Seeed Studio RTU RS485 Light Intensity Sensor | Setup Guide
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    Seeed Studio RTU RS485 Light Intensity Sensor User Guide

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    Seeed Studio RTU RS485 Light Intensity Sensor

    Seeed logo    Seeed Studio RTU RS485 Light Intensity Sensor

    Seeed-Studio-RTU-RS485-Light-Intensity-Sensor-Product

    Introduction

    The Seeed Studio RTU RS485 Light Intensity Sensor, also known as the S-Light-01 ambient light sensor, measures ambient illuminance with high accuracy and consistency. It is widely used in scientific research, solar power, greenhouse, and weather station applications.

    • Measurement range to 200000lux
    • Output interface with RS-485, Voltage
    • Level indicator and spring-loaded for installation
    • Waterproof to IP66 can be used outdoors directly
    • High accuracy and consistency with excellent stability
    • Reverse power protection and Built-in TVS/ESD protection

    Specifications

    Below are the detailed specifications for the Seeed Studio RTU RS485 Light Intensity Sensor, including its power supply, measurement range, and installation requirements.

    Output Interface Analog Voltage 0-2V (Output resistance ~0ohm) RS485 Modbus-RTU
    Power Supply 3.9-30V/DC 3.9-30V/DC
    Power

    Consumption

    		 7mA@24V DC 7mA@24V DC
    Illuminance Range Range:0～200000 Lux, Accuracy:±6% , Resolution:1lux
    Direction Error 30°±3%,60°±6%,80°±24%（Cosine Characteristics）
    IP Ratings IP66
    Operating

    Temperature

    		 -40~85°C
    Installation Screw hole * 3
    Cable Length 2 meters
    Dimension 75*55*58mm

    Wiring

    Seeed-Studio-RTU-RS485-Light-Intensity-Sensor-Fig-2

    All RS485 communication parameters for the Seeed Studio RTU RS485 Light Intensity Sensor (Modbus Slave Address, baud rate, parity, databits, stopbits) are set in internal registers. For connecting to microcontrollers like the Seeed Studio XIAO ESP32S3 series, ensure proper wiring and power supply. The factory setting is ADDRESS=1, BAUDRATE=9600bps, PARITY=NONE, DATABITS=8bits, STOPBITS=1bit. Sometimes you may forget the communication settings.

    In this case, you can open the shield module and press the SET button for more than 3 seconds. The communication parameters are reset to factory settings, allowing the Seeed Studio RTU RS485 Light Intensity Sensor to communicate using default settings. Please re-power up the sensor to make the new settings effective.

    Dimension

    Seeed-Studio-RTU-RS485-Light-Intensity-Sensor-Fig-3

    Installation

    Adjust the screw and check the horizontal bubble to ensure the Seeed Studio RTU RS485 Light Intensity Sensor is properly and horizontally installed.

    Output Signal Conversion

    Output

    Interface

    		 Parameters Range Conversion Formula
    Analog Voltage Output 0-2V ILLU: 0-200000 lux ILLU=RANGE* VLOTAGE/2.00.When RANGE=2000 lux and VOLTEGE=1.0V,then ILLU =2000*1.00/2.00=1000

    lux
    RS485

    Modbus-RTU

    		 ILLU: 0-200000 lux ILLU =(32-Bits REGISTER VALUE).When REGISTER

    VALUE=1000,then ILLU= 1000 lux

    Modbus Protocol

    • Modbus Protocol is widely used to establish master-slave communication between intelligent devices or sensors. The Seeed Studio RTU RS485 Light Intensity Sensor uses this protocol to transmit data accurately. A MODBUS message sent from a master to a slave contains the address of theslave, the function code (e.g., ‘read register’ or ‘write register’), the data, and a checksum sum (LRC or CRC).
    • The sensor is an RS-485 interface with the Modbus protocol. The default serial communication settingsisslaveaddress 1, Modbus RTU, 9600bps, 8 data bits, and 1 stop bit. All communication settings can be changed with a Modbus command and take effect after re-powering up the sensor.
    • The following Modbus function codes are supported by the sensor.
      • Modbus Function Code 0x03is  used for reading holding registers
      • Modbus Function Code 0x04: used for reading input register.
      • Modbus Function Code 0x06 is used for writing a single holding register.
      • Modbus Function Code 0x10: used for writing multiple holding registers.

