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AUTOMATIC SWITCHING OF STREET LIGHTS BY USING LDR AND RELAY

CONTENTS:

ABSTRACT

INTRODUCTION

HARD WARE DESCRIPTION

WORKING

APPLICATIONS

RESULT

CONCLUSION

Dept of ECE, LBRCE(AUTONOMOUS), MYLAVARAM


ABSTRACT

Automatic Street Light Control System is a simple yet powerful concept, which

uses transistor as a switch. By using this system manual works are 100% removed. It

automatically switches ON lights when the sunlight goes below the visible region of our

eyes. This is done by a sensor called Light Dependant Resistor (LDR) which senses the

light actually like our eyes. It automatically switches OFF lights whenever the sunlight

comes, visible to our eyes.



INTRODUCTION

By using this system energy consumption is also reduced because nowadays the manually

operated street lights are not switched off even the sunlight comes and also switched on earlier

before sunset. In this project, no need of manual operation like ON time and OFF time setting.

LDR and RELAY are the main components of the project. The resistance of light dependant

resistor (LDR) varies according to the light falling on it. This LDR is connected as biasing

resistor of the transistor. According to the light falls on the LDR, the transistor is operated in

saturation and cut off region. By makes use of the transistor switching condition operates the

light through relay. This project uses regulated 230V, power supply.



HARD WARE DESCRIPTION



This circuit comprises of 9 types of the components.

1. Resistors: 1k,1k

2. Transistors: SL100, BC107

3. Preset:100k

4. LDR

5. Battery-9V DC

6. Relay: SPDT (may be 10 amps)

7. Fuse: 1A

8. Lamp: any wattage lamp

9. Power Supply: 230V



VARIABLE RESISTOR:(PRESET-100K)

A preset is a three legged electronic component which can be made to offer varying resistance in

a circuit. The resistance is varied by adjusting the rotary control over it. The adjustment can be

done by using a small screw driver or a similar tool. The resistance does not vary linearly but

rather varies in exponential or logarithmic manner. Such variable resistors are commonly used

for adjusting sensitivity along with a sensor.

The variable resistance is obtained across the single terminal at front and one of the two other

terminals. The two legs at back offer fixed resistance which is divided by the front leg. So

whenever only the back terminals are used, a preset acts as a fixed resistor. Presets are specified

by their fixed value resistance.



TRANSISTORS:

A transistor is a semiconductor device used to amplify and switch electronic signals and power. It is composed of a semiconductor material with at least three terminals for connection to an external circuit. A voltage or current applied to one pair of the transistor's terminals changes the current flowing through another pair of terminals. Because the controlled (output) power can be higher than the controlling (input) power, a transistor can amplify a signal used in many common electrical devices.



LIGHT DEPENDENT RESISTOR (LDR):

S= ΔR/ ΔH

Ri Rt = +(Rf- Ri)(1- exp(t/ tou)

Where, ΔR=change in resistance; Ω, and

ΔH=change in irradiation;W/m2,

Rf = dark resistance, Ω;

Ri= final resistance after application of beam, Ω;

Rt= resistance at any time.

RELAY:



Main Features Switching capacity available by 10A in spite of small size design for highdensity P.C.

board mounting technique.

UL,CUL,TUV recognized.

Selection of plastic material for high temperature and better chemical solution

performance.

Sealed types available.

Simple relay magnetic circuit to meet low cost of mass production.

CIRCUIT DIAGRAM:



WORKING OF THE CIRCUIT:

The resistance of light dependant resistor (LDR) varies according to the light falling on it.

This LDR is connected as biasing resistor of the transistor. According to the light falls on the

LDR, the transistor is operated in saturation and cut off region. By makes use of the transistor

switching condition operates the light through relay. This project uses regulated 230V, power



supply. We use an ldr (light dependent resistor). here in this circuit ldr has low resistance in

brightness(only few ohms) and very high resistance in complete darkness(nearly 1M ohm).so

the transistor Q1 becomes on in day times and Q2 becomes off and hence the relay remains in

NC(normally closed) state and the lamp will not glow. at night the transistor Q1 becomes OFF

and Q2 becomes ON and hence the relay goes to NO(normally open) state and the lamp glows

and the sensitivity of the device can be varied by adjusting the potentiometer.



APPLICATIONS:

Balcony / stair case / parking Lightings

Street lights

Garden Lights

RESULT:Dept of ECE, LBRCE(AUTONOMOUS), MYLAVARAM


Hence the output is obtained from the glowing of bulb and the input voltage is given from the ac

supply voltage of 230V.As the light falls on ldr the bulb does not glow and when shadow or light

disappears the bulb glows and hence the automatic switching of light using ldr and relay is done.

CONLUSION:



Major applications of street lighting includes: prevention of accidents and increase in

safety. Studies have shown that darkness results in a large number of crashes and fatalities,

especially those involving pedestrians; pedestrian fatalities are 3 to 6.75 times more likely in the

dark than in daylight. Street lighting has been found to reduce pedestrian crashes by

approximately 50%. Furthermore, lighted intersections and highway interchanges tend to have

fewer crashes than unlighted intersections and interchanges. Towns, cities, and villages use the

unique locations provided by light poles to hang decorative or commemorative banners.

Many communities in the U.S. use light poles as a tool for fund raising via light pole banner

sponsorship programs first designed by a U.S. based light pole banner manufacturer.


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