Re: Wire Size for BPT Steppers

The three things to consider when specificing wire size:

Average current of the load
Length of the run
allowable heat rise/voltage drop

Notice that voltage is not mentioned. I would use the wire sizes
mentioned in one of the other posts. Always over design.

Twisting any conductor that has signal tends to cancel out noise.
While it does help with radiated noise (noise coming FROM the wires),
it works much better on absorbed noise (noise from the surrounding
sources). In english this means that if the wires are from or to
devices that are reading signals (encoders, sensors, step/direction
signals) they should be either shielded or twisted or both. Since
some systems have the drivers remote from the motors, that length of
wire tends to become a antenna for transmitting noise. All those low
frequency square waves have harmonics that span decades of
frequencies. If you plan on running the motor drive circuits more
that a couple of feet from the motor then you might consider even
using shielded twisted 16 or 14 GA wire. On the other hand if you
put your Geikos close to the motor and put some large capactitors
close to them on the DC feed, you will not have to worry as much
about transmitted noise. You can run pure DC to the motor controller
across heavy unshielded wire without them becoming giant noise
generators. The step and direction signals to the Geckos need to be
run in shielded wire.

Hope this is not too confusing.