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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Thu, 12 Apr 2001 18:43:35 GMT
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Viewed:
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835 times
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Chris,
This idea would require an additional motor, but, an alternate approach
might be to create your wheel with 36 alternating grey and white (perhaps
by having a third or fouth shade/color you could have more information)
segments. Then, in each segment have 5 radial bars at preset distances from
the center. These bars would be turned on or off ie. black or white and
would describe the segment number. You would now have six pieces of binary
information which will allow you to count to 64. However, to read this, you
would have to scan radially but you will end up knowing the absoloute
position of the wheel. It would also infer that the wheel was not turning,
however, once you knew the position, you could rapidly move the wheel N
segments. The programing and the calculation would be fast and simple, but
the scanning would be slower.
Phil.
In lugnet.robotics, Jason S. Mantor writes:
> Pretty neat Chris. You've very nearly recreated a special kind of
> optical encoder that was developed by my former employers called a virtual
> absolute encoder. It didn't use diferent colors but it used a "time-window"
> to read the last few states off of a disc which had "white noise" encoded on
> the data track. The look up is *very* fast becuse the "white noise" is
> generated using a simple linear feedback shift register.
> As for speeding up the system you've got, I'm not sure I can help
> there... It seems that you've done a very good job optimizing it for compact
> storage. I was trying to fathom a hash function to help here, but I haven't
> come up with one that wouldn't take much more space to store the table. I'm
> intrigued though : )
> -JSM
>
> "Chris Osborn" <fozztexx@pez.fullsystem.com> wrote in message
> news:GBn6Mw.L02@lugnet.com...
> >
> > I'm having a hard time finding a good algorithm for the encoder wheel
> > I came up with for use on my webcam. The way I packed the bits in the
> > lookup table has made it hard to get any speed out of the algorithms.
> >
> > I'm using NQC, and the LEGO OS seems incredibly slow.
> >
> > I've got a write-up with pictures on the whole thing at
> >
> > http://www.fozztexx.com/LEGO/Webcam/
> >
> > --
> > 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
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Message is in Reply To:
 | | Re: Struggling with encoder wheel
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| Pretty neat Chris. You've very nearly recreated a special kind of optical encoder that was developed by my former employers called a virtual absolute encoder. It didn't use diferent colors but it used a "time-window" to read the last few states off (...) (24 years ago, 12-Apr-01, to lugnet.robotics)
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