自製 CO2、溫溼度感應器

co2_tempature_humdity.ino

#include <Wire.h> 
#include <LiquidCrystal_I2C.h>
#include <DHT.h>

#define         MG_PIN                       (0)     //define which analog input channel you are going to use
#define         DC_GAIN                      (8.5)   //define the DC gain of amplifier
#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
 
//These two values differ from sensor to sensor. user should derermine this value.
#define         ZERO_POINT_VOLTAGE           (0.324) //define the output of the sensor in volts when the concentration of CO2 is 400PPM
#define         REACTION_VOLTGAE             (0.020) //define the voltage drop of the sensor when move the sensor from air into 1000ppm CO2

#define DHTPIN 8
#define DHTTYPE DHT11   // DHT 11
 
float           CO2Curve[3]  =  {2.602,ZERO_POINT_VOLTAGE,(REACTION_VOLTGAE/(2.602-3))};   
LiquidCrystal_I2C lcd(0x27,20,4);  // set the LCD address to 0x27 for a 16 chars and 2 line display 

DHT dht(DHTPIN, DHTTYPE);

byte dat[5]; 

void setup() {
    lcd.init();   // initialize the lcd 
    lcd.backlight();  

    dht.begin();
}
 
void loop() {
    float volts = MGRead(MG_PIN);
    float temperature = dht.readTemperature();
    float humidity = dht.readHumidity();
    
    lcd.clear();
    printRPM(MGGetPercentage(volts,CO2Curve));     
    printHumdityTemp(temperature, humidity);
       
    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) {
    return pow(10, ((volts/DC_GAIN)-pcurve[1])/pcurve[2]+pcurve[0]);
}

void printRPM(float percentage) {
    lcd.setCursor(0,0);
    lcd.print("CO2 RPM: ");
    lcd.print(percentage); 
}

void printHumdityTemp(int temperature, int humdity) {
    lcd.setCursor(0,1);
    lcd.print("TEMP: ");
    lcd.print(temperature);
    lcd.print(" HUM: ");
    lcd.print(humdity);    
}