A PROJECT REPORT ON

THE FABRICATION OF REGULATED DC POWER SUPPLY

SUBMITTED TO

ELECTRICAL DEPARTMENT

BABARIYA INSTITUTE OF TECHNOLOGY

VARNAMA, VADODARA

YEAR - 2014

SUBMITTED BY

1. SAURABH DAYAL SINGH 130050109106

2. MAULIK DEORE 130050109018

3. ALLAN ABRAHAM 130050109004

4. BHAVIN BARAD 130050109006

5. ASTHA CHAUHAN 130050109014

6. DEVASHREE KUTE 130050109020

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ACKNOWLEDGEMENT

We are deeply indebted to “ Mr. Saifee Kezarbhai Kanjetawala and Mr. Milan A. Chaudhari Assistant Professor in Department of Electrical Engineering. At Babariya Institute Of Technology , Varnama (Vadodara)”. For his inspiring and encouraging guidance without which this project work could not have been completed in spite of his busy schedule. He always had time to attend the problem faced by us in our project work. We will always remember his quick analysis, comprehensive solution and critical reviews; he has been given throughout the project work. Cordial and earnest thanks to staff of Babariya Institute of Technology, Varnama (Vadodara) for his valuable suggestion and help remembered in conducting the project work .But at last, but not least we express over indebtedness to our parents and all other family members for their patience and help extended in this end over.

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CONTENTS

1. CHAPTER-1 INTRODUCTION

1.1 INTRODUCTION………………………………………………………….…………..04

1.2 THEORETICAL BACK GROUND………………………………………….………. .05

1.3 AIM OF THE PROJECT…………………………………………………………….…07

2. CHAPTER-2 PROJECT DESCRIPTION

2.1 BLOCK DIAGRAM………………………………………………………………… …08

2.2 BLOCK DESCRIPTION………………………………………………………….…….08

2.3 CIRCUIT DIAGRAM………………………………………………………..………….13

2.4 COMPONENT USED…………………………………………………………...………14

2.5 STEPS OF WORKING…………………………………………………………….……18

2.6 HOW TO CONSTRUCT………………………………………………………...………18

3. CHAPTER-3 FABRICATION PROCESS

3.1 FABRICATION TECHNIQUES ……………………………………………………..….19

3.2 VARIOUS TOOLS AND EQUIPMENTS…………………………………………….…20

3.3 SOLDERING………………………………………………………………………..…… 21

3.4 TIPS WHILE WORKING……………………………………………………………...…22

3.5 PICTURE OF WORKING MODEL…………………………………………...…………22

3.6 PRECAUTION……………………………………………………………………………23

3.7 TESTING………………………………………………………………………….………23

4. CHAPTER-4 CONCLUSION

4.1 CONCLUSION……………………………………………………………………………24

4.2 RESULT………………………………………………………………………………...…24

4.3 APPLICATION……………………………………………………………………………25

4.4 ADVANTAGES…………………………………………………………………………...25

5 . CHAPTER-5 REFERENCE

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CHAPTER-1 INTRODUCTION

1.1 INTRODUCTION

A power supply is a device that supplies electrical energy to one or more electric loads. The term is

most commonly applied to devices that convert one form of electrical energy to another, though it

may also refer to devices that convert another form of energy (e.g., mechanical, chemical, solar) to

electrical energy. For electronic circuits made up of transistors and/or ICs, this power source must

be a DC voltage of a specific value.

In general, electronic circuit using transistors require a source of DC power for example in tube

amplifiers, DC voltage is needed for plate, screen grid. Similarly the emitter and collector bias in a

transistor must also be direct current. Batteries are rarely used for this purpose as they are costly.

In practice DC power for electronic circuits is most conveniently obtained from commercial AC

lines by using rectifier-filter system, called a DC power supply. The rectifier-filter combination

constitutes an ordinary DC power supply. The DC voltage from an ordinary power supply remains

constant. So long as AC mains voltage or load is unaltered. However, in many electronic

applications, it is desired that DC voltage should remain constant irrespective of change in AC

mains or load under such situations, voltage regulating devices are used with ordinary power

supply. This constitutes regulated DC power supply and keeps the DC voltage at fairly constant

value.

