Introduction: Dark Sensor ( Light Sensor / Automatic Street Light )

Here is my new simple Electronics project about  Automatic Street Light Control System or Dark Sensor.

it is a simple and powerful concept , which uses transistor ( BC 547 NPN) as a switch to switch ON and OFF the street light system automatically .
It automatically switches ON lights when the sunlight goes below the visible region of our eyes. ( e.g in evening after Sunset ).

it automatically switches OFF lights when Sunlight fall on it ( e.g in morning ) , by using a sensor called LDR (Light Dependent Resistor) which senses the light just like our eyes.

Needs no manual operation for switching ON and OFF...

Step 1: Things You Need...


* 1    BC547 transistor
* 1   220 k resistor
* 1   330 ohms resistor
* 1   LED (any colour )
* 1   9v battery
* 1   battery clip
* 1   LDR ( light dependent resistor  )

Step 2: AND...

* Connecting wires
* soldering rod and wire
* wire stripper
* Cutter

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Step 3: Circuit Diagram

solder the transistor on the board and solder one wire of the LDR to the emitter and other to the base  , solder the negative wire of the LED to the base of the transistor with a 330 ohms resistor and also solder 220k resistor with the one side of the 330 ohmsresistor .

Step 4: Finsih... Uuuhuuuu... :p

The simple circuit is ready for testing now . Connect 9v battery terminals to the circuit as show in fig and see the output . As you block light falling on Light dependent resistor (LDR), the LED glows .

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