I’m building a sensor “pack” with an Arduino for detecting bad things in/around the home, especially kitchen, basement, and bathroom. (The places where there is water/leaks, gas, etc.)
I’m a little stuck on the simple way to detect moisture. Most of the sensors I see online are either soil moisture sensors that provide a variable voltage in the presence of moisture, or a liquid level sensor that does something similar for various water levels.
I’m not sure either would work. I want to detect the presence of water where there should be none… pass/fail. This would be useful in setting off an alarm should, for example, a washing machine hose bursts or a water heater is leaking. So I want to place the sensor on the floor near a potential leak point and as soon as the sensor gets wet, set off the alarm.
Someone told me an old trick would be to stick two wires into a dry sponge and sprinkle salt on it. Haven’t tried this method yet but I wonder if anyone has experience with any of this, or if you know of a commercially available water detector sensor that would work.
Very inexpensive rain sensors are available, based on a bit of PCB material and perhaps an amplifier board. However, for an Arduino to detect water leaks, all you need in addition to the PCB part is a resistor to make a voltage divider, connected to an analog input.
The salt in the sponge is to improve the conductivity since completely clean water (read - distilled water) will have very low conductivity.
BINGO! That’s the one! Not sure why I didn’t find that… thanks. Simple enough to build, but for $1.95, the Adafruit board is a bit more controlled, as you say.
Yeah, I realize what the salt is for. But honestly, my town water is so hard I was thinking of using a seismometer instead, LOL. And on the floor under my washing machine, the chance of pure water is literally nil.
The Adafruit one looks good, I didn’t know they had those.
If the application is for monitoring an unattended area, I’d think some humidity sensors, too. A lot of leaks start small and it would be cool to catch it at the ‘bit of damp’ stage and well before it becomes a standing pool. It’s happened to me; a small p trap drip under a bathroom sink went unnoticed so it got gross and sloppy. If I’d had a sensor in there to send an alert if RH exceeds, say, 80% for more than an hour (to accommodate normal bathing environment swings), I’d have probably caught it within a day or two. Stick another one behind the washing machine, dishwasher, sump, etc.
These would be in addition to the straight up water sensors under discussion.