I rigged up a crude little water level sensor to monitor my Christmas tree and send me alerts when it gets thirsty. With the help of two strips of aluminum stuffed in a FoodSaver bag, an Adafruit HUZZAH32 – ESP32 Feather Board, and a little Arduino code, our humble tree has become part of the IoT revolution! Physics lab flashback The sensing probe that goes in the water is basically just a parallel plate capacitor straight out of undergrad physics. The water flows between the plates and works as a dielectric. The relative permittivity (aka dielectric constant) of water is Continue Reading