MQ4 Gas Sensor: A Definitive Guide

Gas leaks are hazardous; not only can a gas leak cause air pollution, but it may also lead to fire outbreaks and even death. Hence Gas sensors work by notifying us whenever there is a gas leak by releasing an output signal similar to the amount of gas leak. The Mq4 gas sensor is the most used methane gas sensor in the market, as it isn't necessarily affected by other gases or alcohol. This article looks at the features, applications, working principles, alternatives, and how you can use an Mq4 gas sensor.  

MQ4 Gas Sensor Pin Configuration

  Firstly, let us look at the MQ4 gas sensor module and understand the function of each sensor.  

MQ-4 Gas Sensor module

MQ-4 Gas Sensor module pinout

  Now that you understand the various module functions, we can look at the MQ4 pinout.  

MQ4 pinout

Features and Specification

• Straightforward drive circuit
• Long-lasting & Quick response time
• Inconsequential smoke and alcohol sensitivity
• Has high sensitivity for Methane (CH4)and natural gas
• Wide range coverage than most detector technologies
• Semiconductor type sensor
• More than 24 hour preheat time
• 20Ω load resistance
• Lower than 95%RH(Related humidity)
• 750 MW ≥ heat consumption
• 14 to 122 degrees Fahrenheit operating temperature
• 1 TTL Compatible interface output (ALR) and 1 TTL compatible  interface input (HSW)
• 200ppm to 10000ppm gas detection concentration
• 5V±0.1 VCC power requirement
• 5V and 0.1 DO Output
• 0.1V to 0.3V AO output
• 21% oxygen concentration ( when in standard condition)

MQ-4 Working Principle

  The mq4 works primarily by sensing the amount of methane or natural concentration gas in the air.  

Natural gas leak detector alarm

  Therefore immediately the mq4 senses methane, the sensor's analog pin produces an analog signal similar to the quantity of CH4 in the air. Please note that you can measure the sensor's analog output using an analog to digital converter (ADC) microcontroller. However, many of the current microcontrollers have inbuilt ADC attachments. You can use the attachments to read the analog Output of sensors, such as the MQ4 sensor. Secondly, once the microcontroller reads the analog output signal of the CH4 gas sensor, it then performs signal conditioning. Signal conditioning turns the read analog voltage into the amount of methane concentration present in the air. From the reading obtained, the system will respond in a manner you had conditioned it. This response could be audible alarm triggering or complete system shut down. The Mq4 gas sensors' digital Output also follows a likewise process. On sensing methane gas, the LED inbuilt in the digital Output lights up as soon as the digital pin goes high. You can use the digital pin for other unrelated activities that require a microcontroller. For example, air quality testers. Also, note that many people prefer the MQ-4 gas sensor over ultrasonic gas detectors since ultrasonic gas detectors cannot measure gas concentration.  

An ultrasonic gas detector

Alternate Options

• MQ-2
• MQ306A
• MQ-5
• MQ-214
• MQ-6
• MQ131
• MQ138
• MQ216
• MQ-9
• MQ-7

How to use MQ4 Gas Sensor

  This section guides you on properly connecting the mq4 gas sensor with the Arduino Uno interface. Plus how you can optimally use the mq4  gas sensor.  

Materials you will require

• Network screening Arduino Uno
• Breadboard or Protoboard
• MQ-4 gas sensor

Procedure

  First, link the MQ-4  power supply pins to the ground pin(GND) and connect them to the  Arduino Uno 5 Volt pins. Doing so will power up the sensor. Secondly, link your MQ-4 gas sensors digital and analog pins to the Arduino Uno digital and analog pins, respectively. Doing so enables the transfer of readings.  

Arduino Uno

  You can use the table below as a reference when connecting the MQ-4 and Arduino Uno pins.

  Finally, connect an LED to light up and indicate whenever the sensor detects methane gas or carbon monoxide presence in the surrounding. Congratulations, your MQ-4 gas sensor is ready. To test your methane gas detection sensitivity, introduce it to methane gas. Your sensor's analog output voltage LED and digital pin should go up similarly. Keep doing so while checking if the device needs additional calibration. You can use the connection diagram below for guidance.  

MQ-4 Gas sensor connection diagram

MQ-4 methane gas sensitivity adjustment

  The MQ-4 sensor has varying resistance values for different gases concentration. That is to say that a critical component of using the device is how well you adjust the device's sensitivity. Therefore experts advise you use a value of (RL) Load resistance ranging between 20Ω to 47Ω. Also, calibrate the gas sensor for 5000ppm of CH4 in air accumulation.  

Points to note when using an MQ-4 gas sensor

  Leave the gas sensor on to allow for preheating before you use it. Only decide the methane gas sensors' actual point after considering humidity and temperature influence. The reason is, many gas sensors suffer from cross-sensitivity caused by moisture.  

A smoke detector

  You can read the MQ-4 datasheet for more information on the subject. Write and stick to a calibration routine to ensure effective performance. A typical calibration schedule should be twice every three months.  

MQ4 Gas Sensor Applications

• Alarm systems
• Mobile gas detectors
• Environmental gas detectors

Carbon Monoxide Detector 

• Coal mines
• Smoke detectors
• Combustible gas detectors

Summary

  No one would like to experience a gas leak, yet they do occur and are more common than you could imagine. After reading this article, we hope you can effectively use your MQ-4 gas sensor to warn you of such leaks effectively. Thereby significantly lowering the chances of accidents. We have come to the end of the article, but you can quickly contact ourPCB for any inquiries you may have.