>
> If your stepper isn't moving very fast, and you aren't grossly overloading the
 stepper so it misses steps or slips, you
> should be able to just use the stepper by itself.
> The whole POINT of a stepper motor is, it moves a set amount each
> phase change.

This is known as feed-forward where, given no errors, the actuator
will proceed to a known position/state,  fine in some applications,
unacceptable in others.
This can be controlled by feed-back. The question is... how much
feedback is needed. As stated ... a simple switch or photo-interupter
could be used to locate the device on power - up, e.g. a wheel turns
until the switch is closed, the wheel is now in a known position and
the feed-forward characteristics can now be employed.
One can now add more and more known position switches e.g. 0deg,
90deg, 180deg until a suitable control for your application is
reached.
We have found that in rugged environments.. steppers lose their way
for lots of reasons.. not just overloading. Shock can halt a step,
power glitch, foreign body jamming mechanism etc.
_____________________________

Lance Allen
Technical Officer
Uni of Auckland
Psych Dept
New Zealand
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