Cats presence motoring

Hello dear readers,

Im Greg, newbies in the arduino world.
I have an Arduino Uno and I would like some help on the feasability for my project.

Here is it :
I have 2 cats (P + K) and both have a chip under their skin.

I also have a RFID cat flat the allow them to come in and out of the house without having other cats entering too...

My project is to monitor their entrance and exit.
The problem is that I have 2 cats. If I had only one I would use a PIR sensor but it's not the case.

I would like to monitor their entry and exit by displaying a red led when P is OUT and green when he is IN
Same with cat K.
I could see the leds status from my indoor camera which I can already control from anywhere using my phone...

It means 2 RFID readers that would read the signals :
reader 1 placed at first door
reader 2 placed at exit door
The cats have to go through both doors to exit the house (which is what they are actually doing)

The feasability consist into reading the RFID signal from the cat flaps.

If I can read signal from the catflap 1 and (let say) 30s later it read the cat flap 2 = cat P. is out (because the reader would have read it's cat P. and not cat K.)

To do so I need to write the program (2nd step)

My main question is :
Is my idea feasable and/or, do you have better idea for the monitoring in general ?
How can I read and interpret the signal from the reader of the cat flap (status I/O)
to re-entry in the house, the cat flap reads the chip of the cat and open an electro magnet which unlock the door. Cat can get it.
I dont't mind disablign the electro magnet and using the output of the catflap to use the signal...
But Because I need to define the status of each cat (P and K) I need to make a program that differ the chip reading.

Can someone help me pleasE?

If I am not clear enough please let me know.

Big thanks already.


It should be possible to reverse engineer the circuitry of the cat flap to get the signals of interest, but that requires taking apart the flap and inspection/modification by someone very familiar with electronics.

It may be easier to use a separate RFID reader that can identify the cat passing through, and then two sensors (e.g. IR break beam) to tell which direction it's moving in. Some smarts in coding can even tell you if it just sticks its head out and then goes back in. As long as your flaps are small enough you don't have the problem of two cats moving through together, though they may be passing through head to tail so for your sensors it looks like one big cat passing through.

You have to make sure that the range of your RFID is such that you can read the cat that passes through, but not its friend trying to move through at the same time (I'm sure at times they WILL want to go out at the same time).

It's a pretty hard problem actually to do reliably, even with just two of those furballs to keep track of.