DIY Personal UV Dosimeter
Europe is going through an immense heat wave. 🫠🌞
Stepping outside reminds me of those post-apocalyptic movies/games where you can only spend a limited time outdoors before taking some kind of health damage 🙈
So I thought, why not just embrace this feeling and build a little wearable that tracks my sun (UV) exposure while being on the go and warns me when It starts to become a health risk.
Current prototype
- 3D-printed case, clipped to my backpack strap so my body doesn't shade the sensor too much.
- GUVA-S12SD analog UV sensor (with a thin PTFE diffuser on top as a cheap cosine corrector)
- Passive buzzer
- Seeed XIAO nRF52840 board (onboard RGB LED)
- Small 150mah LiPo
How it works
- Reads UV every few seconds and converts it to a UV Index
- Integrates a "sunburn" dose that slowly "heals" while I'm out of the sun
- Separately keeps a rolling 7-day dose as a sliding window with no healing. This is supposed to limit the long-term skin cancer risk.
- Red blink + buzzer alarm when I cross a dose or UV threshold ("get in the shade, now!")
- Logs everything (UV, dose, weekly %) over BLE so I can watch it live on my phone (just using serial logging over ble for now)
- Power saving: it drops into a slow "night mode" in the dark and goes completely quiet, then chirps a little wake-up tone in the morning
- battery lifetime seems to be around 48 hours.
I don't want to oversell it, though
- A GUVA is a broadband UV sensor and is not ideal for measuring how UV is affecting the skin (I guess off by 15%). But the "scientifically correct" sensor would probably cost a few hundred bucks.
- The dose + recovery model probably won't pass any scientific review. I'm neither a medical professional nor a scientist. But it seems to be a good approximation.
- It doesn't know about my use of sun protection like sunscreen. But since it's quite unlikely that every inch of my skin isn't protected, I still take the dosage warning seriously.
- The wiring is a total mess. 😅
I'm a software engineer, but my electronics skills are rather limited. I would love the device to be only half its size, but to achieve that I will probably need a custom PCB. I'm trying now to learn kicad and PCB design. Wish me luck 🤞