Updated regression model selection

examples/Alcoholimeter/Alcoholimeter.ino

@@ -37,7 +37,7 @@ void setup() {
   Serial.begin(9600); //Init serial port
 
   //Set math model to calculate the PPM concentration and the value of constants
-  MQ3.setRegressionMethod("Exponential"); //_PPM =  a*ratio^b
+  MQ3.setRegressionMethod(1); //_PPM =  a*ratio^b
   MQ3.setA(0.3934); MQ3.setB(-1.504); // Configurate the ecuation values to get Alcohol concentration
   /*
     Exponential regression:

examples/AlgorithmTester/AlgorithmTester.ino

@@ -16,14 +16,19 @@
 #define Voltage_Resolution 5
 #define type "MQ-Board"
 #define ADC_Bit_Resolution 10 // For arduino UNO/MEGA/NANO
+// On this program pin value doesn't matter
 #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 pin8 A6 //Analog input 6 of your arduino
-#define pin9 A9 //Analog input 9 of your arduino
+#define pin9 A7 //Analog input 7 of your arduino
+#define pin10 A6 //Analog input 6 of your arduino
+#define pin11 A7 //Analog input 7 of your arduino
+#define pin12 A6 //Analog input 6 of your arduino
+#define pin13 A7 //Analog input 7 of your arduino
 //#define calibration_button 13 //Pin to calibrate your sensor
 
 //Declare Sensor
@@ -35,9 +40,15 @@ MQUnifiedsensor MQ6(placa, Voltage_Resolution, ADC_Bit_Resolution, pin6, type);
 MQUnifiedsensor MQ7(placa, Voltage_Resolution, ADC_Bit_Resolution, pin7, type);
 MQUnifiedsensor MQ8(placa, Voltage_Resolution, ADC_Bit_Resolution, pin8, type);
 MQUnifiedsensor MQ9(placa, Voltage_Resolution, ADC_Bit_Resolution, pin9, type);
+MQUnifiedsensor MQ131(placa, Voltage_Resolution, ADC_Bit_Resolution, pin10, type);
+MQUnifiedsensor MQ135(placa, Voltage_Resolution, ADC_Bit_Resolution, pin11, type);
+MQUnifiedsensor MQ303(placa, Voltage_Resolution, ADC_Bit_Resolution, pin12, type);
+MQUnifiedsensor MQ309(placa, Voltage_Resolution, ADC_Bit_Resolution, pin13, type);
 
-int ratio[10] = {};
+double ratio[4] = {};
-int expectedValue[10] = {};
+double expectedValue[4] = {};
+double calculatedValues[4] = {};
+double error[4] = {};
 
 void setup()
 {
@@ -45,73 +56,367 @@ void setup()
   Serial.begin(9600);
   //init the sensor
   MQ2.init();
-  MQ2.setRegressionMethod("Exponential"); //_PPM =  a*ratio^b
+  MQ2.setRegressionMethod(1); //_PPM =  a*ratio^b
   MQ2.setA(574.25); MQ2.setB(-2.222); // Configurate the ecuation values to get LPG concentration
   MQ2.setR0(9.659574468);
 
   MQ3.init(); 
-  MQ3.setRegressionMethod("Exponential"); //_PPM =  a*ratio^b
+  MQ3.setRegressionMethod(1); //_PPM =  a*ratio^b
   MQ3.setA(4.8387); MQ3.setB(-2.68); // Configurate the ecuation values to get Benzene concentration
   MQ3.setR0(3.86018237);
 
   MQ4.init(); 
-  MQ4.setRegressionMethod("Exponential"); //_PPM =  a*ratio^b
+  MQ4.setRegressionMethod(1); //_PPM =  a*ratio^b
   MQ4.setA(1012.7); MQ4.setB(-2.786); // Configurate the ecuation values to get CH4 concentration
   MQ4.setR0(3.86018237);
 
   MQ5.init(); 
-  MQ5.setRegressionMethod("Exponential"); //_PPM =  a*ratio^b
+  MQ5.setRegressionMethod(1); //_PPM =  a*ratio^b
   MQ5.setA(1163.8); MQ5.setB(-3.874); // Configurate the ecuation values to get H2 concentration
   MQ5.setR0(71.100304);
   
   MQ6.init(); 
-  MQ6.setRegressionMethod("Exponential"); //_PPM =  a*ratio^b
+  MQ6.setRegressionMethod(1); //_PPM =  a*ratio^b
   MQ6.setA(2127.2); MQ6.setB(-2.526); // Configurate the ecuation values to get CH4 concentration
   MQ6.setR0(13.4285714);
   
   MQ7.init(); 
-  MQ7.setRegressionMethod("Exponential"); //_PPM =  a*ratio^b
+  MQ7.setRegressionMethod(1); //_PPM =  a*ratio^b
   MQ7.setA(99.042); MQ7.setB(-1.518); // Configurate the ecuation values to get CO concentration
   MQ7.setR0(4);
   
   MQ8.init(); 
-  MQ8.setRegressionMethod("Exponential"); //_PPM =  a*ratio^b
+  MQ8.setRegressionMethod(1); //_PPM =  a*ratio^b
   MQ8.setA(976.97); MQ8.setB(-0.688); // Configurate the ecuation values to get H2 concentration
   MQ8.setR0(1);
   
   MQ9.init(); 
-  MQ9.setRegressionMethod("Exponential"); //_PPM =  a*ratio^b
+  MQ9.setRegressionMethod(1); //_PPM =  a*ratio^b
   MQ9.setA(1000.5); MQ9.setB(-2.186); // Configurate the ecuation values to get LPG concentration
   MQ9.setR0(9.42857143);
+
+  MQ131.init();
+  MQ131.setRegressionMethod(1); //_PPM =  a*ratio^b
+  MQ131.setA(23.943); MQ131.setB(-1.11); // Configurate the ecuation values to get O3 concentration
+  MQ131.setR0(385.40);
+
+  MQ135.setRegressionMethod(1); //_PPM =  a*ratio^b
+  MQ135.setA(102.2); MQ135.setB(-2.473); // Configurate the ecuation values to get NH4 concentration
+  MQ135.setR0(76.63);
+  MQ135.init(); 
+
+  MQ303.setRegressionMethod(1); //_PPM =  a*ratio^b
+  MQ303.setA(6.2144); MQ303.setB(-2.894); // Configurate the ecuation values to get Isobutano concentration
+  MQ303.setR0(10);
+  MQ303.init(); 
+
+  MQ309.setRegressionMethod(1); //_PPM =  a*ratio^b
+  MQ309.setA(1000000); MQ309.setB(-4.01); // Configurate the ecuation values to get CO concentration 
+  MQ309.setR0(10);
+  MQ309.init(); 
+
   //Print in serial monitor
-  Serial.print("MQ2 to MQ9 - test program");
+  Serial.println("MQ2 to MQ9 - test program");
 }
 
