Animal Tagging -- reader?

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Hi, all

My cat is being tagged with one of those RFID chips. Now I want to read the
Cat gets into places where I do not want it to go and I want to set up a
detector there that will scare it away. Ue of IR detection will not work as
people get there too. So, since cat is already tagged, I'd like to use it.
I am after a detector that will read the ID from a distance of a bout
1-1.5m. Reader does not have to be self-contained. I will have to interface
it to a micro anyway to implent the "scaring" part.

Any help is appreciated.

If sending anything by e-mail, please send to


Re: Animal Tagging -- reader?

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 LOL! When I don't want my cats to go somewhere, I close a door!

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 It will, if you make some attempt to differentiate between
people-sized bits of IR, and cat-sized bits of IR.

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 With respect Sir, it's not gonna happen. The RFID 'capsules'
they're using on animals have such a tiny antenna that it may
as well not have one at all. That is certainly the case at
the distances you're talking.

 We keep a cache of assorted RFID 'chips' to show to students
during the Supply Chain Management lecture on bar codes, rfid,
etc. Some have quite large antennas - the ones that the Hong
Kong Airport Authority attach to every item of checked luggage
that flows out of the place are about 50mm x 200mm - and of
course most of that is antenna. The antenna in an animal capsule
is tiny by comparison - a small coil of copper wire.

 I had to take my young bloke back to the RSPCA recently to get
his number checked (someone made a typo, got it wrong, blocked
some little old lady registering her cat up on the Central
Coast! In a system of RFID and bar codes, someone *still*
ended up manually typing a (very) long number!).

 So I had a chance to have another good look-see at the RFID
readers they're using. They're a battery powered device with
a large coil antenna - a diameter in the order of 100mm at
a guess.

 Common practice is to insert the capsule between the shoulder
blades. In my boy's case, it has slipped off, and down one side
of his shoulder (you can feel it under his skin) - perhaps 20-30mm
away from where you might expect it to be

 That distance is enough to make it really difficult to read
his number. It takes several attempts, 'scanning' over his
shoulders with the reader pressed on his skin.

 This isn't a one-off. I've seen similar difficulties with
reading on others, dogs too, in the past.

 What this means for you is that it's going to be nigh-on-
impossible to get a reading of any sort at a distance of

 Having said that, you don't necessarily need a *reading*
as such. What you need to do is identify the presence of a
device that 'talks' when excited by an RF field. That's
going to be a *lot* easier (and a lot cheaper) than
understanding what it is actually talking about. I'm
assuming here that you don't need to confirm that it is
specifically *your* cat that is where you don't want it
to be???

 Anyway, not needing to know the actual number means that
you get to up your 'read' distance to something like
25-50mm. Still doesn't really solve your problem, does

 I think back to the IR thing might be a better bet. You
*can* get the 1000-1500mm read to happen with the capsule
implanted in your cat, but there are serious health-and-
safety implications and, notwithstanding that there's nothing
ferrous about your cat, you're still going to end up with
him/her being *so* magnetically polarised that you'll have
trouble with him/her sticking to the fridge all the time!

 I haven't even *touched* on the bit where RF generally is
a total black art, or the amounts of money involved in
reading RFID. You're using a micro. Go IR. A bunch of
recievers at diffent heights. If the one near the ground
is the only one lit up then its a cat or a human playing
silly-buggers who deserves to be scared away anyway :-)


"When all you have is a flamethrower, everything looks like a
 speed camera." (Peter)

Re: Animal Tagging -- reader?

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as already said... forget it.
detection range is around 5cm...
perhaps you could expand your idea slightly, and use an RFID tag on the
cat's collar.

eg: keyfob style 21mm round, easily
superglued to collar or back of current nametag.

range is likely to be less than you want however; the card readers tend to
have very short detection distances for security reasons...

Re: Animal Tagging -- reader?


We moved to a new house and there is a pathway behind the house. Pathway is
about 1.5m wide. It ends at the door that leads to frontyard and cat gets
there through the door as it is not solid.
1. I do not want to make door soild. It is made out of metal rods and looks
quite nice.
2. Somehow our cat does not like climbing, so I am not concerned of it
climbing the fence and escaping this way.

So, the idea is to install some detector on the pathway near the door and
scare the cat away. I thought about IR detector, but this pathway i used by
us and our gardener and I do not want the device to trip on humans.

I though about using RFID tags, but then remembered our cat already has one
implanted. If I can not use this one, I will have to put one on the collar.
Any pointers to cheap reader and tags? I only need couple of tags and a
single reader and do not want pay big $$$. RFID kits from TI are few hundred


"mark jb" <nukeleer at internode dot on dot net> wrote in message
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Re: Animal Tagging -- reader?

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you don't need rfid tags. simple resonant tags (like they use at K-Mart to
catch shoplifters) would suffice. (these are just a coil with a capacitor

as for a detector you might have to google for that.

I's try chicken wire (etc) on the gate first just to be sure that a barrier in
that place is all you need.


Re: Animal Tagging -- reader?

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 His cat already has a tag implanted, so that's why he was
heading down the RFID path IIRC.

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 Well that's the obvious, inexpensive and sensible solution to the
problem, but where's the fun in that? :-)

"When all you have is a flamethrower, everything looks like a
 speed camera." (Peter)

Re: Animal Tagging -- reader?

If you used two IR beams/detectors - one high (3ft) and one low (6"), and
connected their output to an AND gate, it would trip on the cat, but not humans

Might be the cheap and easy way


Rudolf Ladyzhenskii wrote:

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Re: Animal Tagging -- reader?

This is an idea.

Anyway, thanks for replies.
Will play with it.


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