# DIY - UV Light Sensor

When temperatures rise in the summer and we spend more time outdoors, we increasingly try to protect ourselves from the UV rays of the sun, for example with sunscreen. But is there only this UV radiation in summer? What does it look like when the sun is obscured and how much do the values fluctuate? Find out how much UV radiation reaches the earth and measure the UV intensity with your senseBox!

## Aims of the station

In this station, we use a UV light sensor to measure the intensity of UV light in microwatts per square centimeter (μW / cm²). Then we want to convert the value into the UV index.

## Materials

• UV-light sensor VEML6070

## Basics

Ultraviolet light

Ultraviolet (UV) light is invisible electromagnetic radiation to humans with a wavelength shorter than visible light but longer than that of X-rays. UV light covers the wavelengths from 100 nm to 380 nm. Because of the absorption in the earth's atmosphere - especially in the ozone layer - only little UV-B radiation (100 - 300 nm) penetrates to the earth's surface. UV-A radiation (300 - 380 nm), which is less harmful to human skin, is less absorbed by the atmosphere.t.

UV light intensity is measured in microwatts per square centimeter (μW / cm²). Our sensor measures in the range of approx. 300 - 400 nm, so it absorbs only UV-A radiation (for more details see the Datasheet)).

## Construction

Connect the sensor to the senseBoxMCU as shown in the graphic.

## Programming

Make sure you have the latest board support package installed because you need the correct software libraries. How to do that was explained to you in step 2 !
First, an instance of the sensor must be created.

#include "SenseBoxMCU.h"
VEML6070 vml;


setup()-function

In the setup()-function the sensor now should be started:

void setup(){
vml.begin();
}


loop()-function

In the loop()-function, we can use the getIlluminance() command to get the current measured light intensity:

void loop(){
vml.getUvIntensity();
}

If you want to see the UV index you have to declare a function before that will do it for you. How to do that you will learn in the next step!

Transformation to UV-Index

Since the UV-Index is often used in everyday life, we now want to write a method that converts the measured value into a UV index:

/*
* getUVI()
* expects the knife of the UV sensor as an input parameter
* and returns the corresponding value on the UV index
*/
float getUVI(int uv) {

float refVal = 0.4; // Reference value: 0.01 W / m 2 is equivalent to 0.4 as UV index
float uvi = refVal * (uv * 5.625) / 1000;
return uvi;
}


## Exercise

Exercise 1

In the serial monitor, try using the getUVI ()-function to print out the UV index.