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The SCD40 and SCD41 are high-performance "True" CO2 sensors. Unlike cheaper VOC sensors that estimate CO2 levels, these use photoacoustic technology to measure the actual concentration of CO2 in the air.

The setup for the Raspberry Pi 5 (and older models) involves the I2C interface.

1. Hardware Connections (I2C)

2. Enable I2C on the Raspberry Pi

1. Run sudo raspi-config in the terminal.

2. Navigate to Interface Options > I2C.

3. Select Yes to enable it.

4. Reboot your Pi.

5. (Optional) Check if the sensor is detected by running i2cdetect -y 1. The SCD4x should appear at address 0x62.

3. Install the Python Library

# It is recommended to use a virtual environment on the Pi 5mkdir co2_project && cd co2_projectpython3 -m venv .venvsource .venv/bin/activate# Install the librarypip3 install adafruit-circuitpython-scd4x
 
4. Python Example Code

import timeimport boardimport adafruit_scd4x# Initialize I2C bus and sensori2c = board.I2C()scd4x = adafruit_scd4x.SCD4X(i2c)print("Serial number:", [hex(i) for i in scd4x.serial_number])# Start the sensor's internal measurement cyclescd4x.start_periodic_measurement()print("Waiting for first measurement (takes ~5 seconds)...")try:    while True:        if scd4x.data_ready:            print(f"CO2: {scd4x.CO2} ppm")            print(f"Temperature: {scd4x.temperature:.1f} °C")            print(f"Humidity: {scd4x.relative_humidity:.1f} %")            print("-" * 20)        time.sleep(2)except KeyboardInterrupt:    # Important: Stop measurements to save power/sensor life    scd4x.stop_periodic_measurement()    print("Measurements stopped.")
 
Key Differences for SCD41 Users

• Single Shot Mode: The SCD41 can take a single measurement and go back to sleep, which is better for battery-powered projects. The SCD40 must remain in "periodic" mode.
• Extended Range: The SCD41 reads up to 5,000 ppm (and even up to 40,000 ppm in "extended" mode), whereas the SCD40 is optimized for indoor air quality up to 2,000 ppm.

Pro Tips

If you are using this sensor for a commercial project in South Africa (like a school ventilation monitor), look into Automatic Self-Calibration (ASC). By default, these sensors calibrate themselves based on the lowest CO2 reading they see every week. If your room is never fully ventilated (never hits 400ppm), the sensor's readings will "drift." You can disable ASC in the code if you prefer to do a manual calibration outdoors.

1.3-inch 4-pin I2C OLED Display Module (SH1306, 128x64 Pixels)

The 1.3-inch OLED display is a high-contrast, compact screen ideal for adding user interfaces, data readouts, or graphical feedback to your microcontroller projects. Featuring the SH1306 driver, this module offers a resolution of 128x64 pixels and produces bright, crisp visuals with deep blacks, as each pixel is self-illuminating and requires no backlight.

This specific model comes pre-soldered, allowing for immediate integration into your projects without the need for manual header installation. Its I2C (IIC) interface ensures simple, space-saving communication, requiring only four pins to operate.

Key Features

• Display Quality: 128x64 high-resolution display with a wide viewing angle and high contrast ratio.
• Driver IC: Uses the reliable SH1306 controller, widely supported by popular libraries.
• Compact & Low Power: Small 1.3-inch form factor that consumes very little power, perfect for battery-operated devices.
• Simple Interface: Uses the I2C protocol, keeping your wiring clean with only four connections (VCC, GND, SCL, SDA).
• Pre-Soldered: Equipped with a pre-soldered header for immediate use on breadboards or custom PCBs.
• Versatile Compatibility: Compatible with Arduino, Raspberry Pi, ESP32, ESP8266, and other popular development boards.

Technical Specifications

Typical Applications

• Smart Wearables: Creating readable interfaces for custom fitness trackers or watches.
• Project Monitoring: Displaying real-time sensor data from temperature, pressure, or air quality sensors.
• Menu Systems: Building navigation menus for hand-held control devices.
• Portable Instruments: Compact, high-visibility readouts for custom testing equipment.

What's in the box?

1 x 1.3inch OLED display

Resources