On Tuesday 05 May 2020 17:48:01 Dan Henderson wrote:

> I have a PMDC motor I’ve scavenged along with the MC-2100 motor
> control from a treadmill rated for 1.5 hp @ 90 volts. I’ve been
> testing it with LinuxCNC v2.7.15 in a mock-up environment I built for
> testing. I’m able to control the spindle speed via PWM pulses to the
> controller (HD2 pin 4). M3 S500 will get me somewhere between 520 and
> 580 rpm. You can hear the motor whine fluctuating with the RPM. I’ve
> also installed a CUI ATM 10 encoder on the back and seem to have it
> working with both an index and phase A signal. I have the jumpers on
> it set to 200 PPR but it can go all the way to 2048. I’m using a cheap
> china 5 axis BOB connected via parallel cable.
>
> Does anybody have any idea why I’m get so much flux on the rpm? Surely
> this isn’t normal? I know enough about the HAL to be dangerous. Is
> there some things I can check to smooth this out? Thanks.
>
If using a software encoder, as opposed to a mesa card, the time delay 
between samples at the 1 kilohertz servo loop can do odd things.  Among 
others, the lag in the input opto-isolators of that bob can even cause 
missed pulses from the encoder to the software. Try a much lower speed 
to see if it stabilizes.  If handy with a soldering iron, bypassing 
those opto's can help, a lot.
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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)
If we desire respect for the law, we must first make the law respectable.
 - Louis D. Brandeis
Genes Web page <http://geneslinuxbox.net:6309/gene>


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