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Thread: CYGN-B

  1. #551
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    Quote Originally Posted by laserist View Post
    The photo with the pots & caps are joystick parts, there should be a round aluminum disk about an inch in diameter with a 1/4 inch hole on axis and a threaded radial hole in it for the joystick shaft, and a second threaded radial hole to lock it onto the y? axis pot. The L-brackets with the two 3/8 inch holes gets a hub with a setscrew that lets it clamp onto the x axis pot and the y axis pot goes through the other hole. The L-bracket with the 3/8 inch hold and the two threaded holes is the x axis pot mount. The pots pictured are 1mOhm reverse audio taper pots that turn the voltage follower on the JSGC into 1st order low pass filters for dampening. The mess of little aluminum parts and springs are mostly scan glass parts with a scattering of em-20 mounts and apertures. The little board is a JSGN - Joystick gain control board. It lived inside the joystick boxes, and controlled gain and offset of the joystick pots. It was designed backwards. They put the gain in front of the offset which made aligning the gain and offset an iterative process instead of an align the offset then align the gain process.
    I have never seen a slotted can galvo, but the thing in the photo is what I imagine one would look like. Or is that the round aluminum disk about an inch in diameter with a 1/4 inch hole on axis that is part of the joystick? Shown in the photo is as much as I can get of the joystick together. I don't see how the ball threads onto those brass sleeves, nor what connects the stick onto the pot.

    I notice that em-20 mounts and apertures are among the items I have previously received from Brian. These may now become relevant, as I have today received from Steve a constellation of many galvos, all vintage GSI, hence the need for all the scan amps. The crux of the business is four XY mounts with galvos. Thank you for this contribution, Steve. This hardware brings the goal of a 4 channel system that will look the same as the original Laserium scan system significantly closer.

    There is much to be worked out, namely the amps and the obtaining and mounting of RGB modules. Then, the 4 channel RYGB torquer circuits. My current tasks are the 351 (as ASCII hex) import to bela function, and a parts orders for the the amps which Steve has, and for which Ron has recently provided the documentation for. As well, a parts order for for the Danube board is being worked up.
    Attached Thumbnails Attached Thumbnails joystick_parts.jpg  


  2. #552
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    The steel rod and the three pieces of brass tubing are for a scan glass mechanism. There are a number of old and new style scan glass mounts in the mess I sent.

    For the joystick: You need a one inch disk with a 1/4 inch hole in the center that also has a hole drilled and tapped radially to attach to the pot. It may have a slotted clamp or setscrews to hold it on the pot's shaft. Screw a threaded rod into the disk, slide a piece of brass tubing over the threaded rod and screw the ball on the shaft.
    "There are painters who transform the sun into a yellow spot, but there are others who, with the help of their art and their intelligence, transform a yellow spot into the sun." Pablo Picasso

  3. #553
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    Email me on the existing amps.

    Steve
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  4. #554
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    Default Chopper cup

    Greg, that cylindrical can with the slots was the chopper mechanism from the original Mark 4 projector before the advent of AOM's or PCAOM's. We chopped the beam, which went through the two slots, mechanically. That cup was mounted on a big-ass, but slow, scanner. The one nice aspect of this type of chopper is that the beams "tailed off" in intensity rather than having "sharp edges" like those produced by AOM's. You couldn't do most of the effects we do with AOM's, but it had its own aesthetic.

    Ron

    Click image for larger version. 

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    Last edited by ronhip; 08-12-2022 at 21:33.

  5. #555
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    For the record the slotted can chopper was used on the Mark VI until the Beatles show mods.
    "There are painters who transform the sun into a yellow spot, but there are others who, with the help of their art and their intelligence, transform a yellow spot into the sun." Pablo Picasso

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    What does a Danube Board do?

    Steve
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  7. #557
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    Quote Originally Posted by mixedgas View Post
    What does a Danube Board do?

