🌵 Indoor WiFi-connected temperature and humidity sensor 🍶

power LiPO
wireless WiFi
sensor Humidity
mcu ESP8266
battery life 1 month
bom items 36
bom cost USD $26.92
vendors 5
completed May 2019

Lessons learnt

Good practices to continue for future projects

  • Buy electronics modules for V1.0 Make it work, make it right, make it better
  • Ensure main BOM components are available from vendors before schematic or layout
  • Check pin, pitch, manufacturer part number, function before buying BOM parts
  • Do a power tree analysis starting with power source before the schematic design
  • Test out paper mockups for mechanical dimensions
  • Do a mechanical consideration before laying out the footprint
  • Design a power on/off switch to start/stop using the battery
  • Leave out the module's on-board LED as a possible separate indicator E.g. Not linking GPIO02 to EN for the shift register
  • Don't use main chip's power output to enable other components, use another GPIO pin. E.g. Not linking 5V on WeMos to Vin of a sensor or shift register
  • Ensure the mechanical housing has an opening above any environmental sensors E.g humidity, UV index, air pressure
  • Make 2 units, not just 1 especially for non-interactive projects - one for deployment, one for iteration/testing
  • Tag the repository with the version number when the PCB is sent out for manufacturing


For next iteration

  • No more modules
  • Reduce total BOM components
  • Do not use ESP8266's LED GPIO pin
  • Do not use ESP8266's 5V pin to power other components
  • Increase battery life by cutting off power to the sensors during sleep
  • Device an easy way to erase on board WiFi credentials and cloud connectivity details without the need to flash and re-flash the erasing firmware E.g. press a button
  • Tag the repository with the version number when the PCB is sent out for manufacturing
  • Make the measurement interval configurable without re-flashing the firmware

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Design tools

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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.