The MQ4 gas sensor is a compact and highly specialized device designed to detect the presence of methane gas with exceptional sensitivity. It exhibits low sensitivity towards other gases while demonstrating a robust response to methane gas specifically. When exposed to an environment with varying concentrations of CH4, the sensor generates an output signal that accurately reflects the detected methane levels. This sensor has garnered significant credibility and has been widely employed in various applications such as alarm systems, gas detection circuits, and even in challenging environments like coal mines. Its reliability and effectiveness make it an ideal choice for industries and settings where methane gas detection is critical for safety and operational purposes.

 

Package Includes:

• 1x MQ4 CH4 Sensor Module

 

Features:

• Straightforward drive circuit: The module has a user-friendly drive circuit, making it easy to integrate into various systems and applications.
• Long-lasting & Quick response time: The sensor is designed for durability and exhibits a rapid response time, ensuring efficient and reliable gas detection.
• Inconsequential smoke and alcohol sensitivity: The sensor has negligible sensitivity to smoke and alcohol, allowing for accurate methane gas detection without interference from these substances.
• High sensitivity for Methane (CH4) and natural gas: The module offers exceptional sensitivity specifically towards methane and natural gas, enabling precise detection even at low concentrations.
• Wide range coverage: The sensor provides a wide detection range, allowing it to monitor methane gas concentrations spanning from 200ppm to 10000ppm.
• Semiconductor type sensor: The MQ4 sensor is based on a semiconductor technology, which enhances its sensitivity and accuracy in detecting methane gas.
• More than 24 hours of preheat time: The module requires a preheat time of over 24 hours before it can provide reliable and consistent gas detection results.
• 20Ω load resistance: The sensor requires a load resistance of 20Ω to ensure optimal functioning.
• Lower than 95% RH (Relative humidity): The module should be operated at a relative humidity lower than 95% to maintain its performance and longevity.
• 750 MW ≥ heat consumption: The module consumes heat at a rate of at least 750 MW during operation.
• 14 to 122 degrees Fahrenheit operating temperature: The sensor operates within a temperature range of 14 to 122 degrees Fahrenheit, allowing it to function effectively in a variety of environmental conditions.
• 1 TTL Compatible interface output (ALR) and 1 TTL compatible interface input (HSW): The module offers a TTL compatible output interface (ALR) and an input interface (HSW) for seamless integration with other systems.
• 5V±0.1 VCC power requirement: The sensor module requires a power supply of 5V with a tolerance of ±0.1V.
• 5V and 0.1 DO Output: The module provides a digital output (DO) of 5V when methane gas is detected and 0.1V when no gas is detected.
• 0.1V to 0.3V AO output: The module also features an analog output (AO) that ranges from 0.1V to 0.3V, providing additional information about the gas concentration.
• 21% oxygen concentration (when in standard condition): The sensor can detect the oxygen concentration of the environment and assumes it to be 21% under standard conditions.

 

Description:

The MQ4 gas sensor module is a compact and highly efficient device designed for the detection of methane gas. It exhibits low sensitivity to other gases while demonstrating strong sensitivity specifically to methane. This specialized sensor has proven to be highly reliable and effective in various applications, including alarm systems, gas detection circuits, and even in demanding environments like coal mines. The MQ4 gas sensor module features a well-designed structure and configuration to ensure accurate and precise gas detection. It comprises an AL2O3 micro-ceramic tube, a Tin Dioxide sensitive layer, a measuring electrode, and a heater. These components are securely housed within a robust casing made of plastic and stainless steel net, providing durability and protection. The heater in the module is carefully engineered to create optimal working conditions for the delicate components. It ensures that the sensor operates at the bare minimum required temperature to achieve accurate and consistent results. The module is equipped with six pins, two of which are dedicated to supplying the necessary heating current, while the remaining four pins are utilized to retrieve the signals generated by the sensor. This configuration allows for efficient and reliable communication with external systems and devices. With its unique design, high sensitivity to methane gas, and low sensitivity to other gases, the MQ4 gas sensor module offers a dependable solution for detecting methane gas concentrations in a wide range of applications. Its proven track record in various industries and environments further attests to its reliability and effectiveness in ensuring safety and enabling timely responses to potential gas hazards.

 

Principle of Work:

This is the step-by-step process of how the module works:

