Soil Moisture Sensor Module

Soil Moisture Sensor Module is a popular, cost-effective agricultural sensor designed to measure volumetric water content in soil and growing mediums. Combining a pair of exposed parallel probe forks (acting as a variable resistive soil electrode) with an onboard LM393 dual differential voltage comparator IC, this module detects how conductive the surrounding earth is—dry soil has high electrical resistance, while moist soil conducts electricity better, lowering resistance. Featuring both an analog output for precise moisture percentage mapping and a digital threshold output with a sensitivity adjustment potentiometer, it is an essential component for automated plant watering systems, smart greenhouse irrigation, and agricultural IoT monitoring.

Features

• Equipped with dual exposed nickel-plated fork probes providing effective soil conductivity measurement
• Powered by the LM393 dual differential comparator chip ensuring stable signal conditioning
• Dual output interface: Analog output (AO) for continuous moisture percentage tracking and Digital output (DO) for direct threshold switching
• Onboard multi-turn precision potentiometer allowing users to tune the moisture trigger threshold level
• Active LED indicators for power status (Red) and digital switch trigger detection (Green)
• Wide operating voltage range (3.3V to 5.0V DC), directly compatible with Arduino, ESP32, and Raspberry Pi ADC pins
• Compact PCB layout featuring a pre-drilled mounting hole for secure physical placement in pots or garden beds
• Simple, low-power design ideal for battery-operated agricultural sensor nodes

Applications

• Automated plant watering systems, self-watering flower pots, and greenhouse drip irrigation controllers
• Smart agriculture IoT monitoring networks for crop field moisture tracking
• Botanical research experiments, soil science education, and indoor gardening kits
• Lawn sprinkler automation systems and garden moisture alert alarms
• Polytechnic diploma, university engineering thesis, and Arduino/ESP32 environmental sensing projects

Important Notes:

• Electrolysis / Corrosion Warning: Resistive soil sensors pass a small DC electric current through the soil between the two fork prongs. Over extended periods of continuous power, this causes electrolytic corrosion and oxidation of the bare metal probes. To maximize lifespan, it is recommended to power the sensor using a digital output pin from your microcontroller only during measurement intervals, rather than keeping it permanently powered.
• Component Protection: Keep the upper circuit board containing the LM393 chip and electronic components above the soil level. Only the lower metal fork probe should be inserted into the dirt.
• Calibration: Soil composition, salinity, and temperature affect conductivity. Calibrate your analog readings in your microcontroller code by noting the dry air value vs. fully saturated water soil value.
• Logic Compatibility: Connect VCC to 3.3V or 5V matching your microcontroller logic level, and GND to system ground.

Package includes

• 1 x Soil Moisture Sensor Control Board (LM393)
• 1 x Dual-Fork Soil Probe
• 2 x Jumper Connection Wires