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Cat detector!

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hairyjon

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My poor old grey domestic tabby cat, now16 years old, is getting thoroughly fed up with neigbourhood cats coming in through his catflap. I've tried magnetic collar operated flaps but he doesn't like the weight of the magnet round his neck. I had thought of constructing some circuitry for a barcode reader to read his tabby markings! Anyone got any ideas?:eek:
 
I have the same problem and was thinking along the lines of a cat scanner except one of the interlopers looks very similar to ours, maybe pawprint access using a biometrics reader as on those fingerprint USB keys
 
Hi Paul. Good thought. It would have to be fast acting though 'cos even at his age he comes through it like a bullet out of a gun when his enemies are about!:)
 
Actually our cats have a RFID chip implnted so a RFID reader near the door should work
 
Paul Obrien said:
Actually our cats have a RFID chip implnted so a RFID reader near the door should work
Sounds good but please explain what an rfid is:confused:
 
RFID is radio frequency ID tags. You know at the bookstore sometimes they have that piece of paper between the pages of the book with metal tracings on it? It's to sound the alarms if someone takes the book out of the store. They also come in bulkier plastic encased versions that stick to clothing and such

The tags emits a low power (close range) radio signal to a nearby receiver. Active RFID tags require batteries and have longer range than passive RFID tags (but you want minimum range in this case, so that two minuses). Passive tags do not require batteries. The base station transmits a low power, close range radio signal which is then reradiated by the tag along with a unique radio signature or some other information.. They are powered by the incoming base station signal so they need no batteries. It should be very effective...weighs no more than a piece of paper. Should be more effective than even the magnetic collar.
 
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dknguyen said:
RFID is radio frequency ID tags. You know at the bookstore sometimes they have that piece of paper between the pages of the book with metal tracings on it?

It emits an (close range) radio signal to a nearby receiver. Active RFID tags require batteries. Passive tags do not. They use the radiated energy from the signal of the receiver and bounce it back. SHould be very effective...weighs no more than a piece of paper.
Hi dknguyen. A passive tag sounds good. Is this what is used in 'chipping' a pet? and is it fitted under the animal's skin?:)
 
Possibly. You are talking about tags to identiy the animal right? That is probably the same thing, since it's small, lightweight, and has no batteries to be replaced. It only needs to be activated whenever a reader is brought close to the chip beneath the animal's skin anyways.

I think the sub-derminal chips are lower range than what you might want though...unless the chip is in the cat's head. I think they require a reader to be passed by within cm of the chip (but that probably also has to do with the strength of the base station signal being generated).

I also added more detail to my previous response while you were replying. Added stuff about actual information being reradiated, rather than just reflecting the base station signal.
 
dknguyen said:
Possibly. You are talking about tags to identiy the animal right? That is probably the same thing, since it's small, lightweight, and has no batteries to be replaced. It only needs to be activated whenever a reader is brought close to the chip beneath the animal's skin anyways.

I think the sub-derminal chips are lower range than what you might want though...unless the chip is in the cat's head. I think they require a reader to be passed by within cm of the chip (but that probably also has to do with the strength of the base station signal being generated).

I also added more detail to my previous response while you were replying. Added stuff about actual information being reradiated, rather than just reflecting the base station signal.
Thanks again! This sounds like good stuff and just what is needed. My reply got swallowed up in the ether I think while I went back to your previous message! I will consult my (the cat's-not mine) vet to find out how these things work and hopefully come up with an answer very soon. Poor old cat is getting really fed up!:) :)
 
The cats have a chip about the size of a watch crystal implanted under the skin so if they get lost and have no collar they can still be returned. The vets use a handheld RFID scanner to read the number on the implant. RFID is used in retail, secrity pass cards and most(well, a lot) contactless identification systems
 
hmmm. my last cat died 6 years ago so I'm not up on this. Is this just an Aussie thing or is it also in the US?

By the way, you don't need to chip the cat, a collar would do fine as the tags usually don't weight much.
 
philba said:
hmmm. my last cat died 6 years ago so I'm not up on this. Is this just an Aussie thing or is it also in the US?

As far as I know it's world wide, vets have been 'chipping' pets for many years now, I would certainly expect it to be common place in the USA (and may even have originated there?).
 
Ahh yes, but cats already have the chips and they delight in rubbing the collars against concrete and other rough surfaces until the collars are shredded and fall off, we have lost too many collars. And if these are anything like RFID tags they should operate at 13.??MHz I'll get my GDO out and have a look.
 
Hi Folks thanks for all your replies. I have been working away for a while and it may take me a bit of time to catch up! Watch this space. Thanks.:)
 
Thank you for returning to the forum.
 
I have seen an article where someone has actually succeed with this project, they used an eletricaly operated cat door, the same ones that use a magnet. They didn't say what sort of RFID they were using but I got the impression that it was a tag attached to the collar. The UK & Aus use 134.2KHz for the chips rather than the 125KHz that seems to used everywhere else.
 
Paul Obrien said:
I have seen an article where someone has actually succeed with this project, they used an eletricaly operated cat door, the same ones that use a magnet. They didn't say what sort of RFID they were using but I got the impression that it was a tag attached to the collar. The UK & Aus use 134.2KHz for the chips rather than the 125KHz that seems to used everywhere else.
Hi Paul. Thanks for the info. Problem here is that my cat will not wear a collar. He will do anything and everything to get it off including dangling from a tree by it! So really it needs to be some sort of 'under the skin' type of thing.:)
 
Heres the atricle, really it's a letter to a mag "Silicon Chip" about one of their projects
RFID sensor makes a great cat door
Thank you for designing the RFID module featured in the June 2004 issue. I adapted its design to make a pet door which has now been in service for about nine months now. No longer do I have to put up with the smell of cat spray around the house and as a bonus, bandicoots can no longer get in the house and spread the cats’ food around the laundry.
I did modify it slightly with a bigger ID20 module to increase its range to 15cm and I adapted a commercially made electric cat door which relied on reed switches and a rather large magnet, attached to the cat. I mounted the sensor module in the plastic housing of the door and have the electronics in a wall box nearby. It fires the solenoid in the cat door to open it.
Lloyd Jury,
via email.
The main problem with the cat chip is the way I think it transmits the data. Going from memory, based of an article in the early Nineties, the chip is powered by the search/identifier transmitter via the tuned circuit. The data is fed back to the identifier by altering the tuned circuit so that it is no longer tuned. So a weak signal output level by the identifier can be altered by the chip, much like a Grid Dip Oscillator, therefore increasing the power output to detect the chip at a longer range would tend to mask the returning data.
 
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