How to build a dark sensor using transistor and photoresistor

It is yet another dark sensor circuit using a BC547 NPN transistor and a photoresistor. When the light falling on the photoresistor is blocked, the circuit turns on the LED.

Its output is exactly opposite to the output of a light sensor.

It is one of the low cost, simplest and easiest projects for electronics beginners.

You can watch all the steps in the video.