Re: SUGGESTION ABOUT NEW 3 AXIS DRIVER

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