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Thread: Norm's DAC board

  1. #1
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    Default Norm's DAC board

    Steve R (Mixedgas) and Mike (Mecheng3) Very generously donated (2) G124 galvos and Norm's DAC board for my projector to progress me into the world of better lasershows. THANKS GUYS!!!
    My only attempts thus far were a modified "black widow" (rotating mirrors w/ built-in "show") and a basic-stamp controller driving 2 disassembled relays with mirrors glued on. (fairly pathetic, eheh.. wellthen..)

    So,,, All I need now is Norm's DAC schematic (or assy drawing- [which resistor goes where etc]) and I suppose a decent class A/ AB 10-20 watt audio amp chip to drive the galvos. Right?
    (The original driver IC for the G124s is now obsolete and un-findable on Findchips.com)which covers all the major electronic suppliers in the US.
    Any info would be appreciated.
    Thanks,
    Steve

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    Nevermind, I found this pic on ebay, so everything is pretty self evident.
    There's 4 20K resistors (that must be the blue ones) and 2 10K that are the other ones, looks like. And the cap pol (-) stripe is visible too
    I hope that's right..
    Attached Thumbnails Attached Thumbnails fc74_1.jpeg  


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    20 watt audio amp chip to drive the galvos. Right?
    Regarding the G124, you can build a cheap amp with a darlington pair setup in a push-pull emitter follower. Don't forget to use 2 diodes each to bias the transistors since they are darlington, and drive that with a simple 741 opamp. Most of those parts may still be available at radshack. This is not a very fast scanner, though it is nice for beam effects. To get the most speed out of them, you should look around for Accelerator Amps for the G-124. Yet another Bill Benner design!

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    Thanks Dave, I'll look around for that. I prefer a single IC design for simplicity and symmetry though, and I'm getting lazy in my old age
    Maybe something like this:
    http://www.national.com/ds/LM/LM1876.pdf
    Last edited by steve-o; 09-05-2007 at 08:59.

  5. #5
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    mixedgas is offline Creaky Old Award Winning Bastard Technologist
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    Norm will support you, give me a email that I can send a attachment to and I'll send you the pdf file with schematics for norm's dac, and I'll zip file you the software.

    norms email is Legato [legato*@*videotron.ca]

    remove the two * I put in to block spam

    tell him steve says hello.

    right now I'm using LM3886TF, just like cambridge. If you give it split supplies it acts like a big opamp. 6$ each, needs a couple small caps and a turn on resistor, and then it will drop into that circuit I sent you , or you can do this one with darlingtons:

    http://www.gs-scanners.com/pdfs/manuals/A102_AX200.pdf

    Steve

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    Thanks Steve! PM sent
    Last edited by steve-o; 09-05-2007 at 09:39.

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    Thanks Steve for all the info. The LM3886 looks good for the app. I take it that current for these galvos should be limited to +1A?
    The silkscreen screwups were nice to know on Norm's DAC +/-15V reversed and the cap in backwards would have definitely added to the challenge of the project..
    Thanks Again,
    Steve

    <edit> according to this part of the schematic both the negatives of both C1,C2 are at ground, but that doesnt ohm out on the board according to the instructions (page 4 )
    Attached Thumbnails Attached Thumbnails regulator.JPG  

    Attached Files Attached Files
    Last edited by steve-o; 09-05-2007 at 11:08.

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    I believe that the pic in post #2 is correct, not the markings on page 4 of the instrucctiones.

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    Mmmmmm Greek!
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    allthat... aka: aaron@pangolin

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    instrucctiones
    Spanish, i think

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