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From: winans@sirius.mcs.anl.gov (John Winans)
Newsgroups: comp.robotics,sci.electronics
Subject: Re: Sensing a known location to reference off of
Message-ID: <1991May15.203301.18003@mcs.anl.gov>
Date: 15 May 91 20:33:01 GMT
References: <1991May15.005403.28812@src.honeywell.com>
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In article <1991May15.005403.28812@src.honeywell.com> gcary@SRC.Honeywell.COM (Greg Cary) writes:
>What I need to do is determine when I am passing by a known location, so
>that I can count off the right number of stepper motor steps so that
>I end up at the right CD.  Two methods that come to my mind right away
>are 1) using a microswitch, and 2) interrupting the light between an
>LED emitter/detector pair.  By far the most important thing is that I
>get repeatable results.


My old 8" cpm drives used leaf switches & to detect when the head was over 
track 0 (the head was moved via worm gear on a stepper motor) and they NEVER
failed over the 8 or so times I moved to and from college in the early 80's.

I havealso seen the LED version used in the positioning of a rotating disc that
was part of an HO train turntable.  For this to work, the positioning had to be
more accurate than you would need for stepper motor use, & the turn table
has been operating for more than 10 years.

Either way should work fine.

I would like to know how the stepper is used in this thing.  Is it like a dot
matrix printer (motor spins a pulley that has a string attached that runs the 
length of the page)?  

How many CD's are you going to hold in the thing?

--John


--
! John Winans                     Advanced Computing Research Facility  !
! winans@mcs.anl.gov              Argonne National Laboratory, Illinois !
!                                                                       !
!"The large print giveth, and the small print taketh away"-- Tom Waits  !