RFID tags...How do they work?

Mr. Stein, how thoroughly have searched the Web? Have you gone to the sites of companies manufacturing RFID tags? Have you contacted them or their representatives?

With all the resources available that you have apparently not made use of, it appears you haven't done your homework, and you're asking for assistance too early, from the wrong people.

They work very well for something so small. A couple of months ago, I started setting off the theft prevention alarms in just about every store that had them. Walmart, Target, Kohls, Mervyns - you name it, I set off their alarm. Started to be annoying when I would be walking out of the store with nothing, and the security people would be looking at me like they were thinking whether to ask if I had anything in my pockets.

Took me a while to figure out what was setting off the alarms. I had bought a new leather checkbook cover recently. Hidden in bottom of one of the credit card slots was an RFID tag, paper-thin, and about 1 inch square. Took it out and no more dirty looks from the "loss prevention specialists".

Jerry

Jerry wrote in news:77d361e2-c03d-4a13-92f5- snipped-for-privacy@e10g2000prf.googlegroups.com:

I had a Hooter's refrigerator magnet in my pocket and the alarm went off;there's also a magnetometer.

--
Jim Yanik
jyanik
at
kua.net

Try having a look on Elektor magazine's website

Sometime last year as I recall, they did a feature issue on RFID with lots of articles on how they work. All articles are archived, searchable, and available for download - allbeit for a small fee, although I think you can get enough 'free' credits to download a couple, just by registering with the site (it's reputable, and this will not cause you to be bombarded with spam)

Arfa

On Tue, 12 Feb 2008 12:06:44 -0800 (PST) in sci.electronics.repair, " snipped-for-privacy@yahoo.com" wrote,

You can't repair them. If it's broke, you have to get a new one.

LOL! you are pointing out that this is a .repair group..

Mr. Stein, I'd help you out if I knew something abou these things, but it sounds like you understand them as well as I do. Active RFID's have a battery or power supply. IIRC Passive work by low frequency radio freq about

1hz to power the device by an antenna. It also detects it like this by some means. Semi-active devices? I have no clue. I'd assume that it is some sort of mix of the two. Maybe they store recieved energy by capacitance of some sort. I suggest checking wikipedia and howstuffworks.com

Mike

I don't see how they can be used for the purposes of identity. Say the sub-cutaneous implants for pedigree dogs. All you do is pass a scanner near the dog, obtain the code, buy a blank slug for a few cents/dollars , clone that one, and plant in your phoney dog or dogs. Then which is the genuine one?

-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on

They have a predefined identity code built in.

--
Regards:
              Baron.

Spoofing store anti theft systems is becoming entertainment. Walmart was/still uses the white plastic strip theft prevention. It is a simple device that tells when a strip of metal is magnetized inside the plastic. At the cashier, the strip passes a degausser in the counter. When you pass the largish loop detectors on the way out, they alarm on magnetized strips.

The spoofing comes in when people save the strips from purchases they made then walk into the store with a magnet in one pocket and strips in the other. They remagetize the strips and attach them to store patron's clothing or just shopping carts, then sit at the lunch counter and monitor the doors and wait for the fun to begin.

Disabling the devices is also becoming hacker entertainment. Pocket degaussers and a device to disable the fusible RFID tags - the ones that are just coming into use. They take the guts from a disposable camera flash (tons of those available) and mate it to a coil with an SCR trigger circuit. Hold the coil against the tag and discharge the cap and it is supposed to kill the RFID device.

They claim that the price is still too high on the tags to make them universal - I sort of doubt it. The ones I've seen look like a tiny blob of plastic with a larger loop antenna that appears to be printed on to the paper tag. With some ICs in the 20 cent range in quantity rfid should be dirt cheap in the quantities they anticipate using - especially with Walmart pushing it.

Our google groper needs to do a little research of his own.

I sliced open one from the back of a pack of batteries. Other than a nice source of ferrous shim of 0.03 mm or 1.2 thou/mil thick , not much in there. 3 such pieces , 2 the same length and one a bit shorter.

-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on

news:sci.electronics.design would be the appropriate newsgroup to ask this question.

--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida

You set off their biohazard detector with the chicken fat on the magnet. ;-)

--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida

No, he's correct. The magnetic thingee is not an RFID just anti theft. There are three very thin pieces of metal in there. Two of the strips appear to be mu metal (I'm guessing) and another magnetic iron.

These are "electronic article surveillance" tags, or EAS

I had the operation backwards. From what I'm reading the tag can be deactivated with a magnet and activated with a degaussing device.

The Electromagnetic (EM) system, which is dominant in Europe, is used by many retail chain stores, supermarkets and libraries around the world. In this technology, a magnetic, iron-containing strip with an adhesive layer is attached to the merchandise. This strip is not removed at checkout -- it's simply deactivated by a scanner that uses a specific highly intense magnetic field. (One of the advantages of the EM strip is that it can be re-activated and used at a low cost.)

I too set off the alarm at Walmart and the nice 'greeter' suggested that I may have a tag somewhere on my person that had not been deactivated .. like in my shoes. Sure enough, I found it embedded into a slot in the insole of my shoe. I now happily hop through the security antennas without the embarassing beeps.