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Thread: Emergency signal generator

  1. #1
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    Default Emergency signal generator

    The attached circuit generates a AC coupled quad square into a high impedance load. It costs roughly 6$ to build including the battery. Output is 30 hz +/- 5 hz due to capacitor tolerances. Very useful as a sanity check in emergencies. I will build a more professional level shifted, DC coupled, ILDA compatable version if there is demand. I retain the copyright to this circuit. PhotonLexiconers may build one each for personal use.

    If you use a 74LS76 or 7476 TTL you get a 1.8 volt peak to peak output. If you use a 74HC76 you get a 4.8 volt peak to peak output.

    Drawn in wonderful BMP "Walleye Vision" (Fisheye Vision for non North Americans) so people who have few electronics skills can understand it.

    You get 4 dots on the wall in a square, The faster your galvos, the less visible connection between the dots.

    This circuit is useful for when you are using sound card dacs and you dont know if it is the dac or the galvos that are messed up.

    There are two Y outputs, one rotates clockwise, one counterclockwise, not that you can tell at 30 hz. use a mylar or ceramic cap for c3, c4, c5, unless you are sure your capcitor is non-polar. A wide range of values will work. If you do not install the capcitors you get a nasty DC offset.

    For high to medium impedance inputs, ie most galvo amps.

    I'm NOT responsible if you blow up your galvos. If this circuit is correctly built and powered off a battery that is nearly impossible to do.

    I realize this circuit is a joke to a engineering professionals, but in a pinch has worked well for emergency field troubleshooting. I literally built it in 20 minutes in a friends shop, when a scope was not available to test a pair of Cambridges.

    For purists, this is a walking ring counter using a dual JK Flip-Flop with AC coupled outputs. F out is a quadrature square wave at 1/4 the input frequency.


    Steve
    Attached Thumbnails Attached Thumbnails 4QUADTUNE.bmp  

    Last edited by mixedgas; 04-22-2009 at 09:16.

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    Default

    thats cool, would be nice to have tool with a few different patterns like a circle, vertical line, horizontal line, just some simple ones..
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    mixedgas's Avatar
    mixedgas is offline Creaky Old Award Winning Bastard Technologist
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    Quote Originally Posted by keeperx View Post
    thats cool, would be nice to have tool with a few different patterns like a circle, vertical line, horizontal line, just some simple ones..
    thank you,
    That costs money. I doubt anybody is gonna pay me 60-100$ for a basic one when they can get the whole sound card dac for what, less then 100? If I go any further it will be a 1 frame, frame dumper, with the ILDA pattern, and the Laser Media pattern on board. That is worth something.

    Steve

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    i see your point.. an ilda/LM test would be nice tho..
    especially for Bill to carry in his pocket as he visits projectors.
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    Cool

    Bill already has a product that will fit in your pocket and can display the ILDA test pattern (and a bunch of others). It's called the FlashBack 3! (Load the flash card with the test patterns and plug in the power and ILDA cables and away you go.)

    Adam

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    i will have one soon as well

    its called the RIYA MultiBus
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  7. #7
    mixedgas's Avatar
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    Thats nice, but you still need a second source for testing some times in the field. what is wrong with 6$ instead of 450-560.

    Besides, the first part of the cambridge tuning reads, apply a small signal 30 hz squarewave.....


    Steve

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    Smile

    No, I agree completely Steve. This device is very cool. I was just pointing out that it would be impractical to build one that displayed, say, 12 different test patterns (including the ILDA test pattern), because at that point you'd have a full-fledged controller. But this little baby of yours is neat! I like it...

    Adam

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    Quote Originally Posted by mixedgas View Post
    Besides, the first part of the cambridge tuning reads, apply a small signal 30 hz squarewave.....
    so Bill SHOULD carry one around
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  10. #10
    mixedgas's Avatar
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    Quote Originally Posted by keeperx View Post
    so Bill SHOULD carry one around
    Bill probably has ways of doing step 1 by eye, without a oscilloscope, after all, he did consulting for galvo makers on amp design.

    Steve

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