common ground reversed

Discussion in 'General Electronics Chat' started by Revolution, Jul 28, 2008.

  1. Revolution

    Thread Starter New Member

    Jul 28, 2008
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    hi i am trying to wire a led brake light/tail light to my qaud but the qaud runs a , black=12v, red=ground, white= switched ground. but the led light runs a common ground. 2 positives and 1 negative. i was told i have to open the led light up and do some mods to make it work. does anyone know what im talking about? i dont know anything about this. i thought it be a matter of just hooking it up but i guess not. ill try to attach an diagram that i dont understand of the way i got to make it.
     
  2. Revolution

    Thread Starter New Member

    Jul 28, 2008
    3
    0
    any ideas? or can i use some type of relay?
     
  3. Wendy

    Moderator

    Mar 24, 2008
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    I think we need more information on your LEDs. Evidently they are not separate devices, but their is no way to tell from your info. Are they some kind of kit?

    I also assume they have the resistors built in, but not enough info for that either.

    Need input.
     
  4. Revolution

    Thread Starter New Member

    Jul 28, 2008
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    i dont know much about them but there is a sercet bord inside the light
     
  5. Wendy

    Moderator

    Mar 24, 2008
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    I suspect whoever they is is talking about reversing the LEDs, to connect the other set of wires as common. What you have is common cathode, what you need is common anode. Can you show us what you're talking about (as in a picture)? Was this device, this light, sold as an aftermarket item?

    A relay will not help in this case, the problem is the wires are connected at the wrong points internal, you need to cut them and connect the other side of the LEDs.
     
  6. SgtWookie

    Expert

    Jul 17, 2007
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    1,728
    Wow, a positive ground on a Quad?
    I'm surprised! Are you certain that the battery positive terminal is connected to the frame? This would be a giant leap backwards in technology. Even the British finally abandoned positive earth in the late 1960's. I've converted a few British vehicles to negative earth, including an 1959 MGA Twin Cam OTS and a 1960 Triumph TR3 Bugeye.
    Is your Quad of recent manufacture?

    I'm really having a hard time believing this. Ignore the colors of the wires for a moment. Measure from the positive terminal of the battery to some place on the frame, or to the engine block. If you read 12.6v (or thereabouts) you have a negative earth/ground. If you read near 0v, then you actually do have a positive earth, and I'm shocked.
     
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