From: Jonathan Kirwan
Subject: Re: A simple angular positioning solution?
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NNTP-Posting-Date: Tue, 29 Oct 2002 13:41:08 GMT
Organization: AT&T Broadband
Date: Tue, 29 Oct 2002 13:41:08 GMT
On 29 Oct 2002 02:05:42 -0800, email@example.com
>I am designing something that has a plastic mechanical dial on it,
>which can click into 1 of 4 locations. Each of these locations will
>signify a mode of operation for the device. I must get the processor
>to recognise what position the dial is in, to determine what mode has
>I have experimented with hall effect proximity sensors, and having a
>different 2 bit binary number on each segment of the dial, but both of
>these require having some electronics on the dial which is not the
It seems clear that you need some kind of transducer, somewhere.
An axis shaft could proceed from the dial to an encoding pot?
Actually, if you can accept a shaft at all, all kinds of ready
possibilities come to mind.
>Another idea I had was to have holes and blanks in each segment
>representing binary 1's and 0's. This would require having some
>optical transmitting and sensing circuitry on either side of the dial
>to determine which position it is in.
>Anyway All ideas would be appreciated.
Wish I could better visualize what the limitations are. But you
might paint onto the back of the dial gray-coded black regions
and use a simple reflection of LED emitter to LED detector,
needing two pairs for the two encoding bits. They could be
located away from each other, so as not to interfere. Or some
similar optical scheme. Nothing to wear out, this way.
You tried hall-effect, but you might also use reed relay with
small perm-magnets on the dial itself if you can position the
reed ampules close enough and the mechanical variations aren't
enough to risk missing the proximity.