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AirQuality-Multiple_Gas_Sensor_console.ino
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AirQuality-Multiple_Gas_Sensor_console.ino
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/************************Hardware Related Macros************************************/
#define MQ8_SENSOR (0) //define which analog input channel you are going to use
#define MQ2_SENSOR (0) //define which analog input channel you are going to use
#define MQ6_SENSOR (1)
#define MQ131_SENSOR (2)
#define TGS2600_SENSOR (3)
#define MQ135_SENSOR (4)
#define S2SH12_SENSOR (15)
#define DUST_SENSOR_ANALOG_PIN (11)
#define DUST_SENSOR_DIGITAL_PIN (13)
#define HUMIDITY_SENSOR_DIGITAL_PIN (6)
#define MQ136_SENSOR (7)
#define MQ138_SENSOR (8)
#define TGS2602_SENSOR (14)
#define HCHO_SENSOR (16)
#define MS2610_SENSOR (17)
#define PRESSURE_SENSOR_DIGITAL_PIN (14)
#define RL_VALUE (990) //define the load resistance on the board, in ohms
/***********************Software Related Macros************************************/
#define CALIBRATION_SAMPLE_TIMES (50) //define how many samples you are going to take in the calibration phase
#define CALIBRATION_SAMPLE_INTERVAL (500) //define the time interal(in milisecond) between each samples in the
//cablibration phase
#define READ_SAMPLE_INTERVAL (50) //define how many samples you are going to take in normal operation
#define READ_SAMPLE_TIMES (5) //define the time interal(in milisecond) between each samples in
/**********************Application Related Macros**********************************/
#define GAS_CL2 (0)
#define GAS_O3 (1)
#define GAS_CO2 (2)
#define GAS_CO (3)
#define GAS_NH4 (4)
#define GAS_CH3 (6)
#define GAS_CH3_2CO (7)
#define GAS_H2 (8)
#define GAS_C2H5OH (9) //Alcohol, Ethanol
#define GAS_C4H10 (10)
#define GAS_LPG (11)
#define GAS_Smoke (12)
#define GAS_CO_sec (13)
#define GAS_LPG_sec (14)
#define GAS_CH4 (15)
#define GAS_NO2 (16)
#define GAS_SO2 (17)
#define GAS_C7H8 (18) //Toluene
#define GAS_H2S (19) //Hydrogen Sulfide
#define GAS_NH3 (20) //Ammonia
#define GAS_C6H6 (21) //Benzene
#define GAS_C3H8 (22) //Propane
#define GAS_NHEX (23) //n-hexa
#define GAS_HCHO (24) //HCHO / CH2O Formaldehyde
/*****************************Globals***********************************************/
float COCurve[2] = {37793.94418, -3.24294658}; //MQ2
float H2Curve[2] = {957.1355042, -2.07442628}; //MQ2
float LPGCurve[2] = {591.6128784, -1.679699732}; //MQ2
float SmokeCurve[2] = {3426.376355, -2.225037973}; //MQ2
float LPG_secCurve[2] = {1051.200149, -2.434978052}; //MQ6
float CH4Curve[2] = {1081.498208, -1.443059209}; //MQ6
float H2_secCurve[2] = {137997.7173, -3.76632598}; //MQ6
float H2sec_Curve[2] = {957.1355042, -2.07442628}; //MQ8 -- To be adapted !!!
