Gravity: Analog Electrochemical Carbon Dioxide / CO2 Sensor (0-10000 ppm) MG-811 Sensor - แท้ DFRobot

#define ZERO_POINT_VOLTAGE (voltage/8.5)

#define ZERO_POINT_VOLTAGE (0.282)

/*******************Demo for MG-811 Gas Sensor Module V1.1*****************************
Author: Tiequan Shao: tiequan.shao@sandboxelectronics.com
Peng Wei: peng.wei@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 2012-05-31
************************************************************************************/

/************************Hardware Related Macros************************************/
#define MG_PIN (A0) //define which analog input channel you are going to use
#define BOOL_PIN (2)
#define DC_GAIN (8.5) //define the DC gain of amplifier

/***********************Software Related Macros************************************/
#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 interval(in milisecond) between each samples in
//normal operation

/**********************Application Related Macros**********************************/
//These two values differ from sensor to sensor. user should derermine this value.
#define ZERO_POINT_VOLTAGE (0.220) //define the output of the sensor in volts when the concentration of CO2 is 400PPM
#define REACTION_VOLTGAE (0.030) //define the voltage drop of the sensor when move the sensor from air into 1000ppm CO2

/*****************************Globals***********************************************/
float CO2Curve[3] = {2.602,ZERO_POINT_VOLTAGE,(REACTION_VOLTGAE/(2.602-3))};
//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: (lg400, 0.324), point2: (lg4000, 0.280)
//slope = ( reaction voltage ) / (log400 –log1000)

void setup()
{
Serial.begin(9600); //UART setup, baudrate = 9600bps
pinMode(BOOL_PIN, INPUT); //set pin to input
digitalWrite(BOOL_PIN, HIGH); //turn on pullup resistors

Serial.print("MG-811 Demostration\n");
}

void loop()
{
int percentage;
float volts;

volts = MGRead(MG_PIN);
Serial.print( "SEN0159:" );
Serial.print(volts);
Serial.print( "V " );

percentage = MGGetPercentage(volts,CO2Curve);
Serial.print("CO2:");
if (percentage == -1) {
Serial.print( "<400" );
} else {
Serial.print(percentage);
}

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

if (digitalRead(BOOL_PIN) ){
Serial.print( "=====BOOL is HIGH======" );
} else {
Serial.print( "=====BOOL is LOW======" );
}

Serial.print("\n");

delay(500);
}

/***************************** MGRead *********************************************
Input: mg_pin - analog channel
Output: output of SEN-000007
Remarks: This function reads the output of SEN-000007
************************************************************************************/
float MGRead(int mg_pin)
{
int i;
float v=0;

for (i=0;i<READ_SAMPLE_TIMES;i++) {
v += analogRead(mg_pin);
delay(READ_SAMPLE_INTERVAL);
}
v = (v/READ_SAMPLE_TIMES) *5/1024 ;
return v;
}

/***************************** MQGetPercentage **********************************
Input: volts - SEN-000007 output measured in volts
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(MG-811 output) is provided. As it is a
logarithmic coordinate, power of 10 is used to convert the result to non-logarithmic
value.
************************************************************************************/
int MGGetPercentage(float volts, float *pcurve)
{
if ((volts/DC_GAIN )>=ZERO_POINT_VOLTAGE) {
return -1;
} else {
return pow(10, ((volts/DC_GAIN)-pcurve[1])/pcurve[2]+pcurve[0]);
}
}