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Prop Scope Crash Course — Parallax Forums

Prop Scope Crash Course

NWCCTVNWCCTV Posts: 3,629
edited 2013-12-23 18:33 in Accessories
Where in the "Understanding Signals With The Propscope" can I find info about testing a length of wire(s) to make sure there will not be too much interference or static or whatever to run either my servo or stepper motors? I am trying to work my way through the tutorials but this is something I need to figure out pretty quick like and I do not know what I am looking for.

Comments

  • xanaduxanadu Posts: 3,347
    edited 2013-12-23 10:29
    If you know what the signal should look like, compare it to the signal you get with a long wire. Since interference will vary you may want to put something really noisy next to it to simulate worst case scenario.

    I have been using toridal ferrite cores http://www.digikey.com/product-search/en/filters/ferrite-cores-for-cables-and-wiring/3408554 . The more times you wrap the signal cable around the core the better filtering you get.

    Doing this helps, but I'm not sure it would help any more than something like foil twisted pair shielded to your chassis. I have run some >3' servo wire runs and it seemed fine. I think servo pulses remain on the slow side due to the wiring concerns. If you have something that needs fast PWM things will change faster.
  • NWCCTVNWCCTV Posts: 3,629
    edited 2013-12-23 17:52
    If you know what the signal should look like,
    That's the problem. I have no idea what I am suppose to be looking for.
  • xanaduxanadu Posts: 3,347
    edited 2013-12-23 18:33
    Hook your scope directly to the IO pin and observe. Should be the cleanest it will get right at the pin. I'm guessing that the longer wire will reduce the voltage and your square wave will start to get rounded edges or saw toothed, never really tried looking for noise this way, just signal degradation over distance. Less signal, more susceptible to noise I would think.
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