2022-03-20 12:53:36 -05:00

121 lines
4.8 KiB
C++

/*
MQUnifiedsensor Library - reading an MQ9
Demonstrates the use a MQ9 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>
/************************Hardware Related Macros************************************/
#define Board ("Arduino UNO")
#define Pin (A0) //Analog input 4 of your arduino
/***********************Software Related Macros************************************/
#define Type ("MQ-9") //MQ9
#define Voltage_Resolution (5)
#define ADC_Bit_Resolution (10) // For arduino UNO/MEGA/NANO
#define RatioMQ9CleanAir (9.6) //RS / R0 = 60 ppm
#define PreaheatControlPin5 (3) // Preaheat pin to control with 5 volts
#define PreaheatControlPin14 (4) // Preaheat pin to control with 1.4 volts
/*****************************Globals***********************************************/
//Declare Sensor
MQUnifiedsensor MQ9(Board, Voltage_Resolution, ADC_Bit_Resolution, Pin, Type);
void setup() {
//Init the serial port communication - to debug the library
Serial.begin(9600); //Init serial port
pinMode(PreaheatControlPin5, OUTPUT);
pinMode(PreaheatControlPin14, OUTPUT);
//Set math model to calculate the PPM concentration and the value of constants
MQ9.setRegressionMethod(1); //_PPM = a*ratio^b
MQ9.setA(1000.5); MQ9.setB(-2.186); // Configure the equation to to calculate LPG concentration
/*
Exponential regression:
GAS | a | b
LPG | 1000.5 | -2.186
CH4 | 4269.6 | -2.648
CO | 599.65 | -2.244
*/
/***************************** MQ Init ********************************************/
//Remarks: Configure the pin of arduino as input.
/************************************************************************************/
MQ9.init();
/*
//If the RL value is different from 10K please assign your RL value with the following method:
MQ9.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
// ISSUE 44 - MQ9 needs a low/high temperature cycle like MQ7 #44
Serial.println("Preheating, please wait 2.5 minutes");
digitalWrite(PreaheatControlPin5, HIGH);
digitalWrite(PreaheatControlPin14, LOW);
delay(60000);
digitalWrite(PreaheatControlPin5, LOW);
digitalWrite(PreaheatControlPin14, HIGH);
delay(90000);
digitalWrite(PreaheatControlPin5, HIGH);
digitalWrite(PreaheatControlPin14, LOW);
delay(60000);
digitalWrite(PreaheatControlPin5, LOW);
digitalWrite(PreaheatControlPin14, HIGH);
delay(90000);
digitalWrite(PreaheatControlPin5, HIGH);
digitalWrite(PreaheatControlPin14, LOW);
// End pre-heat cycle
Serial.print("Calibrating please wait.");
float calcR0 = 0;
for(int i = 1; i<=10; i ++)
{
MQ9.update(); // Update data, the arduino will read the voltage from the analog pin
calcR0 += MQ9.calibrate(RatioMQ9CleanAir);
Serial.print(".");
}
MQ9.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 ********************************************/
MQ9.serialDebug(true);
}
void loop() {
digitalWrite(PreaheatControlPin5, LOW);
digitalWrite(PreaheatControlPin14, HIGH);
delay(90000);
digitalWrite(PreaheatControlPin5, HIGH);
digitalWrite(PreaheatControlPin14, LOW);
MQ9.update(); // Update data, the arduino will read the voltage from the analog pin
MQ9.readSensor(); // Sensor will read PPM concentration using the model, a and b values set previously or from the setup
MQ9.serialDebug(); // Will print the table on the serial port
}