My cats wake me up every weekend by scratching/rattling my bedroom door at 6am or earlier. I would like to build a detector and sprayer to train them to let me sleep in a little(just until 8 or 9 am!).
I have a standard water spray bottle that I use when they are being bad. It's harmless to the cats and my carpet, and they hate it. But it needs a good amount of force to trigger, and none of my servos are powerful enough to trigger it. Maybe I could buy a solenoid to control it.
I feel like the standard ways of dispensing water with either a pump or a gravity-fed valve will make a mess on my carpet.
I found an article on instructables about an arduino shooting silly string. But the cats might enjoy that.
Another inexpensive servo. As for conditioning the cats, it may be best to use a push button so they can be sprayed while scratching. I have the same problem, but I just get up and let them in.
But it did bring to mind using a windshield washer pump instead of a spray bottle. Get one from J.C. Whitney, or your local auto parts store. Maybe 5 amps? Under $20.
I like the idea of a windshield washer motor. It would need to get to pressure quite fast but you could do that by having a small diameter spray nozzle.
Detection is easy enough. Just use a Passive IR detector (PIR) and make it directional like in the video clip I put up.
The Arduino would be used to actuate the motor based upon input from the PIR detector. These things generally have a dry contact to trigger the alarm and this could be used to input data to the Arduino.
The Arduino would also regulate the length (duration) of the spray.
They woke me up again at 5am this morning. If I let them in, they knead my face until I get up.
I don't know about a windshield sprayer. Those shoot a pretty intense beam, I'm looking for light mist.
I think I'm going to try a higher torque servo, the price is right and it looks pretty powerful. I'll probably connect it to a staples "easy button" on my night stand. I still haven't decided what kind of sensor to use.
If you want to go low tech, you could make a manual sprayer. Get some aquarium tubing, empty plastic drink bottle, and a spray head from one of the single finger sprayers. Drill a hole in the drink bottle cap and insert the tubing so it goes to the bottom of the bottle. Hot glue the tubing in the bottle cap top to seal it up. Get sufficient tubing to reach from the bed to outside the door. Hot glue the spray head on the door end of the tubing and aim where the cat are. Fill the bottle with water and attach the cap. When the cats start scratching, give the bottle a good squeeze.