 void loop()
 {
     // Testing MQ2 LPG
-    ratio = {};
+    Serial.println("**********************************************************************************************************************************");
-    expectedValue = {};    
+    ratio[0] = 1.8; ratio[1] = 1.05; ratio[2] = 0.8; ratio[3] = 0.5;
-
+    expectedValue[0] = 200; expectedValue[1] = 500; expectedValue[2] = 1000; expectedValue[3] = 3000;
+    calculatedValues[0] = MQ2.validateEcuation(ratio[0]);
+    calculatedValues[1] = MQ2.validateEcuation(ratio[1]);
+    calculatedValues[2] = MQ2.validateEcuation(ratio[2]);
+    calculatedValues[3] = MQ2.validateEcuation(ratio[3]);
+    error[0] = calculatePercentualError(expectedValue[0], calculatedValues[0]);
+    error[1] = calculatePercentualError(expectedValue[1], calculatedValues[1]);
+    error[2] = calculatePercentualError(expectedValue[2], calculatedValues[2]);
+    error[3] = calculatePercentualError(expectedValue[3], calculatedValues[3]);
+    Serial.print("Error(%) MQ2: "); 
+    Serial.print(error[0]); Serial.print(" ");
+    Serial.print(error[1]); Serial.print(" ");
+    Serial.print(error[2]); Serial.print(" ");
+    Serial.print(error[3]); Serial.print(" | Calculated(PPM): ");
+    Serial.print(calculatedValues[0]); Serial.print(" ");
+    Serial.print(calculatedValues[1]); Serial.print(" ");
+    Serial.print(calculatedValues[2]); Serial.print(" ");
+    Serial.print(calculatedValues[3]); Serial.print(" | Expected(PPM): ");
+    Serial.print(expectedValue[0]); Serial.print(" ");
+    Serial.print(expectedValue[1]); Serial.print(" ");
+    Serial.print(expectedValue[2]); Serial.print(" ");
+    Serial.print(expectedValue[3]); Serial.println(" | ");
     // Testing MQ3 Benzene
-    
+    ratio[0] = 4; ratio[1] = 3; ratio[2] = 1; ratio[3] = 0.8;
+    expectedValue[0] = 0.1; expectedValue[1] = 0.21; expectedValue[2] = 4; expectedValue[3] = 10;
+    calculatedValues[0] = MQ3.validateEcuation(ratio[0]);
+    calculatedValues[1] = MQ3.validateEcuation(ratio[1]);
+    calculatedValues[2] = MQ3.validateEcuation(ratio[2]);
+    calculatedValues[3] = MQ3.validateEcuation(ratio[3]);
+    error[0] = calculatePercentualError(expectedValue[0], calculatedValues[0]);
+    error[1] = calculatePercentualError(expectedValue[1], calculatedValues[1]);
+    error[2] = calculatePercentualError(expectedValue[2], calculatedValues[2]);
+    error[3] = calculatePercentualError(expectedValue[3], calculatedValues[3]);
+    Serial.print("Error(%) MQ3: "); 
+    Serial.print(error[0]); Serial.print(" ");
+    Serial.print(error[1]); Serial.print(" ");
+    Serial.print(error[2]); Serial.print(" ");
+    Serial.print(error[3]); Serial.print(" | Calculated(PPM): ");
+    Serial.print(calculatedValues[0]); Serial.print(" ");
+    Serial.print(calculatedValues[1]); Serial.print(" ");
+    Serial.print(calculatedValues[2]); Serial.print(" ");
+    Serial.print(calculatedValues[3]); Serial.print(" | Expected(PPM): ");
+    Serial.print(expectedValue[0]); Serial.print(" ");
+    Serial.print(expectedValue[1]); Serial.print(" ");
+    Serial.print(expectedValue[2]); Serial.print(" ");
+    Serial.print(expectedValue[3]); Serial.println(" | ");
     // Testing MQ4 CH4
-    
+    ratio[0] = 1.9; ratio[1] = 1; ratio[2] = 0.6; ratio[3] = 0.42;
+    expectedValue[0] = 200; expectedValue[1] = 1000; expectedValue[2] = 5000; expectedValue[3] = 10000;
+    calculatedValues[0] = MQ4.validateEcuation(ratio[0]);
+    calculatedValues[1] = MQ4.validateEcuation(ratio[1]);
+    calculatedValues[2] = MQ4.validateEcuation(ratio[2]);
+    calculatedValues[3] = MQ4.validateEcuation(ratio[3]);
+    error[0] = calculatePercentualError(expectedValue[0], calculatedValues[0]);
+    error[1] = calculatePercentualError(expectedValue[1], calculatedValues[1]);
+    error[2] = calculatePercentualError(expectedValue[2], calculatedValues[2]);
+    error[3] = calculatePercentualError(expectedValue[3], calculatedValues[3]);
+    Serial.print("Error(%) MQ4: "); 
+    Serial.print(error[0]); Serial.print(" ");
+    Serial.print(error[1]); Serial.print(" ");
+    Serial.print(error[2]); Serial.print(" ");
+    Serial.print(error[3]); Serial.print(" | Calculated(PPM): ");
+    Serial.print(calculatedValues[0]); Serial.print(" ");
+    Serial.print(calculatedValues[1]); Serial.print(" ");
+    Serial.print(calculatedValues[2]); Serial.print(" ");
+    Serial.print(calculatedValues[3]); Serial.print(" | Expected(PPM): ");
+    Serial.print(expectedValue[0]); Serial.print(" ");
+    Serial.print(expectedValue[1]); Serial.print(" ");
+    Serial.print(expectedValue[2]); Serial.print(" ");
+    Serial.print(expectedValue[3]); Serial.println(" | ");
     // Testing MQ5 H2
-    
+    ratio[0] = 1.8; ratio[1] = 1.3; ratio[2] = 0.8; ratio[3] = 0.68;
+    expectedValue[0] = 200; expectedValue[1] = 500; expectedValue[2] = 3000; expectedValue[3] = 10000;
+    calculatedValues[0] = MQ5.validateEcuation(ratio[0]);
+    calculatedValues[1] = MQ5.validateEcuation(ratio[1]);
+    calculatedValues[2] = MQ5.validateEcuation(ratio[2]);
+    calculatedValues[3] = MQ5.validateEcuation(ratio[3]);
+    error[0] = calculatePercentualError(expectedValue[0], calculatedValues[0]);
+    error[1] = calculatePercentualError(expectedValue[1], calculatedValues[1]);
+    error[2] = calculatePercentualError(expectedValue[2], calculatedValues[2]);
+    error[3] = calculatePercentualError(expectedValue[3], calculatedValues[3]);
+    Serial.print("Error(%) MQ5: "); 
+    Serial.print(error[0]); Serial.print(" ");
+    Serial.print(error[1]); Serial.print(" ");
+    Serial.print(error[2]); Serial.print(" ");
+    Serial.print(error[3]); Serial.print(" | Calculated(PPM): ");
+    Serial.print(calculatedValues[0]); Serial.print(" ");
+    Serial.print(calculatedValues[1]); Serial.print(" ");
+    Serial.print(calculatedValues[2]); Serial.print(" ");
+    Serial.print(calculatedValues[3]); Serial.print(" | Expected(PPM): ");
+    Serial.print(expectedValue[0]); Serial.print(" ");
+    Serial.print(expectedValue[1]); Serial.print(" ");
+    Serial.print(expectedValue[2]); Serial.print(" ");
