Hey all. Does anyone know which discrete device can detect and decode pet microchips? I think an interesting project would be a detector near our cat door that would count the number of times each cat came in and out the door. I figure a small antenna around the door entrance (a cat flap) could query the device (I need to research that some more), then be able to identify the cat by at least the difference between the chip ID. If I can get to that point, then there are all kinds of possibilities, including controlling a cat flap lock that would only allow through our pets, etc.

Do you mean something like an RFID system?

Yes RFID for pets commonly called microchipping.

From petwellbeingblog.com

Microchipping

One of the more common forms of pet identification, microchipping consists of a tiny microchip that is roughly the size of a grain of rice. The microchip is embedded under the pet's skin that lies loosely around its neck. Each microchip is assigned a unique identification number that is then registered with a national database.

When a found pet is taken into a veterinary clinic or animal shelter, the staff will immediately scan the pet with a universal microchip reader. If found, the scanner will then reveal the microchip ID number and which database it is registered with.

The staff can then call the database registry to report the animal found. The database registry then contacts the pet owner.

From animals.howstuffworks.com

Microchip Companies Cite Irreconcilable Frequencies If you'll remember, a scanner uses radio waves to read the number encoded in a microchip. Just as you find your favorite radio stations by tuning into the right frequency, scanners need to be able to read the correct frequency to obtain this number. The problem is pet microchips come with different frequencies, such as 125 kHz, 128 kHz and 134.2 kHz. About 98 percent of the pet microchips in America use 125 kHz, whereas those in Europe use 134.2 kHz [source: USDA].

AVID plc Different scanners can read different frequencies. This is a picture of one of AVID's microchip scanners. In 1996, the International Organization for Standardization (ISO), headquartered in Switzerland, adopted the 134.2 kHz frequency for pet microchips in an attempt to solve incompatibility problems. However, the United States was already largely using the 125 kHz microchip, and critics pointed out that changing to the ISO standard would be difficult and expensive.

Even though universal scanners (also known as "forward and backward reading" scanners) exist that can read different frequencies, most animal shelters don't have these scanners. To make matters more complicated, companies that make microchips don't want this universal scanner to be compatible with their equipment. These companies want people to continue buying their scanners and microchips, so they make sure that only their scanners can read their microchips. They do this by encrypting the frequency at which the microchip is read. Through encryption, companies make it so only scanners with the correct algorithm can decode the radio signal emitted by the microchip. Crystal Import, a company that distributes ISO-compatible microchips even filed a lawsuit against the pet microchip companies AVID and Digital Angel claiming their tactics violated antitrust laws, seeking to force them to reveal the encryption code [source: O'Connor]

So the first problem would be identifying the frequency and then hopefully the chip is not encrypted.

I am trying to understand micro RFID for another project I have in mind, this one will benefit millions of people.

Ralph

@Mongo: Exactly.

@Ralph: Thanks for the useful information!

Initially it sounds like quite a lot of work for what I'd like to do. However, perhaps instead of trying to decode the ID of the chip, it would suffice to just be able to detect the difference between chips. If this difference can be boiled down to an identifiable pattern (without necessarily knowing the chip's decoded value), then the detector could tell which cat has passed through, which is more than enough.

The next step is finding out what is the mechanism which this RFID system uses. I'm guessing it's some sort of transponder, where the chip will respond to an interrogation of some sort by a radio, and if so, if there is a device which can provide the signalling and be able to receive the signal back.

Here is a RFID "skimmer" hack I just found, it gives the idea of what might be involved as far as sensing a RFID. It would need to be modified but for less than $100.00 using hobbyest components it certainly is interesting.

Ralph

Thanks, Ralph. I found this today:

http://www.embedds.com/rfid-reader-based-on-pic-microcontroller/

If someone can do it with a PIC.... :)