MQ-4 Sensor:

 

MQ-4 sensor is a gas detecting sensor. This sensor is mainly use to detect Methane, and CNG Gas. This sensor also sensing  other flammable gases like Butane and propane. Good sensitivity to Combustible gas in wide range. High sensitivity to Natural gas / CNG. Low sensitivity to smoke, flame. Long life and low cost. Simple drive circuit.

There are different MQ series sensor which is used for detecting different gases.

List of different  MQ series sensor are given below.

MQ-2      Methane, Butane, LPG, Smoke.

MQ-3     Alcohol, Ethanol, Smoke

MQ-4     Methane, CNG Gas

MQ-5    Natural gas, LPG

MQ-6     LPG, butane

MQ-7     Carbon Monoxide

MQ-8      Hydrogen Gas

MQ-9       Carbon Monoxide, flammable gasses

MQ131    Ozone

MQ135    Air Quality

MQ136    Hydrogen Sulphide gas

MQ137     Ammonia

MQ138     Benzene, Toluene, Alcohol, Propane, Formaldehyde gas, Hydrogen

MQ214     Methane, Natural Gas

MQ216      Natural gas, Coal Gas

MQ303A   Alcohol, Ethanol, smoke

MQ306A    LPG, butane

MQ307A   Carbon Monoxide

MQ309A   Carbon Monoxide, flammable gas

 

The connections of MQ4 Gas Sensor Module.

VCC to 5V DC

GND to GND

AO to AnalogO

DO to DigitalO

 

MQ-4 Sesnsor  with simple electronic circuit:

Components :

1: MQ- 4 Gas Sensor.

2: LED

3: Buzzer

4: Resistors  1.5 Ohm, 270 Ohm.

5: Bread board

6: Some jumper wires.

7: DC Power source 5v.

Circuit:

MQ-4 Sensor with Arduino:

You can also use MQ-4 sensor with Arduino. This sensor gives you both digital and analog data.

Using with arduino is very simple I am sharing both circuit and Code for arduino.

Code:

                              /* MQ-4 Methane Sensor Circuit with Arduino */

const int AOUTpin=1;               //the AOUT pin of the MQ-4 sensor goes into analog pin A1 of the arduino.

const int DOUTpin=7;              //the DOUT pin of the MQ-4 sensor goes into digital pin D7 of the arduino.

const int ledPin=13;             //the anode of the LED connects to digital pin D13 of the arduino Same for buzzer.

int limit;

int value;

void setup() {

Serial.begin(115200);            //sets the baud rate.

pinMode(DOUTpin, INPUT);        //sets the pin as an input to the arduino.

pinMode(ledPin, OUTPUT);        //sets the pin as an output of the arduino.

}

void loop()

{

value= analogRead(AOUTpin);      //reads the analaog value from the MQ-4 sensor's AOUT pin.

limit= digitalRead(DOUTpin);     //reads the digital value from the MQ-4 sensor's DOUT pin.

Serial.print("Butane value: ");

Serial.println(value);           //prints the Butane value.

Serial.print("Limit: ");

Serial.print(limit);             //prints the limit reached as either LOW or HIGH.

delay(100);

if (limit == HIGH){

digitalWrite(ledPin, LOW);       //if limit has been reached,Both LED and Buzzer turns on as status indicator.

}

else{

digitalWrite(ledPin, HIGH);      //if threshold not reached, LED remains off.

}

}

CIRCUIT: