Newsgroups: comp.robotics
Path: brunix!news.Brown.EDU!qt.cs.utexas.edu!cs.utexas.edu!sdd.hp.com!caen!uvaarpa!vdoe386!norfolk!fculpepp
From: fculpepp@norfolk.vak12ed.edu (Fred W. Culpepper)
Subject: Re: Looking for low-cost wireless data link
Message-ID: <1993Feb16.005022.24232@norfolk.vak12ed.edu>
Organization: Virginia's Public Education Network (Norfolk)
References: <C2AyAu.J35@world.std.com>
Date: Tue, 16 Feb 93 00:50:22 GMT
Lines: 42

Stuart J Adams (sja@world.std.com ) writes:
> d Public Access UNIX, Brookline, MA
> Date: Thu, 11 Feb 1993 20:59:17 GMT
> Lines: 18
> 
> I am trying to find (build/buy) a low-cost wireless data link to connect
> a robot to its host computer. I only need 1200 baud (or better) and a
> hundred feet of (indoor) range.  I have talked to commercial vendors
> that sell spread-spectrum (unlicesed) wireless modems which are perfect
> except very expensive (over $2000).  Also, packet radio is possible
> but required an FCC license, is not particlularly cheap, and has
> latency problems.
> 
> I was wondering if I could use low-cost (kids) walkie talkie's with
> an FSK modulator-demodulator (or maybe a 1200 baud modem) to send/receive
> data over a short range ???
> 

Well, I had a similar problem and didn't see any need to spend
a lot of money for something this simple, so I built a low
power (within FCC limits) modulated oscillator and sent my
instructions to the robot through the code within the
modulation.  I made the transmitter so it would work within the
(AM) broadcast band and then used the audio output from a $5.00
transistor receiver for my data link to the robot.

Admitted, this was not a two-way link, but it was effective for
my need.  The robot was demonstrated within the high school gym
and I simply made a transmitting antenna by running a section
of magnet wire around the walls of the gym.  

To be sure I was not creating interference for which the FCC
could be rather angry, I tried to receive the signal outside
using my automobile radio.  At 10 feet from the gym wall, the
signal vanished into the background noise.

Very effective - very cheap!  Somtimes these are the best
solutions.

Fred W. Culpepper
OLD DOMINION UNIVERSITY (Retired)
fculpepp@norfolk.vak12ed.edu
