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Thread: CYGN-B

  1. #621
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    Quote Originally Posted by Greg View Post
    Was beam torquer an offset to the colormod signal? Or was it a separate optical device?
    [/url]
    Beam torquer, color mod I & II we're all summed together and drove the color mod galvo. In the Concert series projectors the raw beam was dispersed by a prism, then made parallel by a second prism, then through a lens to focus the beams on the beam torquer mirror, then through a second lens to re-collimate the beams. This eliminated the need for color mod correction - which didn't really work well on the original Mark 6. I think the problem was the difference in the mass of the color mod mirror vs the scanner mirrors caused a significant difference in the galvos resonance frequencies and the PDM scan amps - amplified the problem. Obviously focusing all of the beam at a point on the color mod mirror requires a good coating. On the other hand you could use a much smaller mirror in theory, and or a faster scanner...
    "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

  2. #622
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    I'm thinking how to get these shows up and performable / recordable / editable / watchable with as little hardware building as possible. With the scheme given in the attached graphic, one would need their choice of cycloid generator, 4 Bela units, 4 ILDA capable projectors, a couple of joystick pots and a few simply wired push buttons, and the interface board described in the graphic. What is needed is a large number of repetitions of a few simple op amp circuits. Perhaps I will have to try my hand at using the crate of historic wire wrap materials provided by Brian, but this would only generate a one off, and reasons may arise for having more than one of these systems. Alternate suggestions, offers to help with a pc board design / layout, or suggestions of a place I could pay to have one done, and critiques of my naively contrived voltage scaling circuits welcome.
    Attached Thumbnails Attached Thumbnails MultaBela_requirements.png  


  3. #623
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    Quote Originally Posted by Greg View Post
    I'm thinking how to get these shows up and performable / recordable / editable / watchable with as little hardware building as possible. With the scheme given in the attached graphic, one would need their choice of cycloid generator, 4 Bela units, 4 ILDA capable projectors, a couple of joystick pots and a few simply wired push buttons, and the interface board described in the graphic. What is needed is a large number of repetitions of a few simple op amp circuits. Perhaps I will have to try my hand at using the crate of historic wire wrap materials provided by Brian, but this would only generate a one off, and reasons may arise for having more than one of these systems. Alternate suggestions, offers to help with a pc board design / layout, or suggestions of a place I could pay to have one done, and critiques of my naively contrived voltage scaling circuits welcome.
    In reference to the top schematic:
    I don't see how your +-10v to 0->+5v converter schematic is going to work that way it is drawn. It's output will not always be unipolar with the scaled down plus and minus 10v signal swings.

    When the input is +10v the opamp output will be -1.75 +(-2.5) or -4.25. And opposite this on the negative 10v signal swing, and not quite to the 5v target value.

    Divide the bipolar 20v p-p signal down to a bipolar 5v p-p (plus and minus 2.5v) then add an offset of +2.5v. This resulting signal output will an inversion of the original input. This +2.5v offset would be "added" by it being an input on the non-inverting input. If you are going to "add" it on the inverting input the offset voltage polarity must be reversed to -2.5v. If you want to maintain signal polarity integrity but with an added positive offset, add another unity gain inverter at the end.

    Also, to derive the small offset voltage for the opamp circuit you do not need to drive so much current through the 50K pot by using 30v across it (+15v and -15v). Just use a single source voltage polarity (e.g. +15v) that is the same polarity as you want to appear on the wiper of the pot (e.g. +2.5v) and leave the lower side of the pot's resistor grounded.


    In reference to the 2nd schematic:

    The gain of the opamp is 4.7, so worst case, +5v x 4.7 = +23.5v p-p. To center this p-p signal (lower it's DC offset) so the signal is centered around 0v, the non-inverting input needs to be at 23.5v / 2 = 11.75v as a negative voltage input, not positive. And again, all that is needed to get -11.75v from the pot's wiper is for the pot to be connected to -15v and Gnd. But then, this leaves you with a plus and minus 11.75v signal, not a plus and minus 10v signal, so some gain adjustment tweaking with the opamp's feedback resistor is called for as well.
    Last edited by lasermaster1977; 11-29-2022 at 11:22.
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  4. #624
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    Quote Originally Posted by lasermaster1977 View Post
    In reference to the top schematic:
    I don't see how your +-10v to 0->+5v converter schematic is going to work that way it is drawn. It's output will not always be unipolar with the scaled down plus and minus 10v signal swings.

