Automatic Pet Door

Sat, Dec 10, 2022 2-minute read

Automatic Pet Door

I have a dog and recently got a cat. The cat keeps going out the dog door which poses a problem; how do I allow the dog to go out freely but prevent the cat from going out?

Enter a DIY automatic pet door.


  • Dog can go freely
  • Cat must not be able to exit freely
  • Anything on animals must be passive i.e. not battery powered
  • No circuitry must live on the pet door (a flapper)

Idea: tag based access control:

  • the dog door locks when a tag is presented (the cats).

I think the door being default to unlocked works better than the inverse. This way if the cat is at the door whilst the dog it outside the dog would be locked out. This is a design consideration which should prevent the cat from tail gating or ambushing the door when the dog enters or exits.

My current dog door is a flap based system which uses light magnets to keep the flap in place. I want to keep using this as its a pet door which can be used in any sliding door (great for rentals).

The locking mechanism would be stronger magnets which are energised whenever the cat is present preventing the flap from opening.

A few options:

  • Acousto Magnetic detection
  • RF detection


#rfid #rf #diy #iot