After sitting 3 months on this project i thought i share it with the maker community. A budget price UV sensor :)

It can be assembled within 1 hour and can use it for years.

Step 1: Before We Begin

Summer is almost here. Day time is longer and warmer, sun shines a lot and this time we are a lot of our home doing many kinds of activity. But often we forget about our sun up the sky. So what about it??

The thing is the sunshine is very important to all living things on our planet. But dont forget the invisible rays (UV radiaton) can be harmful if you are out on the sun for too long. This is a factor that we have to get serious and need to take precautions.

Step 2: UV Index Scale

The UV Index scale is a great tool to tell you how quickly sunburn can occur if you are not applying proper protection. The ultraviolet levels are measured on a daily basis by the National Weather Service and then are converted to a scale of exposure risks.

0-2: Low
A UV Index reading two or lower means there is a minimal risk of sunburn for the average person. At this level it is suggested to wear sunglasses, use broad spectrum sunscreen and watch out for bright surfaces like sand, water and snow which reflect UV rays, increasing your exposure. The time to burn can vary by skin type, but at a low UV level it is approximately 60 minutes.

3-5: Moderate A UV Index reading between 3 and 5 means there is a moderate risk of sunburn for the average person. At this level it is suggested to seek shade between 10AM and 4PM when the sun’s rays are its strongest. Wearing protective clothing, including a hat and sunglasses, is a great way to limit exposure. Sunscreen should be applied every two hours, even on cloudy days, and reapplied after swimming or sweating. The time to burn can vary by skin type, but at a moderate UV level it is approximately 30 to 45 minutes.

UV INDEX CHART6-7: High A UV Index reading 6 or 7 puts you at a high risk of harm from unprotected sun exposure. Following the steps from the moderate level is suggested. The time to burn can vary by skin type, but at a high UV level it is approximately 15 to 25 minutes.

8-10: Very High A UV Index reading 8 to 10 puts you at a very high risk of harm from unprotected sun exposure. Take extra precautions for both your skin and eyes because damage occurs quickly, typically within 15 minutes. Try to minimize your sun exposure during peak sun times, but if not possible then diligently apply and re-apply sunscreen and SPF lip balm.

11 or more: Extreme A UV Index reading 11 or higher puts you in a very dangerous spot for sunburn with damage occurring in less than 10 minutes if unprotected. At this level it is best to avoid all sun exposure between 10AM and 4PM.

Find out the UV Index Level near you and protect yourself from damaging skin exposure. Research has shown that getting severe sunburn, just once every two years, can triple the risk of melanoma skin cancer.

Try to avoid sun exposure between 10 a.m. and 4 p.m.
If outdoors, seek shade and wear protective clothing, a wide-brimmed hat, and UV-blocking sunglasses. Generously apply broad spectrum SPF 30+ sunscreen every 2 hours, even on cloudy days, and after swimming or sweating. Watch out for bright surfaces, like sand, water and snow, which reflect UV and increase exposure. The Shadow Rule An easy way to tell how much UV exposure you are getting is to look for your shadow:

If your shadow is taller than you are (in the early morning and late afternoon), your UV exposure is likely to be lower. If your shadow is shorter than you are (around midday), you are being exposed to higher levels of UV radiation. Seek shade and protect your skin and eyes.

Step 3: UV Index and Sunburn

0.1 - 2.9 low - No precautions, except particularly sensitive skin people and babies

Proposed sun exposure time [minutes]: 60- 75

3.0 - 4.9 moderate - Wear sunhat, UV blocking sunglasses

Proposed sun exposure time [minutes]: 35- 60

5.0 - 6.9 high - Wear sunhat, UV blocking sunglassesuse sunsceen lotion for uncovered body parts

Proposed sun exposure time [minutes]: 25- 35

7.0 - 7.9 very high - Stay in shade between 11 h and 15 hwear sunhat, UV blocking sunglasses, long-sleeved and loose-fitting clothinguse parasoluse sunscreen lotion

Proposed sun exposure time [minutes]: 20 - 25

8.0 and above extreme - Stay in shade between 11 h and 15 hwear sunhat, UV blocking sunglasses, long-sleeved and loose-fitting clothinguse parasoluse sunscreen lotion

Proposed sun exposure time [minutes]: 15 - 20

So be careful!!!

Step 4: So What Now?

There are a few thing you still can do:

- Dress up properly even in this time of the year

- Use sun milk or other stuff

- Try not to take a long time sun bath

- Or have a little gadget that measures the UV intensity :)

Step 5: Arduino Inside

For this project we will use the Arduino again. We only need a few thing to make this work.

The total cost is less than 6$ and a hour free time aprox.

But for some people this budget UV sensor will not do and buy a calibrated one. This is good, but thoose professional ones can cost a smaller fortune. So if someone has 10 bucks free, can do a basic arduino programming and has a little free time to do it himself then why not make it??!!

Step 6: Parts Needed

The parts needed are the following:

- Any Arduino board (Atmega328 and up)

- Breadboard

- Nokia 5110 lcd

- VEML 6070 I2C UV sensor

- A few jumper wires

Step 7: Connections

The connection are the following

Nokia 5110:

-Reset Digital 12

- CE Digital 11

- DC Digital 10

- DIN Digital 9

- CLK Digital 8

- VCC 3 volts

-BL VCC or ground

- GND Ground

VEML6070:

-VCC 3.3 volt only!

- GND Ground

- SCL Analog 5

- SDA Analog 4

Step 8: Software

I am including the sensor library and the sketch.Download and install the libraries needed. Compile sketch and upload.

Step 9: Measuring the UV Index

When i firstly written this fairly simple sketch i realised that the arduino is reporting the values to the serial monitor. But not the way i wanted :/ As a second thought i realised that he values needed to be divided to look like a UV index chart(somewhere about 230 to 250). As for a help in my country i decided to use a UV map provided by Hungary's No1. weather forecast provider and two android apps that a fetching the aprox UV index.( https://www.idokep.hu/uv)

https://learn.adafruit.com/adafruit-veml6070-uv-li...

So it took me a while to aproximately calibrate the whole thing, because in the past 3 weeks there were nothing but clouds and rain in my area. Today it was plenty of sunshine and spent 3 hours testing.

The main reason why i purchased this sensor, because an analog sensor is a little difficult to calibrate and less accurate.