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1.2 THEORETICAL BACKGROUND:

A regulated power supply is one that controls the output voltage or current to a specific value; the

controlled value is held nearly constant despite variations in either load current or the voltage

supplied by the power supply's energy source. Every power supply must obtain the energy it

supplies to its load, as well as any energy it consumes while performing that task, from an energy

source. Depending on its design, a power supply may obtain energy from:

1. Electrical energy transmission systems. Common examples of this include power supplies

that convert AC line voltage to DC voltage.

2. Energy storage devices such as batteries and fuel cells.

3. Electromechanical systems such as generators and alternators.

4. Solar power.

A. IC 78XX series

The 78xx is a family of self-contained fixed linear voltage regulator integrated circuits. The 78xx

family is commonly used in electronic circuits requiring a regulated power supply due to their

ease-of-use and low cost. For ICs within the family, the xx is replaced with two digits, indicating

the output voltage . The 78xx line is positive voltage regulators: they produce a voltage that is

positive relative to a common ground. There is a related line of 79xx devices which are

complementary negative voltage regulators. 78xx and 79xx ICs can be used in combination to

provide positive and negative supply voltages in the same circuit. There are common

configurations for 78xx ICs, including 7805 (5 volt), 7806 (6 volt), 7808 (8 volt), 7809 (9 volt),

7810 (10 volt), 7812 (12 volt), 7815 (15 volt), 7818 (18 volt), and 7824 (24 volt) versions. The

7805 is common, as its regulated 5 volt supply provides a convenient power source for

most components. Each device in this series has minimum input voltage to be maintained to get

regulated output.

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B. REGULATED DC POWER SUPPLY

I. +5V SUPPLY UNIT -Initially 230 V AC supply is reduced to (24V) with the help of a step

down transformer having a capacity of 500mA. Since the input voltage to the regulator IC

should be more than its output voltage, transformer secondary voltage is 24V. This low voltage

is rectified with the help of bridge rectifier. The ripples are minimized with the help of

capacitor filter to get a smooth DC supply.

The regulated DC voltage is obtained by using a regulator IC 7805. In the case of IC 7805, the

unregulated DC voltage is applied to Pin 1, and the output is taken at Pin 3 and Pin 2 is

grounded. The capacitor filter of rating 100µF is connected at the output of regulator IC to

eliminate the voltage oscillations at the output due to the large voltage oscillations at the input

of the regulator.

II. +12V SUPPLY UNIT -Initially 230 V AC supply is reduced to 24Vwith the help of a step down

transformer. This low voltage is rectified with the help off bridge rectifier. Since the input

voltage to the regulator IC should be more than its output voltage, transformer secondary

voltage is 24 V. The ripples are minimized with the help of capacitor filter to get a smooth DC

supply.

The regulated DC output voltage is obtained by using regulator ICs. For regulated +12V DC

supply, IC 7812 is used and for regulated -12V DC supply. In the case of IC 7812 the

unregulated DC voltage is applied to Pin 1, and the output is taken at Pin 3 and Pin 2 is

grounded. The output is taken at Pin 3 and Pin 1 is grounded. The capacitor of 100µF is

connected at the output as shown in figure to eliminate the voltage oscillations at the output

due to the large voltage oscillations at the input of the regulator.

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1.3 AIM OF A PROJECT

1. To construct a regulated DC power supplies 12 V and 5V source. The power supply

converts the (220-230) V AC into 12 V and 5V DC output.

2. Establishment of regulated DC power supply being used in the labs.

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CHAPTER-2 PROJECT DESCRIPTION

2.1 BLOCK DIAGRAM

2.2 BLOCK DESCRIPTION

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1 . S t e p - D o w n T r a n s f o r m e r

A step down transformer has more turns of wire on the primary coil and less turns of wire on

the secondary coil. This makes a smaller induced voltage in the secondary coil. Compare this with

a step up transformer.

It is called a step down transformer because the output voltage is smaller than the input voltage. If

the secondary coil has half as many turns of wire then the output voltage will

be half the input voltage.

See the transformer equation. Decreasing the voltage does not decrease the power. As

the voltage goes down, the current goes up.

