RS485 Waterproof Ambient Light Sensor(0-200klux) for Arduino- DFRobot

Introduction

This is a completely waterproof digital ambient light sensor that measures the intensity of light in different environments with a detection range of 0~200Klux. It uses the standard Modbus-RTU 485 communication protocol and a DC5-32V wide voltage power supply. It can be used with the TTL to RS485 expansion board (DFR0259) or the Gravity: Active Isolated RS485 to UART Signal Adapter Module (DFR0845) to read the light value on the Arduino UNO R3, quickly build a test environment, and has a simple wiring method and is easy to use. The ambient light sensor has an IP68 waterproof rating and can be completely immersed in water without damage. It is suitable for various indoor and outdoor harsh environments such as weather stations, vegetable greenhouses, outdoor lighting, flower cultivation, factory workshop lighting, and automotive smart lights.

Brightness data reference:

At night: 0.001-0.02 lx;

Moonlit night: 0.02-0.3 lx;

Cloudy indoor: 5-50 lx;

Cloudy outdoor: 50-500 lx;

Sunny indoor: 100-1000 lx;

Summer noon light: about 10*6 lx;

Illumination when reading books: 50-60 lx;

Standard illumination for home video: 1400 lx;

Features

• Waterproof grade IP68
• DC 5~32V wide voltage power supply
• 0~200Klux wide range measurement range
• RS485 interface, standard Modbus-RTU protocol

Applications

• Weather station
• Vegetable greenhouse
• Outdoor lighting
• Flower cultivation Factory workshop lighting
• Automotive smart lights

Specifications:

• Power supply voltage: DC5~32V
• Working current: <10mA
• Output mode: RS485
• Measurement range: 0~200000Lux
• Resolution: 0.01Lux
• Accuracy: ±5%
• Working temperature: -40°C~+80°C
• Protection level: IP68
• Thread length: 10mm
• Opening size: 25mm
• Wrench size: 33mm
• Cable diameter: 4-10mm
• Line length: 1m

Board Overview

Dimensional Drawing

Communication Protocol

1. Basic communication parameters

2. Data frame format definition

Using Modbus-RTU communication protocol, the format is as follows:

Initial structure ≥4 bytes of time

Address code = 1 byte

Function code = 1 byte

Data area = N bytes

Error check = 16-bit CRC code

End structure ≥4 bytes of time

Address code: The address of the sensor, which is unique in the communication network (factory default 0x01).

Function code: The function indication of the command sent by the host. This sensor reads the register function code 0x03 and writes the register function code 0x06

Data area: The data area is the specific communication data. Note that the high byte of 16-bit data is in front!

CRC code: A two-byte check code.

Register address

3. Communication protocol example and explanation

3.1、Read multiple register illumination data instruction

Inquiry frame:

Response frame:

Light value:

00 0C F4 73 (hexadecimal) =849011/1000 =>Light value = 849.011Lux

3.2, Modify the current address

Inquiry frame: (Modify the current address to 0x02)

Response frame:

3.3, Modify address, baud rate

Inquiry frame: (Modify address to 0x01, baud rate to 9600)

After modifying the address or baud rate, the sensor needs to be powered off and reconnected

Response frame:

3.4, query current address, baud rate

Inquiry frame:

Response frame:

The real address of the device read is 01, and the baud rate is 0x03, which is 9600.

3.5, Device factory reset command

Inquiry frame:

Response frame:

Tutorial

Requirements

• Hardware
  • DFRduino UNO R3 (or similar) x 1
  • Gravity: Active Isolated RS485 to UART Signal Adapter Module x1
  • RS485 Waterproof Ambient Light Sensor(0-200klux) x1

• Software
  • Arduino IDE

Connection Diagram

If the power of the RS485 device is small and the required current is less than 12V-160mA, the RS485 to UART signal conversion module does not require a 12V external power supply, making wiring more convenient.

Sample Code

#include <SoftwareSerial.h>
SoftwareSerial mySerial(2,3);
uint8_t Com[8] = { 0x01, 0x03, 0x00, 0x02, 0x00, 0x02, 0x65, 0xCB };
float LUX;
void setup() {
  Serial.begin(9600);
  mySerial.begin(9600);
}
void loop() {
  readLux();
  Serial.print("Lux = ");
  Serial.print(LUX, 3);
  Serial.println(" (lux)  ");
  delay(1000);
}
void readLux(void) {
  uint8_t Data[10] = { 0 };
  uint8_t ch = 0;
  bool flag = 1;
  while (flag) {
    delay(100);
    mySerial.write(Com, 8);
    delay(10);
    if (readN(&ch, 1) == 1) {
      if (ch == 0x01) {
        Data[0] = ch;
        if (readN(&ch, 1) == 1) {
          if (ch == 0x03) {
            Data[1] = ch;
            if (readN(&ch, 1) == 1) {
              if (ch == 0x04) {
                Data[2] = ch;
                if (readN(&Data[3], 6) == 6) {
                  if (CRC16_2(Data, 7) == (Data[7] * 256 + Data[8])) {
                    LUX = (Data[3] * 0x1000000 + Data[4] * 0x10000 + Data[5] * 0x100 + Data[6]) / 1000.000;
                    flag = 0;
                  }
                }
              }
            }
          }
        }
      }
    }
    mySerial.flush();
  }
}

uint8_t readN(uint8_t *buf, size_t len) {
  size_t offset = 0, left = len;
  int16_t Tineout = 500;
  uint8_t *buffer = buf;
  long curr = millis();
  while (left) {
    if (mySerial.available()) {
      buffer[offset] = mySerial.read();
      offset++;
      left--;
    }
    if (millis() - curr > Tineout) {
      break;
    }
  }
  return offset;
}

unsigned int CRC16_2(unsigned char *buf, int len) {
  unsigned int crc = 0xFFFF;
  for (int pos = 0; pos < len; pos++) {
    crc ^= (unsigned int)buf[pos];
    for (int i = 8; i != 0; i--) {
      if ((crc & 0x0001) != 0) {
        crc >>= 1;
        crc ^= 0xA001;
      } else {
        crc >>= 1;
      }
    }
  }

  crc = ((crc & 0x00ff) << 8) | ((crc & 0xff00) >> 8);
  return crc;
}

Expected Results

Print the collected light values

FAQ

Possible reasons for no output or output errors:

1. The sensor is a precision device. Please do not disassemble it by yourself when using it to avoid damage to the product.
2. If the reading value is 0, check whether there is a light source and whether the product protective cover is removed.
3. The 485 bus is disconnected, or the A and B lines are connected in reverse.
4. Check whether the power supply meets the marking.

For any questions, advice or cool ideas to share, please visit the DFRobot Forum.

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