Newsgroups: comp.robotics
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From: sarge@Rational.COM (Matthew C. Sargent)
Subject: Re: IR receivers
Message-ID: <1994Jan14.171849.19539@rational.com>
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References: <1994Jan12.112948.14172@news.cs.indiana.edu>
Date: Fri, 14 Jan 1994 17:18:49 GMT
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Ingo Cyliax (cyliax@cs.indiana.edu) wrote:
: In article <CJ83IL.Isn@ariel.cs.yorku.ca>,
: KEN E WILLMOTT <cs911225@ariel.cs.yorku.ca> wrote:
: >cmcmanis@pepper.Eng.Sun.COM (Chuck McManis)
: >says:
: >
: >>So I've been playing around with some Sharp IR receiver modules, in particular
: >>the GP1U52X and the ISU160. The latter is available from Pure Unobtanium and
: >>is, in my opinion a significant improvement. (no metal box, 1/6th the volume,
: >...
: >
: So what kind of performance are you seeing using these parts ? I have
: been playing around with the Radio Shack version (after removing the
: metal can). I use a 555 to generate carrier and drive a 100mA IR LED
: at about 200mA with a duty cycle of probably around 30%. For a test
: signal I 'modulate' the carrier with a 4Khz signal. Using a scope,
: I look at the output of the detector which should be a 'clean' pulse
: train that looks like the input signal. I haven't had much luck going
: above 4Khz. At this frequency ration (10:1) there are only aprox. 5
: cycles of on-time, it's amazing that the detector can even lock on
: to this, they most definately do not use a PLL.

: Anyway, after 'tuning' the carrrier frequency to get the 'best' output
: signal from the detector (the freq. seems to be critical), I still get a 
: clean output signal at about 18 feet or so. Above 20 ft., the detector
: seems to not be able to detect the signal. I think this is pretty
: reasonable, considering that I haven't done anything special with the
: transmitter, like increase the power level or use multiple LEDs. I
: also don't use any lenses or dispersion filters, except what's already
: in the LED and photo transistor.

Could you post the parts for your setup? I have tried this experiment and
I can rarely get more than 3 feet from the detector. 


: I do seem to get get very repeatable performance using 555 timers as
: oscillators even after power cycles and long off times, indicating that
: the frequency stability is sufficient for this application. I have not
: tested several IR detectors to see how much the center freq. varies between
: units.

: I would be interested in finding out what kind of free-space IR link
: performance people out there are measuring. I'm mostly interested in
: 'high-speed' links but we also have an application here that would use
: 'simple' (2 channel at low-bandwidth) over IR.

: Thanks, -ingo
: -- 
: /* Ingo Cyliax, cyliax@cs.indiana.edu, +1 812 333 4854, +1 812 855 6984 (day) */

--
=============================================================
| Matthew C. Sargent         |  My opinions are my own. Any |
| sarge@rational.com         |  similarity between them and |
|                            |  other opinions, living or   |
|                            |  dead, is accidental.        |
=============================================================