• Power Supply: The module requires a power supply of 5V±0.1 VCC to function properly. This voltage provides the necessary energy for the various components within the module.
• Preheating: The module needs to undergo a preheating phase for more than 24 hours before it can deliver accurate and reliable gas detection results. This preheating process ensures that the sensor reaches its optimal operating temperature for precise detection.
• Heater Activation: The module includes a heater element that plays a crucial role in the detection process. The heater is designed to provide the bare minimum heating conditions required for the delicate components within the sensor.
• Gas Exposure: When the module is exposed to the environment, it interacts with the gases present, including methane gas. The sensor's AL2O3 micro-ceramic tube and Tin Dioxide sensitive layer facilitate the chemical reactions necessary for gas detection.
• Gas Adsorption: Methane gas, being the target gas, is adsorbed onto the Tin Dioxide sensitive layer. This adsorption process creates changes in the electrical properties of the sensor.
• Electrical Response: As the gas is adsorbed, the electrical resistance of the Tin Dioxide sensitive layer undergoes significant alterations. These changes in resistance are directly proportional to the concentration of methane gas present in the environment.
• Signal Output: The module's measuring electrode detects the altered electrical resistance and generates corresponding electrical signals. These signals are then transmitted through the four dedicated output pins of the module.
• Signal Processing: The output signals are retrieved and processed by external systems or microcontrollers connected to the module. The signals can be further analyzed, thresholded, or used to trigger appropriate actions based on the methane gas concentration detected.
• Digital and Analog Outputs: The module provides both digital and analog outputs. The digital output (DO) pin delivers a voltage of 5V when methane gas is detected and 0.1V when no gas is present. The analog output (AO) pin provides a voltage ranging from 0.1V to 0.3V, offering additional information about the gas concentration.
• Integration and Applications: The output signals from the module can be integrated into various systems and applications.

 

 

Pinout of the Module:

Pin Name	Description
VCC	supplies power for the module. You can connect it to 5V output from your Arduino.
GND	is the Ground Pin and needs to be connected to the GND pin on the Arduino.
D0	provides a digital representation of the presence of combustible gases.
A0	provides analog output voltage is proportional to the concentration of smoke/gas.

• The MQ4 Gas Sensor Module is equipped with four pins, with two dedicated to VCC (power supply) and Gnd (ground), while the other two are capable of simultaneously outputting analog and digital data. The module operates within a 5V voltage range, with a tolerance of 0.1%. To ensure consistent power, we utilize the 5V port of an Arduino board.
• Within the module, there are two internal LEDs that serve specific purposes. The power LED illuminates when the board receives power, indicating its operational status. The doubt LED lights up when the trigger value, set by the potentiometer, is surpassed, providing a visual indication of detected gas levels.
• To convert the analog input signal from the gas sensor into a digital signal, the module utilizes an integrated comparator OP-Amp. This conversion process allows for easier processing and analysis of the gas detection data. Additionally, the module incorporates a Trim-pot, enabling adjustment of the sensitivity of the device to suit specific requirements.
• In terms of circuit design, the module includes various resistor capacitors that play important roles in decoupling and filtering. These components contribute to maintaining a stable and reliable signal by minimizing noise and unwanted interference.

 

Applications:

1. Gas Leak Detection Systems: The module is widely used in gas leak detection systems for homes, buildings, and industrial environments. It provides reliable detection of methane gas leaks, allowing for timely actions to prevent accidents and ensure safety.
2. Industrial Safety: Industries such as manufacturing, petrochemical, and mining utilize the module in their safety protocols. It enables the monitoring of methane gas levels in confined spaces, coal mines, and hazardous environments, helping to prevent potential explosions or health risks.
3. Environmental Monitoring: The module can be employed in environmental monitoring systems to detect methane emissions from sources such as landfills, waste treatment facilities, and agricultural activities. This helps in assessing and managing greenhouse gas emissions and their impact on the environment.
4. Gas Appliances and Systems: The module is used in gas appliances like stoves, heaters, and boilers to ensure the safe operation of these devices. It detects leaks or malfunctions in the gas supply, allowing for prompt maintenance or shutdown if necessary.
5. Agricultural Applications: In agricultural settings, the module can be utilized to monitor methane gas levels in animal farming facilities, such as livestock barns or manure storage areas. This assists in managing and reducing methane emissions, which contribute to greenhouse gas effects.
6. Research and Development: The module serves as a valuable tool in research and development projects related to methane gas monitoring and analysis. It enables scientists and engineers to study methane gas behavior, improve gas detection techniques, and develop innovative solutions.
7. Energy Industry: The module is employed in the energy sector for monitoring methane gas levels in natural gas production, storage facilities, and distribution systems. This aids in maintaining operational safety, preventing leaks, and optimizing energy efficiency.
8. Smart Home Integration: With its compact size and compatibility with microcontrollers like Arduino, the module can be integrated into smart home systems. It allows for real-time monitoring of methane gas levels and the automation of safety measures or alerts.

 

Circuit:

1. Connect the MQ4 Gas Sensor module to the Arduino UNO using the appropriate wiring connections. Refer to the datasheet or module documentation for the pin connections.
2. Open the Arduino IDE and create a new sketch.
3. Copy and paste the provided code into the Arduino IDE.
4. Upload the code to the Arduino UNO by clicking on the "Upload" button.
5. Open the Serial Monitor in the Arduino IDE to observe the sensor readings. The Serial Monitor will display the detected methane gas concentrations as measured by the MQ4 sensor.
6. To test the sensor's response to smoke, take the device to a smokey environment and observe the readings on the Serial Monitor. Sudden variations in the readings will be visible, indicating the presence of smoke particles.
7. Additionally, if the digital output value from the sensor reaches 1, indicating the presence of a certain threshold of methane gas, an LED connected to the Arduino UNO can be programmed to light up as a visual indicator.

 

Library:

This Module doesn't need any Library to function.

