From: "Bill T." 
To: atm{at}shore.net
Reply-To: "Bill T." 


I prefer microstepping, but it is also possible to achieve extremely smooth
operation from full and half step drives.  If you hook up a particular
stepper to a particular drive and run it at different speeds you'll find
that some speeds are very smooth, and other speeds are rough.  The trick to
getting smooth operation from a non-microstepping motor is to first
discover a (usually narrow) low speed range over which the motor is very
smooth, and then design the mechanical transmission such that the stepper
runs at known-smooth speed during normal operation.  Press the motor frame
against a hard table top along the shaft axis to simulate the damping
effects of mounting.  Load inertia has something to do with the exact
speed/roughness characterics, but in general if a motor runs smoothly at
some speed without a load, it will run even smoother with a load.

Of course this applies only to equatorial type mounts, where the motor only
has to run at one speed most of the time.  If you need the speed bandwidth
required by an altaz mount, use microsteppers.

Calculation has a lot to with engineering, but empiricism goes a long way too.

Bill T.



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