Shadow sensor Circuit
Shadow sensor Circuit

Shadow sensor Circuit

Shadow sensors are widely used to detect the movement of a person in a confined area. Many circuits published earlier have a serious drawback that only one light dependent resistor (LDR) is used for shadow detection.
Needless to say, this is not a perfect solution!

Component required:

  • OP Amp ic 741
  • Resistors R1 =120k

   R2 = 1k

  • Variable resistor VR1 = 10k
  • LED
  • Transistor Q1 BC547

     Q2 BC547

  • Buzzer
  • LDR sensor
  • 9v battery


In this circuit the combinarion of Transistos are used. this sensor can be simply made without using any IC. the circuit is very simple to test on breadboard and very basic for practice. 



  • It can be used on blind person stick.
  • Dark detection
  • Automatic car headlights