Gravity: LTR390 UV Light Sensor Ultraviolet/Visible Light Wiki

1. Introduction

This Gravity: LTR390-UV sensor from DFRobot provides both ambient light and UV sensing with UV spectral response from 280nm to 430nm and raw data output. It features high sensitivity, quick response, and strong anti-interference ability.
With built-in ADC and MCU, this UV module can convert light data to a digital signal capable of being directly output via I2C or UART interface. It can be used for light experiments, outdoor UV detection, and other scenarios requiring UV or ambient light monitoring.

2. Features

Support I2C and UART communication
3.3V & 5V compatible
13 to 20 bits effective resolution
Adjustable gain range: 1, 3, 6, 9 and 18
Interrupt function, programmable upper and lower thresholds
Close to human eye spectral response

3. Application

UV intensity detection
Light intensity detection
Weather experiments for teaching
Light detection experiments
Devices for monitoring UV index
Devices for outdoor UV detection

4. Board Overview

Label	Full Name	Description
D/T	SDA/TXD	I2C Data Line/UART Transmit Data
C/R	SCL/RXD	I2C Clock Line/UART Receive Data
-		Power -
+		Power + (DC 3.3V-5V)

Note: Select I2C or UART mode by DIP switch.

5. Specification

MCU: LTR390-UV-01
Operating Voltage: DC 3.3V to 5V
Operating Current: about 2.73mA (18-bit data acquisition with a time of 100ms)
Communication Interface: I2C/UART
I2C Address: 0x1C
UV Response Wavelength: 280nm to 430nm
ALS Spectral Response Wavelength: 450nm to 700nm
Output Type: digital output
Dimension: 32mm×27mm/1.26×1.06"

6. Dimension

7. Tutorial for Arduino UNO

7.1 Hardware Requirements

DFRduino UNO R3 (or similar) x 1
Gravity: LTR390-UV Sensor

7.2 Software Requirements

Arduino IDE
Download and install the DFRobot_LTR390UV Library (About how to install the library?)

7.3 Connection Diagram

I2C Connection Diagram

Pin Connections:

UV Sensor: + (to) Arduino UNO: 5V

UV Sensor: - (to) Arduino UNO: GND

UV Sensor: D (to) Arduino UNO: SDA

UV Sensor: C (to) Arduino UNO: SCL

UART Connection Diagram

Pin Connections:

UV Sensor: + (to) Arduino UNO: 5V

UV Sensor: - (to) Arduino UNO: GND

UV Sensor: T (to) Arduino UNO: 4

UV Sensor: R (to) Arduino UNO: 5

7.4 Sample Code

I2C Mode

Ambient Light

#include "DFRobot_LTR390UV.h"
DFRobot_LTR390UV ltr390(/*addr = */LTR390UV_DEVICE_ADDR, /*pWire = */&Wire);

void setup()
{
  Serial.begin(115200);
  while(ltr390.begin() != 0){
    Serial.println(" Sensor initialize failed!!");
    delay(1000);
  }
  Serial.println(" Sensor  initialize success!!");
  ltr390.setALSOrUVSMeasRate(ltr390.e18bit,ltr390.e100ms);//18-bit data, sampling time of 100ms 
  ltr390.setALSOrUVSGain(ltr390.eGain3);//Gain of 3
  ltr390.setMode(ltr390.eALSMode);//Set ambient light mode 
}
void loop()
{
  float als = 0;
  als = ltr390.readALSTransformData();//Get data converted from ambient light intensity, which can only be used in ambient light mode
  Serial.print("ALS:");
  Serial.print(als);
  Serial.println("Lux");
  delay(1000);
}

Result

Serial print ambient light data (in an office with strong light).

Note: Ambient Light Reference Range

Place/Environment	Illuminance
Sunny day	30000-300000 lux
Indoors on sunny day	100-1000 lux
Cloudy day	3000-10000 lux
Outdoors on cloudy day	50-500 lux
Indoors on cloudy day	5-50 lux
Indoors at dusk	10 lux
At sunrise and sunset	300 lux
At night	0.001-0.02 lux
Moonlit evening	0.02-0.3 lux
Lightless office	30-50 lux
Exposure to flashlight light	8000-15000 lux

UV Light

#include "DFRobot_LTR390UV.h"
DFRobot_LTR390UV ltr390(/*addr = */LTR390UV_DEVICE_ADDR, /*pWire = */&Wire);

void setup()
{
  Serial.begin(115200);
  while(ltr390.begin() != 0){
    Serial.println(" Sensor initialize failed!!");
    delay(1000);
  }
  Serial.println(" Sensor  initialize success!!");
  ltr390.setALSOrUVSMeasRate(ltr390.e18bit,ltr390.e100ms);//18-bit data, sampling time of 100ms 
  ltr390.setALSOrUVSGain(ltr390.eGain3);//Gain of 3
  ltr390.setMode(ltr390.eUVSMode);//Set UV mode 
}
void loop()
{
  uint32_t data = 0;
  data = ltr390.readOriginalData();//Get UV raw data
  Serial.print("data:");
  Serial.println(data);
  delay(1000);
}

Result

Serial print UV raw data (in the environment without direct sunlight on sunny day).

