Is there a way to control photosensor on security camera?

Discussion in 'General Electronics Chat' started by TSmith, Jan 15, 2013.

  1. TSmith

    Thread Starter Member

    Sep 21, 2010
    57
    2
    I have a few exterior security cameras that I'd like to modify so that they stay in "day" mode unless it is very dark outside. Right now one is permanently stuck on day mode and has good color image at night with the ambient lighting. However, if the light is turned off, it is useless. But with the exterior lights on, the color image at night is better than the B&W image from the cameras that are not broken.

    So what I want to do is modify the cameras so that they stay in Day mode unless it is very dark outside as in the lights being turned off. Now they go into B&W night mode when it is barely dusk outside. Unless it is very dark, I want them to think it is daytime.

    These cameras have what I suspect are basic CdS photocells. I know very little about electronics so bear with me. By what I've read they vary from about 10K ohm in daylight to about 200K ohm in darkness. At first I thought maybe I could put a resistor across the terminals of the sensor but I don't think that would work as I would only be able to increase the resistance making them think it is dark sooner. I think I need to decrease the resistance to achieve my goal. Is there any simple way to do that short of replacing the photosensor with one of a different value?
     
  2. Brownout

    Well-Known Member

    Jan 10, 2012
    2,375
    998
    Give that a try. Using a parallel resistor will decrese overall resistance. If that doesn't work, then you'll need to modify the whole circuit. See this: http://forum.allaboutcircuits.com/showthread.php?t=79653
     
  3. TSmith

    Thread Starter Member

    Sep 21, 2010
    57
    2
    Perfect link, thank you. Will give it a try.
     
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