float CL2Curve[2] = {56.01727602, -1.359048399}; //MQ131
float O3Curve[2] = {42.84561841, -1.043297135}; //MQ131
float O3_secCurve[2] = {45.34696335, 1.743219536}; //MS2610
float CO2Curve[2] = {113.7105289, -3.019713765}; //MQ135
float CO_secCurve[2] = {726.7809737, -4.040111669}; //MQ135
float NH4Curve[2] = {84.07117895, -4.41107687}; //MQ135
float C2H50H_Curve[2] = {74.77989144, 3.010328075}; //MQ135
float CH3Curve[2] = {47.01770503, -3.281901967}; //MQ135
float CH3_2COCurve[2] = {7.010800878, -2.122018939}; //MQ135
float SO2_Curve[2] = {40.44109566, -1.085728557}; //MQ136 http://china-total.com/product/meter/gas-sensor/MQ136.pdf
float CH4_secCurve[2] = {57.82777729, -1.187494933}; //MQ136 http://china-total.com/product/meter/gas-sensor/MQ136.pdf
float CO_terCurve[2] = {2142.297846, -2.751369226}; //MQ136 http://china-total.com/product/meter/gas-sensor/MQ136.pdf
float NHEX_Curve[2] = {2142.297846, -2.751369226}; //MQ138 (1.8,200) (0.8,1000) (0.28,10000)
float C6H6_Curve[2] = {2142.297846, -2.751369226}; //MQ138 (2.1,200) (1,1000) (0.32,10000)
float C3H8_Curve[2] = {2142.297846, -2.751369226}; //MQ138 (1.8,200) (0.8,1000) (0.28,10000)
float C2H5OH_terCurve[2] = {2142.297846, -2.751369226};//MQ138 (3,200) (1.8,1000) (0.7,10000)
float CH4_terCurve[2] = {2142.297846, -2.751369226}; //MQ138 (3,200) (1.8,1000) (0.7,10000)
float C2H5OH_secCurve[2] = {0.2995093465,-3.148170562};//TGS2600
float C4H10Curve[2] = {0.3555567714, -3.337882361}; //TGS2600
float H2_terCurve[2] = {0.3417050674, -2.887154835}; //TGS2600
float C7H8Curve[2] = {37.22590719, 2.078062258}; //TGS2602 (0.3;1)( 0.8;10) (0.4;30)
float H2S_Curve[2] = {0.05566582614,-2.954075758}; //TGS2602 (0.8,0.1) (0.4,1) (0.25,3)
float C2H5OH_quarCurve[2] = {0.5409499131,-2.312489623};//TGS2602 (0.75,1) (0.3,10) (0.17,30)
float NH3_Curve[2] = {0.585030495, -3.448654502 }; //TGS2602 (0.8,1) (0.5,10) (0.3,30)
float HCHO_Curve[2] = {1.478772974, -2.224808489 }; //HCHO (0.59,5) (0.41,10) (0.23,40)
float H2_quaCurve[2] = {2.452065204,-2.282530712}; //HCHO (0.68,5) (0.59,10) (0.29,40)
float C7H8_secCurve[2]= {4.798168577, -0.8100009624}; //HCHO Toluene (0.8,5) (0.5,10) (0.07,40)
float C6H6_secCurve[2]= {5.59434996, -0.6062729607}; //HCHO benzol (0.25,5) (0.8,10) (0.09,40)
float Ro = 10000; //Ro is initialized to 10 kilo ohms
unsigned long SLEEP_TIME = 600; // Sleep time between reads (in seconds)
//VARIABLES
float Ro0 = 4.300; //MQ2 3.83 this has to be tuned 10K Ohm
float RL0 = 2.897; //MQ2
boolean metric = true;
void setup()
{
Ro0 = MQCalibration(MQ8_SENSOR, 0.5, RL0, H2Curve);
}
void loop()
{
//MQ8 CO LPG Smoke
Serial.print("MQ8 :");
Serial.print("H2 :");
Serial.print(MQGetGasPercentage(MQRead(MQ8_SENSOR, RL0), Ro0, GAS_H2, MQ8_SENSOR) );
delay(SLEEP_TIME * 1000); //delay to allow serial to fully print before sleep
}
/****************** MQResistanceCalculation ****************************************
Input: raw_adc - raw value read from adc, which represents the voltage
Output: the calculated sensor resistance
Remarks: The sensor and the load resistor forms a voltage divider. Given the voltage across the load resistor and its resistance, the resistance of the sensor could be derived.
************************************************************************************/
float MQResistanceCalculation(int raw_adc, float rl_value)
{
return (long)((long)(1024 * 1000 * (long)rl_value) / raw_adc - (long)rl_value);
;
}
/***************************** MQCalibration ****************************************
Input: mq_pin - analog channel
Output: Ro of the sensor
Remarks: This function assumes that the sensor is in clean air. It use
MQResistanceCalculation to calculates the sensor resistance in clean air. .
