Photocell Circuit

Discussion in 'The Projects Forum' started by nprichards, Dec 20, 2008.

  1. nprichards

    Thread Starter New Member

    Dec 20, 2008
    I’m trying to build a circuit that uses a photocell to turn on and off a small light. The power source is 12v. I was looking at using RadioShack photocells that produce a dark (i.e. less light) resistance of about 10,000 ohms and a bright resistance (i.e. more light) of about 700 ohm resistance.

    How can I use this photocell to turn on a light when the photocell reads dark and turns off the light when the photocell reads bright?

    Please keep in mind I don’t have any background in electronics other than what I have been able to research on the Web.

    Thanks for any help.
  2. garry.owens


    Dec 17, 2008
    check out the 555 timer circuits as there is one there already done
  3. eblc1388

    Senior Member

    Nov 28, 2008
    Get the PDF at this link and check the pages for different circuits.

    Photocells circuits

    If you want to turn ON/OFF lights with AC mains or high wattage lamps, then you will probably need to use a 12V relay.

    Tell us what type of lamp you want to control and which circuit inside the above pdf you are comfortable with and want to try building.