Arduino Uno and LTR390 UV Light Sensor

In this example we connect a LTR390 UV Light Sensor from liteon to an Arduino Uno

First lets look at some information about the sensor from the manufacturer

This sensor converts light intensity to a digital output signal capable of direct I2C interface.

This is the sensor that I bought

Parts Required

Here are the parts I used

The sensor you can pick up in the $6 price range – you can connect to the sensor using a standard header the classic dupont style jumper wire.

I used a Qwiic cable – since a few sensors seem to use these but this is optional

Schematic/Connection

I used the Adafruit sensor and in this case used the Stemma connection

For the STEMMA QT cables, it uses the Qwiic convention:

Black for GND
Red for V+
Blue for SDA
Yellow for SCL

So color coded for ease of use

arduino and LTR390

Code Example

This example uses a couple of libraries, both of which can be installed using the library manager

You need the Adafruit library for the https://github.com/adafruit/Adafruit_LTR390

You also need an I2C support library from the same folks for the library above to work and that is available from – https://github.com/adafruit/Adafruit_BusIO

This is the simple test example

[codesyntax lang=”cpp”]

/*************************************************** 
  This is an example for the LTR390 UV Sensor

  Designed specifically to work with the LTR390 UV sensor from Adafruit
  ----> https://www.adafruit.com

  These sensors use I2C to communicate, 2 pins are required to  
  interface
 ****************************************************/
 
#include "Adafruit_LTR390.h"

Adafruit_LTR390 ltr = Adafruit_LTR390();

void setup() {
  Serial.begin(115200);
  Serial.println("Adafruit LTR-390 test");

  if ( ! ltr.begin() ) {
    Serial.println("Couldn't find LTR sensor!");
    while (1) delay(10);
  }
  Serial.println("Found LTR sensor!");

  ltr.setMode(LTR390_MODE_UVS);
  if (ltr.getMode() == LTR390_MODE_ALS) {
    Serial.println("In ALS mode");
  } else {
    Serial.println("In UVS mode");
  }

  ltr.setGain(LTR390_GAIN_3);
  Serial.print("Gain : ");
  switch (ltr.getGain()) {
    case LTR390_GAIN_1: Serial.println(1); break;
    case LTR390_GAIN_3: Serial.println(3); break;
    case LTR390_GAIN_6: Serial.println(6); break;
    case LTR390_GAIN_9: Serial.println(9); break;
    case LTR390_GAIN_18: Serial.println(18); break;
  }

  ltr.setResolution(LTR390_RESOLUTION_16BIT);
  Serial.print("Resolution : ");
  switch (ltr.getResolution()) {
    case LTR390_RESOLUTION_13BIT: Serial.println(13); break;
    case LTR390_RESOLUTION_16BIT: Serial.println(16); break;
    case LTR390_RESOLUTION_17BIT: Serial.println(17); break;
    case LTR390_RESOLUTION_18BIT: Serial.println(18); break;
    case LTR390_RESOLUTION_19BIT: Serial.println(19); break;
    case LTR390_RESOLUTION_20BIT: Serial.println(20); break;
  }

  ltr.setThresholds(100, 1000);
  ltr.configInterrupt(true, LTR390_MODE_UVS);
}

void loop() {
  if (ltr.newDataAvailable()) {
      Serial.print("UV data: "); 
      Serial.print(ltr.readUVS());
  }
  
  delay(100);
}

[/codesyntax]

Output

Here is what I saw in Serial monitor

Adafruit LTR-390 test
Found LTR sensor!
In UVS mode
Gain : 3
Resolution : 16
UV data: 0
UV data: 0
UV data: 0
UV data: 0

Links

Datasheet