this is actually used in the NSK Megatorq motors , it has a large
micrstepping motor part and a smaller encoder, the encoder in it is special
in that next to its normal phase outputs (or should i say inputs) it has a Z
winding to detect a reference position.

works excelent

Peter

-----Original Message-----
From: Russell McMahon <apptech@CLEAR.NET.NZ>
To: PICLIST@MITVMA.MIT.EDU <PICLIST@MITVMA.MIT.EDU>
Date: Friday, May 07, 1999 7:00 AM
Subject: Re: PIC-based Oven Controller


>A remarkably effective rotary encoder is a stepper motor. I haven't
>used this in anything serious, but in bench tests it worked very
>well.
>A typical unipolar stepper with 2 coils produces two quadrature
>voltage outputs when rotated. While amplitude is proportional to
>speed of rotation (up to a limit) the voltages output are very
>adequate to swing a comparator or even a transistor base. If you
>don't mind committing two amplifiers or 2 comparators to the task you
>can turn this slower than you would ever need to.
>
>Small steppers are available at very reasonable prices surplus (often
>new but in vast quantity if desired).
>
>
>
>
>                Russell McMahon
>
>
>
>
>
>
>
>>        I kinda like the use of quadrature encoders with a display.
>The
>>use of the rotary control has a nice feel to it while the display
>gives
>>precision in setting.  A quadrature encoder should be less expensive
>than
>>one with a binary output and takes less pins on the PIC.  Also, you
>can