    Registeration

    Parameters Register Addr. (HEX/DEC) Data Type Modbus Function Code(DEC

    )

    		 Range and Comments Default Value
    ILLUMINANCE

    HIGH 16 Bits

    		 0x0000 /0 UINT16

    RO

    		 3/4 0-200000 for

    0-200000lux

    		 N/A
    ILLUMINANCE

    LOW 16 Bits

    		 0x0001 /1 UINT16

    RO

    		 3/4
    STATUS 0x0002 /2 UINT16 RO 3/4 BIT15-BIT2: Reserved BIT1: Sensor Error

    BIT0: Over Range

    		 N/A
    RESERVED 0x0003 /3 UINT16

    RO

    		 3/4 0 0
    RESERVED 0x0004 /4 UINT16

    RO

    		 3/4 0 0
    RESERVED 0x0004 /5 UINT16

    RO

    		 3/4 0 0
    SLAVEADDRESS 0x0200 /512 UINT16

    R/W

    		 3/6/16 0-255 1
    BAUDRATE 0x0201 /513 UINT16

    R/W

    		 3/6/16 0-6

    0:1200bps 1:2400bps 2:4800bps 3:9600bps 4:19200bps 5:38400bps

    		 3:9600bps
    PROTOCOL 0x0202 /514 UINT16

    R/W

    		 3/6/16 0

    0:Modbus RTU

    		 0:Modbus RTU
    PARITY 0x0203 /515 UINT16

    R/W

    		 3/6/16 0-2

    0:None 1:Even 2:Odd

    		 0:None Parity
    DATABITS 0x0204 /516 UINT16

    R/W

    		 3/6/16 1

    1:8 databits

    		 1:8

    databits
    STOPBITS 0x0205 /517 UINT16 3/6/16 0-1 0:1 stopbit
    R/W 0:1 stopbit

    1:2 stopbits
    RESPONSEDELAY 0x0206 /518 UINT16

    R/W

    		 3/6/16 0-255 for 0-2550

    milliseconds

    		 0
    ACTIVEOUTPUTINT ERVAL 0x0207 /519 UINT16

    R/W

    		 3/6/16 0-255 for 0-255

    seconds.

    		 0

    Modbus Register Detail Description

    ILLUMINANCE – HIGH 16 Bits

    ILLUMINANCE – LOW 16 Bits
    Data Range 0-200000 for 0-200000 lux Default: N/A
    Power Down

    Save

    		 N/A
    Example

    When REGISTER(HIGH 16 Bits) = 0x0003 (HEX format) and REGISTER(HIGH16Bits)=0x0D40 (HEX format), then VALUE=(0x0003 *65536+0x0D40) = 200000lux

    STATUS
    Data Range BIT15-BIT2: Reserved, always 0 BIT1: Bit set when sensor error

    BIT0: Bit set when overrange

    		 Default: N/A
    Power Down

    Save

    		 N/A

    Sensor Status

    SLAVEADDRESS — Modbus Slave Address
    Data Range 0-255 Default: 1 or 13
    Power Down

    Save

    		 YES  

     

     
    BAUDRATE — Serial Comm Baudrate
    Data Range 0-5

    0:1200bps 1:2400bps 2:4800bps 3:9600bps

    4:19200bps

    		 Default: 3

    Please re-power on the sensor to take effect after setting.

