Gas Sensor Tutorial

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.

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// 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);
}

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