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Thread: Analog abstracts Z plane rotation?

  1. #1
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    Default Analog abstracts Z plane rotation?

    I am doing in depth experimentation with my analog modular synth setup and see on some of the controllers like the P-4 and Z-5 there is a Z plane rotation parameter and I am trying to figure out how that works electrically. I can use voltage offsets to move the image around the X and Y planes, but for the life of me I can't think of how to make an image spin on the Z axis (like a vinyl record spinning around).
    Googling brings up some math equations, but what type of circuit does the same thing?
    Any help would be hugely appreciated!

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    See Attached current steering rotator. This does a true "Z", You can also turn it around and generate waves with it, by fixing the input voltages.

    It has nasty offsets at 0,90,180, and 270. But nothing that can't be cured and if your spinning, they don't show much.

    I'd update the analog switch to something far more modern. Make sure the switch has VCC and VSS higher then the input voltages.

    Not for the faint of heart... Use 1% resistors on the hexagonal matrix.

    Drive it with a counter clocked by a 74HC4046 vco. You could just drive the upper 8 bits, but that's sloppy kids stuff..

    This is the least parts count solution ever published.

    A Gentleman would buy a Z-5 and get it over with.

    Steve
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    Last edited by mixedgas; 01-07-2015 at 12:10.
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    Brilliant! Thank you so much Steve, this is a great jumping off point.

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    You can get the multiplying dacs from ebay, they are actually quite cheap and the ones I got was genuine working ones.

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    The P4/Z5 uses a number of AD534 analog multipliers to get the job done, along with a quadrature oscillator. I'm pretty sure there's a schematic of a Z rotator in the lightshow handbook, which may or may not be on the PL FTP.

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    I'm wondering if anyone has built MG's Z rotator yet. Have a board laid out that uses a 74LS491 10 bit up down counter, but want to hear other's experience before I commit.
    I have a Z rotator circuit that uses four AD-633 multipliers if anyone is interested. Needs a LF quadrature oscillator to drive it, and unless you have a QO that can start from a set point it runs continuously.
    A very attractive VLFQO can be found here: http://yusynth.net/Modular/EN/QUAD-LFO/index.html DZ also sells a really cool QO at his aldebaran site.

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    I'm also wondering if anyone has built a Z rotator based on a sine/cosine potentiometer. Very hard to find, but you can just "crank" the rotation manually. No counters or oscillators to fuss with.

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    I put a sine/cosine pot in place of one of the joysticks on a Laserium projector about 35 years ago. Nothing to it.

    Quote Originally Posted by glorocks View Post
    I'm also wondering if anyone has built a Z rotator based on a sine/cosine potentiometer. Very hard to find, but you can just "crank" the rotation manually. No counters or oscillators to fuss with.
    "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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    Default Technique?

    Quote Originally Posted by laserist View Post
    I put a sine/cosine pot in place of one of the joysticks on a Laserium projector about 35 years ago. Nothing to it.
    So I guess my next question is: Did you use the sine/cosine pot as a voltage source for a multiplier array (or something along those lines) or was the image signal passed through the pot?
    Are you willing to provide a little more information?

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    The sin-cos pot has fixed taps at 0,90,180, and 270. You need to feed the vertical signal into 0. The inverted vertical signal into 180. The horizontal signal goes into 90 and 270 in a similar manner. The two wipers at 90' to each other on the 360' resistive material are your X and Y signals. It is better to have a dual SIN_COS and feed each axis into its own ring. There are other ways of wiring it, but the main one uses a driven ring.


    My dad pretty much forced me to read the 1960s Navy RADAR NAV manual as a math lesson. Its had its uses.

    I sold my last dual SIN-COS pot at SELEM two years ago.

    Once the Navy and Air force switched their RADARS and targeting systems from Resolvers to Three Phase Synchos, the need for SIN-COS pots drifted into obscurity.
    It was easier to sum signals from Synchros and Synchro Transformers then to try to add and multiply with SIN-COS and DC based Resolvers.


    Steve
    Last edited by mixedgas; 01-21-2015 at 11:21.
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