    PROTOCOL — Serial Comm Protocol
    Data Range 0

    0:Modbus RTU

    		 Default: 0
    Power Down

    Save

    		 YES
    PARITY — Serial Comm Parity
    Data Range 0-2
    0:NONE
    1:EVEN
    2:ODD    		 Default: 0
    Power Down

    Save

    		 YES

    Please re-power on the sensor to take effect after setting.

    DATABITS — Serial Comm Databits
    Data Range 1

    1:8 databits

    		 Default: 1
    Power Down

    Save

    		 YES
    STOPBITS — Serial Comm Stopbits
    Data Range 0-1

    0:1 stopbit

    1:2 stopbits

    		 Default: 0
    Power Down

    Save

    		 YES
    RESPONSEDELAY — Serial Comm Response Delay
    Data Range 0-255 for 0-2550 milliseconds, 0 for disabled Default: 0
    Power Down

    Save

    		 YES
    Example

    When set to 5 and receive a request from the master device, then the sensor will delay 5*10ms=50ms, then respond to the master.

    ACTIVEOUTPUTINTERVAL — Serial Comm Active Output Interval time
    Data Range 0-255 for 0-255 seconds, 0 for disabled Default: 0
    Power Down

    Save

    		 YES

    Modbus Function Code

    For the description below, data starting with 0X/0x means that it’s in HEX format.

    Function Code 3 Protocol 

    • Master Request: AA 03 RRRR NNNN CCCC
    AA 1 byte Slave Address,0-255
    0x03 1 byte Function Code 3
    RRRR 2 byte Starting Register Addr
    NNNN 2 byte Quantity of Register to read
    CCCC 2 byte CRC CHECKSUM
    Slave Response: AA 03 MM VV0 VV1 VV2 VV3… CCCC
    AA 1 byte Slave Address,0-255
    0x03 1 byte Function Code 3
    MM 1 byte Register Data Byte Count
    VV0,VV1 2 byte Register Value (High8bits first)
    VV2,VV3 2 byte Register Value (High8bits first)
    … … Register Value (High8bits first)
    CCCC 2 byte CRC CHECKSUM

    Master Request:01 03 0200 0002 C5B3

    Slave Addr. 1 byte 0x01
    Function Code 1 byte 0x03
    Starting Register

    Addr.

    		 2 byte 0x0200
    Quantity of

    Register to read

    		 2 byte 0x0002
    Checksum 2 byte 0xC5B3

    Slave Response:01 03 04 00 01 00 03 EB F2

    Slave Addr. 1 byte 0x01
    Function Code 1 byte 0x03
    Register Data Byte

    Count

    		 1 byte 0x04
    Register Value:

    Address

    		 2 byte 0x00(HIGH 8 Bits)
    0x01(LOW8 Bits)
    Register Value:

    Baudrate

    		 2 byte 0x00(HIGH 8 Bits)
    0x03(LOW8 Bits)
    Checksum 2 byte 0xEBF2

    Function Code 4 Protocol Example

    Master Request: AA 04 RRRR NNNN CCCC

    AA 1 byte Slave Address,0-255
    0x04 1 byte Function Code 4
    RRRR 2 byte Starting Register Addr
    NNNN 2 byte Quantity of Register to read
    CCCC 2 byte CRC CHECKSUM

    Slave Response: AA 04 MM VV0 VV1 VV2 VV3… CCCC

    AA 1 byte Slave Address,0-255
    0x04 1 byte Function Code 4
    MM 1 byte Register Data Byte Count
    VV0,VV1 2 byte Register Value (High8bits first)
    VV2,VV3 2 byte Register Value (High8bits first)
    … … Register Value (High8bits first)
    CCCC 2 byte CRC CHECKSUM

    Master Request: 01 04 00 00 00 02 71 CB

    Slave Addr. 1 byte 0x01
    Function Code 1 byte 0x04
    Starting Register 2 byte 0x0000
    Addr.
    Quantity of

