Re: [CAD_CAM_EDM_DRO] Re: Stepper Wire ?

zephyrus@... wrote:

> --- In CAD_CAM_EDM_DRO@y..., Jon Elson <elson@p...> wrote:
>
> > Not true. There may be voltages with square corners, but the
> currents
> > are very slowly changing triangle waves, due to motor winding
> inductance.
>
> I'm still wondering about the outcome of this. I'm currently (no pun
> intended) using some scavenged 20ga-7-strand-
> 2-twisted-foil-shielded-pair wire on my motors, but it's not very
> flexible at all and as you say, Jon, I worry about the durability
> of the foil shielding with flexing.
>
> Braid-shielded multistrand flexible cable is $$$, but Newark has some
> Belden unshielded "Infinity" 9-million-flex rated cable (74x38 strand)
> at $1.66/foot for 20-ga 4-conductor.
>
> Are you implying that because of the slowly varying current, that
> shielding is not necessary, or is that wishful thinking on my part?
> My drivers are 2A current limited, and I'm running <=4000 steps/sec.

No, unfortunately. The current may vary fairly slowly, but the voltage
on the individual wires varies as fast as the transistors in the driver can
switch (which is very fast for power MOSFETs.) If you don't have encoders,
and don't want to use a radio in the shop, you may be able to get away
without shielded wire. You can also put L-C filters at the output of the
driver, to keep the noise out of the wire.

Jon