Soil Moisture Sensor
Reports how wet the soil is as an analog reading.
How it works
A soil moisture sensor measures water content in soil. Resistive types use two exposed probes (cheap, but they corrode over time); capacitive types use a coated plate and last much longer — prefer capacitive.
Most modules give an analog output (AO) you read with analogRead, and many add a digital output (DO) that flips at a threshold set by an onboard pot. Calibrate by noting the reading in dry air vs. a glass of water.
Pins
- VCC
- To 3.3–5V.
- GND
- To GND.
- AO
- Analog output — to an analog pin.
- DO
- Optional digital threshold output.
Ratings
- Voltage
- 3.3–5 V
- Output
- Analog (0–1023) + optional digital
Tips
- Buy capacitive — resistive probes corrode in damp soil.
- Calibrate: record dry and wet readings, set your threshold between them.