🌴 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

Lessons learnt

Good practices to continue for future projects

  • Mark polarity for power connectors to safe guard against reverse polarity. E.g. JST connector should have + and - labels on silkscreen
  • Buy good quality LiPo / battery and power connectors E.g. JST connectors


For next iteration

  • Do not use modules as they are big and bulky. E.g. MDBT42Q
  • Use DP3T to power on, wireless off and wireless on options instead of 2 switches
  • Use a smaller and brighter RGB LED
  • Use a single layer board with only SMD parts so that a housing can be catered for the battery at the back
  • Use a smaller rechargeable coin cell battery E.g. CR2450

Similar projects


UV Sensor

Other parts used

Measuring power consumption

Humidity, Temperature and Barometric pressure sensor

Coin Cell




The Gantt Chart below indicates the actual time taken to complete this project. It can be used as a rough guidline when duplicating or iterating similar projects in the future.