David Kreidler's OpenCO2 Mini Sensor Delivers Carbon Dioxide Monitoring on the Go
USB Type-C thumb-sized sensor module connects to Sensirion's Apple iOS software to provide environmental readings anywhere.
OpenCO2's David Kreidler has designed a considerably more compact version of his company's carbon dioxide sensor, designed to plug into the USB Type-C connector of a smartphone for taking readings on the go — and it's called, sensibly enough, the OpenCO2 Mini Sensor.
"Introducing the OpenCO2 Mini Sensor, an ultra compact and powerful indoor air quality monitor designed for health, comfort, and convenience," Kreidler says of his new design. "Measuring just 2×2.7cm [around 0.79×1.06"], this tiny device packs cutting-edge technology into a sleek, clear 3D-printed case that's perfect for attaching to your keychain or slipping into your pocket. Stay informed about your environment wherever you go!"
The heart of the new sensor is the Sensirion STCC4 carbon dioxide sensor in a package combining it with the Sensirion SHT40 temperature and humidity sensor, connected to an Espressif ESP32-S3 microcontroller on a thumb-sized PCB that somehow also finds room for an RGB status LED. It's a different setup to the original OpenCO2 Sensor, which opted for the Sensirion SCD40 and placed it in a 3D-printed desktop housing behind a 1.54" ePaper display with an Espressif ESP32-S3 to drive everything.
The new model is compact, and primarily designed with smartphones in mind — promising "seamless" connection to the Sensirion MyAmbience app on Apple iOS via Bluetooth Low Energy (BLE). Like its predecessor, though, the sensor can also be connected to a Wi-Fi network and integrated into Home Assistant and other smart home platforms — or the RGB LED can be observed to provide a three-stage color-coded at-a-glance look at environmental carbon dioxide concentrations.
"Regular ventilation is key to maintaining healthy indoor air quality. The OpenCO2 Mini Sensor provides a simple, affordable, and portable solution to monitor CO2 levels, helping you make informed decisions to improve your environment," Kreidler claims. "Whether you're a health-conscious individual, a DIY enthusiast, or a smart home integrator, this sensor delivers professional-grade performance in a pocket-sized package."
The OpenCO2 Mini Sensor is now available on Kreidler's Tindie store at $49.95, roughly half the price of the original OpenCO2 Sensor; source code for the original sensor is available on GitHub under the permissive MIT license, but the repository did not appear to contain the firmware for the new model at the time of writing.