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2. Rectifier  

There are several ways of connecting diodes to make a rectifier to convert AC to DC. The  bridge

rectifier the most important and it produces full-wave varying DC. A full-wave rectifier can also

be made from just two diodes if a centre-tap transformer is used, but this method is rarely used

now that diodes are cheaper. A Single diode can be used as a rectifier but it only uses the positive

(+) parts of the AC wave to produce half-wave varying DC.

i. Bridge Rectifier : - A bridge rectifier can be made using four individual diodes, but it is also

available in special packages containing the four diodes required. It is called a full-wave

rectifier because it uses all the AC wave (both positive and negative sections). 1.4V is used up

in the bridge rectifier  because each diode uses 0.7V when conducting and there are always two

diodes conducting, as shown in the diagram below. When AC supply is switched on. During

positive half cycle terminal A is positive and B is negative. This makes diode D1 & D3forward

biases & diode D2& D4reverse biases and we get positive cycle. During –ve half wave cycle,

the A becomes –ve and B becomes +ve. Due to this D2 & D4come under forward bias and

diode D1 & D3 are in reverse bias. Therefore , diodes D2 & D4 conduct while diode D1 & D3

don’t. The shape of wave is shown.

Hence, we can say that the bridge wave rectifier give the pulsating DC voltage which are not

suitable for electronic circuit.

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3. Smoothing

smoothing is performed by large value electrolytic capacitor connected across the DC supply to

act as a reservoir, supplying current to the output when the varying DC voltage from the rectifier is

falling. The diagram shows the unsmoothed varying DC (dotted line) and the smoothed DC (solid

line). The capacitor charges quickly near the peak of the varying DC, and then discharges as it

supplies current to the output.

Smoothing is not perfect due to the capacitor voltage falling a little as it discharges giving a small

ripple voltage. For many circuits a ripple which is 10% of the supply voltage is satisfactory and the

equation below gives the required value for the smoothing capacitor. A large capacitor value must

be doubled when smoothing half- wave rectifier.

So, in this we can conclude that the pulsating DC voltage is applied to the smoothing capacitor.

This smoothing capacitor reduces the pulsating in the rectifier Dc output voltage. The smooth DC

output has a small ripple. It is suitable circuits.

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4. Regulator

The regulator is a circuit that helps maintains a fixed or constant output voltage. Changes in the

load or the AC line voltage will cause the output voltage to vary. Most electronic circuits cannot

withstand the variations since they are designed to work properly with a fixed voltage. The

regulator fixes the output voltage to the desired level then maintains that value despite any output

or input variations. Voltage regulator ICs are available with fixed (typically 5, 12 and 15V) or

variable output voltages. They are also rated by the maximum current they can pass. Negative

voltage regulators are available, mainly for use in dual supplies. Most regulators include some

automatic protection from excessive current ('overload protection') and overheating ('thermal

protection'). Many of the fixed voltage regulator ICs has 3 leads and look like power transistors,

such as the 7805 +5V 1A regulator .They include a hole for attaching a heat sink if necessary.

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2.3 CIRCUIT DIAGRAM

]

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2.4 COMPONENT USED

1. CAPACITOR:- A capacitor is a passive two-terminal electrical component used to

store energy electro statically in an electric field. The 'non- conducting' dielectric acts to

increase the capacitor's charge capacity. A dielectric can be glass, ceramic, plastic film, air,

paper, mica, etc. Capacitors are widely used as parts of electrical circuits in many common

electrical devices. A capacitor stores energy in the form of an electrostatic field between its

plates.

If a battery has been attached to a capacitor for a sufficient amount of time, no current can

flow through the capacitor. However, if an accelerating or alternating voltage is applied across

the leads of the capacitor, a displacement current can flow. The SI unit of capacitance is

the farad (F), which is equal to one coulomb per volt (1 C/V). Typical capacitance values

range from about 1 pF (10−12 F) to about 1 mF (10−3 F). We have used 100uF capacitor.

2. DIODE 1N7001:-In electronics, a diode is a two-terminal electronic component with

asymmetric conductance; it has low resistance to current in one direction, and high resistance

in the other. Today, most diodes are made of silicon, but other semiconductors such

as selenium or germanium are sometimes used.

The most common function of a diode is to allow an electric current to pass in one direction

(called the diode's forward direction), while blocking current in the opposite direction

(the reverse direction). Thus, the diode can be viewed as an electronic version of a check

valve. This unidirectional behavior is called rectification, and is used to convert alternating

current to direct current, including extraction of modulation from radio signals in radio

receivers—these diodes are forms of rectifiers.

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3. PRINTED CIRCUIT BOARD :- (PCB) mechanically supports and electrically

connects electronic components using conductive tracks, pads and other features etched from

copper sheets laminated onto a non-conductive substrate. PCBs can be single sided (one

copper layer), double sided (two copper layers) or multi-layer. Conductors on different layers

are connected with plated-through holes called bias. Advanced PCBs may contain

components - capacitors, resistors or active devices - embedded in the substrate.

