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

93 lines
4.0 KiB
C++

/*
MQUnifiedsensor Library - reading an MQ4
Demonstrates the use a MQ4 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 (A4) //Analog input 4 of your arduino
/***********************Software Related Macros************************************/
#define Type ("MQ-4") //MQ4
#define Voltage_Resolution (5)
#define ADC_Bit_Resolution (10) // For arduino UNO/MEGA/NANO
#define RatioMQ4CleanAir (4.4) //RS / R0 = 60 ppm
/*****************************Globals***********************************************/
//Declare Sensor
MQUnifiedsensor MQ4(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
//Set math model to calculate the PPM concentration and the value of constants
MQ4.setRegressionMethod(0); //_PPM = pow(10, (log10(ratio)-b)/a)
/***************************** MQ Init ********************************************/
//Remarks: Configure the pin of arduino as input.
/************************************************************************************/
MQ4.init();
/*
//If the RL value is different from 10K please assign your RL value with the following method:
MQ4.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 ++)
{
MQ4.update(); // Update data, the arduino will read the voltage from the analog pin
calcR0 += MQ4.calibrate(RatioMQ4CleanAir);
Serial.print(".");
}
MQ4.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-4**********");
Serial.println("| LPG |");
}
void loop() {
MQ4.update(); // Update data, the arduino will read the voltage from the analog pin
//https://jayconsystems.com/blog/understanding-a-gas-sensor
MQ4.setA(-0.318); MQ4.setB(1.133); // A -> Slope, B -> Intersect with X - Axis
float LPG = MQ4.readSensor(); // Sensor will read PPM concentration using the model, a and b values set previously or from the setup
// exposure to 2000 ppm of LPG gas is immediately dangerous to life and health. In this section
if(LPG>=2000) Serial.println("Warning - Very high concentrations detected!");
Serial.print("| "); Serial.print(LPG);
Serial.println(" |");
delay(500); //Sampling frequency
}