This is my air quality monitor. I am using this to log the air quality levels in the house
Complete instructions to create and program have been uploaded to my blog
Looking forward to your comments and suggestions.
http://www.dothediy.com/2015/07/air-quality-monitor.html

 

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Here is the code for this project

#include <LiquidCrystal_I2C.h>
#include <DHT.h>
#include <Wire.h>
#include "RTClib.h"
#include <SPI.h>
#include <SD.h>

#define DHTTYPE DHT11

// select the pins used on the LCD panel
LiquidCrystal_I2C lcd(0x27, 2, 1, 0, 4, 5, 6, 7);

DHT dht(A1, DHTTYPE);
const int chipSelect = 4;
int measurePin = A2;
int ledPower = A3;
int thermistorPin = A1;

int samplingTime = 280;
int deltaTime = 40;
int sleepTime = 9680;

float voMeasured = 0;
float calcVoltage = 0;
float dustDensity = 0;

float avgDust = 0;
int avgDustCnt = 0;

byte termometru[8] = //icon for termometer
{
4, 10, 10, 10, 14, 31, 31, 14
};

byte picatura[8] = //icon for water droplet
{
4, 4, 14, 14, 31, 31, 31, 14
};

byte threeIco[8] = //raise to power 3 character
{
24, 4, 24, 4, 24, 0, 0, 0
};

byte miliIco[8] = //micrograms character
{
0, 17, 17, 17, 19, 29, 16, 16
};


boolean backlit = true;
RTC_DS1307 rtc;

void setup()
{
lcd.begin (16, 2); // for 16 x 2 LCD module
lcd.createChar(1, termometru);
lcd.createChar(2, picatura);
lcd.createChar(3, threeIco);
lcd.createChar(4, miliIco);
lcd.setBacklightPin(3, POSITIVE);
lcd.setBacklight(HIGH);
Serial.begin(9600);
while (!Serial) {
; // wait for serial port to connect.
}
Wire.begin();
rtc.begin();
//Uncomment this line and upload the sketch to arduino after uploading
//again comment it and upload the sketch again this will set the date and time
//rtc.adjust(DateTime(F(__DATE__), F(__TIME__)));
pinMode(A3, OUTPUT);
lcd.home();
if (!SD.begin(chipSelect)) {
Serial.println("Card failed, or not present");
lcd.print("Card failed, or not present");
// don't do anything more:
return;
}
Serial.println("card initialized.");
lcd.print("Card Initialized");
}

void loop()
{
DateTime now = rtc.now();
digitalWrite(ledPower, LOW); // power on the dust sensor LED
delayMicroseconds(samplingTime);

voMeasured = analogRead(measurePin); // read the dust value

delayMicroseconds(deltaTime);
digitalWrite(ledPower, HIGH); // turn the dust sensor LED off
delayMicroseconds(sleepTime);

// 0 - 5V mapped to 0 - 1023 integer values
// recover voltage
calcVoltage = voMeasured * (5.0 / 1024.0);

// linear eqaution taken from [URL]http://www.howmuchsnow.com/arduino/airquality/[/URL]
// Chris Nafis (c) 2012
dustDensity = (0.172 * calcVoltage - 0.0999) * 1000;

avgDust += dustDensity;
avgDustCnt++;
if (avgDustCnt == 1000)
{
// make a string for assembling the data to log:
String dataString = "";
dataString += "Dst" + String(avgDust / avgDustCnt) + ",";
dataString += "Tmp" + String(dht.readTemperature()) + ",";
dataString += "Hum" + String(dht.readHumidity()) + ",";
dataString += String(now.year()) + "/" + String(now.month()) + "/" + String(now.day()) + " ";
dataString += String(now.hour()) + ":" + String(now.minute()) + ":" + String(now.second());
File dataFile = SD.open("airlog.txt", FILE_WRITE);
lcd.clear();
lcd.home();
lcd.write(1);
lcd.print(dht.readTemperature(), 0);
lcd.print((char)223);
lcd.print("C ");
lcd.write(2);
lcd.print(dht.readHumidity(), 0);
lcd.print("%");
lcd.print(" ");
if (now.hour() < 10)
{
lcd.print('0');
}
lcd.print(now.hour(), DEC);
lcd.print(':');
lcd.print(now.minute());
lcd.setCursor(0, 1);
lcd.print("Dust: ");
lcd.print(avgDust / avgDustCnt, 1);
lcd.print(" ");
lcd.write(4);
lcd.print("g/m");
lcd.write(3);
// if the file is available, write to it:
if (dataFile) {
dataFile.println(dataString);
dataFile.close();
// print to the serial port too:
Serial.println(dataString);
} else {
Serial.println("error opening datalog.txt");
}
avgDust = 0;
avgDustCnt = 0;
}
}

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