MQ-9 Carbon Monoxide Gas Sensor Module

The MQ-9 Gas Sensor Module offers a practical solution for experimental gas-detection projects. Its SnO₂ sensing element responds to carbon monoxide and combustible gases, including methane and LPG.

The analog output indicates changes in gas concentration. In addition, the digital output switches when the reading reaches the threshold selected with the onboard potentiometer.

Therefore, this module connects easily to Arduino boards, microcontrollers, alarm circuits, and educational projects.

Key Features

• Detects carbon monoxide, methane, and LPG
• Uses an MQ-9 SnO₂ semiconductor sensing element
• Provides analog and digital outputs
• Includes an adjustable digital-output threshold
• Offers fast response and stable operation
• Connects easily to Arduino and other controllers
• Suitable for prototypes and educational experiments
• Compact module with four connection pins

Technical Specifications

• Sensor Model: MQ-9
• Module Operating Voltage: 5V DC
• Sensor Material: Tin Dioxide (SnO₂)
• Carbon Monoxide Range: 20–2000ppm
• Methane Detection Range: 500–10000ppm
• LPG Detection Range: 500–10000ppm
• Analog Output: Variable voltage signal
• Digital Output: Comparator-based HIGH/LOW signal
• Digital Threshold: Adjustable via potentiometer
• Sensor Heater Voltage, High Stage: 5V ±0.1V
• Sensor Heater Voltage, Low Stage: 1.4V ±0.1V
• High Heating Time: 60 seconds
• Low Heating Time: 90 seconds
• Heater Resistance: 33Ω ±5%
• Heater Consumption: Less than 340mW
• Initial Preheat Time: At least 48 hours
• Operating Temperature: -20°C to +50°C
• Operating Humidity: Less than 95% RH
• Module Dimensions: Approximately 32 × 20mm

Pin Configuration

• VCC: Connect to a regulated 5V power supply
• GND: Connect to the circuit ground
• AO: Analog sensor output
• DO: Adjustable digital alarm output

How It Works

The sensor’s conductivity increases when it detects a target gas. As a result, the voltage at the analog output changes with the sensor resistance.

Meanwhile, the onboard comparator monitors this signal. It changes the digital output state when the signal crosses the selected threshold.

For better results, allow enough warm-up time before taking readings. Additionally, calibrate the sensor using known gas concentrations when concentration estimates are required.

Applications

The module suits experimental projects such as:

• Carbon monoxide detection prototypes
• Combustible gas alarm projects
• Domestic gas leakage experiments
• Industrial monitoring prototypes
• Smart-home projects
• Arduino and microcontroller projects
• Robotics and environmental monitoring
• Educational electronics laboratories

Important Notes

• The sensor requires calibration for meaningful concentration estimates.
• Temperature, humidity, supply stability, and heater timing affect the readings.
• The potentiometer adjusts the digital alarm threshold. It does not calibrate the ppm reading.
• Standard four-pin modules may not perform the complete high-and-low heater cycle automatically.
• Use an external heater-control circuit for measurements that follow the complete datasheet procedure.
• Allow at least 48 hours of initial preheating before calibration.
• Do not use this development module as the only safety device in homes, workshops, or industrial locations.
• For personal protection, use a certified carbon monoxide or combustible-gas alarm.

Package Includes

• 1× MQ-9 Carbon Monoxide & Combustible Gas Sensor Module