5V DC POWER SUPPLY
A PROJECT REPORT ON
Submitted by
MRINAL KESHRI
In fulfilment for the award of the degree
Of
BACHELOR OF ENGINEERING
in
ELECTRONICS AND COMMUNICATION
BABARIA INSTITUTE OF TECHNOLOGY , VADODARA
GUJARAT TECHNOLOGICAL UNIVERSITY, AHMEDABAD
DECEMBER, 2015
BABARIA INSTITUTE OF TECHNOLOGY , VADODARA
ELECTRONICS AND COMMUNICATION
2015
CERTIFICATE
Date:
This is to certify that the dissertation entitled “5V DC POWER SUPPLY” has
been carried out by Mrinal Keshri under my guidance in fulfilment of the
degree of Bachelor of Engineering in ELECTRONICS AND
COMMUNICATION [ 1ST Semester] of Gujarat Technological University,
Ahmedabad during the academic year 2014-15.
Guides:
Head of the department
ACKNOWLEDGEMENT
I would like to express my special thanks of gratitude to my teachers who gave me the
golden opportunity to do this wonderful project on the topic which also helped me in doing
a lot of Research and I came to know about so many new things.
 I am really thankful to them.
Secondly, I would also like to thank my parents and friends who helped us a lot in
finishing this project within the limited time.
 I have also used internet and some standard reference books [H.C. VERMA and
NCERT] for the better understanding of my subject.
ABSTRACT
With today’s technological advancement, new miniaturized electrical and
electronic products continue to emerge and these products require either a very
low AC source or DC source for their operation. Many of the existing power
supply devices with various levels of complexities and sophistication can only
give a single DC output which cannot serve the same purpose when a very low
AC power output is greatly desired. Hence, the need for designing and
developing a multi-output power supply that can serve a dual purpose of
providing DC and AC outputs of different values for use in miniaturized
electrical and electronic appliances as well as for various domestic and
laboratory experimental purposes. In this work, a simple, cost effective and
reliable power supply that produces AC outputs of5V, 10V, 15V, 20V and 25V,
variable DC outputs of 0-20V, regulated DC output of 5V and regulated dual
DC outputs of ±15V was developed. A centre tapped transformer 220/30V
(15V-0-15V) was constructed to produce the desired AC voltage range 0-30V at
interval of 5V, For the DC section, 25V, 20V and 15V from the output of the
transformer were rectified, smoothened and regulated using appropriate discrete
components. The major components used include transistors, comparator
LM393 and regulators LM317, LM7915 and LM7815. Short circuit test, open
circuit test and earthing test were carried out on the developed power supply
unit. The output measurements showed that the power supply was functional
and the measured values gave minima variation from the nominal designed
values. The developed multi output power supply is much useful in
measurements, laboratory works and general applications requiring power
supply. Keywords: miniature, AC source, DC source, multi-output power
supply, accuracy.
TABLE OF CONTENTS
Acknowledgement
Abstract
Introduction to Project
Principle
Working / Implementation of the Project work
Result Analysis
Conclusion
INTRODUCTION
1. Place the leads of four diodes through contact points in an unpopulated
circuit board. Arrange the diodes in a square so that the leads can be
connected together. Also, two of the diodes should have their anodes
adjacent to each other, and the other two diodes should have their
cathodes facing each other. The cathode ends of diodes have bars or
stripes as identifying marks.
2. Use needle-nose pliers to twist together each pair of leads. There should
be four connections. As you go around your square arrangement of
diodes, the twisted leads should consist of cathode-cathode, anodecathode, anode-anode and cathode-anode.
3. Turn on the soldering iron, allow the tip to heat up and use lead-free
solder at the twisted lead pairs. Use diagonal cutters to snip off excess
leads.
4. Prepare four wires to add to your circuit. The length of the wires will
depend on your planned use for your bridge rectifier. Cut the wires to
your desired length, and strip a short amount of insulation from the ends.
Expose enough wire at the ends to make electrical connections.
5. Solder the input wires to your bridge rectifier. Label them as you
proceed. Connect one AC input wire to the anode-cathode twisted leads.
Connect the other AC input to the cathode-anode twisted leads.
6. Solder the output wires to your circuit. The positive DC output connects
to the positive AC wire input to the cathode-cathode twisted leads. The
negative DC output connects to the anode-anode twisted leads.
7. Add insulating pads to the bottom of your circuit board so it doesn't
create a short circuit. Turn off the soldering iron. The bridge rectifier is
ready to convert AC input to a DC output.
PRINCIPLE
Bridge rectifier is an electronics component that is used in a circuit to turn
alternating current (AC) electricity into direct current (DC) electricity. Although
there are single components that can perform this function, you can make your
own bridge rectifier by creating a bridge rectifier circuit with four diodes. A
diode is a radial component with a metal lead protruding from each end. The
diode allows electrical current to pass in one direction, from the cathode, or
positive end, to the anode, or negative end. By electrically connecting the four
diodes, you can make your own bridge rectifier.
Working / Implementation of the Project work
Component List :
1. Step down transformer
2. Voltage regulator
3. Capacitors
4. Diodes
Let’s get into detail of rating of the devices:
Voltage regulator
As we require a 5V we need LM7805 Voltage Regulator IC.
7805 IC Rating:

Input voltage range 7V- 35V

Current rating Ic = 1A

Output voltage range VMax=5.2V ,VMin=4.8V
Transformer
Selecting a suitable transformer is of great importance. The current rating and
the secondary voltage of the transformer is a crucial factor.

The current rating of the transformer depends upon the current required
for the load to be driven .The input voltage to the 7805 IC should be at
least 2V greater than the required 2V output, therefore it requires an input
voltage at least close to 7V.

So I chose a 9-0-9 transformer with current rating 500mA
The best is using a full wave rectifier

Its advantage is DC saturation is less as in both cycle diodes conduct.

Higher Transformer Utilization Factor (TUF).

1N4007 diodes are used as its is capable of withstanding a higher reverse
voltage of 1000v whereas 1N4001 is 50V
Capacitor
It only allows alternating current.
RESULT ANALYSIS
 We observed that we are getting constant DC output.
 There may be some error i.e. output would be about 5V
 CRO also shows the same thing.
CONCLUSION
Due to the need for most domestic and laboratory equipment of small
ratings to be powered by electricity in one form or the other coupled with
the problem of insufficiency of number of specially designed power
supply for the needed domestic application or laboratory experiment as
well as electrical project design, a multi-output power supply unit was
developed. The developed multi-output power supply consists of four
segmental outputs; AC output, variable DC output, regulated dual
rectified DC output and regulated single DC output. The AC outputs
produced 5V, 10V, 15V, 20V and 25V. The variable DC output produced
values ranging from 0-20V while the regulated and regulated dual outputs
produced 5V and ±15V respectively. Tripping circuit was incorporated
with transistors TIP41C and TIP42C and comparator LM393 and was
provided to guard against overloading and short circuit for the DC
circuits while fuses were used to protect the AC circuit. Short circuit test
and earthing test were carried out on the developed power supply unit.
The output measurements showed that the developed power supply was
effective and the measured values gave minima variation from the
nominal designed values. The developed system is cheap, robust and very
useful for domestic application and laboratory experimental purposes.