 

Code:

This Example code continuously reads the analog value from the MQ4 sensor, displays it on the Serial Monitor, and controls the LED based on the state of the digital input. This allows for real-time monitoring of the sensor data and provides a visual indication through the LED based on a certain condition:

const int MQ4pin = A0; // Define the pin for MQ4 Gas Sensor
const int LEDpin = 13; // Define the pin for the LED

void setup() {
pinMode(LEDpin, OUTPUT); // Set LEDpin as output
Serial.begin(9600); // Set the baud rate for serial communication
Serial.println("MQ4 warming up!");
delay(20000); // Allow the MQ4 sensor to warm up
}

void loop() {
int sensorValue = analogRead(MQ4pin); // Read the analog input from MQ4 sensor
Serial.print("Sensor Value: ");
Serial.println(sensorValue);

if (digitalRead(8)) { // Check the digital input pin 8
digitalWrite(LEDpin, HIGH); // Turn on the LED if the digital input is HIGH
} else {
digitalWrite(LEDpin, LOW); // Turn off the LED if the digital input is LOW
}

delay(2000); // Delay for 2 seconds before taking the next reading
}

• The code starts by defining the pin numbers for the MQ4 Gas Sensor (MQ4pin) and the LED (LEDpin).

• In the setup() function:

  • The LEDpin is set as an output using pinMode() to indicate that it will be used to control the LED.
  • Serial communication is initialized with a baud rate of 9600, allowing data to be sent and received through the serial port.
  • A message is printed to the Serial Monitor to indicate that the MQ4 sensor is warming up.
  • A delay of 20000 milliseconds (20 seconds) is added to allow the MQ4 sensor to reach its operating temperature.

• In the loop() function:

  • The analogRead() function is used to read the analog input value from the MQ4 sensor, and the result is stored in the sensorValue variable.
  • The Serial.print() and Serial.println() functions are used to display the sensor value on the Serial Monitor.
  • The digitalRead() function checks the state of the digital input pin 8. If it is HIGH, indicating a certain condition is met, the LED is turned on by setting the LEDpin to HIGH using digitalWrite(). Otherwise, the LED is turned off by setting the LEDpin to LOW.
  • A delay of 2000 milliseconds (2 seconds) is added before the next reading is taken.

 

Technical Details:

• Operating Voltage: 5V±0.1
• Heating voltage: 5V±0.1
• Load Resistance: 2K
• Sensing Resistance Range: 10 – 60K
• CH4 Sensing Range: 300 – 10000 ppm
• Sensor Heat Consumption: ≤ 950 mW
• Relative Humidity: >95% RH
• Standard Oxygen concentration: 21%
• Output Analog Voltage: 2.5 – 4 Volts (5000 ppm CH4)
• Preheating Time: Over 48 Hours

 

Resources:

Tutorial

Tutorial2

 

 

Comparisons:

A comparison between the MQ4 and MQ3 gas sensors:

1. Gas Detection:

   • MQ4: The MQ4 gas sensor is specifically designed for methane (CH4) gas detection. It has high sensitivity to methane and natural gas.
   • MQ3: The MQ3 gas sensor is optimized for alcohol vapor detection. It has high sensitivity to alcohol and can detect the presence of ethanol and other types of alcohol.

2. Sensitivity Range:

   • MQ4: The MQ4 sensor is calibrated to detect methane gas concentrations ranging from 200ppm to 10000ppm.
   • MQ3: The MQ3 sensor is designed to detect alcohol vapor concentrations in the range of 10ppm to 500ppm.

3. Operating Principle:

   • MQ4: The MQ4 sensor operates based on a semiconductor-type gas sensor. It uses a tin dioxide (SnO2) sensitive layer to detect methane gas.
   • MQ3: The MQ3 sensor also operates on the semiconductor principle. It utilizes a tin dioxide (SnO2) sensitive layer to detect alcohol vapor.

4. Sensitivity to Other Gases:

   • MQ4: The MQ4 sensor has low sensitivity to other gases, which reduces the chances of false alarms and provides accurate methane gas detection.
   • MQ3: The MQ3 sensor can exhibit some cross-sensitivity to gases other than alcohol. It may respond to certain volatile organic compounds (VOCs) and other gases present in the environment.

5. Applications:

   • MQ4: The MQ4 gas sensor is commonly used in alarm systems, gas detection circuits, coal mines, and any application where the detection of methane gas is critical.
   • MQ3: The MQ3 gas sensor is widely utilized in breathalyzer devices, alcohol detection systems, and other applications where the detection of alcohol vapor is required, such as in automotive safety systems.

6. Preheat Time:

   • MQ4: The MQ4 sensor typically requires a preheat time of more than 24 hours before it reaches its optimal operating conditions.
   • MQ3: The MQ3 sensor usually has a shorter preheat time compared to the MQ4 sensor.

When choosing between the MQ4 and MQ3 sensors, it is important to consider the specific gas detection requirements of your application. If you need to detect methane gas, the MQ4 sensor is suitable, while the MQ3 sensor is designed for alcohol vapor detection.