Subject:
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Wheel Shaft Encoders
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Newsgroups:
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lugnet.robotics.handyboard
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Date:
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Sun, 18 Aug 1996 18:30:04 GMT
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Original-From:
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John Whitten <brat@naxs^Spamless^.com>
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Reply-To:
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brat@naxs.comNOSPAM
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Viewed:
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1545 times
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> > > I connected successfully a radio shack RC truck (4WS) to the handy board.
> >
> > (snip)
> > > I am still looking for cheap shaft encoders, and good DC motors drawing less
> > > than 600mA.
> >
> > I also have one of the Radio Shack RC trucks. A good solution for shaft
> > encoding would be to glue a couple (or 4) magnets to the inside rim of the
> > rear tires. Then glue a hall effect sensor to the axle. When the wheel
> > spins, the hall effect sensor would sense the magnets.
> You know what makes REALLY good REALLY cheap shaft encoders? Mice! Get an old
> mouse that has a broken button (that's usually what goes on mice) and pull it
> appart. Sometimes, depending upon the kind of mouse, you can get really luckey,
Hello,
I'm new to the Handy Board mailing list. I have been browsing through
the archives and I saw the discussion regarding shaft encoders. I
haven't seen anyone use the technique I've used rather well. Like the
thread suggests, I've tried the magnet trick, the mouse trick and
various homebrew encoders. The method I have discovered that works best
IMHO is painting an encoder strip on the inside rim of the wheel. This
sounds difficult, but I've found a sneaky trick that makes this a very
simple procedure. I use the Radio Shack RC trucks in many of my
projects. They're ideal for this trick since they all have deep-well
wheels. Here's what I do:
1) Spray Paint the interior of the rim with white (or silver) paint. If
you want to be neat about it you can mask off whatever you don't want
paint on.
2) Once the paint is dry, tape a strip of radiator hose clamp to the
inner rim. Again, mask off anything else you don't want painted.
3) Paint over the hose clamp with black paint. Wait for the paint to dry
and then carefully peel the clamp material off. What's left is a very
nice black/white (or silver) encoder strip on the inside of your wheel
rim.
There is only one minor hitch... the point where the two ends of the
hose clamp meet is rarely exactly aligned precisely and so there may be
one or two stripes that might be a little thicker or thinner than the
rest. I personally don't find this a problem. I just use those as index
marks and everything works fine. Plus, if you're like me, you really
don't care exactly how many pulses go by but are only trying to get a
"feel" for the speed, or if the wheel is actually turning.
Then you can get a really tiny photosensor assembly. I use the ones from
Mouser, part #512-QRD1114 and 512-QRB1114 with pretty good success. You
can use whatever electronics you want. I like the mouse trick. Thats an
easy way to interface to PC's and stuff.
Hope this helps,
PS. If you want to contact me, do so at "brat@naxs.com". Their mail
server is down AGAIN so I'm using an alternate account.
John Whitten
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