MINOR PROJECT WORKREPORT

ONREGULATED POWER SUPPLY

Submitted to State Board of Technical Education

For the partial fulfillment of the requirement for the award

Of diploma of Electronics and Communication Engineering

for the

SESSION: 2008 TO 2011

Submitted by: - Submitted to:-

Rajat Aggarwal Mr. Chanan Pawar

0809810040 Sr. Lecturer

Electronics & Comm. Poonam Mehta Engineering

0809810033

Manisha

0809810023

ACKNOWLEDGEMENT

We are deeply indebted to “ Mr. Chanan Pawar Sr. Lecturer in Department of Electronics & Communication Engg. at Ambition Institute Of Polytechnic , Moriwala (Sirsa)”. For his inspiring and encouraging guidance without which this project work could not have been completed inspite 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 through out the project work.Cordial and earnest thanks to staff of Ambition Institute of Polytechnic, Moriwala (Sirsa) 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.

Rajat Aggarwal0809810040

Poonam Mehta0809810033

Manisha0809810023

Ambition Institute of PolytechnicMoriwala (Sirsa)

CONTENTS CHAPTER-1 INTRODUCTION

o Introduction.

o Theoretical background

o Aim to design this project

o Application

o Advantages

CHAPTER-2 PROJECT DESCRIPTIONo block diagram

o block description

o circuit diagram

o circuit description

o component used

o working principle and operation

CHAPTER-3 FABRICATION PROCESSo fabrication techniques

o various tools and equipment

o soldering

o tips and tricks

o precautions

CHAPTER-4 TESTING CHAPTER 5 RESULT AND CONCLUSION Reference

Chapter:-1

INTRODUCTION

INTRODUCTIONRegulated power supply

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 and control 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 circuit 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.

CERTIFICATECertify that the project entitled “variable regulated power

supply” submitted by Rajat Aggarwal 0809810040, Poonam

Mehta 0809810033 and Manisha 0809810023 in partial

fulfillment of the requirement for the award of “Diploma in

Electronics & Communication Engg. by the state board of

Technical Education Punjab Panchkula” is a record student

own project work carried out under my supervision.

Er. Chanan Singh Pawar

Electronics & Comm. Engg.

Ambition Institute of Poly.

Moriwala (Sirsa)

Ambition Institute of PolytechnicMoriwala (Sirsa)

Chapter:-2

PROJECT

DESCRIPTION

BLOCK DESCRIPTIONTransformer: - The low voltage AC output is suitable for lamps,

heaters and special AC motors. It is not suitable for electronic circuits

unless they include a rectifier and a smoothing capacitor.

Transformer + Rectifier: - The varying DC output is suitable for

lamps, heaters and standard motors. It is not suitable for electronic

circuits unless they include a smoothing capacitor.

Transformer + Rectifier + Smoothing: - The smooth DC output

has a small ripple. It is suitable for most electronic circuits.

Transformer + Rectifier + Smoothing + Regulator: - The

regulated DC output is very smooth with no ripple. It is suitable for all

electronic circuits.

CIRCUIT DISCRIPTIONStep Down Transformer :- Transformers convert AC electricity

from one voltage to another with little loss of power.

Transformers work only with AC and this is one of the reasons

why mains electricity is AC.

Step-up transformers increase voltage, step-down transformers

reduce voltage. Most power supplies use a step-down

transformer to reduce the dangerously high mains voltage

(230v) to safer low voltage.

Transformers and their symbol

The input coil is called the primary and the output coil is called

the secondary. There is no electrical connection between the

two coils, instead they are linked by an alternating magnetic

field

created in the soft-iron core of the transformer. The two lines

in the middle of the circuit symbol represent the core.

Transformers waste very little power so the power out is

(almost) equal to the power in. Note that as voltage is stepped

down current is stepped up.

The ratio of the number of turns on each coil, called the turn’s

ratio, determines the ratio of the voltages. A step-down

transformer has a large number of turns on its primary (input)

coil

which is connected to the high voltage mains supply, and a

small number of turns on its secondary (output) coil to give a

low output voltage.

  turns ratio = Vp

 = Np

   and   power out = power in   

Vs Ns Vs × Is = Vp × Ip

Vp = primary (input) voltage

Np = number of turns on

primary coil

Ip  = primary (input) current

  Vs = secondary (output)

voltage

Ns = number of turns on

secondary coil

Is  = secondary (output) current

Rectifier: - There are several ways of connecting diodes to

make a rectifier to convert AC to DC. The bridge   rectifier is

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.

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

& D3 forward biases & diode D2 & D4 reverse biases and we

get positive cycle.

During –ve half wave cycle, the A becomes –ve and B

becomes +ve. Due to this D2 & D4 come under forward bias

and diode D1

& D3 are reverse bias. Therefore, diodes D2 & D4 conduct

while diode D1 & D3 don’t. the shape of wave is shown in

figure.

Bridge Rectifier

Output: full-wave varying DC

Hence, we can say that the bridge wave rectifier give the

pulsating DC voltage which are not suitable for electronics

circuit.

