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Thread: CYGN-B

  1. #331
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    Quote Originally Posted by laserist View Post
    Laserium’s 351 data used three pulse rates. The fundamental pulse duration was .074 mS. A zero toggled the current state for .074 mS and toggled back for .074 mS. A one toggled the current state for .148 mS. (Notice the duration of a zero and one are equal.) The 160 bit frame began with a sync word that toggled the current state for .296 mS 4 times. (notice than one a single bit changing inverts the waveform…) To decode I would skip most of the analog stuff on the 352 card. I’d keep the first 3 op-amp circuits on the card’s input and then use a microcontroller to count the time between the zero crossings of input data to decode.
    That's a good explanation. Attached is a redraw of the 352 card first three op amps schematic. Was DATA RETURN important? I'm putting together an order which includes the capacitors I need to build this.

    Success so far regarding the 5 channel XY-RGB recording of the 6B rebuild output with the DATAQ data logger. Attached shows data capture, laserboy import following custom data format conversion, and the test graphic 6b to laser.
    Attached Thumbnails Attached Thumbnails 352_redraw.png  

    XYRGB_graphs.png  

    XYRGB_LB.png  

    XYRGB_test.jpg  


  2. #332
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    Laserium typically used a Teac 3340 four channel open reel tape deck for playback prior to ADAT. The Teac's had unbalanced outputs, and so did the dBX units the audio channels ran through. The Mark 6 had 600 ohm line balancing transformers for audio (for audio mod) and data mounted on the back of the 351 card cage. Without the data return your signal would be floating and the resulting signal would be totally subject to the whims of your environment. Without the transformers the audio and data would be vulnerable to hum from ground loops.
    "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. #333
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    Quote Originally Posted by laserist View Post
    Laserium typically used a Teac 3340 four channel open reel tape deck for playback prior to ADAT. The Teac's had unbalanced outputs, and so did the dBX units the audio channels ran through. The Mark 6 had 600 ohm line balancing transformers for audio (for audio mod) and data mounted on the back of the 351 card cage. Without the data return your signal would be floating and the resulting signal would be totally subject to the whims of your environment. Without the transformers the audio and data would be vulnerable to hum from ground loops.
    btw: Anyone need or want a Teac 3340? I have one available w/user manual. Send PM if interested.
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  4. #334
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    Vintage audio gear is going for a premium now. There are all kinds of places you could find a value and list it.
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  5. #335
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    The SPGN story so far...

    Quote Originally Posted by laserist View Post
    The spiral card had 3, 0 to 10 volt inputs from the 351 data, and two digital inputs. Out rate, in rate and sweep were the analog signals, spiral reset and diamond spirals were the digital inputs. So you could control how fast the ramp generator ramped up and down, reset the ramp, and the sweep was summed to the image input. The ramp generator produced a ramp and an inverted ramp. Two pairs of 2QMMs modulated the input/sweep as spirals and inverted spirals. Analog switches could apply the other ramp to one input of the multiplier pairs for diamond spirals. I've never looked at the ramp gain. I assumed it's 0-10 V, but the key is the resistance before the 2QMMs. The PDM output was a square wave at the spiral frequency that was used as an offset on one axis of the fixed cycloids. Originally used in "Summer Madness" in Laserium I.
    I have tested the reset function of the SPGN, and it appears to work. By grounding a +5 digital high on the CDC4041A, the reset and inverse reset are produced that feed the inputs of the IH5012, and by eye, testing at low frequencies, appear to reset the ramp.

    Photo shows the SPGN ramp signal and the PDM OUT signal. It would be really interesting to see the data from the portion of Laserock2 which I have a wave file of, and look for SPGN control in the 351 data. I need to put together the parts order for the audio mod card, and the 351 decoder first stage, and then things will be rolling again.

    Sadly this building, which even without the star projector could host great laser shows, or at least once did, is soon to be demolished.

