Re: SUGGESTION ABOUT NEW 3 AXIS DRIVER

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "jeffalanp" <xylotex@h...>
wrote:

> Hi Jon,
>
> You wrote:
> >They are Unipolar, which is another severe strike against them, as
> >most unipolar drives perform poorly when compared to bipolar.
>
> When you say *most unipolar drives* are you perhaps refering mainly
> to the old L/R type drives that use the big old fat ballast
> resistors? A unipolar drive (with no reference to Brewington

drives

> capabilities) CAN be made that is PWM driven, thus allowing
> microstepping, which can help reduce a major concern with missed
> steps due to mechanical resosnance. Also when it comes time to
> reversing current flow, the other phase coil is used, so charge up
> time would be about half when compared to bipolar. The only major
> concern I can see of a modern PWM type unipolar microstepping drive
> is that it can not close a loop to allow current recirculation

during

> off (decay) times (so maybe it still uses a little more current

than

> bipolar).
>
> What makes unipolar drives so horendous? Is it just their relation
> to the old L/R days, or am I still missing something.
>
> Jeff
> (not in any way, shape or form related to Brewington, just a, well,
> shall we say, *curious observer*)
>
> --- In CAD_CAM_EDM_DRO@yahoogroups.com, Jon Elson <elson@p...>

wrote:

> >
> >
> > luisguillermo98 wrote:
> >
> > >I need to know if aomeone has try the the 3 axis driver found at
> > >http://www.brewingtontech.com/index.html..
> > >
> > >tell me about your experience working with it and if it works

fine

> > >like geckodrivers.. any suggestions..
> > >
> > >
> > I can already tell you, it is nowhere as sophisticated as a Gecko
> stepper
> > drive. It is 3 Amps, only. It can only handle 46 V DC supply,

the

> Gecko
> > can handle 80 V. For very small motors, that doesn't matter, but
> for larger
> > motors, it is a problem. Their higher inductance requires move
> voltage
> > to move at the higher speeds. I get good torque at 1440 RPM with
> size
> > 34 motors, which is astounding. The Gecko drives also do x 10
> > microstepping,
> > and have circuits to damp resonance. These Brewington drives are
> > half-step only. I see no indication that it has opto-isolation
> between the
> > drive and the parallel port. They are Unipolar, which is another
> severe
> > strike against them, as most unipolar drives perform poorly when
> compared
> > to bipolar. They say they can accept 10,000 steps/second, but in
> practice
> > I doubt they can get anywhere near this before the motors lose
> steps.
> >
> > And, that's just a start!
> >
> > Jon