Subject:
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Radio Shack CDS cells in parallel
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Newsgroups:
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lugnet.robotics.rcx
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Date:
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Tue, 8 Feb 2000 20:04:29 GMT
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Viewed:
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1589 times
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When I first checked out the Radio Shack CDS cell five packs, the
cells were all alike, about 1/4 inch and flat on two sides. But
when I went back, I found some packs that had different cells.
They had three of the usual small ones and a 1/2 inch one that had
an excellent resistance range and a very large metal cased one that
had a horrible super low resistance range, perhaps defective.
I tried this idea and it worked. You can put several of the small
higher resistance CDS cells in parallel to partially adjust their
resistance and response range.
I made one down looking sensor with the 1/2 inch cell that is very
nice. I made a companion sensor with four of the small CDS cells
in parallel. I selected 4 after a lot of testing with an ohm meter
using the room light indoors during daytime, going from shadow to
full window sunlight, looking for a decent resistance range.
This 4 cell sensor is made on a 2x2 brick with two of the cells on the top
surface, leaving two studs surviving, and one each on the left and
right sides with the wire coming out the back. It specifically does
not look down or forward, as it is designed to be an ambient light
sensing sensor. It is quite sensitive and does well in regular
indoor light. Three sensors might have been a better parallel combination
and positioning all the wires to get the four sensors in parallel
and soldered to the output wires was a bit tricky inside the
brick. I left the center post in the brick for strength.
This is similar to what is called a "global insolation" sensor designed
to be flat and measure all light from the sky.
The idea of using several of the higher resistance CDS cells in
parallel to adjust the light sensing range does seem to work. And
a pair of the smaller Radio Shack CDS cells do fit nicely on top of
a 2x2 brick. You can even manage to save two functioning studs on
top of the brick if you are careful.
I have tested it on the ohm meter and tonight I will check out its range
with the RCX. I have been using the downlooking sensor with the sensor
set to touch and percent modes which seems like quite a nice configuration.
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Message has 1 Reply:
 | | Re: Radio Shack CDS cells in parallel
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| (...) I built a sensor out of one of those and it works fine, so yours is probably defective. I superglued mine to the top of a 2x2 brick with the studs removed. You can see my high tech design at (URL)I tried this idea and it worked. You can put (...) (25 years ago, 8-Feb-00, to lugnet.robotics.rcx)
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