Consumer RFID tag information

[polymorf]

Can anyone point me to any sites that get down and dirty on the inner workings of RFID tags in consumer products? It seems to be relatively simple, and I eventually want to construct a handheld device that would alert me to the presense of nearby RFID tags. Some possible uses of RFID do bug me, and I'd rather not trust companies to tell me whether their products include RFID devices; I'd definitely want to know for myself.

I think I was reading somewhere that the devices that actually do the reading are what illicit a response from the RFID tag. If that's the case, I can't merely build a sweep-type device that looks for emissions from the tags, because there would be no emissions until the reader caused them to respond. This makes sense, since a tag emitting a constant signal would need to be powered, or it would have a very short lifespan.

If anyone cares to break it down for me right here, that's fine too, but links are what I'm looking for. As for the device itself, I plan to keep it simple: one LED for each known frequency, which illuminates when a tag using that frequency is found in a very close range (within 2-3 feet or so). Of course, if such a device already exists with this exact capability, I'd probably just buy it, but it seems to me I could probably save a little cash a learn a little by building it myself. I was always inclined to write programs and create simple devices for myself whenever possible.


Thanks in advance!
pm

 

[dingo]

RFID tags

Works on radio freq to charge a cap inside the tag then the tag transmits its ID back. Range and interference is always a problem for 2 - 3 feet you are looking at high end security access reader or a gate system that shops use. Do google search on RFID, RF anti theft tags.

If you want a 2nd hand system try www.sitebuys.com

As the radio freq charges the cap you need to be one the right freq for it to work, your hand held will only pick up tags that will respond to that freq so unless you scan the whole spectum including microwave you cannot be sure that there is not a working tag present.

 

[laroche73]

passive RFID info

MicroChip has a pretty good collection of app. notes on the subject, you might start with this one:

**broken link removed**