🌴 Outdoor BLE-connected UV sensor keychain 🗝

power LiPO
wireless BLE
sensor UV Index
mcu nRF52
battery life 5 days
bom items 13
bom cost USD $50.47
vendors 4
completed July 2019



  • Read UV Index with the on-board sensor VEML6075 and the battery level
  • Display the UV Index color code with the on-board RGB LED
  • Power on/off the entire device with the on-board power switch
  • Start or stop BLE advertising with the on-board BLE switch
  • Connect via the USB cable to flash the firmware or charge the LiPo
  • Hang it like as keychain using the M6 drill hole
  • Display UV Index and Battery level as a GATT service and characteristic on a BLE client such as the iPhone or Web BLE on Chrome browser

Getting Started

Step 1

Wire up the hardware components with nRF52 Adafruit feather board, VEML6075 sensor board and LiPo battery. Turn on the switch for power and BLE.



Step 2

Flash the firmware onto the nRF52 board to display UV Index and battery level.

Serial console for firmware

Step 3

See the UV and battery level values on the nRF Connect iPhone app

iOS app detect iOS app GATT Services


  • Flashing firmware: Plug in the USB cable into the USB connector
  • Charging the LiPo: Plug in the USB cable into the USB connector. Charging will have the yellow LED on.