+    Serial.print(expectedValue[3]); Serial.println(" | ");
     // Testing MQ6 CH4
-    
+    ratio[0] = 2.6; ratio[1] = 1.9; ratio[2] = 1; ratio[3] = 0.8;
+    expectedValue[0] = 200; expectedValue[1] = 500; expectedValue[2] = 2000; expectedValue[3] = 5000;
+    calculatedValues[0] = MQ6.validateEcuation(ratio[0]);
+    calculatedValues[1] = MQ6.validateEcuation(ratio[1]);
+    calculatedValues[2] = MQ6.validateEcuation(ratio[2]);
+    calculatedValues[3] = MQ6.validateEcuation(ratio[3]);
+    error[0] = calculatePercentualError(expectedValue[0], calculatedValues[0]);
+    error[1] = calculatePercentualError(expectedValue[1], calculatedValues[1]);
+    error[2] = calculatePercentualError(expectedValue[2], calculatedValues[2]);
+    error[3] = calculatePercentualError(expectedValue[3], calculatedValues[3]);
+    Serial.print("Error(%) MQ6: "); 
+    Serial.print(error[0]); Serial.print(" ");
+    Serial.print(error[1]); Serial.print(" ");
+    Serial.print(error[2]); Serial.print(" ");
+    Serial.print(error[3]); Serial.print(" | Calculated(PPM): ");
+    Serial.print(calculatedValues[0]); Serial.print(" ");
+    Serial.print(calculatedValues[1]); Serial.print(" ");
+    Serial.print(calculatedValues[2]); Serial.print(" ");
+    Serial.print(calculatedValues[3]); Serial.print(" | Expected(PPM): ");
+    Serial.print(expectedValue[0]); Serial.print(" ");
+    Serial.print(expectedValue[1]); Serial.print(" ");
+    Serial.print(expectedValue[2]); Serial.print(" ");
+    Serial.print(expectedValue[3]); Serial.println(" | ");
     // Testing MQ7 CO
-    
+    ratio[0] = 1.8; ratio[1] = 1; ratio[2] = 0.4; ratio[3] = 0.25;
+    expectedValue[0] = 50; expectedValue[1] = 100; expectedValue[2] = 400; expectedValue[3] = 1000;
+    calculatedValues[0] = MQ7.validateEcuation(ratio[0]);
+    calculatedValues[1] = MQ7.validateEcuation(ratio[1]);
+    calculatedValues[2] = MQ7.validateEcuation(ratio[2]);
+    calculatedValues[3] = MQ7.validateEcuation(ratio[3]);
+    error[0] = calculatePercentualError(expectedValue[0], calculatedValues[0]);
+    error[1] = calculatePercentualError(expectedValue[1], calculatedValues[1]);
+    error[2] = calculatePercentualError(expectedValue[2], calculatedValues[2]);
+    error[3] = calculatePercentualError(expectedValue[3], calculatedValues[3]);
+    Serial.print("Error(%) MQ7: "); 
+    Serial.print(error[0]); Serial.print(" ");
+    Serial.print(error[1]); Serial.print(" ");
+    Serial.print(error[2]); Serial.print(" ");
+    Serial.print(error[3]); Serial.print(" | Calculated(PPM): ");
+    Serial.print(calculatedValues[0]); Serial.print(" ");
+    Serial.print(calculatedValues[1]); Serial.print(" ");
+    Serial.print(calculatedValues[2]); Serial.print(" ");
+    Serial.print(calculatedValues[3]); Serial.print(" | Expected(PPM): ");
+    Serial.print(expectedValue[0]); Serial.print(" ");
+    Serial.print(expectedValue[1]); Serial.print(" ");
+    Serial.print(expectedValue[2]); Serial.print(" ");
+    Serial.print(expectedValue[3]); Serial.println(" | ");    
     // Testing MQ8 H2
-    
+    ratio[0] = 2.6; ratio[1] = 1; ratio[2] = 0.21; ratio[3] = 0.03;
+    expectedValue[0] = 500; expectedValue[1] = 1000; expectedValue[2] = 3000; expectedValue[3] = 10000;
+    calculatedValues[0] = MQ8.validateEcuation(ratio[0]);
+    calculatedValues[1] = MQ8.validateEcuation(ratio[1]);
+    calculatedValues[2] = MQ8.validateEcuation(ratio[2]);
+    calculatedValues[3] = MQ8.validateEcuation(ratio[3]);
+    error[0] = calculatePercentualError(expectedValue[0], calculatedValues[0]);
+    error[1] = calculatePercentualError(expectedValue[1], calculatedValues[1]);
+    error[2] = calculatePercentualError(expectedValue[2], calculatedValues[2]);
+    error[3] = calculatePercentualError(expectedValue[3], calculatedValues[3]);
+    Serial.print("Error(%) MQ8: "); 
+    Serial.print(error[0]); Serial.print(" ");
+    Serial.print(error[1]); Serial.print(" ");
+    Serial.print(error[2]); Serial.print(" ");
+    Serial.print(error[3]); Serial.print(" | Calculated(PPM): ");
+    Serial.print(calculatedValues[0]); Serial.print(" ");
+    Serial.print(calculatedValues[1]); Serial.print(" ");
+    Serial.print(calculatedValues[2]); Serial.print(" ");
+    Serial.print(calculatedValues[3]); Serial.print(" | Expected(PPM): ");
+    Serial.print(expectedValue[0]); Serial.print(" ");
+    Serial.print(expectedValue[1]); Serial.print(" ");
+    Serial.print(expectedValue[2]); Serial.print(" ");
+    Serial.print(expectedValue[3]); Serial.println(" | ");        
     // Testing MQ9 LPG
-
+    ratio[0] = 2; ratio[1] = 1.4; ratio[2] = 0.7; ratio[3] = 0.23;
-
+    expectedValue[0] = 200; expectedValue[1] = 500; expectedValue[2] = 2000; expectedValue[3] = 10000;
+    calculatedValues[0] = MQ9.validateEcuation(ratio[0]);
+    calculatedValues[1] = MQ9.validateEcuation(ratio[1]);
+    calculatedValues[2] = MQ9.validateEcuation(ratio[2]);
+    calculatedValues[3] = MQ9.validateEcuation(ratio[3]);
+    error[0] = calculatePercentualError(expectedValue[0], calculatedValues[0]);
+    error[1] = calculatePercentualError(expectedValue[1], calculatedValues[1]);
+    error[2] = calculatePercentualError(expectedValue[2], calculatedValues[2]);
+    error[3] = calculatePercentualError(expectedValue[3], calculatedValues[3]);
+    Serial.print("Error(%) MQ9: "); 
+    Serial.print(error[0]); Serial.print(" ");
+    Serial.print(error[1]); Serial.print(" ");
+    Serial.print(error[2]); Serial.print(" ");
+    Serial.print(error[3]); Serial.print(" | Calculated(PPM): ");
+    Serial.print(calculatedValues[0]); Serial.print(" ");
+    Serial.print(calculatedValues[1]); Serial.print(" ");
+    Serial.print(calculatedValues[2]); Serial.print(" ");
+    Serial.print(calculatedValues[3]); Serial.print(" | Expected(PPM): ");
+    Serial.print(expectedValue[0]); Serial.print(" ");
+    Serial.print(expectedValue[1]); Serial.print(" ");
+    Serial.print(expectedValue[2]); Serial.print(" ");
+    Serial.print(expectedValue[3]); Serial.println(" | ");
+    // Testing MQ131 O3
