Although it’s been done 1000 times already, here’s my take on the idea of a plant water monitor. Lower reading means higher moisture content. Based on a modular system one esp can handle up to 32 probes directly, countless more using a hub chip.. To avoid errosion of the probes they’re only powered a few milliseconds per hour, just long enough for the adc to take a reading. In the next PCB revision the adc will be powered down between readings as well for maximum battery life.
The system is powered from two Eneloop cells, it should run for three months. A boost converter will keep the circuit running down to 1.0 volts input.
Data is gathered over MQTT, logged and displayed using node-red on a RasPi.
I’ll post a GitHub repo shortly.