It's important to have in our system a sensor that detects gas so we can apply it in our home in order to detect a gas leak. Now we´re going to describe how to connect to an Arduino board and read the concentration of gas.

In this section, we will use a gas sensor and Methane CH4. In this case, we will use an MQ-4 sensor that can detect concentrations from 200 to 10000 ppm.

This sensor has an analog resistance in its output and can connect to an ADC; it needs a coil energize of 5 volts. The image for the sensor can be seen as follows:

We can find information for the MQ-4 sensor at https://www.sparkfun.com/products/9404.

Connections with the sensor and Arduino board

According to the preceding diagram, we will now see the connections made in the following image:

Open the Arduino IDE, and copy the following sketch:

void setup(){ 
  Serial.begin(9600); 
} 
 
void loop() 
{ 
  float vol; 
  int sensorValue = analogRead(A0); 
  vol=(float)sensorValue/1024*5.0; 
  Serial.println(vol,1); 
  Serial.print("Concentration of gas= "); 
  Serial.println(sensorValue); 
  delay(2000); 
} 

We see the following results on the screen: