pic: A little teaser from 3571

[Caleb Sykes]

Originally Posted by philso

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This is standard practice in industry and is described very thoroughly in literature on Electromagnetic Interference.




The PWM signals are "digital" and have a large noise margin, by design, and their response to noise is non-linear. Increasing the amount of noise induced on your PWM wires will not cause noticeable degradation in performance until you have used up all of your noise margin. Shifting your wires around may change the coupling enough to start causing a problem. Been there, done that, had to write reports about it, didn't get a T-shirt for it.




A current in a wire WILL induce a current in a wire that is parallel to it. That is why it is standard practice in industry to avoid running power wiring and signal wiring together, in the same bundle. Please DO route your signal and power wires separately for this reason.

You are correct in thinking that the Hall Effect is insignificant in situations like this. I have never seen any mention of it in any literature on Electromagnetic Interference or in any of the many courses my employers have paid to have me attended on the subject.

I'm really having trouble understanding how there would be any appreciable electromagnetic interference caused by a single wire with a constant (or at least, low frequency) current running through it. This situation would only cause a slight magnetic field around the wire, and should not be creating any electromagnetic waves. The situation would clearly be different if the current was AC, but we are not dealing with AC currents here.

It is quite possible I am in this way over my head and that I really don't understand what is going on. Could you possibly link to a more detailed description of this interference you are describing? Everything I am finding in searching relates to AC circuits.