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

120 lines
4.3 KiB
C++

/*
MQUnifiedsensor Library - reading an MQ7
Demonstrates the use a MQ7 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
Updated example of MQ-7 AND MQ-309A
modified 20 April 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-7" //MQ7
#define ADC_Bit_Resolution 10 // For arduino UNO/MEGA/NANO
#define RatioMQ7CleanAir 27.5 //RS / R0 = 27.5 ppm
#define PWMPin 5 // Pin connected to mosfet
//Declare Sensor
MQUnifiedsensor MQ7(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
MQ7.setRegressionMethod(1); //_PPM = a*ratio^b
MQ7.setA(99.042); MQ7.setB(-1.518); // Configure the equation to calculate CO concentration value
/*
Exponential regression:
GAS | a | b
H2 | 69.014 | -1.374
LPG | 700000000 | -7.703
CH4 | 60000000000000 | -10.54
CO | 99.042 | -1.518
Alcohol | 40000000000000000 | -12.35
*/
/***************************** MQ Init ********************************************/
//Remarks: Configure the pin of arduino as input.
/************************************************************************************/
MQ7.init();
/*
//If the RL value is different from 10K please assign your RL value with the following method:
MQ7.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 ++)
{
MQ7.update(); // Update data, the arduino will read the voltage from the analog pin
calcR0 += MQ7.calibrate(RatioMQ7CleanAir);
Serial.print(".");
}
MQ7.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 ********************************************/
MQ7.serialDebug(true);
}
void loop() {
// 60s cycle
oldTime = millis();
while(millis() - oldTime <= (60*1000))
{
// VH 5 Volts
analogWrite(5, 255); // 255 is DC 5V output
MQ7.update(); // Update data, the arduino will read the voltage from the analog pin
MQ7.readSensor(); // Sensor will read PPM concentration using the model, a and b values set previously or from the setup
MQ7.serialDebug(); // Will print the table on the serial port
delay(500); //Sampling frequency
}
// 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
MQ7.update(); // Update data, the arduino will read the voltage from the analog pin
MQ7.readSensor(); // Sensor will read PPM concentration using the model, a and b values set previously or from the setup
MQ7.serialDebug(); // Will print the table on the serial port
delay(500); //Sampling frequency
}
// Total: 60 + 90s = 2.5 minutes.
}