Newsgroups: comp.robotics
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From: browen@lyapunov.aoc.nrao.edu (Bruce Rowen)
Subject: Re: Sensing shaft position
In-Reply-To: rick@ee.uwm.edu's message of 16 Jul 1993 18: 03:45 GMT
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Date: Fri, 16 Jul 1993 19:54:27 GMT
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In article <226qi1INNbfu@uwm.edu> rick@ee.uwm.edu (Rick Miller) writes:

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   From: rick@ee.uwm.edu (Rick Miller)
   Newsgroups: comp.robotics
   Date: 16 Jul 1993 18:03:45 GMT
   Organization: Just me.
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   nhowland@cardinal.ksu.ksu.edu (Neal Patrick Howland) writes:
   >I am working on a project in which I need to sense the position and speed of
   >two different shafts.  The shaft I need to sense the position of must be able
   >to rotate freely and I would like to get accuracy of at least 5 degrees.  It
   >has to be able to spin a full 360 degrees in the same direction over and over
   >again, so I can't use any potentiometers that I have ever seen.

Use a servo potentiometer. Basically a normal pot that can rotate 360
degrees without the drag of a "normal" pot. Commonly available item.
You did not mention the shaft diameter, if large enough, you can just
paste/paint on a gray code with an index and use an optical switch in
reflection mode. This will work for speed also, just put a
non-reflective mark on the shaft and use an optical switch/interrupter
in reflective mode with the output tied to a simple frequency-voltage
converter if you want analog speed info.
--
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Bruce Rowen 				National Radio Astronomy Observatory
Scientific Programmer				Array Operations Center
browen@aoc.nrao.edu			  P.O. Box O  Socorro, NM   87801
(505)385-7329					     (505)385-7000
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