Subject:
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Re: Struggling with encoder wheel
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Newsgroups:
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lugnet.robotics
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Date:
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Fri, 13 Apr 2001 09:04:00 GMT
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Viewed:
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2614 times
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As I am not so purist, I think that an angle sensor based on a small
potentiometer (There's a description on Michael Gaspari's site) would be the
simplest solution...
But your absolute encoder is a challenge in itself! What about using two
side-by-side light sensors each discriminating between black and white,
instead of one trying to guess between 4 different levels (and trying to
find transitions between them too)? The number of bits is the same...
Or perhaps one looking at a b&w clock pattern while the other reads the 4
level gray value? (but this would give more calibration problems especially
with power supply variations due to ageing batteries or motors consumption)
Philo
http://www.philohome.com
In lugnet.robotics, Stef Mientki writes:
> hi Chris,
>
> Chris Osborn wrote:
>
> > In article <3AD6C92D.5C9AD92D@yahoo.com>,
> > Andy Gombos <gombos_2000@yahoo.com> wrote:
> > > You could build a rotation sensor found on Michael Gaspari's site, using a
> > > magnetic strip. It is supposed to give 40 or so counts per revolution.
> >
> > Yah, but if I'm gonna build my own sensors, there's a lot I could
> > do. I'm sort of a purist. I'm trying to stick with the stock sensors
> > so that most people can build a copy of my system. Printing out
> > something on a printer and gluing it to cardboard is something most
> > people should be able to do, without having to buy a bunch of special
> > things and special tools.
>
>
> That's in fact a good principle.
> Isn't it possible to improve the dynamic range of the light-sensor by taping the red LED, I read that somewhere but I don't know where.
> Why not use a continuous grayscale, with pure with and black holes in it to get a continuous calibration ?
> Or translate you rotation in a linear movement en using a pure black and white wedge ?
>
>
> I've plans for several rotation sensors, but they will not meet your criteria ;-), here are some of mine ideas
> - using a 10-turn trim potmeter (continuous, low friction, over 360 degrees, small)
> - Hall sensor with a concentric moving magnet (continuous, no friction, 360 degrees)
> - opto-transmittor with a rotating vane
> - grayscale with calibration by using 2 or 3 detectors (inspired by you idea)
>
> >
> > --
> > Chris Osborn Full System, Inc.
> > fozztexx@fullsystem.com 2160 Jefferson St., #240
> > http://www.fullsystem.com/ Napa, CA 94559
> > Webhosting that *works* - 99.99% uptime - First 3 months free
>
> Stef Mientki
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Message is in Reply To:
 | | Re: Struggling with encoder wheel
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| hi Chris, (...) That's in fact a good principle. Isn't it possible to improve the dynamic range of the light-sensor by taping the red LED, I read that somewhere but I don't know where. Why not use a continuous grayscale, with pure with and black (...) (25 years ago, 12-Apr-01, to lugnet.robotics)
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