I just finished the first prototype of an automated cat waterer.
My cat has some sort of chronic kidney problem, and he drinks a lot of water. He’s also picky - he won’t drink the water in a dish, if it’s been sitting out for a day or so. He likes the fresh water in the dog’s dish (because that gets changed several times a day as they gulp it down), and he really likes the water out of the faucet in the bathroom. So much so, that he’s become a nuance - he waits outside the bathroom door, and cries until someone turns on the tap, so he can hop up and drink from the sink.
With that in mind, I designed a system which allows him to have fresh water, without being an annoyance. I bought a 12v Solenoid valve and attached it to a T in the cold water line under the wash sink in the laundry room (where his food is). I used a saddle valve to regulate the flow. I then found an old motion sensor alarm from Radio Shack and used the outputs of the alarm to trigger the water flow (the output goes to a microcontroller circuit which give up to 5 minutes of water every 20 minutes, so he doesn’t just sit there and run the water). The water flows into a bowl, and drains into the sink drain.
I just finished it last night, and I’m training him to use it. I haven’t seen if he’ll go to it on his own yet, but if I activate it myself, he’ll drink from it until he’s not thirsty.
I’ll post photos if anyone is interested.