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  #1  
Old Mon 25 October 2010, 23:43
sprayhead
Just call me: Francis
 
sydney
Australia
Twisted pair shielded cable for stepper motors

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.
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  #2  
Old Tue 26 October 2010, 09:19
bradm
Just call me: Brad #10
 
Somerville(MA)
United States of America
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.
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  #3  
Old Tue 26 October 2010, 13:50
Polder48
Just call me: polder
 
Edam
Netherlands
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.
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  #4  
Old Tue 26 October 2010, 14:31
Richards
Just call me: Mike
 
South Jordan, UT
United States of America
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.
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