waterLeakSensor

Over 10 years ago I bought this very simple water alarm kit from a Fry's Electronics:

I just wanted to solder something and this fit the bill. After sliding a 9V battery into it for the first time I found that the contacts were very sensitive. Happy with my assembly, I set it behind my washing machine so the oscillating buzzer could shriek at the first sight of water.

Present day (we'll call it 2016) and everything I build seems to have an ESP8266. I found my dear water alarm in a junk box, still ready to buzz loudly powered by its original 9V battery. Could I throw a 3.3V regulator on this board, connect to an ESP-01, and get a leak notification? Yes indeed!

I decided to design my own PCB just to try that for the first time, and since the same water alarm kit is still available for only $5, it seemed an economical way to get all those parts without buying in bulk. I made a couple of ugly mockups, but here's the fruits of my "labor:"