MQ-4 Methane Gas Sensor

Gas sensor designed to detect methane and natural gas in the environment

Introduction

The MQ-4 is a semiconductor-based gas sensor used for detecting methane (CH₄) and natural gas. It is widely used in gas leak detection applications and is a valuable component for safety systems. The sensor features an easy-to-use interface and offers both analog and digital outputs.

Pinout

The MQ-4 gas sensor comes with the following pins:

Pin	Name	Description
1	VCC	Power supply input (5V).
2	GND	Ground connection.
3	DO	Digital output, HIGH when gas concentration exceeds threshold.
4	AO	Analog output, voltage increases with gas concentration.

Working Principle

The MQ-4 sensor uses a semiconductor layer (SnO₂) that reacts with methane and other gases. The sensor works by altering the conductivity of the semiconductor when it comes in contact with methane molecules:

When the sensor is exposed to methane or natural gas, the resistance of the SnO₂ layer decreases.
This change in resistance is detected and converted to a voltage that can be read as an output signal.
The analog output (AO) provides a voltage proportional to the concentration of methane.
The digital output (DO) provides a HIGH signal when the gas concentration exceeds the preset threshold.

Features

The MQ-4 methane gas sensor comes with several notable features:

Detects methane (CH₄) and natural gas.
Offers both analog and digital outputs for easy interfacing.
Fast response time and high sensitivity.
Low power consumption.
Used in gas leakage detection and safety systems.

Applications

The MQ-4 sensor is widely used in the following applications:

Gas leak detection in homes and industries.
Monitoring methane levels in industrial plants.
Home safety systems for detecting dangerous gas leaks.
Smart gas detection systems for IoT applications.
Portable gas detectors.

Calibration

For accurate gas detection, the MQ-4 sensor requires calibration:

Allow the sensor to stabilize for at least 24 hours before first use.
Use clean air to set the baseline resistance value.
Introduce known concentrations of methane or natural gas for calibration.
Adjust the analog output according to the concentration level.
Adjust the digital output threshold to trigger when a certain gas concentration is reached.

Troubleshooting

If you encounter issues with the MQ-4 sensor, consider the following troubleshooting steps:

No output: Ensure the sensor is powered correctly and properly connected.
Inaccurate readings: Allow the sensor to stabilize for longer, and check for contamination or humidity.
Fluctuating output: Calibrate the sensor in a controlled environment with known gas concentrations.
Digital output not triggering: Adjust the threshold potentiometer to match the required gas concentration level.