Printed circuit boards are used in all but the simplest electronic products. Alternatives to

PCBs include wire wrap and point-to-point construction. PCBs require the additional design

effort to lay out the circuit but manufacturing and assembly can be automated. Manufacturing

circuits with PCBs is cheaper and faster than with other wiring methods as components are

mounted and wired with one single part. Furthermore, operator wiring errors are eliminated.

4. 12-0-12 TRANSFORMER: - The step down transformer high voltage AC into low voltage

AC. By step down transformer we can take different values of voltage at output. In this

project we have use 12-0-12 step down transformer. 12-0-12 means that the voltage or the

potential difference (pd.) between each of the end terminals of the secondary winding and the

mid-point of the secondary winding of the transformer is 12V. And, between the two ends of

the secondary winding, you will get 12 + 12 = 24V. 500mA means the current delivery

capability of the secondary winding of the transformer.

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5. IC7812:- IC7812 is a famous IC which is being widely used in 12V voltage regulator

circuits.. We only need to use two capacitors, one on the input and second one on the output

of 7812 in order to achieve clean voltage output and even these capacitors are optional to use.

To achieve 12V 1A current, 7812 should be mounted on a good heat sink plate. 7812 has built

in over heat and short circuit protection which makes it a good choice for making power

supplies. High current 7812 voltage regulator can be constructed by adding a transistor to

increase load current capability.

6. IC7805:- 7805 is a voltage regulator integrated circuit. It is a member of 78xx series of fixed

linear voltage regulator ICs. The voltage source in a circuit may have fluctuations and would

not give the fixed voltage output. The voltage regulator IC maintains the output voltage at a

constant value. The xx in 78xx indicates the fixed output voltage it is designed to provide.

7805 provides +5V regulated power supply. Capacitors of suitable values can be connected at

input and output pins depending upon the respective voltage levels.

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Pin no Function Name

1 Input voltage (5v-18v) Input

2 Ground (0v) Ground

3 Regulated output;

5v (4.8v-5.2v)

Output

12-0-12 TRANSFORMER 100µF CAPACITOR

PRINTED CIRCUIT BOARD(PCB) 1N7001 DIODE

IC7812 IC7805

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2.5 STEPS OF WORKING

1. Choose the circuit diagram.

2. Studying each block of circuit and it is work, input and output.

3. Start to construct the circuit and make improvements on it.

2.6 HOW TO CONSTRUCT

1. First of all read the given manual thoroughly and study given in the figure. Also have a look

at PCB and components supplied along with the kit. Each component has to be soldered in its

position on PCB.

2. Identification of resistors is done by color-coding. The color  band on each resistor

corresponds to its exact value.

3. There are different methods in which are defined on capacitors. But usually values are

specified numerically on them. Refer “Basic Electronics” section of the manual for details of

resistor and capacitor identification methods.

4. Can you make out the whole working of circuit and are you able to identify each component

separately as to where each of them has to be placed?

5. If yes, only then proceed further to actually mounting and soldering the parts refer to

“Soldering Instructions” section.

6. Not IC’s but their sockets are to be soldered on PCB. This is to make mounting and

dismounting of IC’s easy while troubleshooting.

7. Start from left most corner of PCB and solder the components one by one on their correct

position of PCB.

8. Before soldering any component see that you have placed it at its right position and with

correct polarity. Give due attention to diodes and electrolytic capacitors, as they are polarity

dependent.

9. Do the soldering of other components in the same way while keeping in mind that

components with long and sensitive leads like capacitors and transistors are soldered last.

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CHAPTER-3 FABRICATION PROCESS

3.1 FABRICATING TECHNIQUES

The fabricating techniques used in this project can be broadly classified into

1. Mechanical fabricating :- consisting of mechanical design.

2. Electrical fabricating :- consisting of electrical design i.e. making PCB, soldering, is making

connection correctly etc.

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3.2 VARIOUS TOOLS AND EQUIPMENTS REQUIRED FOR FABRICATION

WIRE CUTTER SOLDER FLUX PASTE

SOLDERING WIRE DE SOLDERING IRON

DIGITAL MULTI METER SOLDERING IRON

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3.3 SOLDERING

Soldering is a process in which two or more metal items are joined together by melting and

flowing a filler metal into the joint, the filler metal into the joint, the filler metal having a

relative low melting point. soldering is characterized by the melting point of the filler

metal, which is below 4000C (7520F). The filler metal used in the process is called solder.