************************************************************************************/
float MQCalibration(int mq_pin, double ppm, double rl_value, float *pcurve )
{
int i;
float val = 0;
for (i = 0; i < CALIBRATION_SAMPLE_TIMES; i++) { //take multiple samples
val += MQResistanceCalculation(analogRead(mq_pin), rl_value);
delay(CALIBRATION_SAMPLE_INTERVAL);
}
val = val / CALIBRATION_SAMPLE_TIMES; //calculate the average value
//Ro = Rs * sqrt(a/ppm, b) = Rs * exp( ln(a/ppm) / b )
return (long)val * exp((log(pcurve[0] / ppm) / pcurve[1]));
}
/***************************** MQRead *********************************************
Input: mq_pin - analog channel
Output: Rs of the sensor
Remarks: This function use MQResistanceCalculation to caculate the sensor resistenc (Rs).
The Rs changes as the sensor is in the different consentration of the target
gas. The sample times and the time interval between samples could be configured
by changing the definition of the macros.
************************************************************************************/
float MQRead(int mq_pin, float rl_value)
{
int i;
float rs = 0;
for (i = 0; i < READ_SAMPLE_TIMES; i++) {
rs += MQResistanceCalculation(analogRead(mq_pin), rl_value);
delay(READ_SAMPLE_INTERVAL);
}
rs = rs / READ_SAMPLE_TIMES;
return rs;
}
/***************************** MQGetGasPercentage **********************************
Input: rs_ro_ratio - Rs divided by Ro
gas_id - target gas type
Output: ppm of the target gas
Remarks: This function passes different curves to the MQGetPercentage function which
calculates the ppm (parts per million) of the target gas.
************************************************************************************/
int MQGetGasPercentage(float rs_ro_ratio, float ro, int gas_id, int sensor_id)
{
if (sensor_id == MQ2_SENSOR ) {
if ( gas_id == GAS_CO ) {
return MQGetPercentage(rs_ro_ratio, ro, COCurve); //MQ2
} else if ( gas_id == GAS_H2 ) {
return MQGetPercentage(rs_ro_ratio, ro, H2Curve); //MQ2
} else if ( gas_id == GAS_LPG ) {
return MQGetPercentage(rs_ro_ratio, ro, LPGCurve); //MQ2
} else if ( gas_id == GAS_Smoke ) {
return MQGetPercentage(rs_ro_ratio, ro, SmokeCurve); //MQ2
}
} else if (sensor_id == MQ8_SENSOR ) {
if ( gas_id == GAS_H2 ) {
return MQGetPercentage(rs_ro_ratio, ro, H2sec_Curve); //MQ8
}
} else if (sensor_id == MQ6_SENSOR ) {
if ( gas_id == GAS_LPG_sec ) {
return MQGetPercentage(rs_ro_ratio, ro, LPG_secCurve); //MQ6
} else if ( gas_id == GAS_CH4 ) {
return MQGetPercentage(rs_ro_ratio, ro, CH4Curve); //MQ6
} else if ( gas_id == GAS_H2 ) {
return MQGetPercentage(rs_ro_ratio, ro, H2_secCurve); //MQ6
}
} else if (sensor_id == MQ131_SENSOR ) {
if ( gas_id == GAS_CL2 ) {
return MQGetPercentage(rs_ro_ratio, ro, CL2Curve); //MQ131
} else if ( gas_id == GAS_O3 ) {
return MQGetPercentage(rs_ro_ratio, ro, O3Curve); //MQ131
}
} else if (sensor_id == MQ135_SENSOR ) {
if ( gas_id == GAS_CO2 ) {
return MQGetPercentage(rs_ro_ratio, ro, CO2Curve); //MQ135
