On Monday 26 October 2020 18:32:00 Jon Elson wrote: > >> On Monday 26 October 2020 14:16:55 Chris Albertson wrote: > >>> 20% PWM duty cycle and a 24V power supply is about 4.8 volts to > >>> the motor. Many DC motors will not move at 20% of rated volts. > >>> I'd not be surprised if it took 10 or 12 volts to overcome > >>> internal friction. > > A standard test for servo motors is to apply a single "D" > cell. The motor should turn VERY slowly, maybe 5-10 RPM, > but move smoothly. If the movement is "lumpy" or it doesn't > move at all, then it is a poor motor, or having a problem. > > Jon > In which case Jon, is having a huge problem, but I am now a wee bit schmardter after wiring that controller properly. My diagnosis is that its about 2 decades slower internally than one of your pwm-servo's. The switching losses when the pwm is about 2% on time are such that it over heats and shuts down in a couple seconds, AND it leaks enough voltage from the 5 volt supply used to run its internal logic that the motor supply never gets below 4.11 volts, which is not low enough to allow a reset. I slowed it down to a kilohertz in the pwmgen, and that slowed the spindle loop response time badly enough that the wild swings from the pid_s.output were actually sending a reversal to your driver that was then slowing the spindle motor and I could hear the iron complaining. Dropping its Pgain from 20 to 3.5 stabilized that and got rid of the noisy iron singing..
But the switching losses in the olimex board, even at only a 1 kilohertz pwm are killers, getting it hot enough to burn a finger in just 2 or 3 seconds. So, I need a d2a to drive one of the 150 watt class D audio boards after shorting the inputs hi-pass filters caps. And I have the feeling that even as sweet as the SpinX1 is for knocking around a vfd, that it won't be fast enough for this, so I'll need a real d2a that I can shove fresh data thru at servo-thread speeds. Looking for likely suspects I might be able to drive from the 7i76D sserial extension bus. Suggestions? Thanks Jon. > > _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users 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> _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