    Register to read

    		 2 byte 0x0002
    Checksum 2 byte 0x71CB

    Slave Response: 01 04 04 0000 004D 3BB1

    Slave Addr. 1 byte 0x01
    Function Code 1 byte 0x04
    Register Data Byte

    Count

    		 1 byte 0x04
    Register Value:

    Illuminance high 16 bits

    		 2 byte 0x00(HIGH 8 Bits)
    0x00(LOW8 Bits)
    Register Value:

    Illuminance low 16 bits

    		 2 byte 0x00(HIGH 8 Bits)
    0x4D(LOW8 Bits)
    Checksum 2 byte 0x3BB1

    Function Code 6 Protocol Example

    Master Request: AA 06 RRRR VVVV CCCC

    AA 1 byte Slave Address,0-255
    0x06 1 byte Function Code 6
    RRRR 2 byte Register Addr (High8bits first)
    VVVV 2 byte Register Value (High8bits first)
    CCCC 2 byte CRC CHECKSUM

    Slave Response: AA 06 RRRR VVVV CCCC

    AA 1 byte Slave Address,0-255
    0x06 1 byte Function Code 6
    RRRR 2 byte Register Addr (High8bits first)
    VVVV 2 byte Register Value (High8bits first)
    CCCC 2 byte CRC CHECKSUM

    Master Request: 01 06 0200 0002 09B3

    Slave Addr. 1 byte 0x01
    Function Code 1 byte 0x06
    Register Addr. 2 byte 0x0200
    Register Value 2 byte 0x0002
    Checksum 2 byte 0x09B3

    Slave Response: 01 06 0200 0002 09B3

    Slave Addr. 1 byte 0x01
    Function Code 1 byte 0x06
    Register Addr. 2 byte 0x0200
    Register Value 2 byte 0x0002
    Checksum 2 byte 0x09B3

    Function Code 16 Protocol Example

    Master Request: AA 10 RRRR NNNN MM VVVV1 VVVV2 …CCCC

    AA 1 byte Slave Address,0-255
    0x10 1 byte Function Code 0x10
    RRRR 2 byte Starting Register Addr
    NNNN 2 byte Quantity of Register to write
    MM 1 byte Register Data Byte Count
    VVVV1 2 byte Register Value(High8bits first)
    VVVV2 2 byte Register Value(High8bits first)
    … … Register Value(High8bits first)
    CCCC 2 byte CRC CHECKSUM

    Slave Response: AA 10 RRRR NNNN CCCC

    AA 1 byte Slave Address,0-255
    0x10 1 byte Function Code 0x10
    RRRR 2 byte Starting Register Addr
    NNNN 2 byte Quantity of Register to write
    CCCC 2 byte CRC CHECKSUM

    Example

    Write Register 0x0200-0x0201,that is set slave address to 1, andbaudrateto19200bp.

    Master Request:01 10 0200 0002 04 0001 0004 BACC

    0x01 1 byte Slave Addr.
    0x10(HEX) 1 byte Function Code 0x10
    0x0200 2 byte Starting Register Addr
    0x0002 2 byte Quantity of Register to write
    0x04 1 byte Register Data Byte Count
    0x0001 2 byte Register Value: Slave Address 1
    0x0004 2 byte Register Value: Baudrate 19200bps
    0xBACC 2 byte CRC CHECKSUM

    Salve Response:01 10 0200 0002 4070Software Configuration Utility

    0x01 1 byte Slave Addr.
    0x10(HEX) 1 byte Function Code 0x10
    0x0200 2 byte Starting Register Addr(High8bits first)
    0x0002 2 byte Quantity of Register to write(High8bits first)
    0x4070 2 byte CRC CHECKSUM

    Software Configuration Utility

    Seeed-Studio-RTU-RS485-Light-Intensity-Sensor-Fig-19

    Document version

    Seeed-Studio-RTU-RS485-Light-Intensity-Sensor-Fig-20

    Customer Support

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