Soil Moisture Module

  • GND: Ground

  • VCC:Power supply, 3.3v~5V

  • AOUT: Outputs the soil moisture value, the wetter the soil, the smaller its value.

This capacitive soil moisture sensor is different from most of the resistive sensors on the market, using the principle of capacitive induction to detect soil moisture. It avoids the problem that resistive sensors are highly susceptible to corrosion and greatly extends its working life.

It is made of corrosion-resistant materials and has an excellent service life. Insert it into the soil around plants and monitor real-time soil moisture data. The module includes an on-board voltage regulator that allows it to operate over a voltage range of 3.3 ~ 5.5 V. It is ideal for low-voltage microcontrollers with 3.3 V and 5 V supplies.

The hardware schematic of the capacitive soil moisture sensor is shown below.


There is a fixed frequency oscillator, which is built with a 555 timer IC. The generated square wave is then fed to the sensor like a capacitor. However, for the square wave signal, the capacitor has a certain reactance or, for the sake of argument, a resistor with a pure ohmic resistor (10k resistor on pin 3) to form a voltage divider.

The higher the soil moisture, the higher the capacitance of the sensor. As a result, the square wave has less reactance, which reduces the voltage on the signal line, and the smaller the value of the analog input through the microcontroller.


  • Operating Voltage: 3.3 ~ 5.5 VDC

  • Output Voltage: 0 ~ 3.0VDC

  • Operating Current: 5mA

  • Interface: PH2.0-3P

  • Dimensions: 3.86 x 0.905 inches (L x W)

  • Weight: 15g