“In an effort to counter my own forgetfulness to water the plant in my apartment and on my balcony, I tried myself on developing a soil moisture sensor device.
Since I wanted it to run on my balcony, where I don’t have the means to connect everything up to a power socket, it needs to be battery-powered device. And because it is supposed to integrate with my Home Assistant it needs wireless connectivity as well and not just a simple indicator light for example.
As sensors I came across these Capacitive Soil Moisture sensors, which are sold rather cheap, when sourced directly from China. They output an analog signal, which changes based on the capacitance of the surrounding material. The water contents of the soil gives enough of a change in it capacitance to change the senor’s reading.”