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Christmas Light Faders?

Discussion in 'Electronic Repair' started by Steve Reinis, Nov 11, 2003.

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  1. Steve Reinis

    Steve Reinis Guest

    Any way to build a moderately priced light fader for Christmas lights using
    a straightforward circuits and components? I've been finding $400+ devices
    meant for industrial signs, etc that handle 20+ amps per circuit, but I only
    need a few amps switched/faded so I can have some trees in my yard fade
    between blue and white using C7 and C9 christmas lights.

    For years I've been gathering dysfunctional strings of mini "chaser" lights,
    lopping off the lights and wiring on receptacles so I can plug in individual
    strings of 100 count mini lights, but this year I want to use C7/C9 strings
    and they pull too much current for these 'lightweight' devices to switch
    without burning up.

    Any sources of schematics?
  2. How about beefing up the 'lightweight' controllers you have? They
    probably use little 1-amp TO-92 cased triacs to drive the strings
    of mini lights. Just replace the little triacs with 4 or 8 amp
    TO-220 cased devices, mounted off-board (may need a heat sink on
    each) and wired to the controller where the existing triacs came
    from. You may also have to add wire jumpers to the board to
    supplement any traces that carry the full load current.

    Mouser Electronics has a selection of Triacs
    & heat sinks. (No minimum order and reasonable shipping charges.)
    They have "Logic Triacs" & "Gated Triacs" listed. The only difference
    I can tell is in the gate current - the Logics are 3-5 mA, and the
    Gated are 10-25 mA. You would need to get data on the existing
    triacs in your controller to determine what type to get, but since
    they are probably driven from a CMOS microcontroller, the "logic"
    triacs with their lower gate drive requirements would be my choice
    if I couldn't locate data on the existing ones.

  3. Steve Reinis

    Steve Reinis Guest


    Thanks for giving me a good idea to work with. I tried using the controller
    to drive plain ole relays to switch the heavy loads, and that worked great
    for simple flashing on and off patterns, but I had a brainfart and then
    realized that it won't work for actual fading.

    I've got a few of these controllers - I think I'll open one up and see if
    there is enough room to maneuver with my lousy soldering skills.

    -Steve (Never thought of an external, beefier triac.)
  4. James Sweet

    James Sweet Guest

    The other option, using the controller to drive solid state relays may work
    too, but the larger triac idea is likely better. I suggest mounting the
    triacs separately on a piece of perfboard with heatsinks, the gate wire can
    be fairly small, but use beefier wires for the other leads.
  5. Creamed_emu

    Creamed_emu Guest

    Go with PWM - Assuming your using LED's, or even standard lights will work.
    go grab a cheap PIC and get someone to program it for u, have it drive
    something like a 3055 mosfet. Or u could use the 'lightweight' device to
    drive a power transistor?
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