DPRG mailing list archives: [DPRG] Handy Board and Encoders

Wed Sep 5 01:22:02 CDT 2001

A slight math typo:

> ... 50k per second, about 1 pulse every 2 microseconds...

That should be 1 pulse every 20 microseconds.

Still way to fast for Interactive C.  You could keep
up with it using VERY finely tuned assembler but you
could only do 1 channel and you'd have no time for
anything else.

Recommendation is to divide down the frequency of the
signal using a counter chip (as David suggested) or
switch processors to something like a 68332 (Mini Robo 
Mind) that has a TPU hardware that will keep track of
the encoders for you.

				- Dan Miner

> -----Original Message-----
> From: David Peterson [mailto:robologist at yahoo.com]
> 
> Hey Ed,
>  Think those motors you've got run about 1000 rpm out the
> gear shaft, which means the encoder end is twirling at about
> 6000 rpm. Times 500 is 3 million per minute or 50k per
> second, about 1 pulse every 2 microseconds possible (in no
> load). A Basic Stamp 2 can pick up a 2 us pulse, but
> probably not consecutively, so I'm guessing that a
> Handyboard could as well. Storing all those pulses might be
> the real problem. Trying to do 4x mode might be a problem
> too, and the HCTL chip Tom mentioned could help, but think
> it's $18+ (x2) unless it can be sampled. Oh, those encoders
> should be HEDS 9100. Other quad encoder chips include the
> LS7083 and 84 ($3 x 2) at
> http://www.usdigital.com/products/ls7083-84/ which then
> interface with a counter logic chip like a 74xx193. Also
> there's the LS7166 ($12 x 2) and 266 ($16 x 1) too, more
> direct to an MCU. I could be wrong about that price too.
> David P
> 
> ----- Original Message -----
> From: "Ed Okerson" <eokerson at fw.telenic.net>
> 
> > I am working on a robot that has Pittman motors with built
> in encoders.  The
> > encoders appear to be 500 slots per revolution of the
> motor shaft, and the
> > gearbox is 5.9:1.  Is it possible for the handyboard to
> keep up with that
> > pace of pulses?  Or do I need to implement some sort of
> divider to reduce
> > the pulse count?  So far just playing with Interactive C
> and it's encoder
> > routines, it seems to loose many pulses if the motor speed
> is anywhere above
> > the speed of a crippled snail.
> >
> > Ed Okerson