A soil moisture sensor is a practical module that measures the amount of water in the soil to determine the irrigation needs of plants. There are two common types on the market, the classic resistive and the capacitive, which have a much longer life against liquid contact/corrosion. The classic models usually come with an LM393 board and provide both analog (A0), which indicates the humidity level, and digital (D0) output, which is triggered according to a threshold set with a potentiometer. Fully compatible with Arduino and ESP series boards, they are indispensable in automatic pot watering, smart agriculture and greenhouse automation projects.
