MG811 Carbon Dioxide (CO2) Gas Sensor Module, 0-10000ppm

Unlike the SnO2-based MQ-series gas sensors used for general air-quality and smoke detection, the MG811 uses a different electrochemical sensing principle specifically tuned to measure carbon dioxide concentration, giving genuinely more accurate and CO2-specific readings than a general-purpose air-quality sensor could provide for this particular gas.

Measurement range covers 0 to 10,000ppm, comfortably spanning both normal outdoor CO2 levels (roughly 400ppm) and the elevated indoor levels that can build up in a poorly-ventilated room or greenhouse, where CO2 concentration genuinely matters for both human comfort/alertness and plant growth optimization. Two output options are provided: an analog output selectable between 0-2V or 0-4V ranges (where voltage decreases as CO2 concentration rises), and a TTL digital output that triggers based on a threshold set via an onboard potentiometer, giving flexibility in whether a project needs continuous concentration data or just a simple threshold alert.

Operating voltage is 6V DC, a detail worth planning for since it doesn't match the common 3.3V/5V logic rails most microcontroller projects run on directly - the sensor itself needs its own 6V supply (the product page suggests a 4xAA battery holder as one option) separate from whatever logic voltage the connected microcontroller uses. Raspberry Pi users need an external ADC to read the analog output, since the Pi's GPIO pins lack a built-in analog input.

Builders working on an indoor air-quality monitor specifically tracking CO2 buildup, a greenhouse CO2-level controller for optimizing plant growth conditions, or any application needing genuinely CO2-specific measurement rather than general air-quality sensing will find the MG811 a well-suited, purpose-built sensor for that particular gas.