    Steve
    One of the great Laserium choreography numbers was to the "Blue Danube" and consisted of slow, graceful variations of the classic rotating, RYGB, Lissajous figures and cycloids of slightly out-of phase 1:1 sine/cosine signals, coupled with quadrature DC RYGB movements, moving to the music. I'm betting the Danube board was related to this.
    Last edited by lasermaster1977; 08-13-2022 at 20:56.
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  8. #558
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    The Danube board generated a slightly variable 100 Hz sine wave that was controlled by a 0-10V input voltage. It generated fixed 100 and 50 Hz sine waves. The combination of the fixed and variable wave forms generated Lissajous loops and "eights". When the 0-10V signal approached 10v the variable waveform was driven further from 100 Hz causing the loops and "eights" to "tumble". (It was modified to generate a low frequency quadrature signal pair that was used for z axis rotation and as an offset with the introduction of the Mark VI projector.) When Laserium premiered in 1973 Ivan and Charlie used army surplus signal generators to do the Lissajous figures and had 4 friends each with x/y faders to control the four image sizes. Laser Images couldn't afford 5 or 6 laserists per show. So consequently the Danube card and the 351 (later 352) data system were developed. There's actually very little about the choreography of The Blue Danube in "Laserium I" that involved a lot of adjustment of the frequency of the Danube board. Most of the choreography involved a constant fixed rotation for each image channel, master x/y gain that was enhanced by the fixed rotation, and individual image gains. There was a nice fairly tight lumia background effect that was produced with a clear plexiglas wheel with clear epoxy (mixed so bubbles formed in the epoxy) smeared around the wheel. Charlie made these in his garage. The process was "top secret".
    Last edited by laserist; 08-14-2022 at 08:02.
    "There are painters who transform the sun into a yellow spot, but there are others who, with the help of their art and their intelligence, transform a yellow spot into the sun." Pablo Picasso

  9. #559
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    Quote Originally Posted by laserist View Post
    (It was modified to generate a low frequency quadrature signal pair that was used for z axis rotation and as an offset with the introduction of the Mark VI projector.)
    I wonder if anything further is known regarding that modification, as that sounds like a very useful modification.

    So that's a cat's meow. The project includes the original slotted can chopper. I certainly noticed the change from this to the aom. It was like an insanely fast chopper, but with no trails. I thought it a sad loss at the time. There was a number in Laserock2 that, the way I saw performed, used slotted can chopper, CYGN-A, and the 351 gains and offsets scheme to, shall I say, be specific in a beautiful way about something one might not expect such a simple combination of signals to be so specific about.
    Previously posted video of 351 visualization here:
    https://www.youtube.com/watch?v=fkQeG4tbIYc

    Photo shows a reformatting of some of what I got from Steve.
    Attached Thumbnails Attached Thumbnails 8_galvos_on_breadboard.jpg  


  10. #560
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    The Danube loops and eights were generated by clock/divider circuits. (2 pairs of divide by 16 and then divide by 2048/4096 counters. One had a pulse synchronizer that could insert a 0 to 20 KHz clock in one pair.) Those circuits sent square wave pulse trains through integrators to convert to triangle waves and then low pass filters to convert to sine waves for output. The rotation sin/cos outputs were generated by taking the 50 Hz output and phase shifting it 90 degrees to generate a quadrature cosine signal. Then the sine and cosine signals were then sent to two sample and hold circuits that were clocked to generate the Danube rotation/revolution outputs.

    In looking at the Danube schematic to make this post I found I made an error previously describing the board's function. The 100 Hz "A" signal is the fixed frequency and both the 100 and 50 Hz "B" signals were slightly variable. By clocking the sample and hold circuits with the equivalent of a 50 Hz "A" clock the rotation/revolution signals had a theoretical resolution of 4096 points.
    "There are painters who transform the sun into a yellow spot, but there are others who, with the help of their art and their intelligence, transform a yellow spot into the sun." Pablo Picasso

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