Light Sensor ( Street Light Control )

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PHOTO DIODE-CIRCUIT:

The photo diode circuit is commonly used. When ligt strikes on diode then this circuit gives output.
Hense it sense the light and can be used in street lights to make them “ON” at a specific intensity of light. The sensitivty of diode  is different  for different diode.

If you want it to make it more sensitive or if you want to control any device on your desire intensity of light please use the concept of  “Temperature Sensor Circuit” 
(Replace the thermister with Photo diode in that circuit.)

Circuit diagram 1:

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Circuit diagram 2:

Component:

Diagram 1

Photo Diode

LED

Transistor 2N3904

R 100 Ω

R 1KΩ

9V Battery

Diagram 2

Operation:

When light strikes on Photo Diode the current flow in photo diode and it conducts transistor base. The current flow in transistor is due conduction in base of transistor. As a result the LED glows out. The 1kΩ resistor is used to quickly turn off the LED.

Application:

This circuit is used in street lights.

This is also used in automatic house lights.

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