> Can anyone tell me if it's OK to use a "unipolar" stepper (i.e. one
> that has center-tapped coils) *as* a "bipolar"?   i.e., just ignore
> the center tap and use the two series-connected coils as one.  I
> realize that this might not be as low of a resistance value as what I
> might see with an actual "bipolar" single-coil device, but the
> question is... will it work?   My instinct is that it should, but
> perhaps with less startup torque.  What say you all ? Thanks! Jim

Yes, you can do that as long as the coils are separated. If you have an 8
wire motor, you can wire them as unipolar, bipolar (windings in series)
or bipolar (windings in parallel).
You need to keep the _power_ within the manufacturers specifications
so a parallel connected motor can use 1.4 times the rated current and a
series connected can only use 0.7 times the rated current.
The holding torque is based on the actual current so a parallel
connection will be highest. The rate at which the torque drops off will be
higher with a parallel connection than with a series one, but you started
with more. If you want to get accurate microstepping and not a skewed
sinewave, you should reduce those ratings by about 30%.

Steve.


==========================================
Steve Baldwin                          Electronic Product Design
TLA Microsystems Ltd             Microcontroller Specialists
PO Box 15-680, New Lynn                http://www.tla.co.nz
Auckland, New Zealand                     ph  +64 9 820-2221
email: steve@tla.co.nz                      fax +64 9 820-1929
=========================================

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