Ldr Sensor Case Study

PROJECT TITLE: INTELLIGENT AUTOMATED HOME LIGHTING SYSTEM

SUMMARY:Want to know why your monthly electric bill is "so high"?.Take a closer look at the lights or fans , when a person inside the room leaves the room hastily unnoticing the light switched on.
So, what next? Yes the only way for this is INTELLIGENT AUTOMATED HOME LIGHTING SYSTEM. In this system when a person enters the room the tube lights switch on automatically. The light switches off automatically when it detects no person is inside the room. It's now at the tip of your motion! As onemoves one moves inside the room the bulb switches on and as one leaves the room it switches off.
I have used

 But, when light shines onto the LDR, resistance falls.

BLOCK DIG EXPLAINATION OF EACH LDR WORKING:

SENSOR WORKING:
As properties are already stated
Case1: When no person interrupts the light falling on ldr----:The resistance of ldr is low and hence the base of the transistor doesnot get suffecient voltage to turn on the transistor and hence the collector voltage is almost equal to supply voltage that is 5V in this case.
Case2: When a person interrupts the light falling on ldr-----: The resistance of ldr is high and hence transistor switches on and the collector voltage almost becomes equal to zero voltage.
This different collector voltages are picked up by the microcontroller pins and descides decides whether the person is going into the room or out of the room.
LDR SENSOR IS JUST USED FOR EXPERIMENTAL PURPOSE IN REALITY photo-transistors like IR SENSORS SHOULD BE USED BECAUSE OF GOOD SENSITIVITY.
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