    When the input is +10v the opamp output will be -1.75 +(-2.5) or -4.25. And opposite this on the negative 10v signal swing, and not quite to the 5v target value.

    Divide the bipolar 20v p-p signal down to a bipolar 5v p-p (plus and minus 2.5v) then add an offset of +2.5v. This resulting signal output will an inversion of the original input. This +2.5v offset would be "added" by it being an input on the non-inverting input. If you are going to "add" it on the inverting input the offset voltage polarity must be reversed to -2.5v. If you want to maintain signal polarity integrity but with an added positive offset, add another unity gain inverter at the end.

    Also, to derive the small offset voltage for the opamp circuit you do not need to drive so much current through the 50K pot by using 30v across it (+15v and -15v). Just use a single source voltage polarity (e.g. +15v) that is the same polarity as you want to appear on the wiper of the pot (e.g. +2.5v) and leave the lower side of the pot's resistor grounded.
    I'm sorry, I forgot to mention this is an inverting thing, because with abstract cycloids who cares.


    What you described sounds like this actually is that.


    My thinking involved in the top schematic +-10v to 0->+5v is that two voltages are summed. One is +-10V scaled down with a voltage divider to < +-2.5V, and the other is set by the pot voltage divider as what ever offsets the scaled down signal to center near 2.5V.


    I see what you mean about the unnecessary current through the pot, good point.


    Helpful reply, thanks! I'm still looking at what you said regarding the second schematic.

  5. #625
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    Quote Originally Posted by Greg View Post
    I'm sorry, I forgot to mention this is an inverting thing, because with abstract cycloids who cares.


    What you described sounds like this actually is that.


    My thinking involved in the top schematic +-10v to 0->+5v is that two voltages are summed. One is +-10V scaled down with a voltage divider to < +-2.5V, and the other is set by the pot voltage divider as what ever offsets the scaled down signal to center near 2.5V.


    I see what you mean about the unnecessary current through the pot, good point.


    Helpful reply, thanks! I'm still looking at what you said regarding the second schematic.

    So, if you don't care that your circuit yields a 0 to minus 5v result, when the input is at +10v, but when it is as -10v, then what? I took literally that you wanted a 0 to +5v yield.
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  6. #626
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    Quote Originally Posted by lasermaster1977 View Post
    So, if you don't care that your circuit yields a 0 to minus 5v result, when the input is at +10v, but when it is as -10v, then what? I took literally that you wanted a 0 to +5v yield.
    My mistake. I caused confusion by noting "adjust to 2.5V". What I meant is adjust for the inverted output with zero signal in to be 2.5V, not the potential on the wiper of the pot to be 2.5V. I just measured the wipers for the X and Y circuits and both are slightly below -2V. You are right, 0 to +5V (or close to) yield is desired, and this what the circuit is doing, so any thing that suggests it doesn't work must be errors in my notation.

  7. #627
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    Quote Originally Posted by Greg View Post
    My mistake. I caused confusion by noting "adjust to 2.5V". What I meant is adjust for the inverted output with zero signal in to be 2.5V, not the potential on the wiper of the pot to be 2.5V. I just measured the wipers for the X and Y circuits and both are slightly below -2V. You are right, 0 to +5V (or close to) yield is desired, and this what the circuit is doing, so any thing that suggests it doesn't work must be errors in my notation.
    Perfect! Thanks for clarifying your notation. You're on your way!
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  8. #628
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    I looked for but couldn't find TheHermit's recent enthusiastic comments regarding actually doing the doing shows thing again. I hope it comes to that. And if it does, others with passion and experience are welcome to participate. The progress is happening toward a system: 4 x ILDA output 351 + live + joysticks + chopper and colormod, but without cartoons or lumia effects.

