Pulse Generator with Adjustable duty cycle

May 2015

Electronics & Communication Engineering

Semester 6

Indus University

Pulse Generator with Adjustable Duty Cycle

Project members:

Mitwa Palkhiwala(IU1241090028)

Ami Goswami(IU1241090014)

Project guide:

Prof. Hansa Shinghrakhia

CERTIFICATE

This is to certify that the project entitled “Pulse Generator with Variable Duty Cycle” is a bonafied report of the work carried out by MitwaPalkhiwalaand Ami Goswamias a part of subject: Mini Project-II of semester 6

of the degree of Bachelor of Technology in Electronic And Communication Engineering at Indus Institute of Technology & Engineering, Indus University, Ahmedabad, Gujarat.

Project Guide:

Prof. HansaShinghrakhia

Department Of Electronics and Communication Engineering

Indus University, Ahmedabad

Prof. R N Mutagi

Head of Department

Department Of Electronics and Communication Engineering

Indus University, Ahmedabad

ACKNOWLEDGEMENT

“Success can be achieved only by hard work and proper guidance.”

For the successful completion of our project, we would like to express our sincere gratitude to INDUS

UNIVERSITY, AHMEDABAD for providing us an environment for doing this practical work.

We thank Mrs. HansaShinghrakhia, Professor, Electronics and Communication Engineering Department,

Indus University for providing seamless support and knowledge over the past one semester, and also for

providing right suggestions at every phase of the development of our project. We sincerely thank them for their

extensive support, guidance and helping us put our ideas to work and providing us the conducive environment

for carrying through our academic schedules and projects with ease.

We are grateful to Prof. R N Mutagi, Head of Electronics and communication Engineering Department, IITE

for his useful inputs at every stage of our project throughout our academic schedules.

Last but not the least, we bow down our head to the ALMIGHTY GOD, without whose blessings this work

would not have turned into reality.

MitwaPalkhiwala(IU1241090028)

Ami Goswami(IU1241090014)

Semester 6, B.Tech,Electronics and Communication Engineering,Indus University

Table of content

Sr. No. Title Page No.

1. 0 Introduction

2. 0 Circuit design

3.0 Simulation and outputs

4. 0 Application

5. 0 Conclusions

6. 0 References

1. Introduction An electronic circuit capable of producing a waveform that rises abruptly, maintains a relatively flat top

for an extremely short interval, and then rapidly falls to zero i.e circuits whose exclusive function is

generating short duration, rectangular waveforms are usually specifically identified as pulse generators.

The term pulse generator is often applied not only to an electronic circuit generating prescribed pulse

sequences but to an electronic instrument designed to generate sequences of pulses with variable delays,

pulse widths, and pulse train combinations, programmable in a predetermined manner, often

microprocessor-controlled.

In this project, we are going to design a pulse generator having adjustable duty cycle. Duty cycle is

nothing but the percentage of one period in which a signal is active. User may set the duty cycle as per

their requirements.

Pulse

Generator

2. Circuit design

Important formulae:

% duty cycle = Ra+Rb

Ra+2 Rb×100 %

Charging time tc = 0.693(Ra + Rb)C

Discharging time, td = 0.693(Rb)C

Total time , t = 0693(Ra + 2Rb)C

A1

555_VIRTUALGND

DIS

OUTRST

VCC

THR

CON

TRI

D1

1N4148D2

1N4148

Rb1

1MΩKey=A

50%Rb2

6.5kΩC1µF

VCC9V

Ra 6kΩ

XSC1

A B

Ext Trig+

+

_

_ + _

C10.05µF

Calculations:

Let F = 1.3 Hz = >t = 1F

=> t = 792.910 ms

Let C = 1 µF and Ra= 6KΩ

For 30% duty cycle, tc = 0.3t and td = 0.7t

td = 0.693(Rb)C=0.7t Rb = 800KΩ


td = 0.693(Rb)C=0.5t Rb = 572.08KΩ


td = 0.693(Rb)C=0.3t Rb = 343.25KΩ

Component list:

Component Quantity SpecificationsResistors 2 Ra = 6KΏ

Rb2 = 6.5KΏPotentiometer 1 Rb1 = 1MΏCapacitors 2 C = 1µF

C2 = 0.05µFDiodes 2 D1 = 1N4148

D2 = 1N4148Power Supply 1 Vcc = 9VIC 1 NE555

3. Simulation and outputs:

Total time period A1

555_VIRTUALGND

DIS

OUTRST

VCC

THR

CON

TRI

D1

1N4148D2

1N4148

Rb1

1MΩKey=A

50%Rb2

6.5kΩC1µF

VCC9V

Ra 6kΩ

XSC1

A B

Ext Trig+

+

_

_ + _

C10.05µF

30% duty cycle

70% duty cycle

DSO OUTPUT 1

DSO OUTPUT 2

DSO OUTPUT 2

4. Applications:

Pulses can be injected into a device that is under test and used as a stimulus or clock signal or analyzed,

confirming the proper operation of the device or pinpointing a fault in the device.

Pulse generators are also used to drive devices such as switches, lasers and optical components,

modulators, intensifiers as well as resistive loads.

The output of a pulse generator may also be used as the modulation signal for a signal generator. Non-

electronic applications include those in material science, medical, physics and chemistry.

5. Conclusion:

Thus, our objective of making a pulse generator with adjustable duty cycle has been achieved.

As the wiper of potentiometer of 1 MΩ is moved from one end to other, any desired percentage of duty cycle between 0% to 100% can be obtained .

6. References:Books;

Ramakant A. Gayakwad ,”Op-Amps and Linear Integrated Circuits” , Fourth Edition, PHI Publications

David A. Bell , “Operational amplifiers and linear IC’s” , Third Edition, Oxford University Press.

Web Sites ; http://www.learnabout-electronics.org/Oscillators/osc44.php