MQSensorsLib/examples/MQ135-ADS1115/MQ135-ADS1115.ino

/*
  MQUnifiedsensor Library - reading an MQ135
  Demonstrates the use a MQ135 sensor.
  Library originally added 01 may 2019
  by Miguel A Califa, Yersson Carrillo, Ghiordy Contreras, Mario Rodriguez
 
  Added example
  modified 20 March 2022
  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.

  Library link https://github.com/adafruit/Adafruit_ADS1X15
*/
#include <Wire.h>
#include <Adafruit_ADS1X15.h>
//Include the library
#include <MQUnifiedsensor.h>
//Definitions
#define placa "Arduino UNO"
#define type "MQ-135" //MQ135
#define RatioMQ135CleanAir 3.6//RS / R0 = 3.6 ppm  
float factorEscala = 0.1875F;
//#define calibration_button 13 //Pin to calibrate your sensor
//Declare Sensor
MQUnifiedsensor MQ135(placa, type);

 
// Crear objeto de la clase
Adafruit_ADS1115 ads;
 
void setup(void) 
{
 //Init the serial port communication - to debug the library
  Serial.begin(9600); //Init serial port
  delay(200);

  //Set math model to calculate the PPM concentration and the value of constants
  MQ135.setRegressionMethod(1); //_PPM =  a*ratio^b

  /************************************************************************************/ 
  MQ135.init(); 
 
  // Iniciar el ADS1115
  ads.begin();


  Serial.print("Calibrating please wait.");
  float calcR0 = 0;
  for(int i = 1; i<=10; i ++)
  {
    // Obtener datos del A0 del ADS1115
    short adc0 = ads.readADC_SingleEnded(0);
    float voltios = (adc0 * factorEscala)/1000.0;
    MQ135.externalADCUpdate(voltios); // Update data, the arduino will read the voltage from the analog pin
    calcR0 += MQ135.calibrate(RatioMQ135CleanAir);
    Serial.print(".");
  }
  MQ135.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 ********************************************/ 
  Serial.println("** Values from MQ-135 ****");
  Serial.println("|    CO   |  Alcohol |   CO2  |  Toluen  |  NH4  |  Aceton  |");  
}
 
void loop() {
// Obtener datos del A0 del ADS1115
  short adc0 = ads.readADC_SingleEnded(0);
  float voltios = (adc0 * factorEscala)/1000.0;
  MQ135.externalADCUpdate(voltios); // Update data, the arduino will read the voltage from the analog pin

  MQ135.setA(605.18); MQ135.setB(-3.937); // Configure the equation to calculate CO concentration value
  float CO = MQ135.readSensor(); // Sensor will read PPM concentration using the model, a and b values set previously or from the setup

  MQ135.setA(77.255); MQ135.setB(-3.18); //Configure the equation to calculate Alcohol concentration value
  float Alcohol = MQ135.readSensor(); // SSensor will read PPM concentration using the model, a and b values set previously or from the setup

  MQ135.setA(110.47); MQ135.setB(-2.862); // Configure the equation to calculate CO2 concentration value
  float CO2 = MQ135.readSensor(); // Sensor will read PPM concentration using the model, a and b values set previously or from the setup

  MQ135.setA(44.947); MQ135.setB(-3.445); // Configure the equation to calculate Toluen concentration value
  float Toluen = MQ135.readSensor(); // Sensor will read PPM concentration using the model, a and b values set previously or from the setup

  MQ135.setA(102.2 ); MQ135.setB(-2.473); // Configure the equation to calculate NH4 concentration value
  float NH4 = MQ135.readSensor(); // Sensor will read PPM concentration using the model, a and b values set previously or from the setup

  MQ135.setA(34.668); MQ135.setB(-3.369); // Configure the equation to calculate Aceton concentration value
  float Aceton = MQ135.readSensor(); // Sensor will read PPM concentration using the model, a and b values set previously or from the setup
  Serial.print("|   "); Serial.print(CO); 
  Serial.print("   |   "); Serial.print(Alcohol);
  // Note: 200 Offset for CO2 source: https://github.com/miguel5612/MQSensorsLib/issues/29

    
        
  /*
  Motivation:
  We have added 200 PPM because when the library is calibrated it assumes the current state of the
  air as 0 PPM, and it is considered today that the CO2 present in the atmosphere is around 400 PPM.
  https://www.lavanguardia.com/natural/20190514/462242832581/concentracion-dioxido-cabono-co2-atmosfera-bate-record-historia-humanidad.html
  */
  Serial.print("   |   "); Serial.print(CO2 + 400); 
  Serial.print("   |   "); Serial.print(Toluen); 
  Serial.print("   |   "); Serial.print(NH4); 
  Serial.print("   |   "); Serial.print(Aceton);
  Serial.println("   |"); 
  /*
    Exponential regression:
  GAS      | a      | b
  CO       | 605.18 | -3.937  
  Alcohol  | 77.255 | -3.18 
  CO2      | 110.47 | -2.862
  Toluen  | 44.947 | -3.445
  NH4      | 102.2  | -2.473
  Aceton  | 34.668 | -3.369
  */

  delay(500); //Sampling frequency
}