Re: Microstepping thru the Tulips

Hi,

For everyone who is interested in this thread, I took 8 scope pics of
winding currents for a 3.9A/phase motor operated at 24VDC.

The motor pics were taken at 3.75 RPM, 15 RPM, 150 RPM, 375 RPM, 750
RPM, 1500 RPM, 3750 RPM and 7500 RPM.

Yes, that's right, 7,500 RPM at 24VDC for a 3.9A NEMA-23 motor.
That's 250,000 microsteps per second. That step pulse frequency IS
12.5 times higher than the 20kHz PWM switching of the drive. See how
it all works, makes sense and doesn't violate any known law of
physics.

Please go to the Geckodrive Yahoo Group, Files section and see:
Files > G203V step motor drive > MOTOR CURRENT WAVEFORMS

The accompanying .pdf file by the same name describes the 8 gif scope
pictures.

Mariss



--- In CAD_CAM_EDM_DRO@yahoogroups.com, "turbulatordude"
<dave_mucha@...> wrote:

>
> --- In CAD_CAM_EDM_DRO@yahoogroups.com, "Steve Stallings"
> <stevesng@> wrote:
> >
> > violent agreement indeed, except for your assumption
> > of what most folks consider high speed.
> >
> > If we assume Gecko drives microstepping at 10 micro-
> > steps per full step and the known appx. 20KHz PWM
> > rate, then we get a possible 10 rev. per second or
> > 600 RPM with microstepping still nominally functioning.
> >
> > Apply this to a Bridgeport with 5 TPI screws and
> > 2:1 gearing (typical of Boss series) and you get
> > 60 inches per minute. Not blindingly fast, but a
> > long ways from slow.
> >
> > Cheers,
> > Steve Stallings
> > www.PMDX.com
> >
>
> <HUGE snip>
>
> My understanding is that microstepping shows it's best face on slow
> speeds and acceleration, and that at *some* point, becomes
> inconsequential.
>
> but,
>
> those useful speeds are the most common to actually use the motor.
> not rapids, but cutting speeds.
>
> Personally, I could care less of the smootheness of a rapid, as long
> as there were no missed steps.
>
> It seems the question what speed is considdered slow enough to

benifit

> from microstepping and what is too fast to need it ? And that

appears

> to be dependant on power supply voltage, motor inductance and maybe
> some other factors ?
>
>
>
> Dave
>