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[DPRG] Odd numbered segments

Subject: [DPRG] Odd numbered segments
From: David P. Anderson dpa at io.isem.smu.edu
Date: Wed Aug 29 21:01:51 CDT 2001

Hi

The most excellent Dan Miner wrote:

> PS - I thought the quadrature encoder solution of placing the
> sensors 180 degrees apart and using any odd number of bars (except 
> 1) was very clever.  So simple yet it eluded lots of us.  I wish I 
> had thought of it...

I don't follow.  Don't you have to have an equal number of white
and black segments?


                |
                |
               [1]    
                |
                |
               / \
              /   \
             / [2] \
            /       \
           /         \

If you have an odd number of segments, like 3, then the 180 spacing of
the sensors solves the condition that one sensor be on the line and one
be in the center.  That's true.

But the segments consist of rising and falling edges as the sensor moves
>from black to white to black segments.  For 3 segments that would be BWB
or WBW, in either case segment 1 and 3 are the same color, no edge between
them.  So its just a 2 segment encoder with one segment twice as long as
the other. 

                |
                |
       White    |   White
                |
                |
               / \
              /   \
             /     \
            / BLACK \
           /         \

Same for any odd number of segments.  Yes?   

regards,
dpa





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