Mike Rankin

This project is a CO2 monitor using the new, very small STCC4 sensor from Sensirion. For years I've been using the larger SCD40 that was difficult to fit into smaller designs because of it's large size. The SCD40 measures co2 from 400ppm to 2000ppm +/-50ppm in a 10.1mm x 10.1mm footprint and the STCC4 measures from 400ppm to 5000ppm +/-100ppm in a 3mm x 4mm footprint. This Altium designed board is powered by a USB-C phone charger and is the same size as the display using as few parts as possible. A few features I've added are backlight control for dimming, a Qwiic i2c connector for adding other sensors and sensors on the front side. Problems with this design are the delicate push and pull stress on the USB-C connector. Any side to side push on the board while powered up will easily break the connector off the board. The other is the temperature value displayed.

This project has gone through several revisions over several months. This latest uses a pcb track antenna instead of the chip type. Tuning has gone well and it seems to perform well. This version uses an ESP32-S3 processor allowing everything to fit on the backside of a 1.69" screen. An 8-bit bus improves the refresh dramatically over traditional spi displays. It is powered by a USB-C connector or small LiPO battery Two right angle pushbuttons are on one side if needed and two small vertical ones needed only when first powering up the board to bring up the com port. The thermal code provided is rough but shows basic functionality. Hopefully it can be of some help allowing you to make improvements. The design files are all available if you would like to assemble your own and change the design yourself.

STM32 dev board used to get a bit more familiar with the STM32CubeIDE. It is very simple used mostly to experiment with the screen and the i2c bus connector.

NXP dev board also very basic in its design used to get more familiar with the MCUXpress IDE. This one has a few sensors on it as well as the lcd screen and i2c bus connector.