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[aprssig] APRS RFID reader?

Robert Bruninga bruninga at usna.edu
Mon Feb 1 22:37:01 UTC 2010


> The setup I have for race results is self contained 
> with ethernet and usb to computer.. I find around 
> 90% read  success of runners passing through the 
> read area.

What is that read area?  With say a reliable 6 inch read range,
I would think that for a 3 foot wide door mat, one would need
about 6 separate readers probably spaced a foot apart in two
rows.  Each of these I assume has its own "reader" electronics
which really drives up the cost from one $30 reader, to 6.  I
wonder if we can just diode-OR the 9600 baud outputs.  Seems
only ONE would make a detection at the same instant.  Especially
if we spread them out in the direciton of the walker...

I have updated my web page www.aprs.org/aprs-rfid.html to show
the new APRS boots idea...

Bob, WB4APR
> >
> > Robert Bruninga wrote:
> >> I still think APRS-RFID... Is a next thing for APRS
> >> experimenting
> >>
> >> Every ham hat could have a $2 chip in it.
> >>
> >> Then we can tell who enters the clubhouse or EOC... (it
gets
> >> converted to APRS...)
> >> See http://www.aprs.org/aprs-rfid.html
> >>
> >> Problem is, the maximum range reader I can find is only
good for
> >> 10 inches max and it costs about $24:
> >>
http://www.sparkfun.com/datasheets/Sensors/ID-12-Datasheet.pdf
> >>
> >> It has provisions for a  wind your own antenna but still
can
> >> only get to about 10 " (25cm).  But since hams are RF
> >> experimenters, it would seem that we could improve on this.
One
> >> sentence in the limited docs says that there has to be
enough
> >> energy to activate the chip.  This implies to me that the
limit
> >> is on the energy transmitted to the chip, not necessarily
the
> >> read range.  Frequency is 125 KHz.
> >>
> >> To get reliable coverage for people walking through a door,
I
> >> think we need about 48" range...
> >>
> >> Does anyone want to fill us in on the details?  I assume a
125
> >> KHz carrier in the antenna coil provides the energy for the
RFID
> >> chip (this can be scaled up... Just needs more power)...
But
> >> then I guess it has some off cycles so the chip can send
back
> >> the 32 bit code?
> >>
> >> Bob, WB4APR
> >>
> >>
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> >>
> >>
> >
> >
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