A simple, effective way is to strap a magnet or two or three to the
shaft and put a hall effect xsistor where the magnets would sweep by and
count pulses. The more magnets the better the resolution on rotation but
if you are just worried about counting rev's and not about stopping
precisely one magnet will do. The very early add on car cruise controls
used that same method. They tied magnets to the drive shaft. I have an
app where I am doing the same thing and used magnets and a alarm magnet
switch as the sensor. The magnets were pennies apiece and the magnetic
door switch was 99 cents at Radio shack.

-----Original Message-----
From: pic microcontroller discussion list
[mailto:PICLIST@MITVMA.MIT.EDU] On Behalf Of Alan Gorham
Sent: Saturday, October 26, 2002 8:02 AM
To: PICLIST@MITVMA.MIT.EDU
Subject: Re: [PIC]: Counting shaft revolutions


You could look at the optical disks and counting modules made by US
digital. They are available for many different shaft diameters and with
a range of count resolutions.

www.usdigital.com


Alan



>Hello to all,
>
>I'm interested in a device that can be used to count revolutions of a
>slow turning shaft, 10 turns/minute,  with 1 or 2 degree resolution.  I

>will then use a Pic to read and limit the number of turns and
>fractional parts of a turn.  Good resolution is important. Any ideas
>appreciated.
>
>                                                Rod
>
>--
>http://www.piclist.com hint: The PICList is archived three different
>ways.  See http://www.piclist.com/#archives for details.
>
>

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