[Renzo Mischianti]’s friend has to keep a water tank topped up. Problem is, the tank itself is 1.5 km away, so its water level isn’t typically known. There’s no electricity available there either — ...

In a way, the magic of a soil moisture sensor’s functionality boils down to a simple RC circuit. But of course, in practice there is a bit more to it than that. [rbaron] explains exactly how ...