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AUTOMATIC STREET LIGHT CIRCUIT

SUBMITTED BY GUIDED BY

Abhishek (9911005002) Mr.M.K.ParmathmaAjith Kumar(9911005005) Assistant Professor

ECE ,KLU

KALASALINGAM UNIVERSITY

Department of Electronics and Communication Engineering

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OVERVIEW OF MINI PROJECT2

The main purpose of designing this project is to preventloss of current unnecessarily during day time.

During night the bulb will automatically glow .

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COMPONENTS REQUIRED

RELAY

VOLTAGE REGULATOR

FUSE

LIGHT DEPENDENT RESISTOR

RESISTOR

TRANSISTOR

BATTERY

LAMP

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ABSTRACT

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A street light that automatically switches ON when the night falls andturns OFF when the sun rises.

In fact we can use this circuit for implementing any type of automaticnight light.

The circuit uses a LDRto sense the light .

When there is light the resistance of LDR will be low.

So the voltage drop across POT R2 will be high.This keeps thetransistor Q1 ON. The collector of Q1(BC107) is coupled to base ofQ2(SL100).

So Q2 will be OFF and so do the relay. The bulb will remain OFF. When night falls the resistance of LDR increases to make the voltage

across the POT R2 to decrease below 0.6V.

This makes transistor Q1 OFF which in turn makes Q2 ON. The relaywill be energized and the bulb will glow.

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BLOCK DIAGRAM

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CIRCUIT DIAGRAM6

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Relayis an electromagnetic device which is used to isolate two circuitselectrically and connect them magnetically.

They are very useful devices and allow one circuit to switch another onewhile they are completely separate.

They are often used to interface an electronic circuit (working at a lowvoltage) to an electrical circuit which works at very high voltage.

For example, a relay can make a 5V DC battery circuit to switch a 230VAC mains circuit. Thus a small sensor circuit can drive, say, a fan or anelectric bulb.

Arelay switch can be divided into two parts: input and output.

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VOLTAGE REGULATOR

It is a voltage regulator (7805) integrated circuit. It is a member of78xx series of fixed linear voltage regulator ICs. The voltage source in acircuit may have fluctuations and would not give the fixed voltageoutput.

Thevoltage regulator IC maintains the output voltage at a constant

value. The xx in 78xx indicates the fixed output voltage it is designed toprovide. It provides +9V regulated power supply.

Capacitors of suitable values can be connected at input and output pinsdepending upon the respective voltage levels.

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FUSE[1A]

Fuse is an electronics safety device placed in a circuit consisting of areplaceable plug or tube containing wire or metal that will melt andbreak the circuit if the current exceeds a specified amperage.

Blow a fuse: to cause an electrical fuse to melt.

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LIGHT DEPENDENT RESISTOR

An LDR (Light dependent resistor), as its name suggests, offersresistance in response to the ambient light.

The resistance decreases as the intensity of incident light increases,and vice versa.

In the absence of light, LDR exhibits a resistance of the order of mega-ohms which decreases to few hundred ohms in the presence of light.

It can act as a sensor, since a varying voltage drop can be obtained inaccordance with the varying light.

It is made up of cadmium sulphide (CdS).

An LDR has a zigzag cadmium sulphide track. It is a bilateral device,i.e., conducts in both directions in same fashion.

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RESISTOR

Resistor is a passive component used to control current ina circuit.

Its resistance is given by the ratio of voltage appliedacross its terminals to the current passing through it.

Thus a particular value of resistor, for fixed voltage,limits the current through it.

They are omnipresent in electronic circuits.

Resistors can be either fixed or variable.

The low power resistors are comparatively smaller in sizethan high power resistors.

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TRANSISTOR

BC107 is an NPN bi-polar junction transistor. A transistor, stands fortransfer of resistance, is commonly used to amplify current.

A small current at its base controls a larger current at collector &emitter terminals.

BC107 is mainly used for amplification and switching purposes. It hasa maximum current gain of 800.

The transistor terminals require a fixed DC voltage to operate in thedesired region of its characteristic curves. This is known as the biasing.

The voltage divider is the commonly used biasing mode.

For switching applications, transistor is biased so that it remains fullyon if there is a signal at its base.

In the absence of base signal, it gets completely off.

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TRANSISTOR[SL100]

SL100 is a general purpose, medium power NPN transistor. It ismostly used as switch in common emitter configuration.

The transistor terminals require a fixed DC voltage to operate in thedesired region of its characteristic curves. This is known as the biasing.

For switching applications, SL100 is biased in such a way that itremains fully on if there is a signal at its base. In the absence of basesignal, it gets turned off completely.

The emitter leg of SL100 is indicated by a protruding edge in thetransistor case. The base is nearest to the emitter while collector lies atother extreme of the casing.

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BATTERY

It is a collection of one or more electrochemical cells in which storedchemical energy is converted into electrical energy.

One half cell houses theAnode to which the positive ions migrate fromthe Electrolyte and the other houses the Cathode to which thenegative ones drift.

The two cells are may be connected via a semi permeable membranousstructure allowing ions to flow but not the mixing of electrolytes as inthe case of most primary cells or in the same solution as in secondarycells.

The performance of the cell continues to dip gradually as theconcentration of ions in the solutions decrease, marked by an increasein internal resistance eventually leading to the exhaustion of thebattery.

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THE END

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