UART Mode

Ambient Light

#include "DFRobot_LTR390UV.h"
#include <SoftwareSerial.h>
#define UARTMODE //UART mode

SoftwareSerial mySerial(/*rx =*/4, /*tx =*/5);
DFRobot_LTR390UV ltr390(/*addr =*/LTR390UV_DEVICE_ADDR, /*s =*/&mySerial);

void setup()
{
  #define UARTMODE
  mySerial.begin(9600);
  Serial.begin(115200);
  while(ltr390.begin() != 0){
    Serial.println(" Sensor initialize failed!!");
    delay(1000);
  }
  Serial.println(" Sensor  initialize success!!");
  ltr390.setALSOrUVSMeasRate(ltr390.e18bit,ltr390.e100ms);//18-bit data, sampling time of 100ms 
  ltr390.setALSOrUVSGain(ltr390.eGain3);//Gain of 3
  ltr390.setMode(ltr390.eALSMode);//Set ambient light mode 
}

void loop()
{
  float als = 0;
  als = ltr390.readALSTransformData();//Get the data converted from ambient light intensity, which can only be used in ambient light mode
  Serial.print("ALS:");
  Serial.print(als);
  Serial.println("Lux");
  delay(100);
}

Result

Serial print ambient light data (in an office with strong light).

UV Light

#include "DFRobot_LTR390UV.h"
#include <SoftwareSerial.h>
#define UARTMODE //UART mode

SoftwareSerial mySerial(/*rx =*/4, /*tx =*/5);
DFRobot_LTR390UV ltr390(/*addr =*/LTR390UV_DEVICE_ADDR, /*s =*/&mySerial);

void setup()
{
  #define UARTMODE
  mySerial.begin(9600);
  Serial.begin(115200);
  while(ltr390.begin() != 0){
    Serial.println(" Sensor initialize failed!!");
    delay(1000);
  }
  Serial.println(" Sensor  initialize success!!");
  ltr390.setALSOrUVSMeasRate(ltr390.e18bit,ltr390.e100ms);//18-bit data, sampling time of 100ms 
  ltr390.setALSOrUVSGain(ltr390.eGain3);//Gain of 3
  ltr390.setMode(ltr390.eUVSMode);//Set UV mode 
}

void loop()
{
  uint32_t data = 0;
  data = ltr390.readOriginalData();//Get UV raw data
  Serial.print("data:");
  Serial.println(data);
  delay(100);
}

Result

Serial print UV raw data (in the environment without direct sunlight on sunny day).

8. API

 /**
   * @fn begin
   * @brief Init SEN0540 device
   * @return Return value init status
   * @retval 0  Succeed
   * @retval -1 Failed
   */
  int8_t begin(void);

  /**
   * @fn setMode
   * @brief Set data collecting mode for module
   * @param mode select data collecting mode 
   * @return NONE
   */
  void setMode(eModel_t mode);

  /**
   * @fn setALSOrUVSMeasRate
   * @brief Set data bit and sampling time of module, the sampling time must be greater than the time the bit needs
   * @n --------------------------------------------------------------------------------------------------------
   * @n |    bit7    |    bit6    |    bit5    |    bit4    |    bit3    |    bit2    |    bit1    |    bit0    |
   * @n ---------------------------------------------------------------------------------------------------------
   * @n |  Reserved  |        ALS/UVS Resolution            |  Reserved  |   ALS/UVS Measurement Rate           |
   * @n ---------------------------------------------------------------------------------------------------------
   * @n | ALS/UVS Resolution       |000|20 Bit, Conversion time = 400ms                                         |
   * @n |                          |001|19 Bit, Conversion time = 200ms                                         |
   * @n |                          |010|18 Bit, Conversion time = 100ms(default)                                |
   * @n |                          |011|17 Bit, Conversion time = 50ms                                          |
   * @n |                          |100|16 Bit, Conversion time = 25ms                                          |
   * @n |                          |110/111|Reserved                                                            |
   * @n ---------------------------------------------------------------------------------------------------------
   * @n | ALS/UVS Measurement Rate |000|25ms                                                                    |
   * @n |                          |001|50ms                                                                    |
   * @n |                          |010|100ms (default)                                                         |
   * @n |                          |011|200ms                                                                   |
   * @n |                          |100|500ms                                                                   |
   * @n |                          |101|1000ms                                                                  |
   * @n |                          |110/111|2000ms                                                              |
   * @n ---------------------------------------------------------------------------------------------------------
   * @param bit Set data bit 
   * @param time Set sampling time
   * @return None
   */
 void setALSOrUVSMeasRate(eResolution bit,eMeasurementRate time);

  /**
   * @fn setALSOrUVSGain
   * @brief Set sensor gain 
   * @n ---------------------------------------------------------------------------------------------------------
   * @n |    bit7    |    bit6    |    bit5    |    bit4    |    bit3    |    bit2    |    bit1    |    bit0    |
   * @n ---------------------------------------------------------------------------------------------------------
   * @n |                                    Reserved                    |          ALS/UVS Gain Range          |
   * @n ---------------------------------------------------------------------------------------------------------
   * @n | ALS/UVS Gain Range       |000|Gain Range: 1                                                           |
   * @n |                          |001|Gain Range: 3 (default)                                                 |
   * @n |                          |010|Gain Range: 6                                                           |
   * @n |                          |011|Gain Range: 9                                                           |
   * @n |                          |100|Gain Range: 18                                                          |
   * @n |                          |110/111|Reserved                                                            |
   * @n ---------------------------------------------------------------------------------------------------------                  
   * @param data Control data 
   * @return None
   */
  void setALSOrUVSGain(eGainRange data);


  /**
   * @fn readData
   * @brief Get raw data
   * @return Return the obtained raw data
   */
  uint32_t readOriginalData(void);