SparkFun
STC31 CO2 Sensor (Qwiic)
· MPN: SEN-29260
Measure high concentrations of carbon dioxide with a Qwiic breakout built around Sensirion’s STC31 sensor. It is designed for CO2 measurements up to 100% vol...
Measure high concentrations of carbon dioxide with a Qwiic breakout built around Sensirion’s STC31 sensor. It is designed for CO2 measurements up to 100% volume, using a thermal conductivity measurement principle and Sensirion CMOSens® technology for repeatable, stable readings.
The board also includes a separate Sensirion SHTC3 humidity and temperature sensor, allowing the STC31 to provide compensated CO2 measurements that account for humidity, temperature and atmospheric pressure.
As part of the SparkFun Qwiic Connect System, it connects over I2C using the onboard Qwiic connectors, so you can plug it into a compatible development board without soldering. The STC31 I2C address can be configured with split-pad jumpers on the back of the board, while the SHTC3 address is fixed and may require a Qwiic Mux if you need multiple sensors on the same bus.
Arduino example sketches are available through the SparkFun STC3x Arduino library, and Python, MicroPython and CircuitPython support is also provided by the supplier package.
Features:
- Sensirion STC31: CO2 sensor for high-concentration carbon dioxide measurement
- Thermal conductivity sensing: Provides calibrated gas concentration and temperature output
- Sensirion CMOSens® technology: Integrates the sensor element, signal processing and digital calibration onto a single chip
- Sensirion SHTC3: Onboard humidity and temperature sensor
- Compensation: Allows the STC31 to compensate for humidity and temperature
- Qwiic: Plug-and-play I2C connection with no soldering required
- Connectors: Dual Qwiic connectors
- Address selection: STC31 I2C address configurable using split-pad jumpers
- Power LED: Configurable
- I2C pull-ups: Configurable
Specifications:
- Two CO2 Measurement Ranges: 0 to 25 vol% and 0 to 100 vol%
- Measurement Repeatability: 0.2 vol%
- Accuracy (0-25% range): 0.5 vol% + 3% of measured value
- Accuracy (0-100% range): 1 vol% + 3% of measured value
- STC31 sensor: Sensirion STC31 CO2 Sensor
- Calibrated for: CO2 in N2; and CO2 in air
- Measurement ranges: 0 to 25 vol%; 0 to 100 vol%
- Accuracy: 0.5 vol% + 3% measured value; 1 vol% + 3% measured value
- Repeatability: 0.2 vol%
- Temperature measurement range: -20 °C to +85 °C
- Concentration and temperature resolution: 16-bit
- Start-up time: 14 ms
- I2C address (configurable): 0x29 (default), 0x2A, 0x2B, 0x2C
- STC31 supply Voltage: 2.7VMin, 3.3VTyp, 5.5VMax
- STC31 note: Qwiic bus operates at 3.3VMax
- SHTC3 sensor: Sensirion SHTC3 Humidity and Temperature Sensor
- Typical accuracy: ±2 %RH and ±0.2 °C
- Specified humidity range (extended): 0 to 100 %RH
- Specified temperature range: -40 °C to +125 °C
- I2C address (non-configurable): 0x70
- SHTC3 supply Voltage: 1.62VMin, 3.3VTyp, 3.6VMax
- SHTC3 note: Qwiic bus operates at 3.3VMax
A strong choice for gas sensing projects that need high-range CO2 measurement, environmental compensation and quick integration with Qwiic-enabled Arduino, MicroPython or CircuitPython systems.
Jargon buster
Plain-language definitions for the technical terms used above.
- breakout
- A breakout is a small circuit board that makes a tiny or hard-to-solder component easier to connect to with standard pins. It matters because this OLED module can be wired into a microcontroller project without needing to solder directly to the display’s fine contacts.
- CircuitPython
- A beginner-friendly version of Python designed to run directly on microcontroller boards. If a product supports CircuitPython, you can often program it by copying code files onto the board rather than setting up a more complex toolchain.
- CMOSens
- CMOSens is Sensirion’s integrated sensor technology that combines sensing elements and electronics in one package. It matters because it affects how the sensor measures temperature and humidity and how it is supported by the manufacturer’s libraries and datasheets.
- I2C
- I2C is a two-wire communication bus used by many sensors and small modules. It matters because several I2C devices can share the same two wires, but each device needs a compatible address and your controller must support I2C.
- I2C address
- An I2C address is the number a device uses so a microcontroller can tell it apart from other devices on the same I2C bus. It matters because two devices with the same fixed address may conflict if used together.
- LED
- A light-emitting diode is a small electronic component that lights up when current flows through it in the correct direction. In this kit, LEDs create the flashing effect, so polarity and correct soldering matter for the project to work.
- MicroPython
- A version of the Python programming language made to run on microcontrollers. It matters because it lets beginners write readable code to control LEDs, sensors, motors and displays without needing to start with lower-level languages.
- Qwiic
- Qwiic is a plug-in connector system for I2C devices that uses small 4-pin cables, so you can connect compatible sensors without soldering. It matters because your controller or adapter also needs Qwiic, or you will need a cable or breakout to wire it up.
- Thermal conductivity measurement
- Thermal conductivity measurement estimates gas concentration by detecting how well the surrounding air conducts heat. For a CO₂ sensor, this tells you the module is using a direct physical sensing method rather than estimating CO₂ from other air-quality signals.
- UPS
- An uninterruptible power supply is a battery-backed power system that keeps a device running when external power is unplugged or fails. For an embedded computer, it helps prevent sudden shutdowns that can corrupt files or interrupt a project.
Find this product in
STC31 Qwiic Schematic
Schematic · 162.4 KB · Click any page to view full size
STC Field Calibration Guide
User Guide · 328.5 KB · Click any page to view full size
STC31 Datasheet
Datasheet · 897.1 KB · Click any page to view full size
STC Design-In Guide
User Guide · 313.3 KB · Click any page to view full size
Supplier page — sparkfun.com
Supplier Description · 892.3 KB · Click any page to view full size
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