Bidirectional led

Discussion in 'The Projects Forum' started by DancinNancy, Oct 14, 2008.

  1. DancinNancy

    Thread Starter Member

    Oct 1, 2008
    Trying to wire up several leds to be used to emit light as well as be a sensor. I know very little on the subject except that when you reverse bias the led you can use it as a sensor. Any pointers or websites where i could learn about this?
  2. guitarguy12387

    Active Member

    Apr 10, 2008
    You won't get the led to light unless you have a forward bias at some point... can you give any more info on what you're trying to do?
  3. DancinNancy

    Thread Starter Member

    Oct 1, 2008
    I'm trying to use it for a senior project in college. It will be used to show different patterns also used to read which leds are being pressed. I found a video online that showed LED's being used as sensors while they were all lit and didn't know how to do it
  4. Externet

    AAC Fanatic!

    Nov 29, 2005
    Perhaps by turning the leds on and off repeatedly and fast enough to make them appear as constantly on; while sampling the voltage they generate during the off intervals.
    Green leds are better for photodetection.
  5. beenthere

    Retired Moderator

    Apr 20, 2004
    An LED that is biased almost into conduction might make a good light detector. The closer the wavelength to the one emitted should increase sensitivity. The effect would be like a photodiode. You should see some current with light present, and none or much less in the dark.