[aprssig] APRS RFID apps? (spec rev4)

Robert Bruninga bruninga at usna.edu
Thu Feb 18 12:31:14 CST 2010

RFID works!

I got my reader in the mail yesterday, wound a 4.75 inch 58 turn
coil and get detections out to 8 inches.  Also found it easy to
tune the coil, by overwinding and then removing turns until you
get max range.

Photos of my completed unit in a few hours after the final glue
dries.  All it is is a coil, a 9v battery, and then postage
stamp size reader module.. Then just two wires of 9600 baud
RS232 back to the PC... Done!

But I have to revise the spec.  There is only one single Serial
data output per card and the card has to be removed and
re-swiped to get a second reading, and the readings have to be
at least 1 second apart.  Thus we cannot detect the three states
of the foot on the HotSpot (passing, stepping, and standing).
I'm going to leave them in the spec in case we later figure out
a way to do it.

An interesting aside is that this makes a nice pocket scanner.
Even without a PC.  The module has a LDE output.  So in
something the size of a cigarette pack in your pocket you can
"sniff" for RFID tags anywhere.  When the LED lights, it has
seen a tag.  Hook up a beeper and you can get beeps!


> -----Original Message-----
> From: aprssig-bounces at tapr.org 
> [mailto:aprssig-bounces at tapr.org] On Behalf Of Robert Bruninga
> Sent: Friday, February 12, 2010 2:17 PM
> To: 'TAPR APRS Mailing List'
> Subject: Re: [aprssig] APRS RFID apps? (spec rev3)
> I have updated the RFID web page:
> http://aprs.org/aprs-rfid.html
> Including a picture of a $4 door mat that I spray painted to
> look like an APRS RFID HotSpot.
> I also updated the spec slightly to use the !DAO! High
> resolution format so that we can actually form the list of
> people that enter a room to actually be listed in that room
> you zoom in close enough).
> I also made the on-air format into an Experimental packet so
> it is compatible with all existing APRS..
> Bob, WB4APR
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> aprssig at tapr.org
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