Seeed Studio RTU RS485 Light Intensity Sensor

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	755558mm

Wiring

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

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	0-200000 for 0-200000lux	N/A
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

ACTIVEOUTPUTINT ERVAL

0x0207 /519

UINT16

R/W

3/6/16

0-255 for 0-255

seconds.

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: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

1:8 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)
Register Value: Address		0x01(LOW8 Bits)
Register Value: Baudrate	2 byte	0x00(HIGH 8 Bits)
Register Value: Baudrate		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

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)
Register Value: Illuminance high 16 bits	2 byte	0x00(LOW8 Bits)
Register Value: Illuminance low 16 bits	2 byte	0x00(HIGH 8 Bits)
Register Value: Illuminance low 16 bits	2 byte	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

Document version

Customer Support

Website: www.seeedstudio.com
Ph: +86-0755-86095676

FAQs

Q: What is the Seeed Studio RTU RS-485 Light Intensity Sensor?

The Seeed Studio RTU RS485 Light Intensity Sensor is a digital illumination sensor that uses the RS485 Modbus RTU protocol to transmit data and measure ambient light levels. It is intended for use in environmental monitoring applications, smart agriculture, and outdoor and industrial lighting control.

Q: What is the communication protocol used?

The sensor makes use of the reliable industrial communication standaRS-485485 Modbus RTU. This enables up to 32 devices per line—or multiple sensors—to connect on the same bus (multi-drop network).

Q: How do I power the sensor?

Provide a DC voltage (usually 12V) ranging from 5V to 30V. The sensor is appropriate for low-power systems because it uses less than 20 mA.

Q: How do I calibrate the sensor?

Since the sensor is calibrated in the factory, further calibration is typically not required. Use a lux meter as a reference, though, and apply correction coefficients using your controller or software logic if recalibration is necessary.

Q: Can multiple sensors share the sRS-485S485 bus?

If each sensor has a unique Modbus address and a suitable termination resistor (120Ω) at both ends of the bus, up to 32 sensors can share a siRS-485RS485 line.

Q: What is the typical measurement resolution?

With a resolution of 1 lux, the sensor can identify minute changes in light in controlled spaces like greenhouses or indoor automation systems.

Q: What cable length is supported?

With shielded twisted-pair cable (such as CAT5e or RVSP 2×0.5RS-485 RS-485 can support up to 1200 meters. Use appropriate grounding and surge protection for long-distance installations.

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Seeed Studio RTU RS485 Light Intensity Sensor User Guide

Introduction

Specifications

Wiring

Dimension

Installation

Output Signal Conversion

Modbus Protocol

Registeration

Modbus Register Detail Description

Example

Sensor Status

Example

Modbus Function Code

Function Code 3 Protocol

Slave Response: AA 03 MM VV0 VV1 VV2 VV3… CCCC

Master Request:01 03 0200 0002 C5B3

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

Function Code 4 Protocol Example

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

Master Request: 01 04 00 00 00 02 71 CB

Slave Response: 01 04 04 0000 004D 3BB1

Function Code 6 Protocol Example

Slave Response: AA 06 RRRR VVVV CCCC

Master Request: 01 06 0200 0002 09B3

Slave Response: 01 06 0200 0002 09B3

Function Code 16 Protocol Example

Slave Response: AA 10 RRRR NNNN CCCC

Master Request:01 10 0200 0002 04 0001 0004 BACC

Salve Response:01 10 0200 0002 4070Software Configuration Utility

Software Configuration Utility

Document version

Customer Support

FAQs

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