Analog Soil Humidity/Moisture Sensor (Resistance)

When you hear the term ‘smart garden’, one of the things that comes to your mind is a system that measures soil moisture and irrigates your plants automatically. For this purpose, inexpensive sensors have been developed using a straightforward principle of operation. A fork-shaped probe with two exposed metal conductors, acts as a variable resistor (just like a potentiometer) whose resistance varies according to the water content in the soil.

The resistance value of the sensor is inversely proportional to the soil moisture: the more water in the soil means better conductivity and will result in a lower resistance (and viceversa). The probe is connected to a board carrying an LM393 High Precision Comparator to digitize it and is made available at a Digital Output (DO) pin. The raw output is also available at an Analog Output (AO) pin. The module has a built-in potentiometer to adjust the threshold of the digital output (DO), when the moisture level exceeds the threshold value, the output will switch from HIGH to LOW.

This Soil Moisture sensor uses a 2-pin header that connects the probe to the comparator PCB. The comparator PCB also carries a 4-pin header connector that makes it easy to work with and connect to a microcontroller, single-board computer, or solderless breadboard using Dupont-style jumper wires (e.g, Arduino, Raspberry Pi)

Features:

• Operating voltage: 4.5~5.5VDC
• Output Voltage: 0~3.0VDC
• Operating Current: 5mA
• Output type: analog voltage
• Interface: Analog or Digital Output
• Dimensions: 3.86 x 0.905 inches (L x W)