MQ4 MQ-4 Methane Gas Sensor Module

The MQ-4 Methane Gas Sensor Module is an electronic component used to detect the presence and concentration of methane (CH), natural gas, and compressed natural gas (CNG) in the surrounding air. Built around a metal oxide semiconductor (MOS) sensing element, it is highly popular for DIY electronics, home automation, and industrial safety alarms. Key Technical Specifications

• Detection Range: 200 ppm to 10,000 ppm (Parts Per Million), making it ideal for leak detection.
• Operating Voltage: Exactly 5V DC.
• Current Consumption: Approximately 150 mA.
• Target Gases: High sensitivity to Methane and Natural Gas; lower sensitivity to alcohol, LPG, and smoke.
• Sensing Material: Tin Dioxide (SnO) layered over a ceramic tube, protected by a stainless steel mesh.
• Preheat/Warm-up Time: Requires at least 24 hours for initial stabilization, and 1 to 2 minutes of preheating during standard power-ups.

Pin ConfigurationThe module breaks out the raw sensor into four easy-to-use pins for microcontrollers like Arduino, Raspberry Pi, or ESP8266:

How It Works

1. The Internal Heater: The sensor contains an internal Ni-Cr alloy heating coil. This element heats the sensing layer up to around 90C to make it reactive.
2. Resistance Change: In clean air, the tin dioxide (SnO) sensing material has high electrical resistance. When methane gas comes into contact with the heated surface, the surface density of oxygen decreases, allowing current to flow more easily and reducing the sensor’s internal resistance.
3. Dual Output Generation:
   • Analog Output (AO): The onboard circuit converts this resistance shift into a variable voltage. More methane means higher voltage.
   • Digital Output (DO): The module utilizes an onboard LM393 comparator chip. You can turn the small blue potentiometer (variable resistor) to set a specific gas threshold. Once the gas concentration crosses that point, the DO pin drops to 0V (LOW) and a status LED illuminates.

Crucial Usage Considerations

• The “Burn-In” Period: When using a brand-new MQ-4 sensor for the first time, it must stay powered on continuously for 24 to 48 hours. This stabilizes the sensing chemical element for accurate readings.
• Standard Warm-Up: Every time you cycle the power, the module will feel warm to the touch. Wait roughly 60120 seconds before trust-reading the data so the heater reaches normal operating temperature.
• Interference: While optimized for methane, the sensor will react slightly to high concentrations of LPG, propane, hydrogen, or heavy cooking smoke. Keep it clear of cooking fumes to prevent false alarms.