re:stepper pwr suplies wasRe: motor/leadscrew/ps recomendations

--- In CAD_CAM_EDM_DRO@egroups.com, ballendo@y... wrote:

> John DG wrote:
> >I have a 24 volt 8.6 amp switching power supply I WAS going to use
> >with Dan's 5 AMP controllers. The operative word here is WAS<snip>
> >By the way, my 5 volt DC comes from a 300 watt PC power supply<s>
> >but I won't try to use a switcher for stepper power again! (I don't
> >need that kind of stress in my life!!)

> Ballendo
>
> P.S. Experts, What ARE the "gotchas" in using switching power
> supplies with stepper motors, if any?

Decoupling with large low-impedance capacitors
is all you have to do. Most switchers expect
to be driving a fairly constant DC current and
use very small output filtering caps. If the
load current changes the switcher can usually
adjust to regulate voltage. But when you try and
drive a chopper stepper from it, you are drawing
severe "pulses" of power from it which it's caps
and reguation won't handle.

From the output of the switcher use a small
series resistor, say 0.5v drop at max current,
and then add some big filter caps of a high
quality low impedance type like used in audio
amps. Most stores sell these. also there should
be about a 1/3 of your total capacitance value
as close to the driver bridge as possible,
as usually these are some distance from the
power supply and main caps.
-Roman