Soldering is distinguished brazing by use of a lower melting-temperature filler metal; it is

distinguished from welding by the base metals not being melted during the joining process.

In a soldering process, heat is applied to the parts to be joint by capillary action and to bond

to the materials to be joined by wetting action. After the metal cools, the resulting joints are

not as strong as the base metal, but have adequate strength , electrical conductivity and

water tightness for many uses . soldiering is an ancient technique mentioned in Bible

and there is evidence that it was employed up to 5000 years ago in Mesopotamia

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3.4 TIPS WHILE WORKING

Soldiering is something that needs to be practiced. These tips should help you began successful so

you can stop practicing and get down to some serious building.

1. Use heat sinks. Heat sinks are must for the leads of sensitive components such as on

2. Keep the iron tip clean. A clean iron tip means better heat conduction and a better joint. Use

a wet sponge to clean the tip between joints.

3. Double check points. It is good idea to check all the soldiers joints with an Ohm meter after

they are cooled. If the joint measures anymore than a few tenths of an ohm, then it may be a

good idea to re solder it.

4. Use the proper iron. Remember that bigger joints will take longer to heat up with an 30W iron

than with a 150w iron. While 30W is good for printed circuit boards and the like, higher

wattages are great when soldiering to a heavy metal chases.

5. Solder small parts first. Solder resistors , jumper leads, diodes and any other small parts

before you solder larger parts like capacitors and transistors. This makes assembly much

easier.

3.5 PICTURE OF WORKING MODEL

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3.6 PRECAUTIONS

1 . Mount the components at the appropriate places before soldering.

2 . Follow the circuit description and components details, leadsidentification etc. Do not start

soldering before making it confirm that all components are mounted at right place.

3. Do not use a spread solder on board, it may cause short circuit.

4. Do not sit under the fan while soldering.

5. Position the board so that gravity tends to keep the solder where you want it.

6. Do not over heat the components at the board. Excess heat may damage the component or

board.

7. The board should not vibrate while soldering otherwise you have a dry or cold joint.

8 . Do not put the kit under or over voltage source. Be sure about the voltage either dc or

ac while operating the gadget.

3.7 TESTING

This testing step comes after the fabrications process. First of all we have tested the soldering

section of power supply, after that in the this we have checked that we are receiving the output

required or not, i.e. 5V and 12V from the power supply section.

After finding that the power supply section is working as per our requirement we gone through the

whole circuit and check if there are no loosened wires, breaking of tracks etc.

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CHAPTER-4 CONCLUSION

4.1 CONCLUSION

After all work we did on our project we have learned.

1. We always see a DC power supplies in laboratories and a DC charger for example for

mobiles, laptops, cameras and so many thing.

2. It is the first time we learnt about its major stages. We done soldering, used multi meter and

worked with ICs as per our electrical and electronics workshop course.

3. We can convert AC to DC power supply.

4. Step down the voltage by transformer(step down transformer).

5. It is the first time that we deal with transformer in these details .

6. We have studied how voltage regulator works in detail .

7. It is the first time we deal with many IC’s.

4.2 RESULT

1. We have obtained the output a regulated DC power supplies 12 V and 5V source at

output terminal.

2. The power supply converts the (220-230) V AC into 12 V and 5V DC output.

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4.3 APPLICATION

1. Automation

2. Data Processing

3. Electro mobility 

4. Industrial 

5. Lighting

6. Motorcycles, E-Bikes and Small Electric Vehicles 

7. Power Management 

8. Renewable Energy 

9. Smart Grid

10. Motor Control & Drives

4.4 ADVANTAGES

1. 78xx series ICs do not require additional components to provide a constant, regulated source

of power, making them easy to use.

2. Economical and efficient uses of space.

3. 78xx series ICs have built-in protection against a circuit drawing too much power.

4. They have protection against overheating and short-circuits, making them quite robust in most

applications.

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REFERENCES

1. Peter ,Kurscheidt , leistungs elektronik,1977

2. Power electronic books (Mohammad Rasheed)

3. Basic Electronics (J S Katre)

4. Mini Projects books

5. www.wikipedia.com

6. www.circuitstoday.com

7. electronics.howstuffworks.com

8. www.poweresim.com

9. www.technologystudent.com

10. www.engknowledge.com

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