Re: Stepper Wire ?

Hi,

Jon is right up to a point. The current is for the most part a
triangle wave, however there is also an extremely fast rising, high
current pulse at every current slope change. This is the current
necessary to charge and discharge motor winding and cable parasitic
capacitance. It is this current that causes noise.

I recommend a 5-conductor shielded cable. 4 wires are for the two
motor windings, the 5th wire connects to motor case at one end and
your single-point ground at the other. The shield connects to the
single-point ground as well. Do not connect the motor end of the
shield.

The wire guage is of secondary importance. Its only effect is
resistive; Whatever voltage drop it develops is subtracted from the
power supply, leaving the balance for the motor. Even a couple of
volt drop would not be significant.

Mariss

--- In CAD_CAM_EDM_DRO@y..., zephyrus@r... 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.
>
> Best regards,
>
> Randy