multifunction power supply for embedded system

7/27/2019 multifunction power supply for embedded system

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MULTIFUNCTON POWER SUPPLY

Submitted by: Under the

guidance of:

Prabhat Kumar Patel Prof. S. S. SharmaVijay Laxmi Sahu

Samay Nath Shukla


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CONTENTS

Introduction

Basic components

Component description

Designing consideration Circuit diagram

Working

Advantages and Scope

Conclusion


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INTRODUCTION

There are many system which requires a constant voltage supply for

their working with some additional features to perform reliable operation. This

type of multifunction power supply can be used to provide a constant voltage

which involves special features like:

Power fail detection

Zero cross signal for main power supply

Inbuilt battery back-up

In case of power failure, there is an inbuilt battery which comes into

action.


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Components

Step-down transformer (230/12V)

LM317 IC (adjustable voltage regulator)

LM7805 IC (5V voltage regulator)

74HC14 (hex inverter schmitt trigger)

bridge rectifiers

Zener diode LED

Resistor and Capacitor

Connectors

Fuse

On/off switch


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Components description

1) LM317 ICIt is an adjustable 3 terminal positive voltage regulator over an output voltage

range of 1.2V to 37V.

The output voltage equation for regulator is

Vout

= 1.25Vin

(1+ R2/R

1) + IR

2


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2) LM7805 IC

It is a fixed voltage regulator which gives a constant output voltage

of +5V.


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3) 74HC14

it provides 6 inverting buffer with Schmitt trigger. Basically Schmitt trigger

is an inverting comparator with positive feedback. This converts an irregular shapedwaveform to a square wave or pulse.


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4) Bridge Rectifier

It is used for the conversion of AC supply into DC.

5) Zener diode

It is used for maintaining a constant voltage when it is in saturation

region.

6) Other components

Resistor, capacitor, LED, fuse, step-down transformer etc are also used for the

purpose of different functions along with protection of this power supply.


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Designing Consideration

Bridge Rectifier : BR1= 2.5Amp , BR2= 1Amp

Zener Diode: ZD1= 4.7V , ZD2= 7.5V

Resistors : R1= 200ohm , R2,R3,R5= 1kilo-ohm , R4= 700ohm ,

R6= 500ohm , R7= 10ohm , R8= 200ohm ,

R9,R10,R11,R12= 1kilo-ohm

Capacitors : C1= 100nF , C2= 10nF , C3,C5,C7= 0.33uF ,

C4= 4700uF , C6= 1nF , C8= 220uF

Miscellaneous: S1on/off switchF1- 2.5A fuse

F2- 1A fuse


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CIRCUIT DIAGRAM


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WORKING

The mains power supply of 230V AC is step down to 12V by the step down

transformer. The RC components connected across the supply prevents noise to

enter, which may come from supply side.

The secondary output of the transformer is fed to the two bridges BR1 and BR2

and output of approx. 10.8V is obtained.

10.8V obtained is given as input to IC1 LM317 and IC2 7805. IC2 gives us

constant power supply of +5 volts and the O/P of IC1 can be adjusted using the

potmeter1, to supply power to battery for charging purpose .

This charged battery can be utilized to give power to some components ofembedded system during the power failure.


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Working continued.

Now the question is how we know that power failure hasoccurred?

Transistoris used to solve out this problem but thetransistor should be specifically of switching type .

During the normal state +10volts supplies to the transistor and since the

threshold of zener is 7.5V, for the value of voltage above than this zener is in

on state and the output is 0 volts but when the power failsvoltage at TP2 falls

below 10V and transistor stops conducting and CON5 provides high signal

at pin3.


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ZERO CROSSING DETECTION

The outputs from pins 2, 3 and 4 of connector CON6 provide different

signals with a frequency that is double the frequency of the mains power supply

(100 Hz). These signals are active near zero crossings of the mains power supply

and can be used for several purposes, such as:

1. The control unit can use them to measure the frequency of the mains power

supply.

2. These can be used to synchronise the operation of the control unit with zero

crossings of the mains power supply.

3. he amplitude of signal TP4 is proportional to the secondary voltage of the

transformer. The control unit can measure it and determine the secondary voltageof X1.


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ADVANTAGES

The components used are popular low cost components withother facilities of :

+5V output

battery charger

zero crossing signal

power fail detection

SCOPE

Since the circuit is cost efficient due to use of low cost

components and it is performing multiple functions so it can be utilized inembedded system to perform reliable and stable operation.

.


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CONCLUSION

Since the circuit design and configuration is best for those type ofsystem which requires +5V constant supply and where failure of power

supply should not effect the working which may causes undesirable

effects so we will ultimately improve our control and performance of

embedded system.


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Thank You

multifunction power supply for embedded system

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