Subject:
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Re: Shaft Encoders
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Newsgroups:
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lugnet.robotics.handyboard
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Date:
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Sat, 8 Nov 1997 15:32:20 GMT
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Original-From:
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David Kott <dakott@kott.my.domain*nospam*>
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Viewed:
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3259 times
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> From dakott Thu Nov 6 06:23:12 1997
>
> We are interested in connecting two shaft encoders to the wheels of our
> Handy Board - controlled mobile robot and use the ICW encoder instructions.
>
> Does anyone know of a good source of encoders? Is there anyone willing to
> share your experience with the Handy Board and encoders?
We used the line of "S1" optical encoders from US Digital Corp.
(http://www.usdigital.com) and found them to work superbly. The encoders are
light (~.07 lb) and small (~1.7" x 1.3"). The company is a "Value Added
Retailer" and adds housings/bearings/whathaveyou to the well known
Hewlett-Packard HEDS modules. This is the specific part I ordered:
S1-512-B
Which gives me a 512 cycle/rev. precision (they offer them in many different
resolutions) w/ a ball bearing shaft. The final price as shipped was around
$57.00 US. They worked great w/ the encoder routines supplied w/ the IC 2.81
Handy Board Pcode.
I didn't actually use the full quadrature output.. just one of the
channels, but I chose the primary resolution accordingly.
We were using them to supply some closed loop feedback for an AGV
speed control system and odometer. I don't have any hard numbers for how
"fast" you can spin the 512's buuuuuuuuuuut... I had a 5/8" coupler that was
running on the ground at about 15 MPH.. which translates into
15 mph * 88 fps * 1/ 60 mph * 12 ipf * 8/5 rev. per inch * 512 Hz/rev = 92 KHz
Pretty good update time on the HB... I haven't looked THAT deeply into the
Pcode, but, at an interrupt rate of 1000Hz, and an 8 bit Pulse Accumulator
minus some (reasonable?) overhead.. you get around 200 K counts/second.
I *think* I *may* have gotten the link out of "Norms Industrial Electronics
Website" at http://www.compusmart.ab.ca/ndyrvik/nieencod.htm. In *any* case..
this particular website had 20 or so links to rotory encoder manufacturers and
was the 2nd or 3rd "hit" on a search at eXcite.com under "rotary encoders"
*shrug*.. sorry for the ambiquity there... :-}.
Don't forget to order cables.. or at least connectors.. high(ish) speed digital
connections are finicky.
-d
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