layout title permalink sequence state_machine items user_stories design Design /design 5 true name url height width depth dimension_unit weight weight_unit Adafruit Bluefruit nRF52 Feather https://www.adafruit.com/product/3406 51 23 8 mm 5.7 g name url height width depth dimension_unit weight weight_unit Adafruit UV Sensor VEML6075 https://www.adafruit.com/product/3964 17.0 15.3 2.9 mm 0.8 g name url height width depth dimension_unit LiPo battery 380mAh at 3.7V https://www.aliexpress.com/item/Limskey-3-7V-380mAh-25C-Lipo-Battery-for-For-Hubsan-X4-H107-H107L-H107D-JD385-JD388/32846516934.html?spm=2114.search0103.3.69.12983204ovX5ra&ws_ab_test=searchweb0_0,searchweb201602_6_10065_10068_319_10059_10884_317_10887_10696_321_322_10084_453_10083_454_10103_10618_10307_537_536,searchweb201603_52,ppcSwitch_0&algo_expid=067ab389-d2ff-4f23-98e8-7aef2b13aeef-9&algo_pvid=067ab389-d2ff-4f23-98e8-7aef2b13aeef&transAbTest=ae803_4 37 19 8 mm user actions user goal reason power ON the device it can measure the UV Index periodically goal reason power OFF the device it can power down completely to save battery consumption goal reason switch ON the wireless BLE it can transmit the data to another BLE device goal reason switch OFF the wireless BLE it can stop transmitting the data to another BLE device goal reason view the changing colors of the on-board RGB LED I know the current range of UV Index goal reason view the numerical values of the UV Index and battery level data on another BLE device I know those values accurately goal reason hang the entire keychain through the M6 drill hole I can be hands-free when outdoors