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something doesn't add up... - Page 2 — Parallax Forums

something doesn't add up...

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  • PublisonPublison Posts: 12,366
    edited 2015-03-01 12:20
    Gadgetman wrote: »
    No it isn't...

    Here's a ShapeOko proving that you can move fast using steppers...
    https://www.youtube.com/watch?v=80uqW4dgLFA

    OK,

    I was going on 30-35 year old technology.
  • GadgetmanGadgetman Posts: 2,436
    edited 2015-03-01 13:29
    No problem.

    I believe there are videos of even faster ShapeOkos, but I can't find them right now.

    Technology is advancing so quickly that if you blink... you miss out on 2 fads and a Sony product...

    30 years ago, most stepper-driven machinery used direct-control of the H-bridges powering the steppers, and the MCU/CPU had to not just pulse the IO, but set up bit patterns for each pin, too.
    These days, a StepStick or similar driver which is fed with a 'direction' and 'step' signal handles all the pattern-generation. It even handles microstepping...
    That makes it much easier to control.
  • Mark_TMark_T Posts: 1,981
    edited 2015-03-01 14:58
    To get steppers moving fast you need:

    low inductance windings (ie high current bipolar motors - 1 ohm or less is common)
    high supply voltage (overcome back EMF from motion and inductance, 80 to 120V is common for industrial drivers)
    current control using chopper circuit.
    careful control of resonance (various techniques, microstepping, mechanical or electronic damping).
  • Martin HodgeMartin Hodge Posts: 1,246
    edited 2015-03-01 19:43
    Andrew, thank you very much. Any light you can shed will be most appreciated.
  • WBA ConsultingWBA Consulting Posts: 2,934
    edited 2015-03-02 09:03
    Email sent off this morning to my contact, I'll let you know.
  • Martin HodgeMartin Hodge Posts: 1,246
    edited 2015-03-02 17:56
    Cancel that, someone else got it.
  • WBA ConsultingWBA Consulting Posts: 2,934
    edited 2015-03-03 16:41
    Martin, that's probably a good thing. He didn't have much to be positive for this machine. The biggest issue would be maintenance/parts. He wasn't sure about the noise but said that should definitely be a factor.
    So, by his comment "you get what you pay for" and this was dirt cheap, I think you won by missing out on it.
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