the help of challenge and truthness everything will can be possible in this world, just don’t give up . In this way we did our project.”

SURAJ SAHAROLL: D136054005 NO: 05246

SUVRO SENGUPTAROLL: D136054005 ROLL: 05247

SUKRIT DEYROLL: D136054005 NO: 05242

SUBHADIP DASROLL: D136054005 NO: 05241

“I am very interested to do this kind of project and also interested in electronic components . Since at beginning I work very hard for this project.”

“I have interest to know about the electronics subject and I Want to do creative work in this field. Though this project I am able to fulfill my ambition. This project gives me the Touch of creativity. ”

“To contribute to the growth of the project by working in a challenging and responsible position and providing my worth to the best of my abilities.”

“Each person in this world have a special job to do, hence, I think the god to send me to accomplish my dream job which is engineering. I fill proud to work with this kind of project.”

TABLE OF CONTENT

Project background

Introduction

Pulse width modulation

History

Application of Project

Circuit components

Circuit diagram

Circuit descrption

Lab equipment tools

Project image

Faculty contribution

Reference

Comment on project

PROJECT BACKGROUND:

We always try to do creative work in

electronics field. We fulfill our desire through this project. We choose this project for some reason .Once in our class when we were studying about PULSE WIDTH MODULATION we thought of making this project under expert supervision. Then we choose this project after a discussion among the group members.

APPLICATION OF PROJECT (DEVICE)

Pulse width modulation is used to reduce the total power delivered to a load without resulting in loss, which normally occurs when a power source is limited by a resistive element.

PWM is also used in efficient voltage regulators. By switching voltage to the load with the appropriate duty cycle, the output will approximate a voltage at the desired level. The switching noise is usually filtered with an inductor and a capacitor.

PWM is sometimes used in sound (music) synthesis, in particular subtractive synthesis, as it gives a sound effect similar to chorus or slightly detuned oscillators played together. Crude form of PWM has been used to play back PCM digital sound on the PC speaker.

Variable-speed fan controllers for computers usually use PWM.

Light dimmers for home use employ a specific type of PWM control.

History

In the past, when only partial power was needed (such as for a sewing machine motor), a rheostat (located in the sewing machine's foot pedal) connected in series with the motor adjusted the amount of current flowing through the motor, but also wasted power as heat in the resistor element. It was an inefficient scheme, but tolerable because the total power was low. This was one of several methods of controlling power. There were others—some still in use—such as variable autotransformers, including the trademarked 'Autrastat' for theatrical lighting; and the Variac, for general AC power adjustment. These were quite efficient, but also relatively costly.

For about a century, some variable-speed electric motors have had decent efficiency, but they were somewhat more complex than constant-speed motors, and sometimes required bulky external electrical apparatus, such as a bank of variable power resistors or rotating converter such as Ward Leonard drive .

However, in addition to motor drives for fans, pumps and robotic servos, there was a great need for compact and low cost means for applying adjustable power for many devices, such as electric stoves and lamp dimmers.

One of early applications of PWM was in the Sinclair X10, a 10 W audio amplifier available in kit form in the 1960s. At around the same time PWM started to be used in AC motor control.

PULSE WIDTH MODULATION

An Introduction

Pulse width modulation is also known as pulse duration modulation. Three variations of pulse width modulation are possible. In one variation, the leading edge of the pulse is held constant and change in pulse width with signal is measured with respect to the leading edge. In other variation the tail edge is held constant with respect to it, pulse width is measured. in the third variation centre of the pulse is held constant and pulse width changes on either side of the centre of the pulse.

PWM is a method of transmitting information on a series of pulses. The data that is being transmitted is encoded on the width of these pulses to control the amount of power being sent to a load. In other words, pulse width modulation is a modulation technique for generating variable width pulses to represent the amplitude of an input analog signal or wave. The popular applications of pulse width modulation are in power delivery, voltage regulation and amplification and audio effects.

