A Smart Cat Deterrent

Recently our geriatric Siamese cat has started peeing on the floor.  We are going to take her into our vet to determine if she has a UTI,  but it's quite possible that she is just going senile.  She's exhibiting other behavior that suggests this is the case.  We're not to the point of putting her down for that yet,  because we have no carpet on our floors.  Slate and hardwood.  But we DO have some wool area rugs at risk.

So I started thinking about a way to restrict her access to places she visits when she transgresses.  There are some commercial and DIY solutions that combine a motion sensor with some sort of deterrent -- making a loud noise and some sort of electronically-activated spray system are out there.  But they also are activated by a human entering that space.  Some kind of sophisticated image recognition system would likely work to differentiate between people and their pets but would be relatively expensive.  In contrast, a relatively simple logic scheme using two PIR motion sensors looks like it could work.  They would be at two different heights -- one close to the ground and the other about 2-3 feet high.  If both are activated, something tall (like a human) just entered the space.  If only the bottom one is activated, it must be something smaller like a cat.  In that case, the logic circuit will activate a piezo tweeter that emits sound obnoxious to a cat.  This will teach the cat -- hopefully -- to stay away from that area.  If the frequency is above about 15KHz we won't hear it (not much anyway), but the cat definitely will.

PIR motion detectors usually have a fairly wide field of view.  So it may be necessary to place a tube around the top one to restrict its field of view so it won't trigger when a cat enters the area.

To test the idea out I ordered several PIR sensors, a couple of piezo tweeters and a 5V/12V wall-wart power supply from ebay.  The 12V supply will be used for the piezo driver circuit.  I have several Arduinos lying around so I will use one of them to perform the logic and output a high frequency signal to the piezo driver.  So far I have far less than the $$ charged for a commercial device, and it should work better.  Such a deal.  And if need be, I will have enough sensors and tweeters to protect another area.