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[DPRG] More quad encoder stuff

Subject: [DPRG] More quad encoder stuff
From: Dan Miner miner at centtech.com
Date: Fri Aug 31 23:00:03 CDT 2001

> On Thu, 30 Aug 2001, R. Bickle wrote:
> 
> > Why would you need to use gray code encoding for robots?
> > 
> > This is very useful for absolute encoders, but motor encoders can be
> > incremental much more easily.
> > 
> > Rick

You don't need gray code for an encoder - but it MIGHT be useful.
Where gray codes are certainly useful is in situations where
multiple bits switching at once can cause extra noise (due to
ground bounce, coupling and other "nasties") -OR- 
synchronization problems.  

Consider the three bit code for 3=011 that is incremented
to the code for 4=100.  Note that all three bits change at once.
Not a problem *IF* they all change at once.  But what if the
upper bit changes first, then the other 2.  011 -> 111 -> 100.
= 3 -> 7 -> 4.  Not good.

This is where gray codes could be most useful for an absolute
encoder since the relative alignment of the sensors is less
critical than with a binary encoding.

				- Dan Miner

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