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Thread: Analog Galvo Driver

  1. #1
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    Question Analog Galvo Driver

    Hello, this is my first thread. I'm enjoying the forum quite a bit.

    Im trying to build an all analog driver system to drive X-Y scanners for use with some old gas lasers.

    Back in the mid-1980s, a group of us junior college geeks enjoyed harvesting HeNes and 60X Argons from Surplus Sam of Southern California. Some of us pointed these lasers through galvos for a then, state of the art, spiro projection setup.

    I used to have a system my friend Jeff designed, and I built, using Burr-Brown 4423 Quadrature Oscillators. The 4423 is a neat, but dated chip, which outputs both analog sine and cosine ideal for an X-Y mirror setup. No DACs needed. It made some beautiful images.

    I think my ex-wife got rid of the console system along with a bunch of defunct PCs, because it was built inside a PC chassis.

    My searches on the net for "analog driver scanner laser schematics" are not producing the results I want. Many of the hits are for digital to analog systems. I recognize, in this day and age, digital is the way to go. But Id like to build a complete analog system, again, using the above mentioned Burr-Brown oscillators.

    Can anyone point me in the right direction for locating an existing design?
    Are there any analog veterans left in this industry?

  2. #2
    mixedgas's Avatar
    mixedgas is offline Creaky Old Award Winning Bastard Technologist
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    You cannot easily get the 4423s, and when you can, they sell on the order of 90$ each. TI killed them when they bought Burr Brown. The military "special" use for them faded away as better avionics technology evolved. I have two I can part with, but the rest in the basement already belong to some one else.

    The commercial clone is 135$ a piece, minimum order 10. I know who has the last stack of 4423s in the country, but he was in a flood a while back and I'm not sure the chips were dry.

    I can make you the phase rom board, if you want quasi analog. It uses a analog VCO at 512X the desired
    output frequency + some circuit magic, plus I build a little jitter into the oscillator to kill the jaggies. When it is low pass filtered, it looks just like pure analog.

    I also have a pure analog VCO design, puts the 4423 to shame. But I spent years refining it and it comes with a NDA signature requirement.

    I also have voiceband to quasi quadrature done in analog.

    I actually prefer the analog vco/digital hybrid, and you would be shocked whose console it was developed for. I bought the rights to the design from his estate.

    I'm not interested in publishing the schematics, sorry. Analog took too much effort to develop to give away. It is the one thing I'll never disclose on the forum.

    The NDA is simply so I do not see a flood of cheap clones from Asia. There are those on here who will call me elitist for that, but those who know analog will tell you its a lot of work and expensive to develop.

    I do have a two axis rotator design as well. I'd need to find a modern replacement for one chip in it, however thats easy.

    Steve
    Last edited by mixedgas; 02-19-2013 at 08:03.

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    I have no problem signing an NDA and protecting IP. I suspect most of our Asian brothers have little respect for IP, though.

    Now that you mention it, I seem to recall having to jump through several hoops to get those 4423s, which involved signing a document and sending it back to the supplier, registered mail!

    I appreciate the information you provided, but it's hard to discern if there is any kind of offer in there. I invite you to clarify by PM, if that makes you feel better.

    While I will consider buying a system outright, I was seeking guidance on building. Laying out the console and putting the build together is most of the fun.

    I think this time, around, I want to provide numbers to the console, so I can reproduce and dial back favorite projections. One of my troubles with my old system, was it was just knobs. When I saw a projection I really liked, reproducing it later was not an easy task. I recall my notations were something like:

    Xfreq = 2 o'clock
    Xamp = 9 o'clock
    Yfreq = 6 o'clock
    Yamp = 11 o'clock
    etc.

    Man, those seem like primitive times compared to modern-day technology.

  4. #4
    mixedgas's Avatar
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    Its a bit of a offer, and I can offer you something to making reproducing a given pattern very easy. Well, getting within 95% of what you used to have on the screen. The final bit of phase as you get very close in frequency is not something easily measured, and the eye does that last bit very well. We can do anything from the 2 pieces of 4423 to whatever you need.

    PM me.

    Steve

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    Another very easy way to capture the output from analog consoles is to use a USB DAC (aka standard modified 5.1 soundcard) but use the inputs too and record to some audio software. Then add a mixer to the console and mix/switch the output back into the galvo system for playback.

    I am also very interested in analog grapics, I have been using Serge and Buchla synthesizers for this but dedicated hardware is the way to go I think! I might drop you a PM too some day Mixedgas but right now two small things called "divorce" and "Spitz A3P" sort of takes all my time!

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    reproduction is secondary. I have a half dozen of the 4423s I hope to put to good use.
    I thought this time around, I might design a method making reproduction easier.
    Perhaps an analog/digital hybrid, as mixedgas suggests.
    I'm not seeking anything fancy. But certainly something I can tune to the galvos.

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    do you have any footage from your synths?

    Quote Originally Posted by dar303 View Post
    Another very easy way to capture the output from analog consoles is to use a USB DAC (aka standard modified 5.1 soundcard) but use the inputs too and record to some audio software. Then add a mixer to the console and mix/switch the output back into the galvo system for playback.

    I am also very interested in analog grapics, I have been using Serge and Buchla synthesizers for this but dedicated hardware is the way to go I think! I might drop you a PM too some day Mixedgas but right now two small things called "divorce" and "Spitz A3P" sort of takes all my time!
    suppose you're thinkin' about a plate o' shrimp. Suddenly someone'll say, like, plate, or shrimp, or plate o' shrimp out of the blue, no explanation. No point in lookin' for one, either. It's all part of a cosmic unconciousness.

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    Quote Originally Posted by swamidog View Post
    do you have any footage from your synths?
    I'm very interested in this as well and I know Stuka will want to see this too..
    Mark

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    i'm trying to recreate some of the old school effects with LSX and it would be fun to see just how far off i am..

    Quote Originally Posted by ImageLight View Post
    I'm very interested in this as well and I know Stuka will want to see this too..
    Mark
    suppose you're thinkin' about a plate o' shrimp. Suddenly someone'll say, like, plate, or shrimp, or plate o' shrimp out of the blue, no explanation. No point in lookin' for one, either. It's all part of a cosmic unconciousness.

  10. #10
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    Default Old school analog

    Here is a pic of my first console built in the mid eighties a time of analog magic and miracles in this game, if you had the money to buy the lasers needed to blow eyeballs away with stunning abstracts.

    I dont know how I afforded this back then I was poor as a church mouse but as the song lyric goes You can always get what you want but if you try sometime you just might find you get what you need.

    This was designed by myself and an electrical engineer friend I built it and hand wired each board.

    I plugged the power supply in a couple of weekends ago and fortunately I had the fore site not to plug it into the console it smoked instantly I guess the caps dried out I need to get a new supply and hook it up. I was thinking for mixing it with the output of the LSX to do a hybrid analog digital abstract generator.

    Quote Originally Posted by swamidog View Post
    i'm trying to recreate some of the old school effects with LSX and it would be fun to see just how far off i am..
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