fhage@virga.rap.ucar.edu (Frank Hage) (05/16/91)
gcary@SRC.Honeywell.COM (Greg Cary) writes: >What I need to do is determine when I am passing by a known location... [] >By far the most important thing is that I get repeatable results. I recently worked on an X-RAY Crystallography goniostat where reproducible postioning to +/- 0 steps was required (exact positioning). This is probably overkill for your application. It used 2 optical sensors(with slots) and associated pins; One to sense a coarse position and one to sense the motor shaft position. AND the signals together to detect the reference position. Approach the reference point from one direction only, a step at a time. My software moved towards the reference position at speed, looking for the crossing, then decelerated, and moved back a step at a time. The sensors were fixed, the pins were attached to moving parts. Some other Ideas; 1. Have an adjustable physical stop, run the "stage" against it. As you move away, start counting steps. 2. Mount an optical sensor on the moving "stage", have a "pin" at each CD reference position, don't worry about counting steps. Avoid micro switches if you want repeatable results. -Frank Hage, fhage@ncar.ucar.edu -National Center for Atmospheric Research