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LED lightcurtain / christmas tree lights

Discussion in 'Electronic Repair' started by N_Cook, Mar 1, 2013.

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  1. N_Cook

    N_Cook Guest

    KAM LED lightcurtain control box dropped and now no function.
    DC rails are right , not yet checked crystal and 555 sub cct function
    This has 4 channel output , 20V drive to an array of coloured LEDs. Assuming
    the NXP micro is defunct, and the owner does not use the DMX or mic input or
    even speed variation , just simple unvarying sequence, would it be possible
    to salvage the curtain and use a christmass tree LED lightstring controller
  2. N_Cook

    N_Cook Guest

    555 working. 16M Crystal osc working, but the only other pin with any
    activity is an unused external timing pin of divided clock f.
    Caps check ok, forcing a reset no change, as sprung pin socket for the NXP
    P89V51 micro added an intermediary 40pin turned pin socket. Any more last
    rites before consigning to the big dumpster?
    I've not checked the SN75176 DMX serial chip yet for perhaps latched o/p

    I suppose using the variable 555 output to clock a 4 stage shift register
    and couple to the existing 4x TIP122 buffers would be sufficient for the
    owner's purposes rather than trying to find a suitable chrismass tree set
  3. N_Cook

    N_Cook Guest

    Pulling the micro and trying a 4013 clocked by the 555 and feedback between
    the 2 flip-flops gives quite a pleasant pseudo-random sequencing to the 4
    strings. Just have to hope it does not have a latch up state - I've
    forgotten how to determine that, clocked through a few hundred cycles
    without hickup.
    For anyone else , in the future, where to put the ouput of the mic amp to
    give a beat sync to the lights?
  4. N_Cook

    N_Cook Guest

    I suppose for sound syncing, or'd with the 555 clock would be ok if the mic
    amp gives L to H transistion on the beat
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