1-2 MQ-4

一、元件介紹

感測：甲烷，CNG天然氣

二、接線範例

三、程式範例

Arduino程式參考：http://www.geekstips.com/mq4-sensor-natural-gas-methane-arduino/

/*
 Arduino MQ4 gas sensor - Geekstips.com
 This example is for calculating R0 which is
 the resistance of the sensor at a known concentration 
 without the presence of other gases, or in fresh air
*/
void setup() {
  Serial.begin(9600); //Baud rate
}

void loop() {
  float sensor_volt; //Define variable for sensor voltage
  float RS_air; //Define variable for sensor resistance
  float R0; //Define variable for R0
  float sensorValue; //Define variable for analog readings
  for (int x = 0 ; x < 500 ; x++) //Start for loop
  {
    sensorValue = sensorValue + analogRead(A0); //Add analog values of sensor 500 times
  }
  sensorValue = sensorValue / 500.0; //Take average of readings
  sensor_volt = sensorValue * (5.0 / 1023.0); //Convert average to voltage
  RS_air = ((5.0 * 10.0) / sensor_volt) - 10.0; //Calculate RS in fresh air
  R0 = RS_air / 4.4; //Calculate R0

  Serial.print("R0 = "); //Display "R0"
  Serial.println(R0); //Display value of R0
  delay(1000); //Wait 1 second
}

其他參考：https://github.com/paveldhq/lib-sensor-analog-mq4