On Sun, 26 Jun 2011 12:15 +1000, "cdb"  wrote:

> :: I would probably use Sureflap doors, which can
> :: be trained to trust each cat's implanted RFID microchip. And if I
> :: had multiple cats I'd hack the door to get the RFID numbers to track
> :: each one separately.
>=20
> Rolling my own has been on my to do list for some years now. I had
> thought=20
> of using the implanted microchip but I thought that with the standard=20
> passive range of RFIS of about 2-3" this wouldn't allow enough time for a=
=20
> chased moggy to be recognised and the flap unlock,  ending up with said=20
> moggy wearing the catflap. I assume you've found this not to be the case?

I have never had a cat that thought the house was a safe haven from
other beasts, or maybe that the delay of going through any door was
worth risking.

That being said, I have experimented with the seeedstudio 125KHz RFID
receivers, and if you make a larger coil you can extend the read
distance to about 6 inches. There's a tradeoff as you increase the
diameter of the coil so if you make the coil too big the distance drops
off again.

If you put the coil in front of the cat door, as if it were an awning
before the entry, you can get recognition by the time the head hits the
door. Or so my experiments would suggest, I no longer have a cat.

Friendly regards,

Bob

--=20
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