using led as a light sensor


Posted on Feb 6, 2014

This circuit shows how to use an ordinary LED as a light sensor. It makes use of the photovoltaic voltage developed across the LED when it is exposed to light. LEDs are cheaper than photodiodes and come with a built-in filter, which is useful when the application involves colour discrimination. The photo-voltage of a red LED (its bandgap voltage) is typically about 2V. The source impedance of this voltage is about 800M? in daylight, rising to infinity in darkness. A TL071 JFET input op amp is used to amplify and buffer this extremely high impedance signal..


using led as a light sensor
Click here to download the full size of the above Circuit.




Leave Comment

characters left:

Related Circuits

  • New Circuits

    .

     


    Popular Circuits

    Loudspeaker as a Microphone
    Complete Ar/Kr Ion Laser Power Supply Schematics
    Add a sensor to a board and measure something with it
    police lights
    Mains clearance in a TRIAC driver
    communication with AVR microcontroller



    Top