MQ 135 코드 학습 중

찾아보니 MQ 135 코드가 2가지 종류가 있다...

하나는 저번 글에서 언급했던 국내 개발자의 것이고

다른 곳에서 보니 MQ2 센서 기준으로 한 코드 하나가 더 있다

근데 이건 무슨일인지 작동이 안간다

코드는 다음과 같다

/*******************Demo for MQ-2 Gas Sensor Module V1.0*****************************

Support: Tiequan Shao: support[at]sandboxelectronics.com

 

Lisence: Attribution-NonCommercial-ShareAlike 3.0 Unported (CC BY-NC-SA 3.0)

 

Note: This piece of source code is supposed to be used as a demostration ONLY. More

sophisticated calibration is required for industrial field application.

 

Sandbox Electronics 2011-04-25

************************************************************************************/

 

/************************Hardware Related Macros************************************/

#define MQ_PIN (0) //define which analog input channel you are going to use

#define RL_VALUE (5) //define the load resistance on the board, in kilo ohms

#define RO_CLEAN_AIR_FACTOR (9.83) //RO_CLEAR_AIR_FACTOR=(Sensor resistance in clean air)/RO,

//which is derived from the chart in datasheet

 

/***********************Software Related Macros************************************/

#define CALIBARAION_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

//normal operation

 

/**********************Application Related Macros**********************************/

#define GAS_LPG (0)

#define GAS_CO (1)

#define GAS_SMOKE (2)

 

/*****************************Globals***********************************************/

float LPGCurve[3] = {2.3,0.21,-0.47}; //two points are taken from the curve.

//with these two points, a line is formed which is "approximately equivalent"

//to the original curve.

//data format:{ x, y, slope}; point1: (lg200, 0.21), point2: (lg10000, -0.59)

float COCurve[3] = {2.3,0.72,-0.34}; //two points are taken from the curve.

//with these two points, a line is formed which is "approximately equivalent"

//to the original curve.

//data format:{ x, y, slope}; point1: (lg200, 0.72), point2: (lg10000, 0.15)

float SmokeCurve[3] ={2.3,0.53,-0.44}; //two points are taken from the curve.

//with these two points, a line is formed which is "approximately equivalent"

//to the original curve.

//data format:{ x, y, slope}; point1: (lg200, 0.53), point2: (lg10000, -0.22)

float Ro = 10; //Ro is initialized to 10 kilo ohms

 

void setup()

{

Serial.begin(9600); //UART setup, baudrate = 9600bps

Serial.print("Calibrating...\n");

Ro = MQCalibration(MQ_PIN); //Calibrating the sensor. Please make sure the sensor is in clean air

//when you perform the calibration

Serial.print("Calibration is done...\n");

Serial.print("Ro=");

Serial.print(Ro);

Serial.print("kohm");

Serial.print("\n");

}

 

void loop()

{

Serial.print(MQRead(MQ_PIN));

Serial.print("LPG:");

Serial.print(MQGetGasPercentage(MQRead(MQ_PIN)/Ro,GAS_LPG) );

Serial.print( "ppm" );

Serial.print(" ");

Serial.print("CO:");

Serial.print(MQGetGasPercentage(MQRead(MQ_PIN)/Ro,GAS_CO) );

Serial.print( "ppm" );

Serial.print(" ");

Serial.print("SMOKE:");

Serial.print(MQGetGasPercentage(MQRead(MQ_PIN)/Ro,GAS_SMOKE) );

Serial.print( "ppm" );

Serial.print("\n");

delay(200);

}

 

/****************** 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)

{

return ( ((float)RL_VALUE*(1023-raw_adc)/raw_adc));

}

 

/***************************** 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

and then divides it with RO_CLEAN_AIR_FACTOR. RO_CLEAN_AIR_FACTOR is about

10, which differs slightly between different sensors.

************************************************************************************/

float MQCalibration(int mq_pin)

{

int i;

float val=0;

 

for (i=0;i<CALIBARAION_SAMPLE_TIMES;i++) { //take multiple samples

val += MQResistanceCalculation(analogRead(mq_pin));

delay(CALIBRATION_SAMPLE_INTERVAL);

}

val = val/CALIBARAION_SAMPLE_TIMES; //calculate the average value

 

val = val/RO_CLEAN_AIR_FACTOR; //divided by RO_CLEAN_AIR_FACTOR yields the Ro

//according to the chart in the datasheet

 

return val;

}

/***************************** 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)

{

int i;

float rs=0;

 

for (i=0;i<READ_SAMPLE_TIMES;i++) {

rs += MQResistanceCalculation(analogRead(mq_pin));

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, int gas_id)

{

if ( gas_id == GAS_LPG ) {

return MQGetPercentage(rs_ro_ratio,LPGCurve);

} else if ( gas_id == GAS_CO ) {

return MQGetPercentage(rs_ro_ratio,COCurve);

} else if ( gas_id == GAS_SMOKE ) {

return MQGetPercentage(rs_ro_ratio,SmokeCurve);

}

 

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 *pcurve)

{

return (pow(10,( ((log(rs_ro_ratio)-pcurve[1])/pcurve[2]) + pcurve[0])));

}

뚫어져라 쳐다보니까 이게 어떤식으로 구동되는 건지는 감이오는데 자꾸 데이터 출력 값이 0이 뜬다.

MQ_Read 값도 정상이고 rs_ro_ratio 값도 잘 뜨는데 pcurve 값이 문제인것 같다.

아마 MQGetPercentage 단계에서 문제가 발생하는 것 같은데 아직 pcurve 값을 어떻게 조정해야하는지는 잘 모르겠어서 못쓰고 있다

///===============================================================

/// The load resistance on the board

#define RLOAD 0.0

/// Calibration resistance at atmospheric CO2 level

#define RZERO 128.5

/// Parameters for calculating ppm of CO2 from sensor resistance

#define PARA 116.6020682

#define PARB 2.769034857

 

 void setup() {

 Serial.begin(9600);

}

 

void loop() {

 int val = analogRead(0);

 val = (1023./(float)val) * 5. - 1.* RLOAD;

 float Resistance;

 Resistance = val;

//

 float PPM;

 PPM = PARA * pow((Resistance/RZERO), -PARB);

//

 Serial.println(PPM,1);

아참

 

  delay(1000);

}

///===============================================================

이건 간단한 코드

외부에서 400ppm이 나오도록 RZERO 값만 조정해주면 끝난다

코드를 뜯어보니까 대충 원리는 똑같은 것 같은데, 구글링 해봐도 비슷하고, 근데 차이를 모르겠다, 실력 부족이겠지?

일단은 간단한 아래쪽 코드를 쓰는 방안으로 가닥을 잡았다

아참, 코드 출처는 각각

http://makeshare.org/bbs/board.php?bo_table=arduinosensor&wr_id=43

http://analog2u.tistory.com/52

이곳이다.