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Ingredient

Capacitive soil moisture sensor

Also known as: v1.2 capacitive sensor, soil moisture probe

Two-electrode capacitive probe that measures soil water content by dielectric — soil with more water has higher dielectric constant, which shifts the sensor's resonant frequency, which the onboard 555-timer-and-comparator circuit converts to an analog voltage. Critically, capacitive probes do *not* corrode in soil the way resistive probes do, which is why they're the right ingredient for any deployed soil-moisture node. ~$2–5 each in bulk; reads on a single analog pin; works on 3.3V or 5V; calibrated by reading air-dry and water-saturated values per individual sensor (manufacturing tolerance is poor).

Inputs / outputs

  • Power: 3.3V or 5V, ~5 mA active
  • Output: analog voltage, ~1.0V (saturated) to ~3.0V (dry) on 3.3V supply (varies; calibrate)
  • Insertion depth: 4–8 cm root zone is standard; deeper for tree applications

Combines with

Any MCU with an analog input. Wireless-node patterns combine with ESP32 + MQTT, or Arduino + LoRa.

Solves / unlocks

  • Threshold-driven irrigation (open valve below moisture setpoint)
  • Crop-specific moisture profiling (different setpoints by bed)
  • Water budget tracking (correlate flow-meter pulses with moisture rise)
  • Drought stress alerts (moisture below crop wilting point → MQTT alert)

Constraints

  • Calibrate every sensor — manufacturing tolerance is poor; air-dry and water-saturated readings vary 10–20%.
  • Soil-type dependent — a single threshold doesn’t transfer between sandy and clay soils; calibrate per bed.
  • Salinity confound — high-EC nutrient solutions affect readings; pair with EC sensor when fertigating.
  • Cheap probes are not waterproof above the sensor body — coat the upper electronics with epoxy before burying.

Source

See also

Auto-generated from this entry’s typed relations: frontmatter, grouped by relation type so the editorial signal isn’t flattened.

  • Member of: [[ingredient]]
  • Combines with: [[arduino-uno]] · [[esp32]] · [[solenoid-valve]] · [[peristaltic-pump]] · [[lorawan]]

What links here, and how

Inbound connections from across the wiki, grouped by lens and by relationship. These appear automatically — every entity page declares what it links to, and that data populates here on the targets.

Practical

combines with

  • Arduino Uno analog read on A0; trigger pump or solenoid above/below threshold
  • ESP32 battery-powered field nodes; deep-sleep between reads, MQTT publish on wake
  • ESPHome ADC-input + soil-moisture filter + threshold automation in pure YAML
  • FarmBot Genesis FarmBot's soil-sensing tool reads moisture before deciding to water
  • LoRaWAN long-range wireless soil-moisture mesh across acres without WiFi
  • Meshtastic soil-moisture mesh across watershed scale without any gateway infrastructure
  • Peristaltic pump container/raised-bed irrigation: moisture below threshold → pump on
  • Solenoid valve the canonical moisture-driven irrigation loop

contains

combines

11 inbound links · 6 outbound