Modding High-end pet door

I currently own and am using a High Tech Pet electronic pet door ( and would like to modify it to:
1) Read/activate via a small RFID tag instead of the very large (for a cat) sonic transmitter. The cat is feral (we lock him at night in the garage), so he sometimes gets in fights and loses his entire collar. The transmitters are $40 each! He's lost three so far.
2) Switch mode to "in only" at a preset time very night and "in and out" mode every morning.

I like the features of this door, and it's already installed. It's extremely weatherproof and resilient. Most Lexan/acrylic cat flaps I've seen or owned aren't even in the same league as this one, which is why I would prefer to keep this door as opposed to modding a different brand of door.

I know how to solder and have a very basic understanding of electronics. I could probably muddle through a DIY, but I'm not even sure it can be done. Is it as simple as locating the receiver on the board and replacing it with an RFID reader? Or is that wishful thinking? Thanks in advance for any insight, advice, help. :)

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S2kvan (author) 4 years ago
He is microchipped. We actually have a SureFlap pet door that we use inside for another cat. It reads her microchip, but it's not ideal because she has to have her head inside the thing before it opens. (Chip is between shoulder blades.)

RFID tags are small and cheap, and the outdoor kitty has to wear a collar and tags anyway. I just hate losing the $40 transmitter.
Since he's chipped, all you need to do is modify the antenna to have a bit more range.
If the cat is chipped it already has an RFID chip. But as you noted you have to be pretty close to read those tags. But the timing circuit can be implemented if you can isolate the circuit that locks the door. Than you can have a micro controller with real time clock activate and deactivate the lock when you want it too.
Transitioning from a radio transmitter and receiver to RFID isn't going to be easy and will require much more than a basic knowledge of electronics. Not to mention you'll have to get an RFID system that will work at a small range rather than having the tag sit right on top of the receiver.
S2kvan (author)  mpilchfamily4 years ago
Fair enough. So barring that, I wonder if it's possible to create smaller, cheaper transmitters that are compatible with the door. And any thoughts on the timer/ click thing? That is pretty important to me, too.
Is the cat chipped ?