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Old Nov 24, 2002, 09:32 AM
DESIGNOSAUR
DesignGeek's Avatar
United States, MI, Wixom
Joined Jun 2002
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Twisting wires to reduce interference: how does it work?

Seen it mentioned a few times that you should twist the wires from ESC to motor and battery to ESC to reduce interference. First of all does this really do anything?
Second, how/why does this work?
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Old Nov 25, 2002, 07:46 PM
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Mr.RC-CAM's Avatar
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Twisted pairs conduct AC currents 180 out of phase in each wire, thus effectively canceling the radiated field at a distance from the wires. This reduction in the field can aid those situations that are affected by the unwanted radiated signal.

Twisted pairs are used with heavy current carrying conductors that have an AC power/signal on them. It is just one of the many methods to reduce EMI/RFI issues.

Each noise reduction method attacks different types of interference. In many cases an arsenal of tricks are used, since interference is rarely a simple problem. But given the ease of trying twisted pair, it should be one of the first things on the list.

RC-CAM
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Old Nov 28, 2002, 10:55 AM
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Manhattan, Kansas, United States
Joined Oct 2001
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DesignGeek,

In long runs of wire a lot of people use twisted pair wiring when they are utilizing a differential input. Basically both wires will incounter the same amount of interference which is OK with a differential signal. Why is this OK? When we say that the signal is differential, the signals on each wire (with the interference) are subtracted from one another thus canceling the noise.

(just an example, not saying you have a simple 5V signal, I'm leaving out details)
For example say we have a twisted pair of wires, one has a 5V signal, the other has a 2V signal. Also imagine that there is 2V noise emitted from somewhere in the room, now the 1st signal is 7V and the second is 4V. If we subtract the original signals from each other w/o noise (5V-2V=3V). If we subtract the orginal signals with the added noise from each other (7V-4V=3V). You can see that we have the same signal because the noise cancels itself out.

-Mike
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