    Shown is the infancy of one channel of the system. All channels will be identical except for the value that says which channel a given projector is to output. Since last update the dots on the oscilloscope that made the previously posted video look interesting have been debugged away. The two pots standing in for two joysticks (coming) are doing offsets the way they should.

    The next test should be interesting: set a value 1 to 4 for which channel to output, and see that channel on my ILDA projector. Then the chopper and colormod input signals can be tested.

    Sorry I don't have any good questions at this moment. I have observed the substitute circuit given previously by Brian for the 2QMM is working in the spiral generator rebuild, but not completely the way it should. I can't request attention for this until a methodical investigation has been carried out though, and until the 4 channel system is in place and all the shows have been transferred, I won't have time to get back into the details of the spiral generator.

    I can't find anything suggesting a multi channel audio use of beta video cassettes. Ron, am I correct you mean betamax? Or should I be thinking betacam? I could add your Metalica ADAT to the archive, but you have a huge amount of stuff on "beta" that I don't have and if that can possibly be preserved, it should be. Also, would you take the tapes I have if I ship them to you once they have been transferred?
    Attached Thumbnails Attached Thumbnails channel_of_351_to_ILDA_prototype.jpg  


  9. #629
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    Greg,

    Yes, I mean betamax. We used Sony SuperBETA-HiFi decks for playback - Model SL-HF350. I don't remember the track layout specifically, but audio was probably for audio and video was somehow encoded with imagery. Brian has a much better memory for this kind of thing. It wasn't very good (tended to be glitchy), but sufficed for much more time than it should have until we switched to ADATs. I have the deck we used in San Francisco literally sitting 2 feet from me right now.

    Yes, I agree that these things should be preserved somehow, but my garage is already full of Laserium crap and I'm not willing (or able) to store any more. Jon already dropped a few more boxes of stuff on me some months ago that I still have to go through, most importantly two full boxes of 35mm and super-35 slides I've never seen, and have yet to evaluate for digitization. This is in addition to all the boxes of slides I HAVE already gone through and rejected, but can't bring myself to disposing of (the "selected" slides are now in archival binders sitting on the desk behind me (8 binders!) Those are all digitized and in the archive (and yet I still keep the original film - I'm such a packrat...)

    Ron



    Quote Originally Posted by Greg View Post
    I looked for but couldn't find TheHermit's recent enthusiastic comments regarding actually doing the doing shows thing again. I hope it comes to that. And if it does, others with passion and experience are welcome to participate. The progress is happening toward a system: 4 x ILDA output 351 + live + joysticks + chopper and colormod, but without cartoons or lumia effects.

    Shown is the infancy of one channel of the system. All channels will be identical except for the value that says which channel a given projector is to output. Since last update the dots on the oscilloscope that made the previously posted video look interesting have been debugged away. The two pots standing in for two joysticks (coming) are doing offsets the way they should.

    The next test should be interesting: set a value 1 to 4 for which channel to output, and see that channel on my ILDA projector. Then the chopper and colormod input signals can be tested.

    Sorry I don't have any good questions at this moment. I have observed the substitute circuit given previously by Brian for the 2QMM is working in the spiral generator rebuild, but not completely the way it should. I can't request attention for this until a methodical investigation has been carried out though, and until the 4 channel system is in place and all the shows have been transferred, I won't have time to get back into the details of the spiral generator.

    I can't find anything suggesting a multi channel audio use of beta video cassettes. Ron, am I correct you mean betamax? Or should I be thinking betacam? I could add your Metalica ADAT to the archive, but you have a huge amount of stuff on "beta" that I don't have and if that can possibly be preserved, it should be. Also, would you take the tapes I have if I ship them to you once they have been transferred?

  10. #630
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    Actually recording shows was after my time. There was a digital recording system that Bill Whitlock and his crew pioneered before I relocated to L.A. it also recorded on Betamax. I saw the hardware, but I never saw it work. The game over point for me was if it hit a dropout you had to restart from the beginning. I'm sure it had some good stuff for it's time, but I thought it was stupid for Laser Images to develop it. I thought that somebody with deeper pockets just had to be working on multichannel digital recording!
    "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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