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sprayhead
Mon 25 October 2010, 22:43
HI,

I have seen that most people seem to not use twisted pair cabling between motors and drives.

Should we or not use twisted pair between driver and motor?

F.

bradm
Tue 26 October 2010, 08:19
That is a great question! I'm tying my brain in knots trying to come up with an opinion.

Fundamentally, the signal you are sending to the motor is a low-frequency high-power one, where impedance matters to the performance of the system. However, a characteristic of most drivers is to produce higher frequency noise which we want to avoid transmitting.

Twisted pairs might attenuate some of the noise at the cost of additional impedance. Of course shielding helps with this too. I suspect the additional impedance isn't an issue at all for us, but the benefit over just a shielded wire is low - and I wouldn't substitute unshielded twisted pair for shielded wire.

Which means, I don't think it matters in this case.

Polder48
Tue 26 October 2010, 12:50
Francis,

Brad covered the electrical issues. There's also a mechanical issue. Twisted pair is a solid core wire and that's a problem being continually bended in the e-chain. Broken cables is probably not what you're after. My 2 cts.

Richards
Tue 26 October 2010, 13:31
If you do a little research on 'twisted pair' wiring, you'll find that twisted pair wiring with stepper motors makes little sense. There is no 'differential mode' transmission and therefore no advantage to twisted pair wiring. If you "Google" twisted pair wiring, you'll see for yourself that just having a 'twisted pair' set of wires is not nearly sufficient to accomplish the goal. "Twisted Pair" wiring has a common mode signal where the noise on one wire is canceled on the other wire. That will to happen by just using two twisted wires.