Wiring the brake light kit on a GIVI Top Trunk

Discussion in 'Mechanics Garage' started by dmr788351, Apr 19, 2011.

  1. NormK

    NormK New Member

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    For starters a resistor won't change the brightness of the light. Does this light have a tail light and stop light function in it or is it just a stop light, if it is just a stop light then I have no idea how you can make an LED do 2 functions, and then you have the potential to get a back feed. The light needs an earth wire for it to function. How many wires do you have coming from the light?
     
  2. rjgti

    rjgti New Member

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    normk, a resistor will make a diff. use a pot in series to set your brightness
     
  3. NormK

    NormK New Member

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    I can understand the pot making a difference but if you are using the one set of LED's it might work but then you would also need to fit a diode in each wire to prevent feedback, all getting very complicated just to wire up a light in a top box
     
  4. SLOVFR

    SLOVFR Member

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    You are all making this way harder than it is....
     
  5. lorenzo123

    lorenzo123 New Member

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    I'm a total newbie in electrical construction.

    So, I use this simulation applet:
    https://phet.colorado.edu/en/simulation/circuit-construction-kit-ac

    Create a simple circuit with a battery (12v for instance),
    a bulb and an Ammeter just before the bulb.

    Do the same with a resistor on the wire before the Ammeter.
    You will see amperage is lower; and you can check with the voltmeter,
    there is a voltage drop as well.

    So, from what I understand, with a resistor on the wire I could make the Left and right LED strip lights dimmer on running light.

    See that video: the guy is wiring a VESPA LED kit on a givi box:
    https://www.youtube.com/watch?v=Kk0v6nwbkPQ
    go straight to the end of the video where the guy is wiring the Givi harness with the lights of the vespa.

    He is using one single LED strip light.
    The LED strip has only 2 wires: + and -
    And he is using this same LED strip for running light and tail light.
    The LED seems just brighter when he hits the brake.

    I don't know what's in the Givi harness.
    But I suspect there are a relay + resistor in the givi harness.

    About this idea of resistor + harness,
    I got inspired by this post: http://www.advrider.com/forums/showthread.php?t=65468


    I think this could work.
    I'll test that out next week when I get my LED strips.

    My concern now, I still don't understand why
    if I connect tail + brake + test light together,
    the light turns on only when brake is applied.

    You mentioned it could be an earthing issue.
    I did some research. Apparently, on a motorbike (and the same for a car)
    the negative pole of the battery is connected to the frame of the bike.

    That way, you don't need to run a negative wire,
    the whole frame of the bike acts as a negative pole.


    When I wired tail + brake + test light together,
    I wired the negative wire of the test light to the existing
    negative wire used for brake and tail.

    So, it could be that my brake and tail light
    don't have a good earthing. Not good enough to support an extra connection.

    I'll test with using a different spot on the frame to "ground" my test light.
    If it works, that would solve this enigma.

    If not, it could be that there are not enough amps on the wire
    (because when I hit the brake, it works).
    I could test that with my LED strip (which consumes so little amps).

    Lots of testing ahead. But we'll get there :D
     
  6. rjgti

    rjgti New Member

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    a quick ?, do your tail lights and brake light work normally when nothing is added to the wiring?
     
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