/* MQUnifiedsensor Library - calibrating an MQ2 to MQ9 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 27 May 2019 by Miguel Califa Wiring: https://github.com/miguel5612/MQSensorsLib_Docs/blob/master/static/img/MQ_Arduino.PNG Please make sure arduino A0 pin represents 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 Mega") #define Pin2 (A2) //Analog input 2 of your arduino #define Pin3 (A3) //Analog input 3 of your arduino #define Pin4 (A4) //Analog input 4 of your arduino #define Pin5 (A5) //Analog input 5 of your arduino #define Pin6 (A6) //Analog input 6 of your arduino #define Pin7 (A7) //Analog input 7 of your arduino #define Pin8 (A8) //Analog input 8 of your arduino #define Pin9 (A9) //Analog input 9 of your arduino #define PWMPin (5) // Pin connected to mosfet /***********************Software Related Macros************************************/ #define RatioMQ2CleanAir (9.83) //RS / R0 = 9.83 ppm #define RatioMQ3CleanAir (60) //RS / R0 = 60 ppm #define RatioMQ4CleanAir (4.4) //RS / R0 = 4.4 ppm #define RatioMQ5CleanAir (6.5) //RS / R0 = 6.5 ppm #define RatioMQ6CleanAir (10) //RS / R0 = 10 ppm #define RatioMQ7CleanAir (27.5) //RS / R0 = 27.5 ppm #define RatioMQ8CleanAir (70) //RS / R0 = 70 ppm #define RatioMQ9CleanAir (9.6) //RS / R0 = 9.6 ppm #define ADC_Bit_Resolution (10) // 10 bit ADC #define Voltage_Resolution (5) // Volt resolution to calc the voltage #define Type ("Arduino Mega 2560") //Board used /*****************************Globals***********************************************/ //Declare Sensor MQUnifiedsensor MQ2(Board, Voltage_Resolution, ADC_Bit_Resolution, Pin2, Type); MQUnifiedsensor MQ3(Board, Voltage_Resolution, ADC_Bit_Resolution, Pin3, Type); MQUnifiedsensor MQ4(Board, Voltage_Resolution, ADC_Bit_Resolution, Pin4, Type); MQUnifiedsensor MQ5(Board, Voltage_Resolution, ADC_Bit_Resolution, Pin5, Type); MQUnifiedsensor MQ6(Board, Voltage_Resolution, ADC_Bit_Resolution, Pin6, Type); MQUnifiedsensor MQ7(Board, Voltage_Resolution, ADC_Bit_Resolution, Pin7, Type); MQUnifiedsensor MQ8(Board, Voltage_Resolution, ADC_Bit_Resolution, Pin8, Type); MQUnifiedsensor MQ9(Board, Voltage_Resolution, ADC_Bit_Resolution, Pin9, Type); unsigned long oldTime = 0; void setup() { //Init serial port Serial.begin(9600); //init the sensor MQ2.init(); MQ2.setRegressionMethod(1); //_PPM = a*ratio^b MQ2.setA(574.25); MQ2.setB(-2.222); // Configure the equation to to calculate LPG concentration MQ2.setR0(9.659574468); MQ3.init(); MQ3.setRegressionMethod(1); //_PPM = a*ratio^b MQ3.setA(0.3934); MQ3.setB(-1.504); //Configure the equation to calculate Alcohol concentration value MQ3.setR0(3.86018237); MQ4.init(); MQ4.setRegressionMethod(1); //_PPM = a*ratio^b MQ4.setA(1012.7); MQ4.setB(-2.786); // Configure the equation to to calculate CH4 concentration MQ4.setR0(3.86018237); MQ5.init(); MQ5.setRegressionMethod(1); //_PPM = a*ratio^b MQ5.setA(97124); MQ5.setB(-4.918); //Configure the equation to calculate Alcohol concentration value MQ5.setR0(71.100304); MQ6.init(); MQ6.setRegressionMethod(1); //_PPM = a*ratio^b MQ6.setA(2127.2); MQ6.setB(-2.526); // Configure the equation to to calculate CH4 concentration MQ6.setR0(13.4285714); MQ7.init(); MQ7.setRegressionMethod(1); //_PPM = a*ratio^b MQ7.setA(99.042); MQ7.setB(-1.518); // Configure the equation to calculate CO concentration value MQ7.setR0(4); MQ8.init(); MQ8.setRegressionMethod(1); //_PPM = a*ratio^b MQ8.setA(976.97); MQ8.setB(-0.688); // Configure the equation to to calculate H2 concentration MQ8.setR0(1); MQ9.init(); MQ9.setRegressionMethod(1); //_PPM = a*ratio^b MQ9.setA(1000.5); MQ9.setB(-2.186); // Configure the equation to to calculate LPG concentration MQ9.setR0(9.42857143); /***************************** MQ CAlibration ********************************************/ // Explanation: // In this routine the sensor will measure the resistance of the sensor supposedly before being