Subject:
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Re: IR sensors
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Newsgroups:
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lugnet.robotics.handyboard
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Date:
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Tue, 3 Aug 1999 22:59:09 GMT
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Original-From:
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jf <jfourier@netcom^StopSpam^.com>
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Viewed:
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2228 times
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I've been using the Miniboard to send and receive IR messages among
other things. I find that the board is right on the edges of being
fast enough to generate the 40KHz carrier and thus, I don't use it
that way. Rather, I use the Miniboard to control, basically turn on
and off an auxiliary circuit, either a 555 or a 4060 w/ceramic oscillator,
which then runs one or two IR LEDs through a simple transistor circuit
at pretty high, but non-steady, amperage, say 1 A, 1.5 A.
We took apart a commercial remote and found that the current limiting
resistor was very small thus the amps going through the IR LED were
pretty high.
Be mindful (Jedi saying) that I am not an authority on all this,
but merely have had some experience.
My method of IR reception (please post if you come up with another)
is to use a slight variation of the circuit that comes with those
Sharp (or Radio Shack---their website might have it still) modules
and hook it to the Pulse Accumulator. Pulses can be long or short
with spacing in between. The Pulse Accumulator measures the pulse
lenght and discriminates between Noise, Short Pulse and Long Pulse.
It also starts a OC interrupt upon the reception of each pulse,
which can also be stored. When the OC interrupt kicks in, an end-of-message
is assumed. That is, if there is a pause after a bunch of pulses,
then that is considered the end of a message and parsing or whatever
is done.
I find that I can exchange msgs pretty well between two stationary
positions, but that movement makes for unreliable reception.
I'm using the msgs for timing, so fast receiver action is needed.
However, for usual IR remote type applications, or non-time-critical
uses, schemes can be implemented to increase robustness.
I'm still working with the stuff, so if more details are needed, post
again.
jfourier@netcom.com
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