Subject:
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IR concept
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Newsgroups:
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lugnet.robotics.handyboard
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Date:
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Fri, 28 Mar 1997 21:12:04 GMT
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Original-From:
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Adam <ADAM@RING.ZENOX.stopspamCOM>
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Viewed:
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1470 times
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An alternate IR system....
I've been scanning through some of the IR stuff to see if
I can't pick out a good solid system for collision avoidance
on a short range (approx. 6-10cm) scale, but everything seems
like alot of trouble.
Some guys at Humber (where I currently am studying Computer
Engineering) have let me in on their methodology. It's pretty
good (effective and simple).
The basic concept envolves an IR diode and transistor with the
transistor running through a darlington pair to increase sensitivity
before picking up the signal via an analog hookup on the HB.
You say: "What about noise?" Ahhhh....
The magic is in the code. You see the IR diode is hooked up to
a triggering device through a transistor (either an onboard digital
output from HB OR and offboard ascillator ie. 555 timer)
Onboard method:
Take a reading from the IR transistor (call this noise)
Now, turn of the IR diode and take another reading.
Find the difference in the readings and you have a signal
with ambient effects eliminated. This has been tested and
prooven.
Offboard method:
Instead of feeding a signal to turn on the diode, use a 555
set up to oscillate the diode and take the same signal to a
digital input on the HB. When the signal (from 555) is low
(diode OFF) read transistor for noise. When the signal is
high (diode ON) read for IR emmission+noise. The difference
in the readings will give you the real data.
The darlington pair is simply 2 2N4124 and a few resistors.
The key device is the sensor. Not sure of the part no. right
now, but I'll look it up. The while system could be built for
under $10. A good ranging system such as this would run about
$35 dollars as sold by Infusion Systems.
I'm curious to know what others have to say about this approach.
Thanks.
----------------------------------------------------------
Adam B. Cox check out my web page
Computer Engineer http://www.zenox.com/~adam
Zenox Communications Corp. vmail: 416-241-7000 (x224)
----------------------------------------------------------
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Message has 2 Replies:
 | | Re: IR concept
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| In addition.... Perhaps I could use the on board IR header to turn on the 4 IR diode array with each diode in series with a current limit resistor and in parallel with the IR output header..?? (I think this has been suggested before.) (...) (27 years ago, 28-Mar-97, to lugnet.robotics.handyboard)
| | | Re: IR concept
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| (...) [Digitize the output from an IR LED with and without a signal present to achieve some common mode noise rejection.] This type of system is susceptible to being 'blinded' by high intensity IR sources (try it outside :-) I used a similar (...) (27 years ago, 29-Mar-97, to lugnet.robotics.handyboard)
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