SCD41 Miniature NDIR CO2 Sensor Module - I2C Breakout Board (400-5000ppm)

Specifications

• Sensor Core: SCD41

• Measurement Range (CO2): 400 ppm – 5,000 ppm

• Accuracy: ±(40 ppm + 5% reading)

• Supply Voltage: 2.4V – 5.5V DC (Wide range support)

• Interface: I2C (Address: 0x62)

• Dimensions: Compact ~10mm x 10mm x 7mm (Module size varies slightly by breakout revision)

• Integrated Data: CO2, Temperature (-10°C to 60°C), Relative Humidity (0-100% RH)

Key Applications

• Smart HVAC Systems: Demand-controlled ventilation based on actual occupancy.

• Indoor Air Quality Monitors: Desktop monitors for office and school use.

• Vertical Farming & Greenhouses: Precise CO2 Injection Monitoring for Plant Growth.

• IoT Weather Stations: Adding indoor pollutants data to standard weather logging.

Project Evolution

From Simple Logging to Smart Action If you have mastered basic temperature logging with a DHT11 or DHT22, you are ready for this. A temperature sensor tells you if you are hot; the SCD41 tells you if you are groggy due to lack of oxygen.

• The Upgrade: This module allows you to build a "Sentient" Ventilation System. Instead of running a fan all day, your Arduino can trigger a relay to turn on the exhaust fan ONLY when CO2 levels cross 1000 ppm.

• Effort Level: Intermediate. Requires understanding I2C communication and installing the Sensirion Arduino Library.

• Hardware Needed: Any microcontroller with I2C (Arduino Uno, ESP32, Raspberry Pi Pico).

Virtual Technician: Wiring & Safety

Warning: While the chip supports 5V, ensure your microcontroller's logic levels match. The module typically includes a regulator, but for 3.3V boards (ESP32/RP2040), connect VCC to 3.3V to be safe.

Standard I2C Pinout:

• VIN/VCC: 3.3V - 5V DC

• GND: Common Ground

• SCL: I2C Clock (Connect to A5 on Uno / D22 on ESP32)

• SDA: I2C Data (Connect to A4 on Uno / D21 on ESP32)

Note: The SCD41 requires a few seconds to stabilise after being powered up. Do not query it faster than every 5 seconds.

Helpful Tutorials & Resources

• SCD41 CO2 Sensor_Datasheet

• SCD41 Arduino Library & Guide
  

Frequently Asked Questions (Technical SEO)

• What is the difference between SCD41 and the cheaper SCD40? The SCD41 is the "Pro" version. It supports a wider voltage range (down to 2.4V), has higher accuracy, and critically, supports "Single Shot" mode for low-power battery operation, which the SCD40 lacks.
• Does this measure "True" CO2 or "Estimated" eCO2? It measures True CO2. Unlike CCS811 or SGP30 sensors that guess CO2 levels based on VOCs (smells), the SCD41 uses Photoacoustic NDIR technology to physically count CO2 molecules.
• How accurate are the readings? The sensor is rated for ±(40 ppm + 5% of reading). In a standard room with 1000 ppm, the error margin is roughly ±90 ppm, which is excellent for HVAC and safety monitoring.
• What is the I2C address of the SCD41? The I2C address is fixed at 0x62. It cannot be changed via software.
• Can I use multiple SCD41 sensors on one Arduino? Since the address is fixed (0x62), you cannot daisy-chain them directly. You will need an I2C Multiplexer (like the TCA9548A) to communicate with multiple sensors individually.
• Does it require calibration out of the box? Generally, no. It comes factory calibrated. However, for best accuracy, we recommend running it in fresh air (400 ppm) for at least 1 hour after you first install it.
• What is Automatic Self-Calibration (ASC)? ASC is a built-in algorithm that assumes the lowest CO2 reading over a 7-day period is "fresh air" (400 ppm). If you use this indoors constantly where windows never open, you should disable ASC to prevent drift.
• How do I perform a Forced Recalibration (FRC)? If your readings seem off, place the sensor outside in fresh air for 3 minutes. Send the perform_forced_recalibration(400) command using the library to reset the baseline to 400 ppm.
• Can I use this with a 5V Arduino Uno? Yes, the module typically has a voltage regulator and level shifting compatible with 5V. However, check your specific breakout board; connecting 5V to a raw 3.3V sensor pin will destroy it.
• Is it compatible with Raspberry Pi? Yes, it works perfectly with Raspberry Pi via the GPIO I2C pins. You may need to enable "I2C Clock Stretching" on the Pi if you experience timeout errors.
• What is "Single Shot" mode? This is a low-power feature unique to the SCD41. Instead of measuring constantly, you can command the sensor to take one reading and then sleep. This reduces current consumption to micro-amps, ideal for batteries.
• How fast can I read data from the sensor? The minimum sampling interval is 5 seconds. Polling it faster than this will result in duplicate data or I2C errors.
• Does altitude affect the CO2 readings? Yes, pressure changes affect gas density. The SCD41 has a command set_ambient_pressure(pressure_hPa) which you should use if you are at high altitudes for maximum accuracy.
• Why is my temperature reading higher than room temperature? The sensor generates a small amount of heat during operation. The library allows you to set a "Temperature Offset" to compensate for this self-heating.
• Can I use this sensor outdoors? It is designed for indoor use. While it can measure outdoor air, it must be protected from direct water, rain, and direct sunlight, which can interfere with the optical cavity.
• What libraries are available for coding? Sensirion provides official libraries for Arduino ("Sensirion I2C SCD4x"), Python (for Raspberry Pi), and it is fully supported in ESPHome and Tasmota for home automation.
• How long does the sensor last? The expected lifetime is over 10 years depending on the environment. The photoacoustic source is solid-state and does not burn out like old incandescent bulbs.
• Does it detect smoke or carbon monoxide (CO)? No. This sensor is specific to Carbon Dioxide (CO2). It will not detect smoke, CO, or natural gas leaks.
• What happens if I touch the sensor element? Avoid touching the white filter area. Oil and dirt from fingers can clog the membrane, slowing down response time or affecting humidity readings.
• Why is the startup time slow? After powering on, the sensor needs about 10-30 seconds to stabilize its internal heater and optical elements before the first valid reading appears.