+    ratio[0] = 5; ratio[1] = 2; ratio[2] = 0.7; ratio[3] = 0.5;
+    expectedValue[0] = 5; expectedValue[1] = 20; expectedValue[2] = 70; expectedValue[3] = 100;
+    calculatedValues[0] = MQ131.validateEcuation(ratio[0]);
+    calculatedValues[1] = MQ131.validateEcuation(ratio[1]);
+    calculatedValues[2] = MQ131.validateEcuation(ratio[2]);
+    calculatedValues[3] = MQ131.validateEcuation(ratio[3]);
+    error[0] = calculatePercentualError(expectedValue[0], calculatedValues[0]);
+    error[1] = calculatePercentualError(expectedValue[1], calculatedValues[1]);
+    error[2] = calculatePercentualError(expectedValue[2], calculatedValues[2]);
+    error[3] = calculatePercentualError(expectedValue[3], calculatedValues[3]);
+    Serial.print("Error(%) MQ131: "); 
+    Serial.print(error[0]); Serial.print(" ");
+    Serial.print(error[1]); Serial.print(" ");
+    Serial.print(error[2]); Serial.print(" ");
+    Serial.print(error[3]); Serial.print(" | Calculated(PPM): ");
+    Serial.print(calculatedValues[0]); Serial.print(" ");
+    Serial.print(calculatedValues[1]); Serial.print(" ");
+    Serial.print(calculatedValues[2]); Serial.print(" ");
+    Serial.print(calculatedValues[3]); Serial.print(" | Expected(PPM): ");
+    Serial.print(expectedValue[0]); Serial.print(" ");
+    Serial.print(expectedValue[1]); Serial.print(" ");
+    Serial.print(expectedValue[2]); Serial.print(" ");
+    Serial.print(expectedValue[3]); Serial.println(" | ");
+    // Testing MQ135 NH4
+    ratio[0] = 2.6; ratio[1] = 1.9; ratio[2] = 1.1; ratio[3] = 0.75;
+    expectedValue[0] = 10; expectedValue[1] = 20; expectedValue[2] = 100; expectedValue[3] = 200;
+    calculatedValues[0] = MQ135.validateEcuation(ratio[0]);
+    calculatedValues[1] = MQ135.validateEcuation(ratio[1]);
+    calculatedValues[2] = MQ135.validateEcuation(ratio[2]);
+    calculatedValues[3] = MQ135.validateEcuation(ratio[3]);
+    error[0] = calculatePercentualError(expectedValue[0], calculatedValues[0]);
+    error[1] = calculatePercentualError(expectedValue[1], calculatedValues[1]);
+    error[2] = calculatePercentualError(expectedValue[2], calculatedValues[2]);
+    error[3] = calculatePercentualError(expectedValue[3], calculatedValues[3]);
+    Serial.print("Error(%) MQ135: "); 
+    Serial.print(error[0]); Serial.print(" ");
+    Serial.print(error[1]); Serial.print(" ");
+    Serial.print(error[2]); Serial.print(" ");
+    Serial.print(error[3]); Serial.print(" | Calculated(PPM): ");
+    Serial.print(calculatedValues[0]); Serial.print(" ");
+    Serial.print(calculatedValues[1]); Serial.print(" ");
+    Serial.print(calculatedValues[2]); Serial.print(" ");
+    Serial.print(calculatedValues[3]); Serial.print(" | Expected(PPM): ");
+    Serial.print(expectedValue[0]); Serial.print(" ");
+    Serial.print(expectedValue[1]); Serial.print(" ");
+    Serial.print(expectedValue[2]); Serial.print(" ");
+    Serial.print(expectedValue[3]); Serial.println(" | ");
+    // Testing MQ303 Isobutano
+    ratio[0] = 0.4; ratio[1] = 0.3; ratio[2] = 0.19; ratio[3] = 0.08;
+    expectedValue[0] = 100; expectedValue[1] = 300; expectedValue[2] = 1000; expectedValue[3] = 10000;
+    calculatedValues[0] = MQ303.validateEcuation(ratio[0]);
+    calculatedValues[1] = MQ303.validateEcuation(ratio[1]);
+    calculatedValues[2] = MQ303.validateEcuation(ratio[2]);
+    calculatedValues[3] = MQ303.validateEcuation(ratio[3]);
+    error[0] = calculatePercentualError(expectedValue[0], calculatedValues[0]);
+    error[1] = calculatePercentualError(expectedValue[1], calculatedValues[1]);
+    error[2] = calculatePercentualError(expectedValue[2], calculatedValues[2]);
+    error[3] = calculatePercentualError(expectedValue[3], calculatedValues[3]);
+    Serial.print("Error(%) MQ303: "); 
+    Serial.print(error[0]); Serial.print(" ");
+    Serial.print(error[1]); Serial.print(" ");
+    Serial.print(error[2]); Serial.print(" ");
+    Serial.print(error[3]); Serial.print(" | Calculated(PPM): ");
+    Serial.print(calculatedValues[0]); Serial.print(" ");
+    Serial.print(calculatedValues[1]); Serial.print(" ");
+    Serial.print(calculatedValues[2]); Serial.print(" ");
+    Serial.print(calculatedValues[3]); Serial.print(" | Expected(PPM): ");
+    Serial.print(expectedValue[0]); Serial.print(" ");
+    Serial.print(expectedValue[1]); Serial.print(" ");
+    Serial.print(expectedValue[2]); Serial.print(" ");
+    Serial.print(expectedValue[3]); Serial.println(" | ");
+    // Testing MQ309 CO
+    ratio[0] = 6; ratio[1] = 5; ratio[2] = 4.3; ratio[3] = 4;
+    expectedValue[0] = 1000; expectedValue[1] = 3000; expectedValue[2] = 5000; expectedValue[3] = 7000;
+    calculatedValues[0] = MQ309.validateEcuation(ratio[0]);
+    calculatedValues[1] = MQ309.validateEcuation(ratio[1]);
+    calculatedValues[2] = MQ309.validateEcuation(ratio[2]);
+    calculatedValues[3] = MQ309.validateEcuation(ratio[3]);
+    error[0] = calculatePercentualError(expectedValue[0], calculatedValues[0]);
+    error[1] = calculatePercentualError(expectedValue[1], calculatedValues[1]);
+    error[2] = calculatePercentualError(expectedValue[2], calculatedValues[2]);
+    error[3] = calculatePercentualError(expectedValue[3], calculatedValues[3]);
+    Serial.print("Error(%) MQ309: "); 
+    Serial.print(error[0]); Serial.print(" ");
+    Serial.print(error[1]); Serial.print(" ");
+    Serial.print(error[2]); Serial.print(" ");
+    Serial.print(error[3]); Serial.print(" | Calculated(PPM): ");
+    Serial.print(calculatedValues[0]); Serial.print(" ");
+    Serial.print(calculatedValues[1]); Serial.print(" ");
+    Serial.print(calculatedValues[2]); Serial.print(" ");
+    Serial.print(calculatedValues[3]); Serial.print(" | Expected(PPM): ");
+    Serial.print(expectedValue[0]); Serial.print(" ");
+    Serial.print(expectedValue[1]); Serial.print(" ");
+    Serial.print(expectedValue[2]); Serial.print(" ");
+    Serial.print(expectedValue[3]); Serial.println(" | ");
+    
+    Serial.println("Test finalizado, por favor verifica que no existan errores >= 0.3 -> significa que no sea mayor al 30%");
+    delay(60000);
 }
 
