Soil Moisture Sensor Module

Soil Moisture Sensor Module can be used to detect the moisture of the soil or judge if there is water around the sensor. It has both analog and digital outputs. We can vary the digital output sensitivity of this module using a potentiometer and the sensor is based upon resistance.

Soil moisture sensor consists of two conducting plates which function as a probe and acting as a variable resistor together. They are used to measure the volumetric content of water. The two probes allow the current to pass through the soil, which gives the resistance value to measure the moisture value. When the sensor is inserted into the water, the resistance will decrease and get better conductivity between plates. Dry soil conducts electricity poorly, so when there is less water, then the soil will conduct less electricity, which means that there will be more resistance.

The working of the Soil Moisture Sensor is very simple. It works on the principle of voltage comparison. Moisture sensor module consists of four pins i.e. VCC, GND, DO, AO. Digital out pin is connected to the output pin of LM393 comparator IC while the analog pin is connected to Moisture sensor. The internal Circuit diagram of the Moisture sensor module is given below.