Modbus RS485 soil moisture sensor

$ 10.77

Digital (RS485 – based) soil moisture and temperature sensor

This is a contact-less capacitive soil moisture sensor, an update to the I2C soil moisture sensor. This particular version of the sensor is suited for more professional installations where long cable runs is a requirement. It adds a local voltage regulator to mitigate the voltage drop and RS485 transceiver to accommodate long wires, also reverse polarity and an additional ESD protection level is added.

This is the easiest and the most robust way to read soil moisture and temperature values into Raspberry Pi. See the tutorial how to do it.

The main features:

  • Capacitive soil moisture sensing
  • Temperature sensing
  • Good stability with temperature
  • Good stability with power variation
  • Suitable for long cable runs
  • Uses industrial Modbus protocol

10 in stock

SKU: RS485SOIL Categories: , ,


Technical data

  • Supply voltage – 5V
  • Bus can be run on both 3V and 5V
  • Default serial settings: 19200, 8-bit frame, no parity, 2 stop bits
  • Default Modbus address: 1
  • Current consumption: Active: 9mA, Deep sleep: 11uA

Principle of operation

Sensor makes periodic measurements (by default, once every 500ms), delays between measurements can be updated by writing to one of the Modbus registers. The results of the measurements are kept in specific Modbus registers and can be read by master any time unless the sensor is in deep sleep.

Deep sleep is entered by writing a number of seconds to sleep into a special sleep register. The sensor will put the transceiver and all the periphery into the lowest possible power consumption mode and sleep for the specified amoutn of time. After the sleep the sensor will wake up, start taking measurements and be available on the bus till the next sleep command.

Serial communication parameters as baud rate, parity and address can be updated by writing to related registers. The sensor will reset and boot with the new parameters if any of those registers are written.

Full Documentation

  • Full Documentation on  GitHub


This sensor is open source hardware



Additional information

Weight 0.05 kg
Dimensions 20 × 3 × 1 cm


Open Source



Simple, Rugged