Soil Moisture Sensor Module – Resistive Hygrometer with Analogue & Digital Output (1 Piece)
R29.00
Price incl. VAT (15%) R3.78
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Soil Moisture Sensor Module – Resistive Hygrometer with Analogue & Digital Output (1 Piece)
Product Details
Soil Moisture Sensor Module – Technical Specifications:
| Sensor Type | – Resistive Soil Moisture Sensor |
| Operating Voltage | – 3.3V to 5V DC |
| Operating Current | – ≤ 20mA |
| Output Type | – Dual Output (Analogue + Digital) |
| Digital Output | – TTL (HIGH = Dry / LOW = Wet) |
| Analogue Output | – 0V to VCC (Higher Voltage = Drier Soil) |
| Onboard Comparator | – LM393 |
| Sensitivity Adjustment | – Onboard Potentiometer (Digital Threshold) |
| Indicator LEDs | – Power LED (Red) + Digital Output LED (Green) |
| Probe Material | – Nickel-Plated Dual Copper Traces |
| Interface | – 4-Pin Header (VCC, GND, DO, AO) |
| Operating Temperature | – -10°C to +85°C |
| Dimensions (Control Board) | – 32 × 16mm |
| Dimensions (Probe) | – 60 × 20mm |
| Quantity | – 1 Piece |
| Compatible Platforms | – Arduino, ESP8266, ESP32, Raspberry Pi, STM32 |
Handy Tips for Using the Soil Moisture Sensor Module:
1: This module has four pins — VCC (power), GND (ground), DO (digital output), and AO (analogue output). The digital output gives a simple HIGH/LOW signal based on a moisture threshold set by the onboard potentiometer — ideal for simple wet/dry trigger events such as activating a pump or relay. The analogue output gives a continuously variable voltage proportional to soil moisture — useful when you need to know exactly how dry or wet the soil is, not just whether it has crossed a threshold.
2: The onboard potentiometer adjusts the sensitivity threshold for the digital output only. Turn it clockwise to increase sensitivity (triggers at lower moisture levels) and anticlockwise to decrease it (triggers only at higher moisture levels). Use a small flathead screwdriver and test in both dry and wet soil to dial in your desired trigger point.
3: Only power the sensor when actively taking a reading — do not leave it permanently powered with the probes inserted in soil. Continuous current through the probes causes electrolytic corrosion of the nickel plating over time, significantly shortening the sensor's lifespan. In your code, control power via a digital output pin on your microcontroller and switch it on for only 1–2 seconds per reading cycle.
4: This is a resistive soil moisture sensor — it measures electrical resistance between the two probes. Wet soil conducts electricity better than dry soil, which lowers resistance and changes the output voltage accordingly. It is well suited to general hobby and educational use. For long-term outdoor or precision applications, a capacitive soil moisture sensor is recommended as it does not suffer from probe corrosion over time.
5: When reading the analogue output, note that the voltage relationship is inverse — a higher analogue voltage means drier soil, and a lower voltage means wetter soil. This is the opposite of what many beginners expect. On an Arduino, use the following mapping to convert the raw reading into a human-readable moisture percentage: map(analogRead(AO), 1023, 0, 0, 100) — this returns 0% for completely dry and 100% for fully saturated soil.
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