13-02-2013, 04:36 PM
AUTOMATIC STREET LIGHT CONTROL USING LDR
AUTOMATIC STREET.ppt (Size: 5.32 MB / Downloads: 2,411)
ABSTRACT
This project aims at designing and executing the advanced development in embedded systems for energy saving of street lights with light depending resistor.
The present system is like, the street lights will be switched on in the evening before the sun sets and they are switched off the next day morning after there is sufficient light on the roads.
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 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.
LIGHT DEPENDENT RESISTOR AND ITS CIRCUIT SYMBOL
A Light Dependent Resistor (LDR) is special type of resistor that reacts to changes in light level.
The resistance of the LDR changes as different amounts of light fall on the top 'window' of the device. This allows electronic circuits to measure changes in light level.
When the light level is low the resistance of the LDR is high. This prevents current from flowing to the base of the transistors. Consequently the LED does not light.
WORKING PROCEDURE
LDR offers Very high Resistance in darkness. In this case the voltage drop across the LDR is more than 0.7V.
LDR offers Very low Resistance in brightness. In this case the voltage drop across the LDR is less than 0.7V.
This voltage is more sufficient to drive the transistor into saturation region
In saturation region, IC (Collector current) is very high. Because of this IC , The relay gets energized, and switches ON the lamp.