Re: missed keystrokes problem, back with a vengeance.
On Wednesday 01 February 2017 23:06:51 Jerry Stuckle wrote:
> On 1/29/2017 1:48 PM, Gene Heskett wrote:
> > Alan, ALL of the motor drivers are switchmode, with the current
> > regulation running at or above 20 KHz. And these noise spikes are
> > ringing at nominally 100 MHz. I have managed to get the xy motor
> > noise under control by takeing out the switchmode psu's, and putting
> > in tordoid transformers, bridge rectifiers, and the biggest
> > electrolytic I had in the drawers that had sufficient withstand
> > voltage. Its a star ground system, and the output cables to the
> > motors are shielded, and the shield grounded as it goes by this
> > single bolt ground on its way out of the box. The shielding extends
> > both ways from that point but is not connected either at the motor,
> > or at the driver, just at the bolt. This is std in such noisy
> > machinery.
>
> I would also recommend bypassing those electrolytics with 0.01uf or so
> disk capacitors (or similar). Electrolytics have higher impedance at
> higher frequencies. Bypass capacitors help with high frequency
> spikes.
I must be getting old, I had forgotten that, oh wait, can I plead
oldtimers since I'm 82 these days? The noise I am looking at with a
gigahertz sampler scope is largely in phase with itself.
I am in the process of rewiring the whole MaryAnn so its all inside
metal, and no motor wiring shares conduit with power or signalling
circuits except about 4" of the VFD output as it goes thru a 4 square
with a 2 pole switch and a utility duplex on its face, in the side and
out the bottom headed for the motor. Some of it is ancient steel 1/2"
BX and some is 3/8" ALU BX, but its all clamped down tight. And the
power wiring will be doubly switched except for the pi and 7i90, both
running on the same 5v 4A supply. Logic from LCNC will turn on
everything else thru 40 amp SSR's. And all sourced from the same 20 amp
254 (two pole) volt breaker, so its all on one ground, which was not the
situation last week. And nothing gets hooked back up to the 7i90 unless
the noise on it is under a volt after its shielding is bolted down.
Thats the plan anyway.
Cheers, Gene Heskett
--
"There are four boxes to be used in defense of liberty:
soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
Genes Web page <http://geneslinuxbox.net:6309/gene>
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