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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Tue, 29 Dec 1998 19:06:35 GMT
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Viewed:
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1154 times
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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.
The big trick here would be to write code to account for the large value shift
when the disc passes from white to black or black to white, as both the
difference and the sign will give erroneous readings at this point.
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