Added unit tests! to validate library calculations

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

@@ -0,0 +1,115 @@
+/*
+  MQUnifiedsensor Library - reading an MQ309
+
+  Demonstrates the use a MQ309 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 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 <MQUnifiedsensor.h>
+
+//Definitions
+#define placa "Arduino UNO"
+#define Voltage_Resolution 5
+#define pin A0 //Analog input 0 of your arduino
+#define type "MQ-309" //MQ309
+#define ADC_Bit_Resolution 10 // For arduino UNO/MEGA/NANO
+#define RatioMQ309CleanAir 11 //RS / R0 = 11 ppm 
+#define PWMPin 5 // Pin connected to mosfet
+
+//Declare Sensor
+MQUnifiedsensor MQ309(placa, Voltage_Resolution, ADC_Bit_Resolution, pin, type);
+unsigned long oldTime = 0;
+
+void setup() {
+  //Init the serial port communication - to debug the library
+  Serial.begin(9600); //Init serial port
+  pinMode(PWMPin, OUTPUT);
+
+  //Set math model to calculate the PPM concentration and the value of constants
+  MQ309.setRegressionMethod(1); //_PPM =  a*ratio^b
+  MQ309.setA(1000000); MQ309.setB(-4.01); // Configure the equation to calculate CO concentration value
+
+  /*
+    Exponential regression:
+  GAS     | a       | b
+  H2      | 1532.9  | -1.951
+  CH4     | 980.24  | -1.68
+  CO      | 1000000 | -4.01
+  ALCOHOL | 473622  | -3.647
+  */
+
+  /*****************************  MQ Init ********************************************/ 
+  //Remarks: Configure the pin of arduino as input.
+  /************************************************************************************/ 
+  MQ309.init(); 
+  /* 
+    //If the RL value is different from 10K please assign your RL value with the following method:
+    MQ309.setRL(10);
+  */
+  /*****************************  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 calcR0 = 0;
+  for(int i = 1; i<=10; i ++)
+  {
+    MQ309.update(); // Update data, the arduino will read the voltage from the analog pin
+    calcR0 += MQ309.calibrate(RatioMQ309CleanAir);
+    Serial.print(".");
+  }
+  MQ309.setR0(calcR0/10);
+  Serial.println("  done!.");
+  
+  if(isinf(calcR0)) {Serial.println("Warning: Conection issue, R0 is infinite (Open circuit detected) please check your wiring and supply"); while(1);}
+  if(calcR0 == 0){Serial.println("Warning: Conection issue found, R0 is zero (Analog pin shorts to ground) please check your wiring and supply"); while(1);}
+  /*****************************  MQ CAlibration ********************************************/ 
+  MQ309.serialDebug(true);
+}
+
+void loop() {
+  // 60s cycle
+  oldTime = millis();
+  while(millis() - oldTime <= (30*1000))
+  {
+    // VH 0.9 Volts
+    analogWrite(5, 2); // 255 is 100%, 2.295 is aprox 0.9% of Duty cycle for 60s
+    MQ309.update(); // Update data, the arduino will read the voltage from the analog pin
+    MQ309.readSensor(); // Sensor will read PPM concentration using the model, a and b values set previously or from the setup
+    MQ309.serialDebug(); // Will print the table on the serial port
+    delay(500); //Sampling frequency
+  }
+
+  // 90s cycle
+  oldTime = millis();
+  while(millis() - oldTime <= (120*1000))
+  {
+    // VL 0.2 Volts
+    analogWrite(5, 1); // 255 is 100%, 0.51 is aprox 0.2% of Duty cycle for 120s
+    MQ309.update(); // Update data, the arduino will read the voltage from the analog pin
+    MQ309.readSensor(); // Sensor will read PPM concentration using the model, a and b values set previously or from the setup
+    MQ309.serialDebug(); // Will print the table on the serial port
+    delay(500); //Sampling frequency
+  } 
+  // Total: 30 + 120s =  2.5 minutes.
+}