Finding lost keys

[tmetro-blu-5a1Jt6qxUNc at public.gmane.org (Tom Metro)]

Doug wrote:
> ...there is an RFID FOB thing on my keychain for the gym.  Is it
> possible to find the FOB with some source of radio
> transmitter/receiver thingie?

I've considered this sort of thing myself, because they would offer some 
advantages over traditional key finder devices:

-RFID tags are cheap, so it would be economical to attach them to dozens 
of items, not just a few high-value items, like your keys.

-each tag has a unique serial number, so in theory you could walk into a 
room with a scanner and instantly get an inventory of all your tagged items.

-they don't use batteries. One less battery to change every few years.

-they're smaller than typical RF key finder devices.

I've suggested this approach to one of the small manufacturers of key 
finders. Probably something they had already considered. I didn't get a 
response, but I suspect...

Building the detector is probably not cost effective currently. Or it 
would have impractical physical proportions. The challenge is that you 
need to transmit enough RF energy to the tag in order for it to power up 
and send back a reply. To cover a large area that either requires a 
large antenna or scanning the space with a small antenna within inches 
of the tag.

Supposedly the shipping industry does have systems that can read RFIDs 
from a pallet of merchandise, but I believe they use rather large 
antenna loops to accomplish that. Probably with a diameter measured in 
feet. And even then, I suspect it wouldn't cover the square footage of a 
typical residential room.

I believe the hand-held reader guns, that you might have seen, have 
rather short range, and the people tracking RF tags (the kind you use to 
locate where someone is in a building; not the kind that you wave near a 
reader to open a door) used in some businesses and universities are 
probably actively powered.

I imagine if you wanted to install a loop of wire in each of your rooms 
(say tucked under the crown molding), you could build your own working 
system. :-)

  -Tom

-- 
Tom Metro
Venture Logic, Newton, MA, USA
"Enterprise solutions through open source."
Professional Profile: http://tmetro.venturelogic.com/