MG811 CO2 Sensor Module – 0-2V Voltage Output for Carbon Dioxide Detection

Description

The MG811 CO2 Sensor Module is a solid-electrolyte electrochemical sensor board designed for detecting carbon dioxide concentration in air quality control, fermentation processes, and greenhouse environments. This module variant provides a 0–2V analog voltage output, making it directly compatible with the ADC inputs of standard microcontrollers like Arduino, ESP32, and STM32 without requiring external signal conditioning.

At the heart of the module is the MG811 solid-electrolyte CO2 sensor, which operates on a battery principle. When heated to its operating temperature and exposed to CO2, an electrode reaction generates an electromotive force (EMF) between the sensitive and reference electrodes. The output voltage has a logarithmic inverse relationship with CO2 concentration—as CO2 levels rise, the voltage decreases . The onboard conditioning circuit amplifies this high-impedance signal and scales it to the 0–2V output range, which is well within the safe input range of most 5V microcontrollers .

The module requires a 6.0V ± 0.1V heating voltage to bring the sensor to its operating temperature, with a heating current of approximately 140–200mA . Because the heater draws significant current, the module cannot be powered from a USB port alone—an external power supply (typically 7–12V) is required to power the microcontroller board when using this sensor . The module also includes a digital output (DOUT) with an adjustable potentiometer threshold, which can trigger an onboard LED and provide a simple alarm signal when CO2 levels exceed a set point .

Important Note: The MG811 is an electrochemical sensor that requires careful calibration before meaningful measurements can be made. DFRobot’s official guidance recommends powering the sensor in clean air for approximately 48 hours to stabilize, then measuring the output voltage and entering that value into the calibration code (dividing the measured voltage by the amplifier gain of 8.5) . The sensor is best suited for trend monitoring and threshold-based alarm applications rather than laboratory-grade absolute CO2 measurement. The sensor is not waterproof and should be kept dry. Operating temperature range is -20°C to +50°C .

Whether you are building a greenhouse CO2 enrichment controller, an indoor air quality monitor, or a fermentation process alarm, the MG811 sensor module provides a targeted electrochemical solution for carbon dioxide detection with the documentation and community support of a widely used DFRobot-compatible platform.

Features

• MG811 solid-electrolyte CO2 sensor — Good sensitivity and selectivity to carbon dioxide

• 0–2V analog voltage output — Directly compatible with standard microcontroller ADCs

• Logarithmic voltage response — Output voltage decreases as CO2 concentration increases

• 6.0V heater with onboard conditioning circuit — Maintains optimal sensor temperature and amplifies the high-impedance signal

• Adjustable digital threshold — Potentiometer sets alarm trigger point with LED indication

• Dual outputs — Analog for trend monitoring, digital for threshold alarms

• Low humidity and temperature dependency — More stable than many semiconductor gas sensors

• Wide application range — Greenhouse CO2 control, fermentation monitoring, indoor air quality

• DFRobot-compatible module — Extensive documentation, sample code, and community support

• Long lifespan — Solid electrolyte construction for stable long-term operation

Technical Specifications