TI-H: Simple IR link

To: ti-hardware@lists.ticalc.org
Subject: TI-H: Simple IR link
From: Andy Johnson <prjohnson@utahlinx.com>
Date: Sat, 08 Aug 1998 19:54:39 -0600
Delivered-To: ti-hardware-outgoing@towerguard.unix.edu.sollentuna.se
Reply-To: ti-hardware@lists.ticalc.org


I was thinking of a way to make a simple IR link, using RadioShack parts.
Here's what I came up with.  Unfortunately, it requires the use of custom
software, but that isn't much of a problem.

I used a 555 to generate a 40 kHz carrier, controlled by pin 4 on the chip,
then ran the output through a transistor into an IR Led.  The receiver is
just a GP1U52X (RS 276-137).  I'm not sure about the electronic
characteristics of the linkport, but that shouldn't be a big problem to
fix.  I've only used one of the calc's wires on each end, allowing one to
be used as transmit and the other as receive.  If timing is a problem, the
driver software can use transitions instead of pulses (1-0 = 0, 0-1 = 1,
you get the idea).  I expect the speed to be around 1200 bps, and range to
be about 10 ft, but lenses and high powered LEDs could fix that.

I've posted the schematic at
http://www.utahlinx.com/users/prjohnson/IR_link.gif Please excuse the
sloppy drawing, and tell me what you think.
--
Andy Johnson <prjohnson@utahlinx.com>

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