Stepper motor noise (was Re: Chopper Transient Suppression)

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "Alan Marconett" <KM6VV@...>
wrote:

>
> Hi Wayne,
>
> You're probably just hearing the chopping frequency.
> Shouldn't be terribly loud. Come over, and give a
> listen to mine! (Gecko drives, of course!).

Yes, it was chopper noise, and it was, in fact, a bug
in my firmware. There is a clock prescaler in the PIC
microcontroller and I set it to a value of 2 instead of 0.
This meant the clock was being divided by 8 rather than 2.
So my refresh frequency was 6250Hz (=25000/4) rather than
25000. As soon as I fixed the firmware error and fired
everything up, the motors are silent when standing still.
There is a pleasant whirrring sound when they are in motion.
I am pretty jazzed.

I'll contact you off list about visiting your CNC
system. I'll haul mine along for comparison.
Now that the holidays are over, it should be easier
to find a mutually convenient time to meet.

-Wayne

[snip]

> > Thanks. I cranked the blanking up to 4uS and the stepper motor
> > vibration is now gone. The stepper motors still produce
> > a high pitch screeching noise. Since I've never actually
> > seen or heard anybody else's CNC machine to compare against,
> > I have no idea whether my stepper noise is typical or excessive.
> >
> > Thanks for the prompt feedback.
> >
> > -Wayne
> >
>