Cactus: Measure humidity in kitchen cupboards

ESP8266, WeMos, Si7021, battery shield, IFTTT.

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How much does the humidity decrease when we put a dehumidifier in our kitchen cupboards?

This project will use a WeMos module (ESP8266) to get the values of humidity and temperature from a Si7021 sensor and send it to IFTTT to log in a spreadsheet every 4 hours. It will be battery powered by a LiPo and even without any connectivity to WiFi, a button press will indicate the humidity level via a bar LED display.


Complete BOM with details on the manufacturer, cost, vendor, part number, etc

Comma-Separated Values - 2.57 kB - 05/13/2019 at 07:16



KiCad schematic

Adobe Portable Document Format - 1.51 MB - 05/13/2019 at 07:16



Footprint layout of the PCB

Adobe Portable Document Format - 318.70 kB - 05/13/2019 at 07:16


  • 1 × WeMos ESP8266 module
  • 1 × WeMos battery shield To power via a LiPo
  • 1 × Si7021 Adafruit temperature and humidity breakout board
  • 5 × Red SMD 0805 LEDs To display the humidity levels on-board when pressed a button
  • 4 × M2 spacers

View all 7 components

  • Deployed: Week 2

    sayanee05/14/2019 at 06:06 0 comments

    For 1 week, the device has been pinging back to the cloud with average humidity value as well as the battery values as recorded in the Google sheets.

    The humidity values were pretty consistent from 87 RH% to 92 RH%.

    The LiPo battery voltage levels came down steadily from a fully charged value of 4.2V to 3.9V.

    I just put in the dehumidifier beside the device. So let's see whether the humidity levels change at all.

  • Deloyed

    sayanee05/13/2019 at 07:05 0 comments

    Cactus is now finally deployed in the kitchen cupboard without any dehumidifier as a control. Every 4 hours it is pinging IFTTT with the humidity values as well as the LiPo battery voltage. Follow the live log in Google Sheets right here!

    After a week, I will put in a dehumidifier to see whether the humidity levels are affected.

  • Mechanical considerations before designing the PCB

    sayanee08/27/2017 at 22:56 0 comments

    1. Place the PCB on top of the 2 AA battery holders
    2. Connect the battery wires on one of the shorter edge of the PCB
    3. Solder the ESP-12F on the other shorter edge of the PCB
    4. Bar LEDs are lining up on the longer edge of the PCB
    5. Place the ESP-12F module within the dimensions of the battery holder so that the final form can stand vertically as well

View all 3 project logs

  • 1
    Setup IFTTT

    Setup an IFTTT webhook to receive a POST request with data and add a row to a Google Spreadsheet.

  • 2
    Turn on the device with LiPo

    Connect to the access point "Cactus {MAC_ACCRESS}"

  • 3
    Configure WiFi and IFTTT credentials

    Go to the web page http://cactus.local to fill in the WiFi credentials and IFTTT webhook key.

View all 5 instructions

Enjoy this project?



hardyboyz4u wrote 03/01/2020 at 20:42 point

Where is the code ?

also what's the resistor value for battery to A0 ? 

  Are you sure? yes | no

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