Arduino Temperature Data Logger with SD Card Module.

Arduino Temperature Data Logger with SD Card Module.

This article shows you how to create a temperature Arduino data logger. We’ll use the DHT11 to measure temperature, the real time clock (RTC) module to take time stamps and the SD card module to save the data on the SD card.

Components Required.


Printed Circuited Board (PCB).

I want to turn my breadboard circuits into real boards and make my project look more professional, so I decided to Design my own coustom PCB for this project.

Designing the PCB

To design the circuit and PCB, we used EasyEDA which is a browser based software to design PCBs.

Designing the circuit works like in any other circuit software tool, you place some components and you wire them together. 

Then, you assign each component to a footprint.

Having the parts assigned, place each component. When you’re happy with the layout, make all the connections and route your PCB.

Save your project and export the Gerber files.

Ordering the PCBs at PCBWay

This project is sponsored by PCBWay. PCBWay is a full feature Printed Circuit Board manufacturing service.

Turn your DIY breadboard circuits into professional PCBs – get 10 boards for approximately $5 + shipping (which will vary depending on your country).

Once you have your Gerber files, you can order the PCB. Follow the next steps.

1. Download the Gerber files –click here to download the .zip file.

2. Go to PCBWay website and open the PCB Instant Quote page. 

3. PCBWay can grab all the PCB details and automatically fills them for you. Use the “Quick-order PCB (Autofill parameters)”.

4. Press the “+ Add Gerber file” button to upload the provided Gerber files.

And that’s it. You can also use the OnlineGerberViewer to check if your PCB is looking as it should.

Now select the shipping method , the one you prefer and has cost efficient.

You can increase your PCB order quantity and change the solder mask color. I’ve ordered the Blue color.

Once you’re ready, you can order the PCBs by clicking “Save to Cart” and complete your order.

PCBWay has lots of other staggering solder mask, Now they can produce pink, orange, grey, even the transparent solder mask.

Apart from this they also provide Black core PCB.

After approximately one week using the DHL shipping method, I received the PCBs at my place.

As usual, everything comes well packed, and the PCBs are really high-quality. 

The letters on the silkscreen are really well-printed and easy to read. Additionally, the solder sticks easily to the pads.

Now grab all the components whose list is mention above, and soldered on the PCB.

After soldiering rest of components PCB look like this neat, clean and well arranged.

SD Card.

Note: make sure your SD card is formatted and working properly.

Installing the DHT sensor library.

For this project you need to install the DHT library to read from the DHT11 sensor.

1.Click here to download the DHT-sensor-library. You should have a .zip folder in your Downloads folder.

2.Unzip the .zip folder and you should get DHT-sensor-library-master folder

3.Rename your folder from DHT-sensor-library-master to DHT

4.Move the DHT folder to your Arduino IDE installation libraries folder

5.Finally, re-open your Arduino IDE


Copy the following code to your Arduino IDE and upload it to your Arduino board.

#include <SPI.h> //for the SD card module
#include <SD.h> // for the SD card
#include <DHT.h> // for the DHT sensor
#include <RTClib.h> // for the RTC

//define DHT pin
#define DHTPIN 2     // what pin we're connected to

// uncomment whatever type you're using
//#define DHTTYPE DHT11   // DHT 11 
#define DHTTYPE DHT22   // DHT 22  (AM2302)
//#define DHTTYPE DHT21   // DHT 21 (AM2301)

// initialize DHT sensor for normal 16mhz Arduino

// change this to match your SD shield or module;
// Arduino Ethernet shield and modules: pin 4
// Data loggin SD shields and modules: pin 10
// Sparkfun SD shield: pin 8
const int chipSelect = 5; 

// Create a file to store the data
File myFile;

// RTC
RTC_DS1307 rtc;

void setup() {
  //initializing the DHT sensor

  //initializing Serial monitor
  // setup for the RTC
  while(!Serial); // for Leonardo/Micro/Zero
    if(! rtc.begin()) {
      Serial.println("Couldn't find RTC");
      while (1);
    else {
      // following line sets the RTC to the date & time this sketch was compiled
      rtc.adjust(DateTime(F(__DATE__), F(__TIME__)));
    if(! rtc.isrunning()) {
      Serial.println("RTC is NOT running!");
  // setup for the SD card
  Serial.print("Initializing SD card...");

  if(!SD.begin(chipSelect)) {
    Serial.println("initialization failed!");
  Serial.println("initialization done.");
  //open file"DATA.txt", FILE_WRITE);

  // if the file opened ok, write to it:
  if (myFile) {
    Serial.println("File opened ok");
    // print the headings for our data
    myFile.println("Date,Time,Temperature ºC");

void loggingTime() {
  DateTime now =;
  myFile ="DATA.txt", FILE_WRITE);
  if (myFile) {
    myFile.print(now.year(), DEC);
    myFile.print(now.month(), DEC);
    myFile.print(, DEC);
    myFile.print(now.hour(), DEC);
    myFile.print(now.minute(), DEC);
    myFile.print(now.second(), DEC);
  Serial.print(now.year(), DEC);
  Serial.print(now.month(), DEC);
  Serial.println(, DEC);
  Serial.print(now.hour(), DEC);
  Serial.print(now.minute(), DEC);
  Serial.println(now.second(), DEC);

void loggingTemperature() {
  // Reading temperature or humidity takes about 250 milliseconds!
  // Sensor readings may also be up to 2 seconds 'old' (its a very slow sensor)
  // Read temperature as Celsius
  float t = dht.readTemperature();
  // Read temperature as Fahrenheit
  //float f = dht.readTemperature(true);
  // Check if any reads failed and exit early (to try again).
  if  (isnan(t) /*|| isnan(f)*/) {
    Serial.println("Failed to read from DHT sensor!");
  //debugging purposes
  Serial.print("Temperature: "); 
  Serial.println(" *C");
  //Serial.println(" *F\t"); 
  myFile ="DATA.txt", FILE_WRITE);
  if (myFile) {
    Serial.println("open with success");

void loop() {

Getting the data from the SD card.

Let this project run for a few hours to gather a decent amount of data, and when you’re happy with the data logging period, shut down the Arduino and remove the SD from the SD card module.

Insert the SD card on your computer, open it, and you should have a DATA.txt file with the collected data.

You can open the data with a text editor, or use a spreadsheet to analyse and process your data.

Thanks for reading!!

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