Palm

🌴 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

V2.0

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

  1. QSun app and tracker
  2. UV-badge
  3. #badgelife

Processor

  1. nRF52 Adafruit Bluefruit board schematic
  2. Adafruit Feather 32u4 Bluefruit LE with USB or LiPo JST connector

UV Sensor

  1. VEML6075 Adafruit Breakout board footprint
  2. VEML6075 Adafruit Breakout board schematic
  3. VEML6075 datasheet from manufacturer Vishay
  4. Arduino UV Index Meter - Working with Ultraviolet Light
  5. SENS-43UV analog UV sensor
  6. Analog UV Light Sensor Breakout from Adafruit
  7. SI1145 Digital UV Index / IR / Visible light sensor breakout board from Adafruit with I2C bus connection
  8. VEML6070 breakout board with I2C

Other parts used

  1. RGB LED SMD datasheet
  2. Toggle Switch SPDT

Measuring power consumption

  1. Measuring current for nRF52832
  2. Online Power profiler
  3. High pulse drain impact on CR2032 coin cell battery capacity
  4. CR2032 Coin Cell battery life estimation with NRF52 as beacon
  5. Using the correct Bluetooth LE Advertising and Connection Parameters for a stable connection
  6. nRF52832 Product Specification v1.1

Humidity, Temperature and Barometric pressure sensor

  1. Adafruit BME280 breakout board from Adafruit with I2C or SPI
  2. What's the difference between the BMP280 and the BME280 atmospheric sensors

Coin Cell

  1. 20mm Coin Cell Breakout with On-Off Switch CR2032

Firmware

  1. nRF52 Arduino
  2. Si1145 Arduino library by Adafruit
  3. VEML6070 Arduino firmware library

BLE

  1. Adafruit nRF52 Feather device pinout
  2. Adafruit nRF52 Feather pinout
  3. Adafruit nRF52 Feather schematic

Schedule

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.