 double calculatePercentualError(double expectedValue, double calculatedValue)
 {
     // Return the diference between two measures
-    return abs(calculatedValue-expectedValue)/expectedValue
+    return abs(calculatedValue-expectedValue)/expectedValue;
 }

examples/Calibration/Calibration.ino

@@ -46,7 +46,7 @@ unsigned long contador = 0;
 void setup() {
   //Init serial port
   Serial.begin(115200);
-  MQ2.setRegressionMethod("Exponential"); //_PPM =  a*ratio^b
+  MQ2.setRegressionMethod(1); //_PPM =  a*ratio^b
   MQ2.setA(574.25); MQ2.setB(-2.222); // Configurate the ecuation values to get LPG concentration
   //init the sensor
   MQ2.init(); 

examples/ESP8266/ESP8266.ino

@@ -37,7 +37,7 @@ void setup() {
   Serial.begin(9600); //Init serial port
 
   //Set math model to calculate the PPM concentration and the value of constants
-  MQ3.setRegressionMethod("Exponential"); //_PPM =  a*ratio^b
+  MQ3.setRegressionMethod(1); //_PPM =  a*ratio^b
   MQ3.setA(4.8387); MQ3.setB(-2.68); // Configurate the ecuation values to get Benzene concentration
   /*
     Exponential regression:

examples/MQ-131/MQ-131.ino

@@ -36,7 +36,7 @@ void setup() {
   Serial.begin(9600); //Init serial port
 
   //Set math model to calculate the PPM concentration and the value of constants
-  MQ131.setRegressionMethod("Exponential"); //_PPM =  a*ratio^b
+  MQ131.setRegressionMethod(1); //_PPM =  a*ratio^b
   MQ131.setA(23.943); MQ131.setB(-1.11); // Configurate the ecuation values to get O3 concentration
 
   /*

examples/MQ-135/MQ-135.ino

@@ -36,7 +36,7 @@ void setup() {
   Serial.begin(9600); //Init serial port
 
   //Set math model to calculate the PPM concentration and the value of constants
-  MQ135.setRegressionMethod("Exponential"); //_PPM =  a*ratio^b
+  MQ135.setRegressionMethod(1); //_PPM =  a*ratio^b
   MQ135.setA(102.2); MQ135.setB(-2.473); // Configurate the ecuation values to get NH4 concentration
 
   /*

examples/MQ-2/MQ-2.ino

@@ -36,7 +36,7 @@ void setup() {
   Serial.begin(9600); //Init serial port
 
   //Set math model to calculate the PPM concentration and the value of constants
-  MQ2.setRegressionMethod("Exponential"); //_PPM =  a*ratio^b
+  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:

examples/MQ-3/MQ-3.ino

@@ -36,7 +36,7 @@ void setup() {
   Serial.begin(9600); //Init serial port
 
   //Set math model to calculate the PPM concentration and the value of constants
-  MQ3.setRegressionMethod("Exponential"); //_PPM =  a*ratio^b
+  MQ3.setRegressionMethod(1); //_PPM =  a*ratio^b
   MQ3.setA(4.8387); MQ3.setB(-2.68); // Configurate the ecuation values to get Benzene concentration
   /*
     Exponential regression:

examples/MQ-303A/MQ303.ino

@@ -36,7 +36,7 @@ void setup() {
   Serial.begin(9600); //Init serial port
 
   //Set math model to calculate the PPM concentration and the value of constants
-  MQ303.setRegressionMethod("Exponential"); //_PPM =  a*ratio^b
+  MQ303.setRegressionMethod(1); //_PPM =  a*ratio^b
   MQ303.setA(6.2144); MQ303.setB(-2.894); // Configurate the ecuation values to get Isobutano concentration
 
   /*

examples/MQ-309A/MQ-309.ino

@@ -36,7 +36,7 @@ void setup() {
   Serial.begin(9600); //Init serial port
 
   //Set math model to calculate the PPM concentration and the value of constants
-  MQ309.setRegressionMethod("Exponential"); //_PPM =  a*ratio^b
+  MQ309.setRegressionMethod(1); //_PPM =  a*ratio^b
   MQ309.setA(1000000); MQ309.setB(-4.01); // Configurate the ecuation values to get CO concentration
 
