Subject:
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Re: (long) Rotation Sensor from "Extreme Creatures" Fiber Optics
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Newsgroups:
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lugnet.robotics
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Date:
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Sat, 2 Jan 1999 00:40:41 GMT
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Original-From:
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Ron Beck <rtb@richmond.IHATESPAMinfi.net>
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Viewed:
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4052 times
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Karim Nassar wrote:
>
> Ben Kimball wrote:
>
> > > -Now, if i could just tell which direction it was rotating...that would be
> > > somthing.
>
> You could make a paper disc that has a radial pattern of 3 repeating colors that
> the light sensor can distinguish... for example: red, blue, white, red, blue,
> white... Then by watching the pattern of colors that go by the light sensor, the
> RCX can determine what direction the disc is turning in.
>
> A variation on that theme: Suppose you printed out a little paper disc that has
> a radial gradient from white to black (gradual shift from white to black in a
> circle). If you put a light sensor in front of it, as it turns, you could
> sample the light reading every so often and subtract the sequential readings
> from each other. The difference would be either positive or negative. This
> would tell you in what direction it is turning. Also, if you sampled it at a
> high enough rate, you could use the absolute value of the difference to
> determine the degree of rotation... though this might be more difficult.
Nice idea, Karim. The gradient idea keeps it down to one sensor. If
you are willing to use two sensors, then the usual method is to add a
second photo sensor out of phase by half a slot. You interrupt when the
first sensor goes low (or high). The interrupt routine increments the
counter if the second sensor is high, and decrements the counter if the
second sensor is low.
--
Did you check the web site first?: http://www.crynwr.com/lego-robotics
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