Improved Infrared Detector Circuit

This improved infrared detector is specifically intended for use with commercial IR remote control handsets. This little circuit is useful for quick go/no-go testing of just about any remote control transmitting Infrared (IR) light signal.

The key component of the IR detector is a sensitive photo transistor 2N5777. All infrared remote controls transmit pulse bursts. The photo transistor detects the modulated IR signal from the remote control handset under test and its output is processed by next BC557 and fed to the final LED driver transistor BC557.

As a result the red LED in the circuit starts blinking in tune with the received signal. Please note that the LED lights up constantly when day light or other source of continuos IR light is detected.

Infrared Detector Circuit Diagram

infrared detector circuit diagram

The infrared detector circuit may be powered by just about any standard 9V compact battery or a wall adaptor capable of supplying 9VDC at about 100mA.The only setting up required is to adjust the 100K variable resistor.The construction drawing shows how the circuit may be cased in a small ABS case.

Block Diagram of the IR detector

ir detector block diagram


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  • breakthedawn

    Circuit is not well designed. The 100kOhm trim potentiometer can be adjusted to 0 Ohms (fully adjusted to one side) which can cause damage to the transistor.

  • Student

    Can any body tell me the working principle of photo transistor.

    • pkdatta

      to student
      why dont you google and you would have very basic to very elaborate explanation with photo/line sketch
      about working’s of a photo transistor/ photo detector/photo resister

  • Dilip Ganatra

    Can I use your circuit to detect red hot metal ? I mean only the receiver part.

    • T.K.Hareendran

      You can try my new circuit “Simple Flame Monitor”,ofcourse with some minor modifications.

  • D.Mohankumar

    Photo diode is not suitable for this circuit.2N 5777 can be substituted by L14F1 photo transistor.Circuit will work.Base pin of the photo transistor should be left unconnected

    • kartik

      but sir from where i will get the photo transistor 2n5777 or l14f1 it is not found in my city jabalpur (,,mp ,,India)

  • Lesitha

    Let me know an equivalent for light transistor 5777.May I use a photo diode instead?