Newsgroups: comp.robotics
Path: brunix!sgiblab!sdd.hp.com!news.cs.indiana.edu!cyliax@cs.indiana.edu
From: "Ingo Cyliax" <cyliax@cs.indiana.edu>
Subject: Re: IR receivers
Message-ID: <1994Jan12.112948.14172@news.cs.indiana.edu>
Organization: Computer Science, Indiana University
References: <2gcf1e$i2c@handler.Eng.Sun.COM> <CJ83IL.Isn@ariel.cs.yorku.ca>
Date: Wed, 12 Jan 1994 11:29:44 -0500
Lines: 44

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.

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) */
