Capacitive Soil Moisture Sensor
₵25.00
Capacitive Soil Moisture Sensor (typically v1.2) measures soil moisture levels using capacitive sensing rather than resistive sensing. Unlike older resistive sensors, its exposed electrode traces are insulated, preventing corrosion over time when buried in damp soil.
Key Specifications
| Parameter | Value / Description |
| Operating Voltage | $3.3\text{V} – 5.5\text{V DC}$ |
| Output Voltage | $0\text{V} – 3.0\text{V DC}$ (Analog output) |
| Interface | 3-Pin PH2.0-3P / 2.54mm Header |
| Sensor IC / Timer | NE555 or TLC555 timer chip |
| Dimensions | $98\text{ mm} \times 23\text{ mm}$ |
| Weight | Approx. $15\text{ g}$ |
Pinout Connection
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VCC: Power Supply ($3.3\text{V}$ or $5\text{V}$) -
GND: System Ground -
AOUT/AU: Analog Output Signal (connect to MCU Analog Pin, e.g.,A0)
How It Works & Calibration
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Capacitive Measurement: The probe forms a capacitor with the surrounding soil. As moisture levels change, the soil’s dielectric constant shifts, altering the output frequency/voltage.
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Inverted Output:
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Dry Air (0% Moisture): High voltage output ($\approx 2.8\text{V} – 3.0\text{V}$).
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Water (100% Moisture): Low voltage output ($\approx 1.2\text{V} – 1.5\text{V}$).
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Calibration: Record the analog reading in open air ($V_{\text{dry}}$) and submersed in water up to the red line ($V_{\text{wet}}$) to map raw ADC values to a $0\% – 100\%$ scale using your microcontroller code.
Key Features & Applications
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Corrosion Resistant: No exposed metal electrodes in direct contact with wet soil.
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Microcontroller Compatible: Easy to interface with Arduino, ESP32, ESP8266, and Raspberry Pi.
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Applications:
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Smart irrigation and automated plant watering systems
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Soil moisture logging for greenhouses and agriculture
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STEM and garden automation projects
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