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From: kilian@cray.com (Alan Kilian)
Subject: Re: IR BEACONS
Message-ID: <1993Aug27.141912.10966@hemlock.cray.com>
Lines: 43
Nntp-Posting-Host: gopher
Organization: Cray Research, Inc.
Date: 27 Aug 93 14:19:11 CDT


Here is what I would do:

1) Take four 74LS193 4-bit preloadable counter chips and set them to
   count down.
2) Take the borrow from the high-order bits' counter and connect it to the
   count-down input on the next lower chip like this:

    Bits      Bits      Bits      Bits
   15-12      11-8      7-4       3-0
   +----+     +----+    +----+    +----+
   |    |     |    |    |    |    |    |
   |    |     |    |    |    |    |    |
   |   B|---->|D  B|--->|D  B|--->|D  B|------->
   |    |     |    |    |    |    |    |        |
   |    |     |    |    |    |    |    |        |
   +----+     +----+    +----+    +----+        |
     ^           ^        ^         ^           |
     +-----------+--------+---------+-----------+
         "load" lines


3) Take a 16 bit dip switch and connect them to the "load" lined on the chips.

4) Then connect an LM555 chip to be an oscillator of whatever duration you like.

5) Connect the output of the last '193 to a flip-flop and then to an IR LED.

What you get is an IR pulse that has a duration of your 16-bit value.

Your reciever can either count the time the pulse is on or the time it
is off and it can get the 16-bit value from that.

You can use a 40 kHz oscillator triggered by the Flip-flop if you want
to avoud problems with ambient light. Then your reciever would take the
output of one of those Sharp IR reciever modules that Radio Shack sells.

You could use 8-bit counters ot 16-bit counters also.

                -Alan "I'm just full of it. (Ideas that is)" Kilian
-- 
 -Alan Kilian           kilian@cray.com 612.683.5499 (Work) 612.721.3990 (Home)
"The cartesian coordinate system is racist, sexist and opressive" -Joan@Siggraph