pre-heated // and on clean air (Calibration conditions), setting up R0 value. // We recomend executing this routine only on setup in laboratory conditions. // This routine does not need to be executed on each restart, you can load your R0 value from eeprom. // Acknowledgements: https://jayconsystems.com/blog/understanding-a-gas-sensor Serial.print("Calibrating please wait."); float MQ2calcR0 = 0, MQ3calcR0 = 0, MQ4calcR0 = 0, MQ5calcR0 = 0, MQ6calcR0 = 0, MQ7calcR0 = 0, MQ8calcR0 = 0, MQ9calcR0 = 0; for(int i = 1; i<=10; i ++) { //Update the voltage Values MQ2.update(); MQ3.update(); MQ4.update(); MQ5.update(); MQ6.update(); MQ7.update(); MQ8.update(); MQ9.update(); MQ2calcR0 += MQ2.calibrate(RatioMQ2CleanAir); MQ3calcR0 += MQ2.calibrate(RatioMQ3CleanAir); MQ4calcR0 += MQ2.calibrate(RatioMQ4CleanAir); MQ5calcR0 += MQ2.calibrate(RatioMQ5CleanAir); MQ6calcR0 += MQ2.calibrate(RatioMQ6CleanAir); MQ7calcR0 += MQ2.calibrate(RatioMQ7CleanAir); MQ8calcR0 += MQ2.calibrate(RatioMQ8CleanAir); MQ9calcR0 += MQ2.calibrate(RatioMQ9CleanAir); Serial.print("."); } MQ2.setR0(MQ2calcR0/20); MQ3.setR0(MQ3calcR0/20); MQ4.setR0(MQ4calcR0/20); MQ5.setR0(MQ5calcR0/20); MQ6.setR0(MQ6calcR0/20); MQ7.setR0(MQ7calcR0/20); MQ8.setR0(MQ8calcR0/20); MQ9.setR0(MQ9calcR0/20); Serial.println(" done!."); Serial.print("Valores de R0 para cada sensor (MQ2 - MQ9):"); Serial.print(MQ2calcR0/10); Serial.print(" | "); Serial.print(MQ3calcR0/10); Serial.print(" | "); Serial.print(MQ4calcR0/10); Serial.print(" | "); Serial.print(MQ5calcR0/10); Serial.print(" | "); Serial.print(MQ6calcR0/10); Serial.print(" | "); Serial.print(MQ7calcR0/10); Serial.print(" | "); Serial.print(MQ8calcR0/10); Serial.print(" | "); Serial.print(MQ9calcR0/10); Serial.println(" |"); if(isinf(MQ2calcR0) || isinf(MQ3calcR0) || isinf(MQ4calcR0) || isinf(MQ5calcR0) || isinf(MQ6calcR0) || isinf(MQ7calcR0) || isinf(MQ8calcR0) || isinf(MQ9calcR0)) {Serial.println("Warning: Conection issue founded, R0 is infite (Open circuit detected) please check your wiring and supply"); while(1);} if(MQ2calcR0 == 0 || MQ3calcR0 == 0 || MQ4calcR0 == 0 || MQ5calcR0 == 0 || MQ6calcR0 == 0 || MQ7calcR0 == 0 || MQ8calcR0 == 0 || MQ9calcR0 == 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 ********************************************/ //Print in serial monitor Serial.println("MQ2 to MQ9 - lecture"); Serial.println("*************************** Values from MQ-board ***************************"); Serial.println("| LPG | Alcohol | CH4 | Alcohol | CH4 | CO | H2 | LPG |"); Serial.println("| MQ-2 | MQ-3 | MQ-4 | MQ-5 | MQ-6 | MQ-7 | MQ-8 | MQ-9 |"); //pinMode(calibration_button, INPUT); } void loop() { oldTime = millis(); while(millis() - oldTime <= (60*1000)) { // VH 5 Volts analogWrite(5, 255); // 255 is DC 5V output readAllSensors(); delay(500); } // 90s cycle oldTime = millis(); while(millis() - oldTime <= (90*1000)) { // VH 1.4 Volts analogWrite(5, 20); // 255 is 100%, 20.4 is aprox 8% of Duty cycle for 90s readAllSensors(); delay(500); } } void readAllSensors() { //Update the voltage Values MQ2.update(); MQ3.update(); MQ4.update(); MQ5.update(); MQ6.update(); MQ7.update(); MQ8.update(); MQ9.update(); //Read the sensor and print in serial port float MQ2Lecture = MQ2.readSensor(); float MQ3Lecture = MQ3.readSensor(); float MQ4Lecture = MQ4.readSensor(); float MQ5Lecture = MQ5.readSensor(); float MQ6Lecture = MQ6.readSensor(); float MQ7Lecture = MQ7.readSensor(); float MQ8Lecture = MQ8.readSensor(); float MQ9Lecture = MQ9.readSensor(); Serial.print("| "); Serial.print(MQ2Lecture); Serial.print(" | "); Serial.print(MQ3Lecture); Serial.print(" | "); Serial.print(MQ4Lecture); Serial.print(" | "); Serial.print(MQ5Lecture); Serial.print(" | "); Serial.print(MQ6Lecture); Serial.print(" | "); Serial.print(MQ7Lecture); Serial.print(" | "); Serial.print(MQ8Lecture); Serial.print(" | "); Serial.print(MQ9Lecture); Serial.println("|"); }