PULSE WIDTH MODULATION AND IT’S REPRESENTATION

PWM CIRCUIT COMPONENTSCOMPONENT VALUE PIECES

CAPACITOR 0.1 μF 2

.0047 μF 1

47 μF 1

100pF 1

.001 μF 3

Resistor 10kΩ 5

15kΩ 1

68Ω 2

4.7kΩ 1

4.7 k varies 1

1kΩ 3

47kΩ 2

100 k POT 1

Monostable Multivibrator IC

74121 1

OP-Amp IC 356 3

Transistor 2N222 1

Zener Diode 6.2v 1

Power Supply +12v / -12v 1

+5 1

CIRCUIT DIAGRAM

Circuit operation

Input clock pulse is given 74121 it is a monostable multivibrator the width of the pulse of monostable multivibrator is maintained by capacitor 0.001 mf and variable resistance of 100k. This pulse is going through a miller integrator circuit. Using D.C 547 and op-amp lm356. The integration of pulse signal is saw tooth ramp signal; this signal is passing through one of the input of adder circuit. Another input of adder circuit is modulating signal. So the output of the adder ckt is shown below

The signal is passing through a comparator using lm 710. The threshold voltage of comparator is choosing using 4.7k variable resistance. So the output of the comparator is pulse voltage. The width of the pulse is dependent upon the input modulating signal voltage as a result the output is PWM wave of input modulating signal. For demodulation we use a second order active LPF using lm 356.

Different Parts Of PWM CircuitPart 1:

In first part a input clock pulse is given to pin no 5 of 74121 IC. It is a MONOSTABLE MULTIVIBRATOR. The output pulse is generated from pin no 1 and it called Short Duration Pulse. The width of the pulse is maintained by a capacitor 0.001µf and a variable resistance of 100K.

Part 2:

The output of the monostable multivibrator is going through a MILLER INTEGRATOR CIRCUIT using D.C 547 and OP-Amp LM356.The output pulse of the integrator is a SAW TOOTH Signal

.

Part 3:

At the third stage the output signal of the integrator circuit is passing through a ADDER CIRCUIT. Here another input signal is added to the circuit which is a Modulating Signal.Then the output of the Adder circuit is passing through a COMPARATOR CIRCUIT using LM 356.The threshold voltage of comparator is choosing using 4.7K variable resistance. So the output of comparator is pulse voltage. The width of the pulse is dependent upon the input modulating signal voltage as a result the output is PWM (Pulse Width Modulation) wave of input modulating signal.

Part 4:

For Demodulation we use a SECOND ORDER ACTIVE LOW PASS FILTER using LM356.

Lab Equipment Tools

CRO,DSO& FUNCTION GENARATOR CONNECTING WIRES

DIGITAL STORAGE OSSILOSCOPE MULTIMETER

SOLDERING IRON &WIRE CONNECTING WIRES

IMAGE OF PROJECT

FACULTY CONTRIBUTION

Mr.Moloy Ghata (Lecturer)

Respected sir,

He is lecturer of our project “PULSE WIDTH MODULATION”. He is the genuine adviser of our project. When we are faced any problem then solved the problem related to this project. Sir gives us hardworking and his contribution in our project and this able us to complete this project.

Mr. Mainak Mukherjee (Lecturer)

Respected sir,

He is a one of the best lecturer of our institute; mainly give us the lesson about the PWM. His special lecture about the topic is helping us to complete this project.

REFERENCE:

BOOKS:

“COMMUNICATION SYSTEM” (ANALOG & DIGITAL)BY: SANJAY SHARMA

“SIGNAL’S & SYSTEM” BY: SANJAY SHARMA

INTERNET: Site

HTTP://WWW.GOOGLE.COM

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HTTP://WWW.ALLDATASHEET.COM

HTTP://WWW.KEILuCOMPILER.COM

HTTP://WWW.SDCC.COM

HTTP://WWW.8051.COM/TUTORIAL /

HTTP://WWW.BTECHGURU.COM

Comment on Project

THANKING YOU