Regulated Power Supply Made by--rajat Aggarwal

MINOR PROJECT WORK REPORT ON REGULATED 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 Aggarwal 0809810040 Poonam Mehta 0809810033 Manisha 0809810023

Ambition Institute of Polytechnic Moriwala (Sirsa)

CONTENTS 

CHAPTER-1 INTRODUCTION

Introduction. o Theoretical background o Aim to design this project o Application o Advantages CHAPTER-2 PROJECT DESCRIPTION o block diagram o block description o circuit diagram o circuit description o component used o working principle and operation CHAPTER-3 FABRICATION PROCESS o fabrication techniques o various tools and equipment o soldering o tips and tricks o precautions CHAPTER-4 TESTING CHAPTER 5 RESULT AND CONCLUSION Reference o

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Chapter:-1 INTRODUCTIO N

INTRODUCTION Regulated 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 rectifierfilter 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.

CERTIFICATE Certify 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 Polytechnic Moriwala (Sirsa)

Chapter:-2 PROJECT DESCRIPTION

BLOCK DESCRIPTION Transformer: - 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 DISCRIPTION Step 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.

Vp Np power out = power in = and Vs Ns Vs × Is = Vp × Ip Vs = secondary (output) Vp = primary (input) voltage voltage Np = number of turns on Ns = number of turns on primary coil secondary coil Ip = primary (input) current Is = secondary (output) current turns ratio =

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 CONSTRUCT 

First 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.

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Identification of resistors is done by color-coding. The color band on each resistor corresponds to its exact value.

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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.

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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?

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If yes, only then proceed further to actually mounting and soldering the parts refer to “Soldering Instructions” section.

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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.

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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 TECHNIQUES The 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

De-soldering iron

Soldering wire

Flux

Wire cutter

Multimeter

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. 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 & TRICKS 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 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. Double check points. It is good idea to check all the soldiers joints

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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.

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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

TESTING The 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.

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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.:-

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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.

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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.