Wesley Elfring's AirQuality V3 Is a Low-Cost Broad-Function Do-It-Yourself MQTT Air Quality Monitor

Talking MQTT to a Home Assistant server, this multi-function sensor can track everything from nitric oxide pollution to light levels.

Self-described "hobby programmer" Wesley Elfring is working on a homebrew air quality sensor built around an Espressif ESP32-S3 microcontroller and modular sensors — having found off-the-shelf equivalents wanting in price or functionality.

"The AirQuality V3 is an air quality sensor made from scratch," Elfring explains of his project. "I wanted a cheaper sensor than the commercially available options, but more capabilities than the open source options like AirGradient. It also gave me a good project to continue on my journey to learn more on developing electronics and embedded software."

The AirQuality V3 board itself is designed as a carrier for an Espressif ESP32-S3 module, which provides both the driving logic and its Wi-Fi connectivity. To this, a number of sensors can be added: a Sensirion SGP41 gas sensor for nitric oxide (NOx) and volatile organic compound (VOC) measurements; a SenseAir S8 for carbon dioxide (CO₂) measurement; a Plantower PMS5003 for particulate matter measurement, with readings for PM1.0, PM2.5, and PM10; a Bosch Sensortec BME280 combined temperature, humidity, and barometric pressure sensor; and a Vishay VEML7700 to measure ambient light levels.

"The sensor periodically polls the sensors (as per the datasheets) and publishes the new values to a MQTT topic," Elfring explains of the device's operation. "Home Assistant is then able to pick up the values automatically trough auto-discovery. OTA updates and configuration is supported through a web interface.

"[The] cost for all components for a single board is about $53. [The] most expensive components are the PMS5003 ($17), SenseAir S8 ($18), the SGP41 gas sensor ($7) and the ESP32-S3 ($4.7). The four-layer PCB itself strongly depends on how many you order, but is around $4 per PCB, bringing the total cost per Air Quality sensor to $57."

Elfring has released design files and source code for the project, under an unspecified open source license, on GitHub.

Gareth Halfacree
Freelance journalist, technical author, hacker, tinkerer, erstwhile sysadmin. For hire: freelance@halfacree.co.uk.
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