/* MQUnifiedsensor Library - reading an MQ2 Demonstrates the use a MQ2 sensor. Library originally added 01 may 2019 by Miguel A Califa, Yersson Carrillo, Ghiordy Contreras, Mario Rodriguez Added example modified 23 May 2019 by Miguel Califa Updated library usage modified 26 March 2020 by Miguel Califa Wiring: https://github.com/miguel5612/MQSensorsLib_Docs/blob/master/static/img/MQ_Arduino.PNG Please take care, arduino A0 pin represent the analog input configured on #define pin This example code is in the public domain. */ //Include the library #include /************************Hardware Related Macros************************************/ #define Board ("Arduino UNO") #define Pin (A2) //Analog input 3 of your arduino /***********************Software Related Macros************************************/ #define Type ("MQ-2") //MQ2 #define Voltage_Resolution (5) #define ADC_Bit_Resolution (10) // For arduino UNO/MEGA/NANO #define RatioMQ2CleanAir (9.83) //RS / R0 = 9.83 ppm /*****************************Globals***********************************************/ MQUnifiedsensor MQ2(Board, Voltage_Resolution, ADC_Bit_Resolution, Pin, Type); /*****************************Globals***********************************************/ void setup() { //Init the serial port communication - to debug the library Serial.begin(9600); //Init serial port //Set math model to calculate the PPM concentration and the value of constants MQ2.setRegressionMethod(1); //_PPM = a*ratio^b MQ2.setA(574.25); MQ2.setB(-2.222); // Configurate the ecuation values to get LPG concentration /* Exponential regression: Gas | a | b H2 | 987.99 | -2.162 LPG | 574.25 | -2.222 CO | 36974 | -3.109 Alcohol| 3616.1 | -2.675 Propane| 658.71 | -2.168 */ /***************************** MQ Init ********************************************/ //Remarks: Configure the pin of arduino as input. /************************************************************************************/ MQ2.init(); /* //If the RL value is different from 10K please assign your RL value with the following method: MQ2.setRL(10); */ /***************************** MQ CAlibration ********************************************/ // Explanation: // In this routine the sensor will measure the resistance of the sensor supposing before was pre-heated // and now is on clean air (Calibration conditions), and it will setup R0 value. // We recomend execute this routine only on setup or on the laboratory and save on the eeprom of your arduino // This routine not need to execute to every restart, you can load your R0 if you know the value // Acknowledgements: https://jayconsystems.com/blog/understanding-a-gas-sensor Serial.print("Calibrating please wait."); float calcR0 = 0; for(int i = 1; i<=10; i ++) { MQ2.update(); // Update data, the arduino will be read the voltage on the analog pin calcR0 += MQ2.calibrate(RatioMQ2CleanAir); Serial.print("."); } MQ2.setR0(calcR0/10); Serial.println(" done!."); if(isinf(calcR0)) {Serial.println("Warning: Conection issue founded, R0 is infite (Open circuit detected) please check your wiring and supply"); while(1);} if(calcR0 == 0){Serial.println("Warning: Conection issue founded, R0 is zero (Analog pin with short circuit to ground) please check your wiring and supply"); while(1);} /***************************** MQ CAlibration ********************************************/ MQ2.serialDebug(true); } void loop() { MQ2.update(); // Update data, the arduino will be read the voltage on the analog pin MQ2.readSensor(); // Sensor will read PPM concentration using the model and a and b values setted before or in the setup MQ2.serialDebug(); // Will print the table on the serial port delay(500); //Sampling frequency }