(MQTT enabled environmental sensor)



MEES is a unit created to monitor air quality in our underground hackerspace.
It can measure relative humidity, temperature, (T)VOC, and eCO2.
It will be installed near 3D plastic and resin printers, so we can start ventilation when air quality decreases.

Used parts:

  • SGP40 - VOC sensor
  • CSS811 - TVOC and eCO2 sensor
  • SI7021 - relative humidity and temperature sensor
  • MR44V100AMAZAATL - I2C FRAM for data logging
  • M24M01-RMN6P - I2C EEPROM for calibration data storage
  • ESP8285 - main CPU with WiFi

Current progress:

  • Design board - DONE
  • Order board - DONE
  • Assembly and test - DONE
  • Develop SW
  • Integrate with ventilation


  • Add pull-up resistor to GPIO2
  • Add clearance on sides of the antenna/use chip antenna
  • Find another USB to UART converter chips, because Silicon Labs chips are unavailable
  • Find another temperature and humidity sensor
  • Enlarge the board & improve thermal isolation between CPU, gas sensors, and temperature sensor
    • maybe a mezzanine board?
    • currently this isn't an issue when the fan is unregulated
  • Add mounting holes
  • Add 4R7+1uF RC element to VDD of SGP40 and CCS811 sensor
  • Add UART pins for particle sensors (HPMA115C0-XXX, SPS30…)
  • Add RF blocking inductor to VDDPA of ESP8285
  • Add RGB LED for indication