   /*

examples/MQ-4/MQ-4.ino

@@ -36,7 +36,7 @@ void setup() {
   Serial.begin(9600); //Init serial port
 
   //Set math model to calculate the PPM concentration and the value of constants
-  MQ4.setRegressionMethod("Exponential"); //_PPM =  a*ratio^b
+  MQ4.setRegressionMethod(1); //_PPM =  a*ratio^b
   MQ4.setA(1012.7); MQ4.setB(-2.786); // Configurate the ecuation values to get CH4 concentration
   /*
     Exponential regression:

examples/MQ-5/MQ-5.ino

@@ -36,7 +36,7 @@ void setup() {
   Serial.begin(9600); //Init serial port
 
   //Set math model to calculate the PPM concentration and the value of constants
-  MQ5.setRegressionMethod("Exponential"); //_PPM =  a*ratio^b
+  MQ5.setRegressionMethod(1); //_PPM =  a*ratio^b
   MQ5.setA(1163.8); MQ5.setB(-3.874); // Configurate the ecuation values to get H2 concentration
   /*
     Exponential regression:

examples/MQ-6/MQ-6.ino

@@ -36,7 +36,7 @@ void setup() {
   Serial.begin(9600); //Init serial port
 
   //Set math model to calculate the PPM concentration and the value of constants
-  MQ6.setRegressionMethod("Exponential"); //_PPM =  a*ratio^b
+  MQ6.setRegressionMethod(1); //_PPM =  a*ratio^b
   MQ6.setA(2127.2); MQ6.setB(-2.526); // Configurate the ecuation values to get CH4 concentration
   /*
     Exponential regression:

examples/MQ-7/MQ-7.ino

@@ -36,7 +36,7 @@ void setup() {
   Serial.begin(9600); //Init serial port
 
   //Set math model to calculate the PPM concentration and the value of constants
-  MQ7.setRegressionMethod("Exponential"); //_PPM =  a*ratio^b
+  MQ7.setRegressionMethod(1); //_PPM =  a*ratio^b
   MQ7.setA(99.042); MQ7.setB(-1.518); // Configurate the ecuation values to get CO concentration
 
   /*

examples/MQ-8/MQ-8.ino

@@ -36,7 +36,7 @@ void setup() {
   Serial.begin(9600); //Init serial port
 
   //Set math model to calculate the PPM concentration and the value of constants
-  MQ8.setRegressionMethod("Exponential"); //_PPM =  a*ratio^b
+  MQ8.setRegressionMethod(1); //_PPM =  a*ratio^b
   MQ8.setA(976.97); MQ8.setB(-0.688); // Configurate the ecuation values to get H2 concentration
 
   /*

examples/MQ-9/MQ-9.ino

@@ -36,7 +36,7 @@ void setup() {
   Serial.begin(9600); //Init serial port
 
   //Set math model to calculate the PPM concentration and the value of constants
-  MQ9.setRegressionMethod("Exponential"); //_PPM =  a*ratio^b
+  MQ9.setRegressionMethod(1); //_PPM =  a*ratio^b
   MQ9.setA(1000.5); MQ9.setB(-2.186); // Configurate the ecuation values to get LPG concentration
 
   /*

examples/MQ-Board-Calibration/MQ-Board-Calibration.ino

@@ -93,42 +93,42 @@ void setup() {
   //init the sensor
   
   MQ2.init();
-  MQ2.setRegressionMethod("Exponential"); //_PPM =  a*ratio^b
+  MQ2.setRegressionMethod(1); //_PPM =  a*ratio^b
   MQ2.setA(574.25); MQ2.setB(-2.222); // Configurate the ecuation values to get LPG concentration
   MQ2.setR0(9.659574468);
 
   MQ3.init(); 
-  MQ3.setRegressionMethod("Exponential"); //_PPM =  a*ratio^b
+  MQ3.setRegressionMethod(1); //_PPM =  a*ratio^b
   MQ3.setA(4.8387); MQ3.setB(-2.68); // Configurate the ecuation values to get Benzene concentration
   MQ3.setR0(3.86018237);
 
   MQ4.init(); 
-  MQ4.setRegressionMethod("Exponential"); //_PPM =  a*ratio^b
+  MQ4.setRegressionMethod(1); //_PPM =  a*ratio^b
   MQ4.setA(1012.7); MQ4.setB(-2.786); // Configurate the ecuation values to get CH4 concentration
   MQ4.setR0(3.86018237);
 
   MQ5.init(); 
-  MQ5.setRegressionMethod("Exponential"); //_PPM =  a*ratio^b
+  MQ5.setRegressionMethod(1); //_PPM =  a*ratio^b
   MQ5.setA(1163.8); MQ5.setB(-3.874); // Configurate the ecuation values to get H2 concentration
   MQ5.setR0(71.100304);
   
   MQ6.init(); 
-  MQ6.setRegressionMethod("Exponential"); //_PPM =  a*ratio^b
+  MQ6.setRegressionMethod(1); //_PPM =  a*ratio^b
   MQ6.setA(2127.2); MQ6.setB(-2.526); // Configurate the ecuation values to get CH4 concentration
   MQ6.setR0(13.4285714);
   
   MQ7.init(); 
-  MQ7.setRegressionMethod("Exponential"); //_PPM =  a*ratio^b
+  MQ7.setRegressionMethod(1); //_PPM =  a*ratio^b
   MQ7.setA(99.042); MQ7.setB(-1.518); // Configurate the ecuation values to get CO concentration
   MQ7.setR0(4);
   
   MQ8.init(); 
-  MQ8.setRegressionMethod("Exponential"); //_PPM =  a*ratio^b
+  MQ8.setRegressionMethod(1); //_PPM =  a*ratio^b
   MQ8.setA(976.97); MQ8.setB(-0.688); // Configurate the ecuation values to get H2 concentration
   MQ8.setR0(1);
   
   MQ9.init(); 
-  MQ9.setRegressionMethod("Exponential"); //_PPM =  a*ratio^b
+  MQ9.setRegressionMethod(1); //_PPM =  a*ratio^b
   MQ9.setA(1000.5); MQ9.setB(-2.186); // Configurate the ecuation values to get LPG concentration
   MQ9.setR0(9.42857143);
 

examples/MQ-Board/MQ-Board.ino

@@ -49,42 +49,42 @@ void setup() {
   Serial.begin(9600);
   //init the sensor
   MQ2.init();
-  MQ2.setRegressionMethod("Exponential"); //_PPM =  a*ratio^b
+  MQ2.setRegressionMethod(1); //_PPM =  a*ratio^b
   MQ2.setA(574.25); MQ2.setB(-2.222); // Configurate the ecuation values to get LPG concentration
   MQ2.setR0(9.659574468);
 
   MQ3.init(); 
-  MQ3.setRegressionMethod("Exponential"); //_PPM =  a*ratio^b
+  MQ3.setRegressionMethod(1); //_PPM =  a*ratio^b
   MQ3.setA(4.8387); MQ3.setB(-2.68); // Configurate the ecuation values to get Benzene concentration
   MQ3.setR0(3.86018237);
 
