Re: Unipolar or Bipolar?

German,

Please understand that "bipolar chopper with as high a voltage as you
dare" has become a common reply here... But that it is often NOT the
best choice.

Your motors will run VERY well with the linistepper. Be SURE to read
Roman Blacks explanation and information on the linistepper site.
You'll see that the idea that hi-speed is only possible with bipolar
chopper drives at high voltage is simply not true...

The xylotex board is a good choice also; and you will not need to
solder it. At 90 bucks or so (the price is going up at the end of
this month!) it isn't much more expensive than the 75 bucks you'll
spend for the microstepping linistepper kits.

With these two options available, I don't think I'd choose a 297/298
style drive unless I got it very inexpensively. Having said that,
there ARE a few places to get a 297/298 drive inexpensively! Deans
cnc has 'em, as does Paul at DIYcnc?

With your motors, I'd choose linistepper or xylotex. I'd give the nod
to linistepper over the xylotex, for cost as long as you are
comfortable soldering. It might work better with your relatively high
inductance motors. But the xylotex board is a GREAT deal at the
current price!

As to your other question, a microstep moves the motor a smaller
distance compared to full step, so it takes less time to accomplish.
But I think you will find that your max speed is more limited by the
speed your controller can output steps; rather than whether ten
microsteps (or 4, or 8, or 12, or 16, or 18; which are your choices
with the drives you mentioned) happens as fast as one fullstep.
Another issue is that although the fullstep will probably be a bit
faster at some speeds, you will have to deal with low speed resonance
effects. This means that the microsteppers will more reliably
position over a wider speed and load range.

Since you are now clear about unipolar versus bipolar, be sure to
understand that a unipolar drive can microstep also. As does the
linistepper.

Hope this helps,

Ballendo

P.S. For those of you who can program your own PICS (16f84 or
16f628), be sure to look into the linistepper kits/boards! There is
plenty of room in the pic for additional features(source code and hex
file are on the linistepper site...) FWIW, I am running motors at
12volts with the same results they formerly had at 34!

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "g_f_bravo_g <factor@f...>"
<factor@f...> wrote:

> Dave,
>
> Many thanks for your response and clarify my concepts about
> unipolar/bipolar.
>
> As understand apply high voltage to the motors with bipolar
> configuration is better than unipolar controller even with the same
> high voltage.
>
> If I use microstepping with bipolar, I obtain smoother response,

but

> what happen with the maximum speed, is same that full step or I am
> wrong?
>
> German
>
> --- In CAD_CAM_EDM_DRO@yahoogroups.com, "turbulatordude
> <davemucha@j...>" <davemucha@j...> wrote:
> > With the high voltage, you would be better served with something
> over
> > 60 volts.
> >
> > The motors themselves are not bi-polar, or uni-polar, only how

you

> > power them makes them bi-polar or uni-polar. Then they are only
> > connected bi-polar or connected, uni-polar.
> >
> > Bi-polar will offer better performance.
> >
> > so that puts you into the chopper, bi-polar, 60-80 volt range.
> > the low amps means you could use quite a few drivers, check the
> > ratings.
> >
> > Microsteping will offer much smoother response and does not cost

a

> > lot more.
> >
> > I think that with the high stepper voltage, you might be better
> with
> > a Gecko, but that is just my opinion.
> >
> > Dave