Subject:
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Re: Project WIRRL Update
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Newsgroups:
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lugnet.robotics
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Date:
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Wed, 23 Oct 2002 19:32:56 GMT
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Original-From:
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PeterBalch <peterbalch@compuserve.com^StopSpam^>
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Viewed:
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769 times
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I have used the Radiometrix BIM-433-F transceiver which is sold via the
usual elecrtonics catalogues. It's a 433MHz half-duplex
transmitter/receiver (34x23x8mm) at 56 UK pounds.
We tested it in a stone building and found we could just communicate at
9600bps at 25m going up and down stairs into the cellar, through doorways,
etc.
Cheaper (and smaller) radios are available. You can get a
transmitter/receiver pair for 13 UK pounds but my experience is that (with
luck) you get what you pay for. More expensive ones go further. And you can
take the manufacturer's claims of "up to 100m" with a pinch of salt.
I subsequently made a small radio-LAN system that would allow a dozen or so
"stations" to communicate. There was one central base-station and several
out-stations. A "packet" was passed between the base and each out-station
in turn with the usual checksums and retries. Occasional packets would test
for other outstations coming online. The whole of the packet switching was
done by PIC chips. Nothing unusual.
So, yes, it is possible and it will work within a building. My development
time was around 80 hours for the h/w and s/w.
But I've been doing h/w and s/w for decades. My guess is that someone at
school or university would take 10 weeks full time.
So, my advice is: forget about doing anything fancy. Just buy two
transmiiters and two receivers operating at different frequencies. Hook
them up using the direct connections I described in an earlier posting. You
might need to invert the sense of the transmit or receive lines. Use a
piece of straight wire (one-quarter wavelength = 170mm) as the aerial. If
it were me, I'd expect to have a working system within a couple of hours.
Life's too short to mess around with anything more complicated unless
you're being paid.
Good luck.
Peter Balch
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