   MQ4.init(); 
-  MQ4.setRegressionMethod("Exponential"); //_PPM =  a*ratio^b
+  MQ4.setRegressionMethod(1); //_PPM =  a*ratio^b
   MQ4.setA(1012.7); MQ4.setB(-2.786); // Configurate the ecuation values to get CH4 concentration
   MQ4.setR0(3.86018237);
 
   MQ5.init(); 
-  MQ5.setRegressionMethod("Exponential"); //_PPM =  a*ratio^b
+  MQ5.setRegressionMethod(1); //_PPM =  a*ratio^b
   MQ5.setA(1163.8); MQ5.setB(-3.874); // Configurate the ecuation values to get H2 concentration
   MQ5.setR0(71.100304);
   
   MQ6.init(); 
-  MQ6.setRegressionMethod("Exponential"); //_PPM =  a*ratio^b
+  MQ6.setRegressionMethod(1); //_PPM =  a*ratio^b
   MQ6.setA(2127.2); MQ6.setB(-2.526); // Configurate the ecuation values to get CH4 concentration
   MQ6.setR0(13.4285714);
   
   MQ7.init(); 
-  MQ7.setRegressionMethod("Exponential"); //_PPM =  a*ratio^b
+  MQ7.setRegressionMethod(1); //_PPM =  a*ratio^b
   MQ7.setA(99.042); MQ7.setB(-1.518); // Configurate the ecuation values to get CO concentration
   MQ7.setR0(4);
   
   MQ8.init(); 
-  MQ8.setRegressionMethod("Exponential"); //_PPM =  a*ratio^b
+  MQ8.setRegressionMethod(1); //_PPM =  a*ratio^b
   MQ8.setA(976.97); MQ8.setB(-0.688); // Configurate the ecuation values to get H2 concentration
   MQ8.setR0(1);
   
   MQ9.init(); 
-  MQ9.setRegressionMethod("Exponential"); //_PPM =  a*ratio^b
+  MQ9.setRegressionMethod(1); //_PPM =  a*ratio^b
   MQ9.setA(1000.5); MQ9.setB(-2.186); // Configurate the ecuation values to get LPG concentration
   MQ9.setR0(9.42857143);
   //Print in serial monitor

examples/smokeDetector/smokeDetector.ino

@@ -31,7 +31,7 @@ void setup() {
   //Init serial port
   Serial.begin(115200);
   //Set math model to calculate the PPM concentration and the value of constants
-  MQ4.setRegressionMethod("Exponential"); //_PPM =  a*ratio^b
+  MQ4.setRegressionMethod(1); //_PPM =  a*ratio^b
   MQ4.setA(30000000); MQ4.setB(-2.786); // Configurate the ecuation values to get CH4 concentration
   /*
     Exponential regression:

src/MQUnifiedsensor.cpp

@@ -1,9 +1,11 @@
 #include "MQUnifiedsensor.h"
 
-MQUnifiedsensor::MQUnifiedsensor(String Placa, double Voltage_Resolution, int ADC_Bit_Resolution, int pin, String type) {
+MQUnifiedsensor::MQUnifiedsensor(String Placa, float Voltage_Resolution, int ADC_Bit_Resolution, int pin, String type) {
   this->_pin = pin;
-  this->_type = type; //MQ-2, MQ-3 ... MQ-309A
+  Placa.toCharArray(this->_placa, 20);
-  this->_placa = Placa;
+  type.toCharArray(this->_type, 6);
+  //this->_type = type; //MQ-2, MQ-3 ... MQ-309A
+  //this->_placa = Placa;
   this-> _VOLT_RESOLUTION = Voltage_Resolution;
   this-> _ADC_Bit_Resolution = ADC_Bit_Resolution;
 }
@@ -11,33 +13,48 @@ void MQUnifiedsensor::init()
 {
   pinMode(_pin, INPUT);
 }
-void MQUnifiedsensor::setA(double a) {
+void MQUnifiedsensor::setA(float a) {
   this->_a = a;
 }
-void MQUnifiedsensor::setB(double b) {
+void MQUnifiedsensor::setB(float b) {
   this->_b = b;
 }
-void MQUnifiedsensor::setR0(double R0) {
+void MQUnifiedsensor::setR0(float R0) {
   this->_R0 = R0;
 }
-void MQUnifiedsensor::setRL(double RL) {
+void MQUnifiedsensor::setRL(float RL) {
   this->_RL = RL;
 }
-void MQUnifiedsensor::setVoltResolution(double voltage_resolution)
+void MQUnifiedsensor::setVoltResolution(float voltage_resolution)
 {
   _VOLT_RESOLUTION = voltage_resolution;
 }
-void MQUnifiedsensor::setRegressionMethod(String regressionMethod)
+void MQUnifiedsensor::setRegressionMethod(int regressionMethod)
 {
+  //this->_regressionMethod = regressionMethod;
   this->_regressionMethod = regressionMethod;
 }
-
+float MQUnifiedsensor::getR0() {
-double MQUnifiedsensor::getR0() {
   return _R0;
 }
-double MQUnifiedsensor::getRL() {
+float MQUnifiedsensor::getRL() {
   return _RL;
 }
+float MQUnifiedsensor::getVoltResolution()
+{
+  return _VOLT_RESOLUTION;
+}
+String MQUnifiedsensor::getRegressionMethod()
+{
+  if(_regressionMethod == 1) return "Exponential";
+  else return "Linear";
+}
+float MQUnifiedsensor::getA() {
+  return _a;
+}
+float MQUnifiedsensor::getB() {
+  return _b;
+}
 void MQUnifiedsensor::serialDebug(bool onSetup)
 {
   if(onSetup)
@@ -52,33 +69,33 @@ void MQUnifiedsensor::serialDebug(bool onSetup)
     Serial.println("Authors: Miguel A. Califa U - Yersson R. Carrillo A - Ghiordy F. Contreras C");
     Serial.println("Contributors: Andres A. Martinez - Juan A. Rodríguez - Mario A. Rodríguez O ");
 
-    Serial.println("Sensor: " + _type);
+    Serial.print("Sensor: "); Serial.println(_type);
     Serial.print("Supply voltage: "); Serial.print(_VOLT_RESOLUTION); Serial.println(" VDC");
     Serial.print("ADC Resolution: "); Serial.print(_ADC_Bit_Resolution); Serial.println(" Bits");
     Serial.print("R0: "); Serial.print(_R0); Serial.println(" KΩ");
     Serial.print("RL: "); Serial.print(_RL); Serial.println(" KΩ");
 
     Serial.print("Model: "); if(_regressionMethod == "Exponential") Serial.println("Exponential"); else Serial.println("Linear");
-    Serial.print(_type + " -> " + "a: "); Serial.print(_a); Serial.print(" | b: "); Serial.println(_b);
+    Serial.print(_type); Serial.print(" -> a: "); Serial.print(_a); Serial.print(" | b: "); Serial.println(_b);
 