Smoothing (Filter): - Smoothing is performed by a 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.

Note: - Note that smoothing significantly increases the average

DC voltage to almost the peak value (1.4 × RMS value).

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 larger capacitor will give less

ripple. The capacitor value must be doubled when smoothing

half-wave DC.

So, in this we concluded that the pulsating DC voltage is

applied to the smoothing capacitor. This smoothing capacitor

reduces the pulsations in the rectifier DC output voltage.

The smooth DC output has a small ripple. It is suitable for

most electronics circuits.

capacitor

Adjustable regulator: - Voltage regulator ICs are available

with fixed or variable output voltages. The regulated DC

output is very smooth with no ripple. It is suitable for all

electronic circuits.

When voltage regulating device is added to this ordinary

power supply, it turns in to a regulated power supply.

Voltage regulator

In this we used adjustable voltage regulator. The adjustable

voltage regulator can be adjusted to provide any DC output

voltage that is within its two specified limits. The most popular

three terminal IC adjustable voltage regulator is the KA317. It

has an input terminal, output terminal and an adjustment

terminal.

An external voltage divider is used to change the DC output

voltage of the regulator. By changing external voltage divider

means variable resistance, a wide range of output voltage can

be obtained. Most regulators include some automatic

protection from excessive current (overload protection) and

overheating

(Thermal protection).

HOW TO CONSTRUCTFirst of all read the given manual thoroughly and study the

circuit 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.

Identification of resistors is done by color-coding. The color

band on each resistor corresponds to its exact value.

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.

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?

If yes, only then proceed further to actually mounting and

soldering the parts refer to “Soldering Instructions” section.

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.

Start from left most corner of PCB and solder the components

one by one on their correct position of PCB.

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.

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.

CHAPTER:-3

FABRICATING

PROCESS

FABRICATING

TECHNIQUESThe fabricating techniques used in this project can be broadly

classified into:

o Mechanical Fabricating, consisting of mechanical design.

o Electrical Fabricating, consisting of electrical design i.e.

making PCB, soldering, is making connection correctly etc.

VARIOUS TOOLS & EQUIPMENTS

NEEDED FOR FEBRICATION

Soldering wire De-soldering iron

Flux

Wire cutter Multimeter

SOLDERINGSoldering 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.

Soft soldering is characterized by the melting point of the filler metal,

which is below 4000 C (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

upto 5000 years ago in Mesopotamia.

TIPS & TRICKSSoldiering 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 heatsinks. Heatsinks 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 any

more than a few tenths of an ohm, then it may be a good idea to

resolder 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.

PRECAUTIONS

1. Mount the components at the appropriate places before

soldering; Follow the circuit description and components details,

leads identification etc. Do not start soldering before making it

confirm that all components are mounted at right place.

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

3. Do not sit under the fan while soldering.

4. Position the board so that gravity tends to keep the solder where

you want it.

5. Do not over heat the components at the board. Excess heat may

damage the component or board.

6. The board should not vibrate while soldering otherwise you

have a dry or cold joint.

7. Do not put the kit under or over voltage source. Be sure about

the voltage either dc or ac while operating the gadget.

CHAPTER:-4

TESTING

BLOCK DIAGRAM

CIRCUIT DIAGRAM

Fig: - Regulated Power Supply

TESTINGThe testing step comes after the fabrications processes or we can say this

is the final step of our project. In this process we have done testing of our

project by hardware section.

Hardware section

In the hardware section, first of all we have tested the soldiering section of

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

output required or not, i.e. 5V from the power supply section. After

founding that the power supply section is working as per our requirement

we moved to another section for testing. We tested the connection of

capacitors, resistors, transistors. Finally we had gone through the whole

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

tools required for testing the hardware section was:

Soldering rod, flux and lead

Twisser and stipper

Digital multimeter

Desoldering gun

COMPONENT USED

Step down transformer :- The step down transformer can convert

high voltageAC into low voltage AC. By step down transformer

we can take different values of voltage at output. In this project

we can use 12-0-12 step down transformer. In this transformer

we give high AC voltage by two red wires & take low AC voltage

output by eight wires. At eight wires we can obtain various

outputs.

Bridge wave rectifier : - In the full wave rectifier we can use four

diodes. These rectifiers can convert AC voltage into DC voltage.

In this circuit we use four diodes of value 4007 to make a full

wave rectifier. These four diodes give full wave at output. One

diode takes 0.7v to operate.We can use two diode to take full

wave at output but for this we require a center tap transformer,

this is not generally use because these are chipper. At output we

obtain pulsating DC volt.:-

Capacitor :- Capacitor are use for either to store the charge or

for smoothing purpose. But in this circuit we use capacitor for

smoothing purpose. It give the DC voltage but this DC voltage

contain some ripple.

Adjustable regulator: - In this circuit we use adjustable regulator

KA317. This regulator is use to take DC voltage. At this DC

voltage no ripples are present.

The terminal 1st is input terminal through which we take the DC

voltage which is provided by the capacitor. 2nd terminal is earthing

terminal & 3rd terminal is output terminal through which we take

the output.