Air Quality Monitoring
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The Air Quality Monitoring project runs on the Silicon Labs EFR32xG24 Explorer Kit, acquires PM, RH/T, VOC, NOx and CO2 measurements from the Sensirion SEN66 sensing platform, and displays them on the Pervasive Displays “Spectra 4” 2.66” four colours screen.
The project is developed with the Arduino IDE, the Silicon Labs core for Arduino and the Basic edition of the Pervasive Displays Library Suite. |
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Hardware
Sensirion SEN66
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The Sensirion SEN66 is an all-in-one sensor that measures particulate matters, temperature, relative humidity, CO2, calculates indexes for VOC and NOX.
The Sensirion SEN66 is connected to the main controller through the I²C bus. The box includes the cable for 4-way JST SH connector with a 1mm pitch, also compatible with Qwiic (Sparkfun) and Stemma QT (Adafruit). |
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Pervasive Displays EXT3.1 extension board and colour 2.66” e-paper screen
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The Pervasive Displays EXT3.1 extension board drives the “Spectra 4” black-white-red-yellow colour 2.66” e-paper screen.
The Pervasive Displays EXT3.1 extension board is connected to the main controller through the SPI bus. |
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Silicon Labs EFR32xG24 Explorer Kit
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The Silicon Labs EFR32xG24 Explorer Kit is based on the EFR32MG24 SOC, a low-power Cortex M33 with multi-protocol 2.4 GHz connectivity, including Matter, BLE and Zigbee.
It includes a Segger J-Link on-board debug probe, a great tool for programming and debugging. Left, the EFR32MG24 SOC with multi-protocol 2.4 GHz radio
Right, the EFM32GG12 MCU with the on-board Segger J-Link |
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Software
Libraries
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Development was done using off-the-shelves libraries.
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Data interpretation
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The major challenge was to interpret the measures and associate the right level of warning.
The project provides five levels, out of the six recommended, with distinctive colours for easy reading. |
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There are many different formulas to calculate the humidex from temperature and relative humidity.
The most challenging measures are the particulate matters. After some search, ChatGPT came to the rescue with detailed lists of thresholds for each size, 1.0, 2.5, 4.0 and 10.0 µm. The full transcript of the session is available at Air Quality Thresholds. Actual monitoring of particulate matters considers accumulated measures with daily limits. |
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Code
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The code is very standard. All the measures use the float type.
The two push buttons of the Silicon Labs EFR32xG24 Explorer Kit provide extra features. Button 0 stops the device; while Button 1 displays the About page. The code reads the values every minute and updates the screen every ten minutes. Despite the compact size of the screen, critical measures instantly pop up. Each section displays the name, unit, value and trend of the measure. The screen below simulates different levels with the corresponding front and background colours. The code is available at the PDI EXT3 Air Quality GitHub repository. |
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Conclusion
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Thanks to the advanced sensor and display technologies, the development of this project was fast and easy.
Extensions could include accumulated measures for the particulate matters and a Matter connectivity for temperature, relative humidity and VOC level. |
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External links
Posted: 28 Apr 2025
