28-06-2012, 12:16 PM
STREET LIGHT CONTROL USING LDR
STREET LIGHT CONTROL USING LDR.doc (Size: 145.5 KB / Downloads: 164)
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.
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 micro controller 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 controller operates the light through relay.
This project uses regulated 12V, 750mA power supply. 7812 & 7805 three
terminal voltage regulators are used for voltage regulation. Bridge type full
wave rectifier is used to rectify the ac out put of secondary of 230/18V step
down transformer.
Advantages:
Highly sensitive
Works according to the light intensity
Fit and Forget system
Low cost and reliable circuit
Complete elimination of manpower
Can handle heavy loads up to 7A
System can be switched into manual mode whenever required
Applications:
Balcony / stair case / parking Lightings
Street lights
Garden Lights