Problem with LED to indicate off switch

Discussion in 'The Projects Forum' started by tee2, Mar 16, 2010.

  1. tee2

    Thread Starter Active Member

    Nov 19, 2004
    46
    3
    I asked a few months ago on how to add a LED to a switch to indicate when the switch is off. Sgtwookie set me up with a plan here.
    http://forum.allaboutcircuits.com/attachment.php?attachmentid=14037&stc=1&d=1259601684

    This is the post.
    http://forum.allaboutcircuits.com/showthread.php?t=30849

    I built it on a breadboard and it work great. I had a red LED for off and a green LED when the the light was on.

    I then built it into my dashboard for my motorcycle. It worked fine while testing it out.

    I just wired into the motorcycle and it doesn't work now. :mad:

    The switch will work to turn the headlight on and off. But the green LED is always on, and the red doesn't come on at all. I tried it with the test setup again and it did work.

    Any idea how I should trouble shoot this? I can post a wiring diagram for the motorcycle if that will help. I think I might be getting some power back feeding and might need a diode.

    Todd
     
  2. flat5

    Active Member

    Nov 13, 2008
    403
    17
    Provide a good picture of what you have done if you can. You most likely made a wiring error.
     
  3. retched

    AAC Fanatic!

    Dec 5, 2009
    5,201
    312
    Resistor too small?
     
  4. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    I'll bet the red LED is shorted.

    Replace the red LED, and increase the resistor from 510 to 680 Ohms.
     
  5. tee2

    Thread Starter Active Member

    Nov 19, 2004
    46
    3
    That was the problem. New LED, and 680Ω rewired on the bike and it worked.:)

    I should have posted this first before wasting all the time I did trying to figuring it out on my own.

    The amount of knowledge on this forum is priceless.

    Thanks to all.

    Now back to my USB problem.:confused:

    Todd
     
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