Gas Sensor Tutorial

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We just received a bunch of MQ Series Gas Sensors. These inexpensive sensors include: MQ2 – Flammable Gas & Smoke MQ3 – Alcohol MQ4 – Methane MQ5 – LPG / Natural Gas MQ6 – LPG / IsoButane / Propane MQ7 – Carbon Monoxide MQ9 – Carbon Monoxide & Flammable Gas

Today’s project is a smoke detector that turns on an LED when smoke concentrations exceed a certain level.  We soldered the sensor to the carrier board, along with a sensitivity resistor and a 3 pin header. The carrier board pins are VCC (+5v), GND, and Out, which connects to A0 on our Arduino. We connected a LED to Pin 13 and Gnd as indication of an alarm state (smoke detected). See the video and the code we used: Next step is a temp sensor for heat detection, and a relay for a siren.

// These constants won't change.  They're used to give names
// to the pins used:
const int analogInPin = A0; // Analog input pin that the potentiometer is attached to
const int ledPin = 13; // LED connected to digital pin 13

int sensorValue = 0; // value read from the sensor




void setup() {
  // initialize serial communications at 9600 bps:
  Serial.begin(9600);
  pinMode(ledPin, OUTPUT); // sets the digital pin as output
}

void loop() {
  // read the analog in value:
  sensorValue = analogRead(analogInPin);
  // determine alarm status
  if (sensorValue >= 750)
  {
    digitalWrite(ledPin, HIGH); // sets the LED on
  }
  else
  {
  digitalWrite(ledPin, LOW); // sets the LED off
  }

  // print the results to the serial monitor:
  Serial.print("sensor = " );
  Serial.println(sensorValue);

  // wait 10 milliseconds before the next loop
  // for the analog-to-digital converter to settle
  // after the last reading:
  delay(10);
}

Steve Spence

Steve Spence

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16 thoughts on “Gas Sensor Tutorial”

  1. Hey. Great post. Just testing this sensor right now. I was wondering if you have calibrated the sensor as documented in the datasheet? If so, which equipment did you use?

  2. Hi, Great post.

    Did you get the MQ7 to work?

    Would you mind telling us how you connected the sensor especially with the PWM part for the heating coil?

    Thank you so much!

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