MQ-7 GAS SENSOR

🔹 MQ-7 Gas Sensor Module – Carbon Monoxide (CO) Detector

The MQ-7 is a high-sensitivity semiconductor gas sensor designed specifically for detecting Carbon Monoxide (CO) concentrations in the air. It features a unique two-cycle operation (heating and measuring) for improved accuracy and stability. Ideal for CO leak detection, indoor air quality monitoring, industrial safety, and automotive exhaust sensing applications.

✅ Specifications:

• Sensor Type: MQ-7 Metal Oxide Semiconductor (MOS)

• Target Gas: Carbon Monoxide (CO)

• Detection Range: 20 – 2000 ppm (CO)

• Operating Voltage: 5V DC

• Heater Voltage:

  • 5V (high temperature cycle: 60s)

  • 1.4V (low temperature cycle: 90s)

• Heater Power Consumption: ≤ 350mW

• 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)

• Dimensions: ~32mm x 20mm x 22mm

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

📦 Operating Principle:
The MQ-7 requires a cyclic operation for optimal performance:

• High temperature period (60 seconds): 5V applied to heater – cleans the sensor

• Low temperature period (90 seconds): 1.4V applied to heater – measures CO concentration

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

📦 Features:
✔️ High sensitivity to Carbon Monoxide (CO)
✔️ Good selectivity (low sensitivity to methane, propane, hydrogen)
✔️ Stable and long life
✔️ Fast response and recovery
✔️ Simple drive circuit (analog voltage output)
✔️ Both analog and digital outputs for flexible interfacing

📦 Applications:
✔️ Carbon monoxide leak detectors (home safety)
✔️ Indoor air quality monitoring
✔️ Underground parking garage ventilation control
✔️ Industrial CO monitoring (warehouses, factories)
✔️ Automotive exhaust analysis
✔️ Boiler and furnace safety systems
✔️ Fire detection (CO from smoldering fires)
✔️ Arduino and IoT-based CO monitoring projects

⚠️ Important Notes:

• Cyclic operation is critical. For accurate readings, the sensor requires the specified 60s/90s heating cycle. Verify if your module handles this automatically.

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

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

• Cross-sensitivity. May respond to hydrogen and other reducing gases; refer to datasheet for selectivity details.

• Requires stable 5V power supply capable of providing sufficient current (~150mA).