Capteur Gaz MQ135

Tutorial: Initialisation Capteur Gaz MQ135 avec Arduino Uno (English)

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From left to right first pins are as follows:

A0        Analog output

D0        Digital output

GND     Ground

Vcc      Supply (5V)

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Specifications of MQ-135 gas sensor (Capteur Gaz MQ135)

• Wide detecting scope
• Fast response and High sensitivity
• Stable and long life Simple drive circuit
• Used in air quality control equipment for buildings/offices, is suitable for detecting
  of NH3, NOx, alcohol, Benzene, smoke, CO2, etc.
• Size: 35mm x 22mm x 23mm (length x width x height)
• Working voltage: DC 5 V
• Signal output instruction.
• Dual signal output (analog output, and high/low digital output)
• 0 ~ 4.2V analog output voltage, the higher the concentration the higher the voltage.

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Required Components:

Following Components are required for this project:

• Arduino UNO
• Breadboard
• MQ-135 Gas sensor module

interfacing of MQ-135 gas sensor with Arduino (Capteur Gaz MQ135)

Wire the circuit as follows:

Arunio A0 pin              with                 Sensor A0

Aruino D0 pin              with                 Sensor D0

Arduino 5Vpin             with                 Sensor Vcc

Arduino GND pin         with                 Sensor GND

When no gas digital output is 1 and analog output gives 1023 max value. When gas is present digital output is 0 and analogue output is much less than 1023. Using potentiometer on chip we can control the turning OFF point of digital pin at some value of analog pin. The sensor needs a load-resistor at the output to ground. Its value could be from 2kOhm to 47kOhm. The lower the value, the less sensitive is the sensor. The higher the value, the less accurate is sensor for higher concentrations of gas. If only one specific gas is measured, the load-resistor can be calibrated by applying a known concentration of that gas. If the sensor is used to measure any gas (like in a air quality detector) the load-resistor could be set for a value of about 1V output with clean air. Choosing a good value for the load-resistor is only valid after the burn-in time

NOTE: Don’t touch the sensor, it will be very hot.

Testing the Circuit:

1. After hardware connection, insert the sample sketch into the Arduino IDE.
2. Using a USB cable, connect the ports from the Arduino to the computer.
3. Upload the program.
4. See the results in the serial monitor.

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Code for interfacing of MQ-135 gas sensor with Arduino (Capteur Gaz MQ135).

int sensorValue; 
int digitalValue; 

void setup() 
{ 
Serial.begin(9600); // sets the serial port to 9600 
pinMode(13, OUTPUT); 
pinMode( 3, INPUT); 
} 

void loop() 
{ 
sensorValue = analogRead(0); // read analog input pin 0 
digitalValue = digitalRead(2); 
if(sensorValue>400) 
{ 
digitalWrite(13, HIGH); 
} else digitalWrite(13, LOW); 
Serial.println(sensorValue, DEC); // prints the value read 
Serial.println(digitalValue, DEC); 
delay(1000); // wait 100ms for next reading 
}

Result:

On serial monitor you can see values of analog pin being detected. Currently in my case they are around about 150 which indicate normal air.

• Normal air returns approximately 100-150
• Alcohol returns approximately 700
• Lighter gas returns approximately 750

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