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's enable pin to turn it on only during active measurements to conserve power. To help make this easier, we've routed these two pins to adjacent through-hole pins.

Note: The PASCO2V01 sensors require a week-long calibration period, measuring every 10 seconds. During that period, the sensor must be outside for at least 30 minutes while taking measurements. Refer to the "Automatic baseline offset correction (ABOC) and forced compensation scheme (FCS)" application note in the Documents tab for complete information about the calibration process.

The SparkFun Qwiic Connect System is an ecosystem of I2C sensors, actuators, shields and cables that make prototyping faster and less prone to error. All Qwiic-enabled boards use a common 1mm pitch, 4-pin JST connector. This reduces the amount of required PCB space, and polarized connections mean you can’t hook it up wrong.

• Three Communication Interfaces:
  • I²C (Default)
    • Address: 0x28
    • 2x Qwiic Connectors
  • UART
  • PWM
• Supply Voltage Ranges:
  • VDD3.3: 3.0-3.6V (3.3V Typ.)
  • VDD12: 10.8-13.2V (12V Typ.)
• Photoacoustic Spectroscopy Measurement System
  • Integrated microcontroller outputs direct ppm measurements
• Three Operating Modes:
  • Idle
  • Continuous
  • Single-Shot
• CO₂ Measurement Range: 0-32,000ppm
• Max CO₂ Measurement Accuracy: ±(30ppm + 3% of reading)
  • Max Accuracy Conditions: Reading between 400ppm & 5,000ppm
• Operating Ambient Temperature Range: 0-50°C
• Operating Relative Humidity Range: 0-85%RH

• Schematic
• Eagle Files
• Board Dimensions
• Datasheet (PASCO2V01)
• PAS CO2 Design In Guidelines
• PAS CO2 Low Power App Note
• PAS CO2 FCS & ABOC Compensation App Note
• Hookup Guide
• Qwiic Info Page
• XENSIV PAS CO2 Sensor Arduino Library
• GitHub Hardware Repo