My cat only drinks from the tap. He doesn't know how to turn the water on or off. So I need a system to get him water when he wants it.
- Clean install
- Provide water when cat goes to the sink
- Don't trigger on humans
- Turn water off when cat is done
- Run for a month between charges
- Tweet/ notify when cat gets water for peace of mind
- Notify on low battery
- Easily integrated and removed
I picked a sink I can easily modify to include a spout, and he's used to drinking from. There is no outlet nearby that I can wire to cleanly. So I'll have to use a battery.
A clean install means no visible wires or tubes running through the sink.
Provide water: turn off/on when cat comes around
ESP 8266 Thing from Sparkfun promises low-current draw and WiFi, nice!
Use a solenoid valve:
Sensor selection/ design will be a trade off between accuracy and visibility.
- Pretty standard way of doing automatic sinks
- Cheap sensors
- Very visible sensor
- Compact or clean looking versions are hard to find ($$)
- Might trigger when I'm using the sink (not desired)
- Clever sensor placement/ design could exclude everything but the cat
- Might be visible
- Not really straightforward
- Minimal, very clean, invisible
- Difficult to design against non-cat triggers (extra weight in the sink will cause it to fire)
- Fun to make
- Could become very good at cat-only triggering
- Visible sensor/ camera
Run for a month between charges
Add up all the current consumers and estimate Oppie's drinking habits. Pretty simple.
- Awake: ~200mA
- Standby: ~0.9mA
- Solenoid valve ~ 400mA
Oppie drinks water for ~ 10 minutes a day. 31 days in a month = 310 minutes.
I picked this thing:
The ESP may actually consume less current while running, but assuming some leakages here and there keeps things conservative.
- Control and actuation is pretty straightforward. No decisions.
- Battery pack looks like it should be sufficient
- I'll use machine vision to detect the cat. Especially considering how cool/easy this thing looks:
Plus the fact that I can get this to trigger only on cats is really neat.