Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!zaphod.mps.ohio-state.edu!ub!csn!boulder!agcsun!jackm From: jackm@agcsun.UUCP (Jack Morrison) Newsgroups: comp.robotics Subject: Re: What is the cheapest shaft encoder you know of? Message-ID: <966@agcsun.UUCP> Date: 14 Jun 91 19:28:08 GMT References: <12518@qisoff.phx.mcd.mot.com> Reply-To: jackm@agcsun.UUCP (Jack Morrison) Organization: Ampex VSD Golden Engineering, Golden, CO Lines: 15 I missed the original posting, but assuming the Subject line covers it, you might consider the method some satellite dish positioners use. As I understand it, they have a magnet on the shaft, and a reed switch that sees it go by each revolution. Then just count the transitions. Not much resolution, but you could put the magnet on a separate shaft that was geared to spin several times for each main shaft revolution. And/or use a disk with several magnets mounted around the circumference. If this violates someone's patent, you didn't hear it from me ;-) -- "How am I typing? Call 1-303-279-1300" Jack C. Morrison Ampex Video Systems 581 Conference Place, Golden CO 80401