Bajdi electronics

Arduino data logging with webserver and RTC

Made a really big sketch today 🙂 I used an Arduino Uno, ethernet shield with sd slot, DS1307 RTC and 2 temperature sensors for this sketch. I used 2 different temperature sensors, one is a DHT22 sensor which can also sense the humidity and the other is a DS18B20 sensor. To get all this to work I needed no less then 8 libraries, the ethernet and sd library take up a lot of space which makes this sketch so big. After compiling the sketch the size is 23634 bytes (of a 32256 byte maximum). It was pretty easy to code, I started from the various examples that come with the Arduino IDE and put them together. I would never have gotten this to work if I had to start from scratch.

The temperature sensors are polled once every 5 seconds, there is not much point in polling them more often to get room temperatures. I did not use the delay or millis function for this but the time from the DS1307. The date, time, and temperature values are written to a CSV file on the SD card every 5 seconds. A CSV file is easily imported in a spreadsheet. All the data is also made available on a webserver. If you need ethernet and a sd slot for a project the latest official ethernet shield is very handy as it has both. I bought mine from the official Arduino shop. You can find similar shields on ebay from Chinese sellers. But there seem to be quite a lot of topics on the Arduino forum of people having trouble with them.

There is one thing this sketch needs to make it better and that’s an automatic update from a timeserver to sync the time with the DS1307 RTC. The DS1307 is not the most accurate chip, even after a day the time will be of by a couple of seconds.

/*
 http://www.bajdi.com
 SD card datalogger and webserver with DS1307 RTC.
 
 This sketch shows how to log data from a DHT22 and DS18B20 sensor to an SD card using the SD library.
 The data from the sensors is updated every 5 seconds and written to the SD card in a CSV file.
 Time stamp is taken from a DS1307 RTC. The data of the DHT22, DS18B20 and RTC is also available on a webserver. 
 */
 
#include <SPI.h>
#include <Ethernet.h>
#include <Wire.h>
#include "RTClib.h"
#include <dht.h>
#include <SD.h>
#include <OneWire.h>
#include <DallasTemperature.h>

const int ONE_WIRE_BUS = 3;                // signal pin of DS18B20 connected to pin 3
OneWire ourWire(ONE_WIRE_BUS);
DallasTemperature sensors(&ourWire);

dht DHT;

RTC_DS1307 RTC;

#define DHTTYPE DHT22 // Sensor type
#define DHT22_PIN 2   // DHT22 signal on pin 2

byte mac[] = { 
  0xDE, 0xAD, 0xBE, 0xEF, 0xFE, 0xED };
byte ip[] = { 
  192,168,1, 10 };

int lastTime = -1;

float temp;            // float for temperature value from DS18B20

Server server(80);

const int chipSelect = 4;      // CS for SD card

void setup()
{
  Serial.begin(9600);
  Ethernet.begin(mac, ip);
  server.begin();
  Wire.begin();
  sensors.begin();            // for DS18B20 sensor
  RTC.begin();
  RTC.adjust(DateTime(__DATE__, __TIME__));
  Serial.print("Initializing SD card...");
  pinMode(10, OUTPUT);

  // see if the card is present and can be initialized:
  if (!SD.begin(chipSelect)) {
    Serial.println("Card failed, or not present");
    // don't do anything more:
    return;
  }
  Serial.println("card initialized.");
}

void loop()
{
  DateTime now = RTC.now();                              // get time from RTC

  int time = now.second();
  if (abs(time - lastTime) > 5)
  {
    int chk = DHT.read22(DHT22_PIN);                       // get data from DHT22
    sensors.requestTemperatures();                         // get data from DS18B20
    temp = sensors.getTempCByIndex(0);                  


    File dataFile = SD.open("datalog.CSV", FILE_WRITE);

    // if the file is available, write to it:
    if (dataFile) {
      dataFile.print(now.day(), DEC);
      dataFile.print('/');
      dataFile.print(now.month(), DEC);
      dataFile.print('/');
      dataFile.print(now.year(), DEC);
      dataFile.print(" , ");
      dataFile.print(now.hour(), DEC);
      dataFile.print(':');
      dataFile.print(now.minute(), DEC);
      dataFile.print(" , ");
      dataFile.print((float)DHT.temperature);
      dataFile.print(" , ");
      dataFile.println((float)temp);
      dataFile.close();
      // print to the serial port too:
      Serial.print("DHT = ");
      Serial.println(DHT.temperature);
      Serial.print("DS18B20 = ");
      Serial.println(temp);
    }  
    // if the file isn't open, pop up an error:
    else {
      Serial.println("error opening datalog.CSV");
    }
    lastTime = time;
  }

  Client client = server.available();
  if (client) {
    // an http request ends with a blank line
    boolean currentLineIsBlank = true;
    while (client.connected()) {
      if (client.available()) {
        char c = client.read();
        if (c == '\n' && currentLineIsBlank) {
          // send a standard http response header
          client.println("HTTP/1.1 200 OK");
          client.println("Content-Type: text/html");
          client.println();
          
          client.print(now.day(), DEC);
          client.print('/');
          client.print(now.month(), DEC);
          client.print('/');
          client.print(now.year(), DEC);
          client.print(' ');
          client.print(now.hour(), DEC);
          client.print(':');
          client.print(now.minute(), DEC);
          client.println("<br />");
          client.print("Arduino powered webserver");
          client.println("<br />");
          client.print("Serving temperature and humidity values from a DHT22 and DS18B20 sensor");
          client.println("<br />");
          client.print("Inside temperature (oC): ");
          client.print(DHT.temperature);
          client.println("<br />");
          client.print("Humidity (%): ");
          client.print(DHT.humidity);
          client.println("<br />"); 
          client.print("Outside temperature (oC): ");
          client.print(temp); 
          client.println("<br />"); 

          break;
        }
        if (c == '\n') {
          // you're starting a new line
          currentLineIsBlank = true;
        } 
        else if (c != '\r') {
          // you've gotten a character on the current line
          currentLineIsBlank = false;
        }
      }
    }
    // give the web browser time to receive the data
    delay(1);
    // close the connection:
    client.stop();
  } 
}