This is an old revision of the document!
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 nearby 3D plastic and resin printers, so we can start ventilation when air quality decreases.
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
Desing board - DONE
Order board - DONE
Assembly and test - DONE
Integrate with ventilation
TODO for REV. B
Add pull-up resistor to GPIO2
Add clearance on sides of antenna/use chip antenna
Find another USB to UART converter, because Silicon Labs chips are unavailable
Find another temperature and humidity sensor
Enlarge board & add better thermal isolation between CPU, gas sensors, and temperature sensor
- > 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 on board for particle sensors (HPMA115C0-XXX, SPS30…)
Add RF blocking inductor to VDDPA of ESP8285