MQ9 GAS SENSOR

 MQ-9 Gas Sensor Module – Carbon Monoxide (CO) & Combustible Gas Detector

The MQ-9 is a dual-mode semiconductor gas sensor designed to detect both Carbon Monoxide (CO) and combustible gases such as methane, propane, and LPG. It operates using a low-temperature and high-temperature heating cycle, providing high sensitivity and good selectivity for CO detection, making it ideal for indoor air quality monitoring, gas leakage detection, and industrial safety applications.

✅ Specifications:

• Sensor Type: MQ-9 Metal Oxide Semiconductor (MOS)

• Target Gases: Carbon Monoxide (CO), Methane (CH₄), Propane, LPG

• Detection Range: 10 – 1000 ppm (CO), 100 – 10,000 ppm (combustible gases)

• Operating Voltage: 5V DC

• Heater Voltage: 5V DC (cycling required for CO detection)

• Heater Power Consumption: ≤ 900mW

• Load Resistance: Adjustable (via onboard potentiometer)

• Output Signals:

  • Analog: 0–5V (proportional to gas concentration)

  • Digital: TTL (trigger threshold adjustable via potentiometer)

• Module Interface: 4-pin header (VCC, GND, DO, AO)

• Onboard Features: Power LED, Status LED, Sensitivity adjustment potentiometer

• Preheat Time: ≥ 48 hours (for initial stabilization)

• Operating Principle: Low temperature detects CO, high temperature cleans sensor and detects combustible gases

• Dimensions: ~32mm x 20mm x 22mm

• Operating Temperature: -10°C to +50°C

📦 Operating Principle (Cycling Required):

• Low Temperature (Heater ON): Sensor detects Carbon Monoxide (CO)

• High Temperature (Heater OFF): Sensor cleans itself and detects combustible gases (methane, LPG, propane)

Note: Some modules include built-in circuitry for automatic cycling; others require external control.

📦 Features:
✔️ High sensitivity to Carbon Monoxide (CO)
✔️ Good selectivity for CO over other gases
✔️ Detects a wide range of combustible gases
✔️ Fast response and recovery time
✔️ Simple drive circuit (analog voltage output)
✔️ Both analog and digital outputs for flexible interfacing
✔️ Long life and stable performance
✔️ Compact module with indicator LEDs

📦 Applications:
✔️ Carbon monoxide leak detectors (home safety)
✔️ Indoor air quality monitoring
✔️ Combustible gas detection (kitchens, factories)
✔️ Industrial safety systems
✔️ Gas alarm and shut-off systems
✔️ Arduino, ESP32, Raspberry Pi projects
✔️ Smart home gas monitoring
✔️ Underground parking ventilation control

⚠️ Important Notes:

• Cyclic operation is critical for CO detection. The sensor requires alternating low and high temperature cycles. Verify if your module handles this automatically or requires external control.

• Preheat time. Allow 24-48 hours of continuous operation for initial stabilization.

• Calibration recommended. For precise measurements, calibrate against known gas concentrations.

• Cross-sensitivity. May respond to hydrogen, alcohol, and other reducing gases. Refer to the datasheet for selectivity details.

• Requires a stable 5V power supply capable of providing sufficient current for the heater (~180mA).