    Brian mentioned we may have once met. I do remember a brief hello to someone important who was up from the States, and who at that moment was involved with something within an open 6B cabinet. That took place in 1981 or 1982 in the planetarium shown in the photos.
    Attached Thumbnails Attached Thumbnails SPGN_reset_works.jpg  

    McLaughlin_toBeDemolished_1.jpg  

    McLaughlin_toBeDemolished_2.jpg  

    McLaughlin_toBeDemolished_3.jpg  


  6. #336
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    Regarding a circuit that simulates the ringing of open loop galvos for use with modern galvos:

    It was suggested in the CYGN-A thread that integrators would be a start.

    The photos show a sweep of the KQO symmetry control showing both the raw signal from the KQO clipper, and the same signal after an integration stage.

    Suggestions welcome.
    Attached Thumbnails Attached Thumbnails integrator.png  

    integrators.jpg  

    integrators2.jpg  


  7. #337
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    Quote Originally Posted by Greg View Post
    Regarding a circuit that simulates the ringing of open loop galvos for use with modern galvos:

    It was suggested in the CYGN-A thread that integrators would be a start.

    The photos show a sweep of the KQO symmetry control showing both the raw signal from the KQO clipper, and the same signal after an integration stage.

    Suggestions welcome.
    Fantastic! I've used similar integrator circuits to mimic open loop galvo ringing response with modern galvos. Love the progress your making with the CYGN-A & B boards.

    What dormant planetarium is that and where in previous post? Looks like a 40 or 50 footer.
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  8. #338
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    Quote Originally Posted by lasermaster1977 View Post
    Fantastic! I've used similar integrator circuits to mimic open loop galvo ringing response with modern galvos. Love the progress your making with the CYGN-A & B boards.

    What dormant planetarium is that and where in previous post? Looks like a 40 or 50 footer.
    Oh, sorry. I forgot the letters have been removed from the building. That is / was the McLaughlin Planetarium in Toronto, Canada. That projector really produced a great looking sky. I'd like to know what actually happened to the projector.

    Here's a previously posted photo showing the raw clipped signal displayed on actual open loop galvos. As can be seen, the effect is much better than what the integrators are producing. Integrators are a small improvement over the raw signal though.
    Attached Thumbnails Attached Thumbnails FXCY_KQO_GS100PD.jpg  


  9. #339
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    Quote Originally Posted by Greg View Post
    Oh, sorry. I forgot the letters have been removed from the building. That is / was the McLaughlin Planetarium in Toronto, Canada. That projector really produced a great looking sky. I'd like to know what actually happened to the projector.

    Here's a previously posted photo showing the raw clipped signal displayed on actual open loop galvos. As can be seen, the effect is much better than what the integrators are producing. Integrators are a small improvement over the raw signal though.
    Nice, and with the real open loop galvos you can see the phase drift of each ringing cycle. I'll dig up some of my favorite under-damped-open-loop galvo slide photos, scan and post some.

    Wow the McLaughlin dome was a 75 footer with a Zeiss projector. Zeiss was the premier star projector. Sad to see that this planetarium lost its orbit.
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  10. #340
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    There is/was this fellow named Dr. Pierre Brosens who is/was early team member or co-founder of GSI.

    Long ago as an undergrad I was delighted to find one of his papers in the library on optimal open loop control.
    I doubt I can draw the curve correctly but the frequency response graph had three regions as frequency increased.
    That is a 30 year old memory. So take with a grain of salt.

    There was a method in the paper of taking a specified width pulse at 1/2 the amplitude of the command signal, inverting it, and adding it to command to put the brakes on any resonance and thus stop the motion quicker.

    The paper is behind a pay wall now and I really doubt I have a 30 year old photocopy of a two page paper.

    From Left to Right, Linear, Resonant, and Ballistic.

    So besides the integrator you add a very narrow bandpass with a lot of gain (Or invert a sharp notch* ) at where you want your resonance.

    Steve
    Attached Thumbnails Attached Thumbnails ThatDarnCurve.png  

    Last edited by mixedgas; 11-10-2021 at 14:08.
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