Help me invade my cats' privacy

December 2, 2005 10:02 PM

RFID cat door: how hard can it be?

I have an electromagnetic cat door. The magnets are big and bulky and have to point in the right direction and they're outrageously expensive to replace. Are there any reasonably priced RFID kits that would let me glue a couple of RFID tags to my cats' tags, with a detector built to simply act like a switch that I could wire straight into the existing door's circuit? (Yes, I understand I'd likely have to up or down the voltage and current going in and out of the detector unless by a massive coincidence it was happy with the 9V/whatever amps the existing circuit uses.)

(A commercial RFID pet door doesn't seem to be available yet, despite how obvious that is...)

posted by Zed_Lopez to Home & Garden (16 answers total)

Sonmicro sells a development kit for $86. SkyeTek sells some also.
posted by hooray at 10:19 PM on December 2, 2005

... glue a couple of RFID tags to my cats' tags ...

Don't have an answer for you, but I thought I'd point out that your vet will probably RFID-tag your cat (internal to its body) for you. In which case, they can identify the cat as yours if it ever gets lost, plus you can read the ID in your cat-door invention.
posted by knave at 11:23 PM on December 2, 2005

Not sure if that will work. I thought they implanted those in the flesh above the shoulder blades, where the animal can dig at it. They put the magnets/tags in the collar because when the animal walks up to the door, this brings their head and the collar close to it. If the tag is further down their back, it might not get close enough to the sensor.

Maybe so, on the other hand. Couldn't say.
posted by scarabic at 11:42 PM on December 2, 2005

Hah, check this out! "With Software (purchased separately) you can ... Automatically open a 'pet door when your pet approaches the door." At $299, it's not exactly cheap though!
posted by knave at 11:54 PM on December 2, 2005

Seems to me that just using a regular cat door would be cheaper and easier.

However, I do understand man's desire to complicate life =)
posted by mmdei at 11:59 PM on December 2, 2005

There's a guy who set this up with a webcam rather than RFID. Google for that. Apparently it's not too hard to write software to distinguish a cat's profile from a raccoon's.
posted by orthogonality at 12:00 AM on December 3, 2005

I was asking about an RFID cat door the other week, and was told that they do exist. I don't have a brandname or a link or anything though, just what I heard (it came from a vet's assistant though).

Now if there was some way for the cat door to NOT open if the RFID-authorised cat had a non-RFID-authorised not-quite-dead rat in its mouth, that would be something! :-)
posted by -harlequin- at 12:16 AM on December 3, 2005

mmdei:
"Seems to me that just using a regular cat door would be cheaper and easier."

Yeah, our neighbours tried that. They now have an oh-so-cute-but-damn-that's-embarressing photo of our cat, uninvited, fast asleep in their laundry basket after having gorged himself out of their cat's bowls. Oh dear.
posted by -harlequin- at 12:19 AM on December 3, 2005

Try Pet Doors USA, Inc. or Catflap.
posted by caddis at 1:14 AM on December 3, 2005

Response by poster: mndel, I chased raccoons out of my house a couple of nights ago. (And it wasn't their first visit; just the first time I caught them.) And the magnets don't fit on breakaway collars that I know of, and we've lost one (one cat managed to lose her collar), and they gouge on the replacement costs. All in all, I consider it a clumsy solution. If it worked well, I'd stick with it.

I saw SonMicro's kit, hooray, but it's not remotely clear to me how I could turn it into a stupid ol' on/off switch. As a hardware hacker, I make a pretty good programmer -- and that's even before you take into account my sucky soldering -- that's why I was hoping to work with something expliticly set up to be a switch.

I've seen Flo Control, but was hoping for something less elaborate.

Thanks for the tip, caddis -- I hadn't seen IR cat doors.
posted by Zed_Lopez at 5:01 AM on December 3, 2005

The IR looks like a good option, but if you still want to try RFID Parallax is now selling an affordable receiver that is a piece of cake to integrate with a microcontroller. $39.
posted by ctp at 9:57 AM on December 3, 2005

Now if there was some way for the cat door to NOT open if the RFID-authorised cat had a non-RFID-authorised not-quite-dead rat in its mouth, that would be something!

...you mean, like this?


posted by Jairus at 11:25 AM on December 3, 2005

I am not sure whether that RFID Parallax board will suffice, as it appears the range is only about 2 1/2 inches. Greater range on passive tags is where the money is in RFID antennas.
posted by caddis at 12:03 PM on December 3, 2005

Response by poster: I don't see why 2.5" wouldn't suffice for this -- they have to be closer than that for the current electromagnetic switch to throw.
posted by Zed_Lopez at 4:44 PM on December 3, 2005

A normal walk through the door won't reliably get the cat's neck anywhere near 2 1/2 inches from the door or perhaps a sidewall with the antenna. If perhaps you could train the cat to rub its neck against an antenna mounted on a sidewall to get the door to open then perhaps it would work. I am not sure that would be a trivial task. A six to nine inch range would seem to be a practical minimum. A cat's nose is about three inches from its neck, and you would like some margin of safety, to account for bad readings, a cat who blocks the sensor by dropping its head (which would seem normal for pushing a door open with the head), etc.
posted by caddis at 7:21 PM on December 3, 2005

your vet will probably RFID-tag your cat (internal to its body) for you. In which case, they can identify the cat as yours if it ever gets lost, plus you can read the ID in your cat-door invention.

This microchip is (a) small and (b) would not be very close to the door (relatively speaking) when the cat tried to enter. And being small, it requires a more powerful (aka more expensive) RFID reader.

The question of reading distance isn't trivial - the proposed RFID-tagged U.S. passports were, in the original version, readable at more than 4 inches without using very powerful equipment (and stored information wasn't encrypted), which posed a significant security threat (as in, "pick out the American in the crowd").
posted by WestCoaster at 8:32 PM on December 3, 2005