} else if ( gas_id == GAS_NH4 ) {
return MQGetPercentage(rs_ro_ratio, ro, NH4Curve); //MQ135
} else if ( gas_id == GAS_C2H5OH ) {
return MQGetPercentage(rs_ro_ratio, ro, C2H50H_Curve); //MQ135
} else if ( gas_id == GAS_CH3 ) {
return MQGetPercentage(rs_ro_ratio, ro, CH3Curve); //MQ135
} else if ( gas_id == GAS_CH3_2CO ) {
return MQGetPercentage(rs_ro_ratio, ro, CH3_2COCurve); //MQ135
} else if ( gas_id == GAS_CO_sec ) {
return MQGetPercentage(rs_ro_ratio, ro, CO_secCurve); //MQ135
}
} else if (sensor_id == MQ136_SENSOR ) {
if ( gas_id == GAS_SO2 ) {
return MQGetPercentage(rs_ro_ratio, ro, SO2_Curve); //MQ136
} else if ( gas_id == GAS_CH4 ) {
return MQGetPercentage(rs_ro_ratio, ro, CH4_secCurve); //MQ136
} else if ( gas_id == GAS_CO ) {
return MQGetPercentage(rs_ro_ratio, ro, CO_terCurve); //MQ136
}
} else if (sensor_id == MQ138_SENSOR ) {
if ( gas_id == GAS_C6H6 ) {
return MQGetPercentage(rs_ro_ratio, ro, C6H6_Curve); //MQ138
} else if ( gas_id == GAS_CH4 ) {
return MQGetPercentage(rs_ro_ratio, ro, CH4_terCurve); //MQ138
} else if ( gas_id == GAS_C3H8 ) {
return MQGetPercentage(rs_ro_ratio, ro, C3H8_Curve); //MQ138
} else if ( gas_id == GAS_NHEX ) {
return MQGetPercentage(rs_ro_ratio, ro, NHEX_Curve); //MQ138
}
} else if (sensor_id == TGS2600_SENSOR ) {
if ( gas_id == GAS_C2H5OH ) {
return MQGetPercentage(rs_ro_ratio, ro, C2H5OH_terCurve); //TGS2600
} else if ( gas_id == GAS_C4H10 ) {
return MQGetPercentage(rs_ro_ratio, ro, C4H10Curve); //TGS2600
} else if ( gas_id == GAS_H2 ) {
return MQGetPercentage(rs_ro_ratio, ro, H2_terCurve); //TGS2600
}
} else if (sensor_id == TGS2602_SENSOR ) {
if ( gas_id == GAS_C7H8 ) {
return MQGetPercentage(rs_ro_ratio, ro, C7H8Curve); //TGS2602
} else if ( gas_id == GAS_H2S ) {
return MQGetPercentage(rs_ro_ratio, ro, H2S_Curve); //TGS2602
} else if ( gas_id == GAS_NH3 ) {
return MQGetPercentage(rs_ro_ratio, ro, NH3_Curve); //TGS2602
} else if ( gas_id == GAS_C2H5OH ) {
return MQGetPercentage(rs_ro_ratio, ro, C2H5OH_quarCurve); //TGS2602
}
} else if (sensor_id == S2SH12_SENSOR) {
if ( gas_id == GAS_SO2 ) {
//return MQGetPercentage(rs_ro_ratio,ro,C2H5OHCurve); //2SH12
return rs_ro_ratio;
}
} else if (sensor_id == HCHO_SENSOR) {
if ( gas_id == GAS_HCHO ) {
//return MQGetPercentage(rs_ro_ratio,ro,HCHO_Curve); //HCHO
return rs_ro_ratio;
}
}
return 0;
}
/***************************** MQGetPercentage **********************************
Input: rs_ro_ratio - Rs divided by Ro
pcurve - pointer to the curve of the target gas
Output: ppm of the target gas
Remarks: By using the slope and a point of the line. The x(logarithmic value of ppm)
of the line could be derived if y(rs_ro_ratio) is provided. As it is a
logarithmic coordinate, power of 10 is used to convert the result to non-logarithmic
value.
************************************************************************************/
int MQGetPercentage(float rs_ro_ratio, float ro, float *pcurve)
{
return (double)(pcurve[0] * pow(((double)rs_ro_ratio / ro), pcurve[1]));
}