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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), MYLAVARAMPage 1
AUTOMATIC SWITCHING OF STREET LIGHTS BY USING LDR AND RELAY
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.
Dept of ECE, LBRCE(AUTONOMOUS), MYLAVARAMPage 2
AUTOMATIC SWITCHING OF STREET LIGHTS BY USING LDR AND RELAY
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.
Dept of ECE, LBRCE(AUTONOMOUS), MYLAVARAMPage 3
AUTOMATIC SWITCHING OF STREET LIGHTS BY USING LDR AND RELAY
HARD WARE DESCRIPTION
Dept of ECE, LBRCE(AUTONOMOUS), MYLAVARAMPage 4
AUTOMATIC SWITCHING OF STREET LIGHTS BY USING LDR AND RELAY
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
Dept of ECE, LBRCE(AUTONOMOUS), MYLAVARAMPage 5
AUTOMATIC SWITCHING OF STREET LIGHTS BY USING LDR AND RELAY
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.
Dept of ECE, LBRCE(AUTONOMOUS), MYLAVARAMPage 6
AUTOMATIC SWITCHING OF STREET LIGHTS BY USING LDR AND RELAY
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.
Dept of ECE, LBRCE(AUTONOMOUS), MYLAVARAMPage 7
AUTOMATIC SWITCHING OF STREET LIGHTS BY USING LDR AND RELAY
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:
Dept of ECE, LBRCE(AUTONOMOUS), MYLAVARAMPage 8
AUTOMATIC SWITCHING OF STREET LIGHTS BY USING LDR AND 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:
Dept of ECE, LBRCE(AUTONOMOUS), MYLAVARAMPage 9
AUTOMATIC SWITCHING OF STREET LIGHTS BY USING LDR AND RELAY
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
Dept of ECE, LBRCE(AUTONOMOUS), MYLAVARAMPage 10
AUTOMATIC SWITCHING OF STREET LIGHTS BY USING LDR AND RELAY
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.
Dept of ECE, LBRCE(AUTONOMOUS), MYLAVARAMPage 11
AUTOMATIC SWITCHING OF STREET LIGHTS BY USING LDR AND RELAY
APPLICATIONS:
Balcony / stair case / parking Lightings
Street lights
Garden Lights
RESULT:Dept of ECE, LBRCE(AUTONOMOUS), MYLAVARAM
Page 12
AUTOMATIC SWITCHING OF STREET LIGHTS BY USING LDR AND RELAY
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:
Dept of ECE, LBRCE(AUTONOMOUS), MYLAVARAMPage 13
AUTOMATIC SWITCHING OF STREET LIGHTS BY USING LDR AND RELAY
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.
Dept of ECE, LBRCE(AUTONOMOUS), MYLAVARAMPage 14
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