Photoacoustic spectroscopy sensor for CO2 measurements

The SparkFun Photoacoustic Spectroscopy CO2 Sensor features the XENSIV PAS CO2 sensor package from Infineon, which measures highly accurate CO2 data in direct parts-per-million (ppm) format over I2C, UART and PWM. The PAS CO2 employs a photoacoustic spectroscopy measurement system that combines narrow-band filtered IR light and a highly sensitive microphone inside the sensing cavity to measure CO2 concentrations from 0 to 32,000ppm with a best accuracy of ±(30ppm + 3%) when reading between 400ppm and 5,000ppm. It also includes a microcontroller that converts the data into direct ppm readout over any of the three communication interfaces.

The IR emitter on the PAS CO2 requires a 12V supply, so we’ve included an AP3012 boost regulator with a series of decoupling capacitors to output a clean 12V from the 3.3V sourced through a Qwiic connection. As a result, this board comes in slightly larger than the standard 1in. x 1in. Qwiic breakouts and measures 1in. x 1.6in. This breakout routes the I2C bus to a pair of Qwiic connectors, but we’ve also broken out all of the PAS CO2 sensor’s pins to 0.1in. spaced headers so users can pick their communication method and power supply of choice.

The PAS CO2’s interrupt pin has unique functionality beyond a typical hardware interrupt to signal alarm thresholds, data ready, and sensor busy statuses. Users can also configure it to activate as an early measurement start notification during continuous reading and tie it to the boost regulator’

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