1. AUTOMATIC STREET LIGHT CONTROL USING LDR

2. TABLE OF CONTENTS Sr. No. Contents Ch.1 Introduction Ch.2
Circuit diagram
Ch.3
Components
Used
Ch.4
Layout
Ch.5
Working
Ch.6
Advantages
Ch.7
Applications

3. INTRODUCTION
Automatic Street Light Control System is a simple yet powerful concept, which uses transistor as a switch. By using this system manual works are removed.
By using this system energy consumption is also reduced. the manual operation of the lighting system is completely eliminated.
By using the LDR we can operate the lights, i.e. when the light is available then it will be in the OFF state and when it is dark then the light will be in ON state, it means LDR is inversely proportional to light

4. CIRCUIT DIAGRAM

5. LAYOUT

6. COMPONENTS USED COMPONENETS QUANTITY TYPE 1. LDR 1 2. Transistor 2
BC107,SL100
3. Resistor
R1=1k,R2=1k
4. Relay
SPDT
5. Preset
100k

7. WORKING
The circuit diagram present here is that of a street light that automatically switches ON when the night falls and turns OFF when the sun rises.
The circuit uses a LIGHT DEPENDENT RESISTOR (LDR)to 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 the transistor Q1 ON. The collector of Q1(BC107) is coupled to base of Q2(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 relay will be energized and the bulb will glow.

8. ADVANTAGES
By using this Automatic system for street light controlling, we can reduce energy consumption because the manually operated street lights are not switched off properly even the sunlight comes and also not switched on earlier before sunset. 
In sunny and rainy days, ON  and OFF time differ noticeably which is one of the major disadvantage of using timer circuits or manual operation for switching the street light system.

9. APPLICATIONS
Can be used in homes as a night lamp by using bulb of small wattage.
As the name suggests this can be used in street lights where it is difficult to reach like mountaineous regions.