Subject:
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Light sensor
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Newsgroups:
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lugnet.robotics
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Date:
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Wed, 1 Mar 2000 19:06:13 GMT
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Viewed:
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1012 times
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Continuing to experiment with the Radio Shack CDS cells, I have found they
are all unique, even those that have the same identical appearance often
have radical differences in response. It is worthwhile to check each one.
I made a special light sensor to detect light sources from a carefully
tested CDS cell. I put it inside a 2x2 brick looking out through a hole
in the side, and with two 1x2 single hole beams in front of it making
a tunnel. This seems to have the predicted acceptance of about 15 degrees
or so. I painted the inside of the holes flat black and glued everything
together on top of a 2x4 plate. I used black parts. This time actual
testing was quite satisfying as the range and performance was about as
expected.
This sensor is to allow one robot to follow another or home in on a light
source. Light is tricky to work with since the human eye adapts so fast.
I have been using an old photographer's light meter to try to get some
real data on light levels. You certainly see the D-squared losses with
a sensor like this as you back off a light source, but it still can
detect the minimum when pointed about inside with limited room lighting.
The ultimate solution to light sensors probably involves a powered op amp
that is gain adjustable with a little screwdriver pot.
---
PS: I called S@H to order the Mars set, it is available and shipping, but
the ultimate expansion set they now say can be backordered for May. Also
it looks like some of the special parts in the ultimate expansion set are
used in throwbot kits available for about $7 each. There is also an
interesting part used as wheels on something called the Catapult Crusher.
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