If you have a dog or cat you let ‘off leash’ at times, you trust that they will stay in your yard — or at least not go too far away from your house or person. Unfortunately, if you’ve tried this, you may have found that Fido or Cleo decide to push their limits, meaning that you’ll have to track them down or nervously await their return.
As an early warning for this sort of behavior, hacker Andrei Erdei decided to create the most basic pet alarm he could think of: a radio transmitter attached to a collar, with a receiver that the pet owner keeps nearby.
When the animal ‘escapes containment,’ taking the transmitter module out of range, the receiver module — powered by an ATtiny85 and an H3V4F Rx — then sounds the alarm with a small speaker, vibration motor, and/or lighting as needed.
The transmitter is also powered by an ATtiny85, using a corresponding H34A Tx. Both sides are housed in a modded AA battery holder, providing both power and space for the electronics.
One could see all kinds of modifications of this design, perhaps putting a flash/beeper on both ends so that the pet in question lights up or beeps to assist with tracking. Of course, that would make things less simple and less cheap, going against the project’s premise of an “Ultra Simple, Ultra Small and Ultra Cheap Pet Monitor.”