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Caddilac Deville LED brake/tail lights, how did they do it?

Discussion in 'Electronic Basics' started by JazzMan, Feb 2, 2006.

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  1. JazzMan

    JazzMan Guest

    I was looking at the above this evening, all of the LEDs
    were of equal brightness and the tail light portion did
    not dim when the brake/turn portion flashed. There looked
    to be probably more than a hundred LEDs per side, how do
    they control and maintain brightness? Is each LED individually
    trimmed and controlled current-wise?

    The lights are a bit too expensive to just go buy one to
    disassemble, and I doubt GM would email me the schematic
    and design particulars, so I thought I'd pose the question
    here where all the smart people seem to hang out. :)

    Please reply to jsavage"at"
    Curse those darned bulk e-mailers!
    "Rats and roaches live by competition under the laws of
    supply and demand. It is the privilege of human beings to
    live under the laws of justice and mercy." - Wendell Berry
  2. Guest

    The Cadillacs I've seen around LA sure don't have uniform brightness on
    the LEDs. That instant turn on/off is creepy to look at IMHO. Couldn't
    they add some capacitors to sloppy up the on/off time?

    The only automotive LED assembly I saw was the center brake light on a
    VW Jetta. It had 3 or 4 strings of LEDs (12 total LEDs) with a resistor
    for each string and 1 series 1N400x for reverse polarity protection. It
    ran a total of 280 mA and was blindingly bright on the bench. The
    series diode had failed but still read a normal diode drop with a Fluke
    8060 though the forward voltage drop was several volts under load.

  3. Probably just multiple constant current regulators driving a series
    string of LEDs. Doubt it would be any fancier than that.
    They might pay a bit more to get the primo LEDs that are more tightly
    matched in brightness.

    Dave :)
  4. Jasen Betts

    Jasen Betts Guest

    There's a thing called Kirchoff's law that says that devices
    connected in series will all experience the same current.
    they could be powering all those LEDs in series using a voltage
    booster or they could be doing it in series groups of 4 from 12V

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