Light Barrier Detector


Posted on Jan 8, 2013

This simple circuit using a single transistor turns ON the relay when light falls on the LDR. The potentiometer is adjusted for the required sensitivity. The power supply is 6V. Be careful about the impedance of the relay. Its impedance should not be less that 60ohm. Its working can be explained as follows: With the light falling on the LDR,its resistance is low and the transistor is saturated and turns the relay ON.


Light Barrier Detector
Click here to download the full size of the above Circuit.

When light is obstructed, the LDRs resistance becomes very high. The potentiometer shorts the transistors base to ground and it is cut off. Hence the relay is OFF.




Leave Comment

characters left:

Related Circuits

  • New Circuits

    .

     


    Popular Circuits

    Digital Compass for PC
    Three-Decade 15Hz To 15Khz Wien-Bridge Oscillator
    ME218A: Soccer Pinball scoreboard
    50MHz frequency counter V-meter & SWR/PWR indicator
    infrared toggle switch for home
    Creating an HID Ballast with Constant Lamp Power Control
    Hartley Oscillator Calculator
    Smart power grid demands innovative design
    Long-Interval Pulse Generator
    automated angklung instrument
    Wireless Transmitter
    RF Module Interfacing Circuit Example
    555 monostable trigger timing circuit
    Anti-theft car audio system circuit diagram
    Time relay three-start circuit
    Vehicle lights at night rendezvous controlled circuit



    Top