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Question SMC3 with limited range potentiometers

Discussion in 'DIY Motion Simulator Building Q&A / FAQ' started by RJ Stausebach, Jan 11, 2022.

  1. RJ Stausebach

    RJ Stausebach New Member Gold Contributor

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    I have not found anything on this in the forums so hope someone can point me in the right direction.
    I have set up SMC3 with Mode2 and after some setting up can run two cheap 50N electrical actuators with potentiometers off it. The feedback is limited though and not centred when looking at the graphs in SMC3utils. This is because the potentiometers have a limited turn over the 50mm stroke of the actuators. They run roughly from 3.5kOhm to 6.5kOhm over their full 10kOhm range, so say from 350 to 650 with a center of around 500.
    Is there a way to scale this so I get a full response, eg. the 300 range available gets scaled to 1024 (or 250 as the case might be) in the SMC3 code or elsewhere?
    Also the center actually seems offset to one half, so running at say the quarter top of the graph, not sure why.
    This is the setup:
    upload_2022-1-11_22-25-28.jpeg

    upload_2022-1-11_22-26-6.jpeg
    the graph green line is indicative of the perceived center position of the actuator, at this point it wasn’t running yet so ignore the rest.
  2. Ads Master

    Ads Master

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  3. Gadget999

    Gadget999 Well-Known Member

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    how did you fit the pots ?
  4. RJ Stausebach

    RJ Stausebach New Member Gold Contributor

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    Last edited: Jan 12, 2022
  5. noorbeast

    noorbeast VR Tassie Devil Staff Member Moderator Race Director

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    At 10mm/s they are really, really slow and not really suitable for motion sims, you want at least fifteen times that speed for a direct actuator, or some similar mechanical design multiplication for indirect use: https://www.xsimulator.net/community/faq/speed-needed-for-good-motion.218/
  6. RJ Stausebach

    RJ Stausebach New Member Gold Contributor

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    Thanks Noorbeast, sounds like back to the drawing board for me! :think
  7. Gadget999

    Gadget999 Well-Known Member

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    You might be able to change the gearing to make them faster

    Can you turn the lots by hand to see if the green line moves in smc3 ?
  8. RJ Stausebach

    RJ Stausebach New Member Gold Contributor

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    I could get them to run and move the green line but only in part of the top half. I would have liked to have scaled the inputs in SMC3 to react to a full range of movement, something I am sure is possible. You could also change the gearing but changing the program inputs would be a whole lot easier. None of which means much if they are too slow to adequately provide motion simulation…