My wife was always telling me to put sunscreen on the kids even if the sky was dark and cloudy. I was skeptical that it was needed in those situations. Therefore I decided to actually see if there is indeed a lot of UV light in different scenarios by building a portable UV sensor with screen.

As I had a mountain of M5StickC Plus' laying around from another project, I ordered the only cheap multi-spectral UVA/B/C sensor I could find, the Sparkfun AS7331. I connected the two together and 3D printed a case and this is what I got!

I am happy to get input on the coding to make the readings more accurate to the UV Index measurements used in the US.

I just completed it, so I have yet to field it and see how different environments have different readings.

To do:
1. Convert to UV Index rating instead of direct measurements
2. Convert it to ESPHome to connect to Home Assistant (or AWS IoT SiteWise)