A common problem among owners of multiple pets is how to feed them separately. If one animal needs special food, is on a diet, or likes to eat from another’s bowl, it becomes difficult to control each pet’s consumption. That is especially true when one pet doesn’t like to finish their bowl of food immediately and leaves it open to theft by another. To solve this problem and prevent one cat from stealing another cat’s special diabetic diet food, Tomas built a selective pet feeder.

Like most of us would, Tomas first thought of using NFC tags on his cat’s collars to grant access to their food bowls. But NFC has a very limited range, which makes it hard to use in a situation like this. After considering other solutions, Tomas realized that one of his cats weighs quite a bit more than the other. If they were a similar weight then this wouldn’t work, but because the difference is substantial, he figured he could use a scale to grant access to the special diet food.

This meant constructing a servo-actuated cover for the special food and a cat-friendly scale. Any Arduino-compatible board can control the operation. The scale is four load cells connected to the development board through an amplifier. A sheet of MDF on top of the load cells provides a large surface for the cat to sit on. If the detected weight corresponds to the diabetic cat, the development board activates the servo to open the 3D-printed door that covers the diet food. If the scale doesn’t detect any weight or if it detects the weight of the other cat, it keeps the door closed.

This is an elegant and simple solution that should be useful for any pet owner that finds themselves in a similar situation.