Subject:
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IR
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Newsgroups:
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lugnet.robotics.handyboard
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Date:
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Thu, 22 May 1997 13:30:26 GMT
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Original-From:
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Fred Cass <fcass@SAYNOTOSPAMnextwavetel.com>
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Viewed:
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1539 times
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Hello all,
I've been playing with IR proximity sensors, and wonder if anyone can
provide some suggestions.
I hooked up an IR LED (Radio Shack 'high output IR LED') to the
Handyboard's IR output with a 330ohm resistor in series (the smallest
value resister I had on hand) . And I use poke(0x1000,0x40) to turn it
on (I think that's what I used)...
I ordered a bunch of IR detectors from Jameco, of the 32kHz variety. I
ordered those to try and set up Keith Soldavin's IR multiplexor. I
would imagine those wouldn't work well with the IR LEDs described above
since the Handyboard modulates 'em at 38kHz.
So I also bought a couple of the Radio Shack 38kHz detectors.
First I tried testing them by turning on the IR output (checking with
camcorder to see if working - ok), then loading HBTEST.C and running
Testdigitals();. Well after a while of testing, I came to the
conclusion that since testdigitals(); was so full of delays from waiting
for the LCD screen to update, I was missing most of the hits. So then I
wrote a quick program that played a tone (tone(440.,.03);) whenever the
port was on, and then I got tons of readings.
Ok, let me finally get to my point here. :)
1. I had a very difficult time getting any consistent reflectance
readings. Does anyone have any suggestions for perhaps setting up the
emitter/detector so that the detector only sees the reflection, and
misses a lot of the noise? One thing I noticed happening was that it
seemed to detect motion rather than just the straight reflection (in
other words, it wouldn't detect anything unless I moved it quickly in
front of the emitter/detector. If I stopped moving, it stopped
detecting. Could this mean that the detectors really aren't 38kHz?)
2. Is there any way to change the frequency of the IR output so I could
use the 32kHz IR detectors? If not, no big deal, I'll build Keith's
circuit which is set up for 32kHz....
Thanks for any input,
-=Fred Cass=-
fcasshb@usa.net
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