From: wb9omc@dynamo.ecn.purdue.edu (Duane P Mantick)
Subject: Re: Long distance IR detection
Organization: Purdue University Engineering Computer Network
Lines: 44

sburton@dres.dnd.ca (Stan Burton) writes:

>I would like to be able to detect the angular position (low accuracy) of an
>IR emitting source at a distance of about 100 meters (more is better) in
>daylight.  The IR source could be emitting a signature; I'm leaning toward
>30 KHz square wave with 50% duty cycle.

>I am considering the use of a quadrant detector from Centronic Inc. to give
>information to a pan/tilt head to point the sensor and thus determine the
>angles.  For the source I am considering wazing the heck out of an IR LED(s),
>possibly an Optek OP290 or Motorola MLED81.  Wazing would mean at least 1 Amp
>current pulses.  At this current the duty cycle of the LED drops to 10% and I
>would need to cycle five of them in turn to get the 50% required.

>Has anyone done something like this?


	Yeesh, you WILL be nailing those IRLEDs.  May I suggest getting your
mitts on the Siemens SFH484-2 IRLED?  This unit is designed to take some big
current pulses if you can get your duty cycle down a bit.  It will output
nearly a watt (975 mW) with REAL short duty cycle times.

(nice thing about the SFH484-2 is that it is CHEAP.  I got mine for about
50 cents a piece, even though I had to buy 100 of them....)

	BTW, I have seen IRLEDs with outputs up to 6 watts...honest,
6 WATTS.  I don't have the book here at work so I can't recall the company
name.  The 6 watter ain't cheap, around $108 but if you want some power,
mamamia, that's pretty hot.  They also have a 4 watt, a 2 watt and a
1 watt device in their line, and will sell small quan. to individuals.
If you are interested, I can find the book at home and get the
pertinent info.

	Now, as for the position detector, you might try ELTEC in Florida.
Phone number listed in the 92/93 ETID is 904-253-5328.  They seem like 
nice people.  Their specialty is passive infrared detection devices,
so they might be able to help you out.

	I'm curious about your applications if you don't mind saying.
The device sounds like it could be useful in a lasertag game, although you'd
need to up your carrier signal concept to 58.8 KHz......

Duane

