DFRobot SEN0602

Moisture, temperature and pH without inventing an EC channel

Sankhya Farms reads the DFRobot SEN0602 with the DFROBOT_3in1_pH profile. The free cloud dashboard receives moisture, signed temperature and pH from the open-source node at 9600 baud. The profile deliberately skips 0002H: this model has no EC measurement, and its pH word remains at 0003H. That detail prevents a common “3-in-1” assumption from shifting the register map.

The three channels suit a fruit tree, vegetable bed, greenhouse, nursery pot, home garden or solid hydroponic substrate where the operator wants to see pH beside the moisture conditions in which it was measured. It can be used as a passive observation system, for example to compare two soil amendments over several weeks. Continuous history does not replace calibration or a laboratory measurement, but it reveals direction and timing that a notebook of occasional readings may miss. Use a liquid-rated sensor for reservoir pH; this page documents a root-zone probe.

How do I find the SEN0602 pH value?

Moisture is 0000H ×0.1%, signed temperature is 0001H ×0.1 °C, and pH is 0003H ×0.1. Do not read 0002H as pH merely because it follows temperature; that address is not the pH field on this device. Sankhya's profile looks up the defined addresses individually and stores the converted values.

Can the SEN0602 monitor a home greenhouse?

Yes. A single node can collect the three readings from one or more uniquely addressed sensors, subject to correct bus wiring and power.

Why keep moisture with pH?

Electrode response and soil chemistry are affected by water conditions. Viewing both does not solve every calibration issue, but it provides useful context for interpreting a pH change.

Bus & electrical specs

Specs sourced from: Official DFRobot wiki (SEN0600–SEN0605 product pages).

Modbus-RTU register map

Function codes 0x03, 0x06 at 9600 bps, 8N1. Data registers are read with 0x03; configuration registers are written with 0x06. PLC column shows the 4xxxx Modbus holding-register convention.

Changing address & baud rate

This probe is configured over the same RS-485 bus using Modbus write commands (function code 0x06). Configure one device at a time on the bus.

• Set the Modbus slave address by writing register 07D0H (PLC 42001) with function code 0x06.
• Set the baud rate by writing register 07D1H (PLC 42002).
• Power-cycle the probe after a configuration write for the change to take effect.

Notes & caveats

Official map. Note pH is at 0x0003 not 0x0002 — no EC register in this sensor.

Common questions

What baud rate does the DFRobot SEN0602 use by default?

9600 bps, 8N1. It is a Modbus-RTU slave; default address 1.

What supply voltage does the DFRobot SEN0602 need?

DC 5–30 V (Low (RS-485 bus-powered class)).

How do I change the DFRobot SEN0602 Modbus address?

Write the device-address register with function code 0x06, one device on the bus at a time, then power-cycle. See the Configuration section above.

Is the DFRobot SEN0602 compatible with the Sankhya platform?

Yes — it is in the Sankhya RS-485 sensor library and the firmware-generation pipeline can produce node firmware for it.

What does the DFRobot SEN0602 not measure?

The DFRobot SEN0602 reports moisture, temperature and pH only — it does not report EC, N-P-K, salinity and TDS. On the same RS-485 bus, add EC: DFRobot SEN0603; N-P-K: DFRobot SEN0605; salinity: DFRobot SEN0603.

How many Modbus registers does the DFRobot SEN0602 expose?

This guide documents 5 registers, read with function code 0x03 and written with 0x06 where the register is RW. Documented entries include Soil moisture, Soil temperature, pH, Device address and Baud rate.

How this differs from similar models

How the DFRobot SEN0602 compares with the other RS-485 models in the Sankhya library. "Drop-in" means the same parameter set and the same register map, read by the same firmware profile.

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