-    Serial.println("Development board: " + _placa);
+    Serial.print("Development board: "); Serial.println(_placa);
   }
   else 
   {
     if(!_firstFlag)
     {
-      Serial.println("| ********************************************************************" + _type + "*********************************************************************|");
+      Serial.print("| ********************************************************************"); Serial.print(_type); Serial.println("*********************************************************************|");
       Serial.println("|ADC_In | Equation_V_ADC | Voltage_ADC |        Equation_RS        | Resistance_RS  |    EQ_Ratio  | Ratio (RS/R0) | Equation_PPM |     PPM    |");
       _firstFlag = true;  //Headers are printed
     }
     else
     {
-      String eq = "";
-      if(_regressionMethod == "Linear") eq = "ratio*a + b";
-      if(_regressionMethod == "Exponential") eq = "a*ratio^b";
       Serial.print("|"); Serial.print(_adc);  Serial.print("| v = ADC*"); Serial.print(_VOLT_RESOLUTION); Serial.print("/"); Serial.print(pow(2, _ADC_Bit_Resolution)); Serial.print("  |    "); Serial.print(_sensor_volt);
       Serial.print("     | RS = ((" ); Serial.print(_VOLT_RESOLUTION ); Serial.print("*RL)/Voltage) - RL|      "); Serial.print(_RS_Calc); Serial.print("     | Ratio = RS/R0|    ");
-      Serial.print(_ratio);  Serial.print( "       |   " + eq + "  |   "); Serial.print(_PPM); Serial.println("  |");
+      Serial.print(_ratio);  Serial.print( "       |   ");
+      if(_regressionMethod != 1) Serial.println("ratio*a + b");
+      else Serial.println("a*ratio^b");
+      Serial.print("  |   "); Serial.print(_PPM); Serial.println("  |");
     }
   }
 }
@@ -86,11 +103,11 @@ void MQUnifiedsensor::update()
 {
   _sensor_volt = this->getVoltage();
 }
-float MQUnifiedsensor::calculatePPM(double ratio)
+float MQUnifiedsensor::validateEcuation(float ratioInput)
 {
   //Usage of this function: Unit test on ALgorithmTester example;
-  if(_regressionMethod == "Exponential") _PPM= _a*pow(ratio, _b);
+  if(_regressionMethod != 1) _PPM= _a*pow(ratioInput, _b);
-  if(_regressionMethod == "Linear") _PPM= _a*ratio + _b;
+  else _PPM= _a*ratioInput + _b;
   return _PPM;  
 }
 float MQUnifiedsensor::readSensor()
@@ -100,8 +117,8 @@ float MQUnifiedsensor::readSensor()
   if(_RS_Calc < 0)  _RS_Calc = 0; //No negative values accepted.
   _ratio = _RS_Calc / this->_R0;   // Get ratio RS_gas/RS_air
   if(_ratio <= 0)  _ratio = 0; //No negative values accepted or upper datasheet recomendation.
-  if(_regressionMethod == "Exponential") _PPM= _a*pow(_ratio, _b);
+  if(_regressionMethod != 1) _PPM= _a*pow(_ratio, _b);
-  if(_regressionMethod == "Linear") _PPM= _a*_ratio + _b;
+  else _PPM= _a*_ratio + _b;
   if(_PPM < 0)  _PPM = 0; //No negative values accepted or upper datasheet recomendation.
   //if(_PPM > 10000) _PPM = 99999999; //No negative values accepted or upper datasheet recomendation.
   return _PPM;
@@ -127,11 +144,11 @@ float MQUnifiedsensor::calibrate(float ratioInCleanAir) {
   if(R0 < 0)  R0 = 0; //No negative values accepted.
   return R0;
 }
-double MQUnifiedsensor::getVoltage(int read) {
+float MQUnifiedsensor::getVoltage(int read) {
-  double voltage;
+  float voltage;
   if(read)
   {
-    double avg = 0.0;
+    float avg = 0.0;
     for (int i = 0; i < retries; i ++) {
       _adc = analogRead(this->_pin);
       avg += _adc;
@@ -145,7 +162,7 @@ double MQUnifiedsensor::getVoltage(int read) {
   }
   return voltage;
 }
-double MQUnifiedsensor::stringToDouble(String & str)
+float MQUnifiedsensor::stringTofloat(String & str)
 {
   return atof( str.c_str() );
 }

src/MQUnifiedsensor.h

@@ -13,30 +13,34 @@
 class MQUnifiedsensor
 {
   public:
-    MQUnifiedsensor(String Placa = "Arduino", double Voltage_Resolution =  5, int ADC_Bit_Resolution = 10, int pin = 1, String type = "CUSTOM MQ");
+    MQUnifiedsensor(String Placa = "Arduino", float Voltage_Resolution =  5, int ADC_Bit_Resolution = 10, int pin = 1, String type = "CUSTOM MQ");
     
     //Functions to set values
     void init();
     void update();
-    void setR0(double R0 = 10);
+    void setR0(float R0 = 10);
-    void setRL(double RL = 10);
+    void setRL(float RL = 10);
-    void setA(double a);
+    void setA(float a);
-    void setB(double b);
+    void setB(float b);
-    void setRegressionMethod(String regressionMethod);
+    void setRegressionMethod(int regressionMethod);
-    void setVoltResolution(double voltage_resolution =  5);
+    void setVoltResolution(float voltage_resolution =  5);
     void serialDebug(bool onSetup = false); //Show on serial port information about sensor
     
     //user functions
     float calibrate(float ratioInCleanAir);
     float readSensor();
-    float calculatePPM(double ratio = 0);
+    float validateEcuation(float ratioInput = 0);
     
     //get function for info
-    double getR0();
+    float getA();
-    double getRL();
+    float getB();
-    double getVoltage(int read = true);
+    float getR0();
+    float getRL();
+    float getVoltResolution();
+    String getRegressionMethod();
+    float getVoltage(int read = true);
     
-    double stringToDouble(String & str);    
+    float stringTofloat(String & str);    
 
   private:
     /************************Private vars************************************/
@@ -45,13 +49,13 @@ class MQUnifiedsensor
     byte _VOLT_RESOLUTION  = 5.0; // if 3.3v use 3.3
     byte _RL = 10; //Value in KiloOhms
     byte _ADC_Bit_Resolution = 10;
+    byte _regressionMethod = 1; // 1 -> Exponential || 2 -> Linear
     
-    double _adc, _a, _b, _sensor_volt;
+    float _adc, _a, _b, _sensor_volt;
     float  _R0, RS_air, _ratio, _PPM, _RS_Calc;  
     
-    String _type;
+    char _type[6];
-    String _placa; 
+    char _placa[20]; 
-    String _regressionMethod;
 };
 
 #endif //MQUnifiedsensor_H