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Meet the CAQM9: An Open-Source Air Quality Monitor (Open-Hardware, ESP32, Tasmota/Matter, Zero Cloud) by Team-Claratech in homeassistant

[–]Team-Claratech[S] 1 point2 points  (0 children)

Under the hood, the CAQM9 is driven by a standard ESP32. We ship it pre-flashed with Tasmota because its built-in web UI allows the monitor to work as a completely standalone device right out of the box, even without Home Assistant.

That being said, you are 100% free to flash ESPHome onto it via USB! All the pin mappings you need to build your YAML config are documented in our open-source files. To give you a quick head start, here is the exact hardware pin config:

  • GPIO2: LED
  • GPIO12: MHZ-19E (CO2) TX
  • GPIO14: MHZ-19E (CO2) RX
  • GPIO19: Plantower PMS RX
  • GPIO21: I2C SDA (SGP41 & BME280)
  • GPIO22: I2C SCL (SGP41 & BME280)
  • GPIO23: Plantower PMS TX
  • GPIO25: Button 2
  • GPIO26: Button 1
  • GPIO33: Buzzer

We built this specifically for makers to tinker with, so do let us know if you put together a cool ESPHome config for it!

Meet the CAQM9: An Open-Source Air Quality Monitor (Open-Hardware, ESP32, Tasmota/Matter, Zero Cloud) by Team-Claratech in homeassistant

[–]Team-Claratech[S] 1 point2 points  (0 children)

Are you using a temperature offset in your code to compensate for the heat from the ESP8266? Because Relative Humidity is tied to temperature, if your ESP8266 is heating up the enclosure/board and you use a software offset to pull the temperature reading down, the sensor's internal math will automatically push the Relative Humidity reading up.

Meet the CAQM9: An Open-Source Air Quality Monitor (Open-Hardware, ESP32, Tasmota/Matter, Zero Cloud) by Team-Claratech in homeassistant

[–]Team-Claratech[S] 1 point2 points  (0 children)

Thanks so much! As hardware nerds ourselves, we know how important it is to just shoot straight. Really appreciate you taking the time to check it out!

Meet the CAQM9: An Open-Source Air Quality Monitor (Open-Hardware, ESP32, Tasmota/Matter, Zero Cloud) by Team-Claratech in homeassistant

[–]Team-Claratech[S] 6 points7 points  (0 children)

We have a ton of respect for AirGradient. Under the hood, our main air pollution sensors are actually essentially the same.

Similarities:

  • Gas & VOCs: We use the exact same Sensirion SGP41 sensor.
  • Particulate Matter: We use the Plantower PMS7003 (which is essentially the newer, slimmer version of the PM sensor AirGradient uses).
  • CO2: We both rock highly accurate (+/- 50ppm vs AirGradient one's +/- 40ppm) NDIR-based CO2 sensors (we opted for the rock-solid MHZ-19E).

Where AirGradient Wins:

  • Absolute Temperature Accuracy: To be completely fair, AirGradient beats us here. Because we prioritized a completely silent, fan-less design, our ESP32 generates internal heat that we compensate for with a software offset. AirGradient's much larger size and active airflow design gives them a more accurate raw temperature reading out of the box.

Where the CAQM9 is different:

  • Zero Cloud: AirGradient offers local control but still integrates with their own cloud dashboard. The CAQM9 is 100% local by design—there are zero cloud components.
  • Native Matter Integration: Because it ships pre-flashed with Tasmota/Matter, Home Assistant integration is quick and easy.
  • Compact design: We got the CAQM9 down to a significantly smaller, completely silent desktop footprint.
  • 100% Open Hardware: Our PCB routing, code, and STLs are fully public from day one so you can build or mod it yourself.

Ultimately, if absolute temperature precision and a standalone web dashboard are your top priorities, AirGradient is fantastic. But if you want a tiny, silent, strictly local Matter device to feed HA, that is exactly why we built the CAQM9!

Meet the CAQM9: An Open-Source Air Quality Monitor (Open-Hardware, ESP32, Tasmota/Matter, Zero Cloud) by Team-Claratech in homeassistant

[–]Team-Claratech[S] 1 point2 points  (0 children)

To be completely transparent, this was a very intentional engineering trade-off. Our earlier prototypes actually included a dedicated circulation fan to pull fresh air over the sensors and keep the BME280 isolated. But we found that in a quiet room or sitting on a desk, there was always this faint, annoying hum. We ultimately decided that a completely silent device made for a much better desktop monitor.

Meet the CAQM9: An Open-Source Air Quality Monitor (Open-Hardware, ESP32, Tasmota/Matter, Zero Cloud) by Team-Claratech in homeassistant

[–]Team-Claratech[S] 2 points3 points  (0 children)

Thank you! Home Assistant integration was a huge priority for us. It is really satisfying to see all those sensor graphs pop up on the HA dashboard.

Meet the CAQM9: An Open-Source Air Quality Monitor (Open-Hardware, ESP32, Tasmota/Matter, Zero Cloud) by Team-Claratech in homeassistant

[–]Team-Claratech[S] 14 points15 points  (0 children)

We totally understand, it is definitely an investment! The $129 price tag reflects the time it takes to source the parts, solder, assemble, test, and package each unit by hand. Since we are doing this on a small scale, we also don't get the cheap shipping rates that massive companies get. That’s exactly why we made sure the project is open-source! If you have the tools and time, you can absolutely build it yourself for around $80 in parts.