Temperature Sensor with Arduino

Skills & Concepts You'll Gain

How to connect and use a DHT11 temperature & humidity sensor
How to install and use an Arduino library
How to read sensor data and print it to Serial Monitor
Understanding digital sensors and how they communicate with Arduino
Foundation for building weather stations, smart fans, and IoT projects

Tech Used: Arduino UNO, DHT11 Sensor, Arduino IDE, DHT Library

Step 1

Understand the DHT11 Sensor

Before connecting anything, let's understand what the DHT11 sensor looks like and what each pin does.

The DHT11 has 3 pins (some modules have 4 - the extra one is not used):

VCC - Power pin. Connect to 5V on Arduino
DATA - Signal pin. This sends temperature and humidity data to Arduino. Connect to Pin 2
GND - Ground pin. Connect to GND on Arduino

If you have a DHT11 module (with a small PCB board), it already has the resistor built in - you can connect it directly without an extra resistor!

Step 2

Wire the Circuit

Connect the DHT11 sensor to your Arduino using the breadboard.

Place the DHT11 sensor on the breadboard
Connect VCC pin → 5V on Arduino
Connect GND pin → GND on Arduino
Connect DATA pin → Pin 2 on Arduino
Connect a 10kΩ resistor between the DATA pin and VCC (this is called a pull-up resistor - it keeps the signal stable)

Wiring Diagram

Ensure correct VCC and GND connections before powering on to prevent damage. The DHT11 is suitable for basic use; for higher accuracy, use a DHT22 sensor. Keep the sensor in an open, well-ventilated area away from heat sources for reliable readings.

Step 3

Install the DHT Library

The DHT11 sensor needs a special library to work easily. Here's how to install it:

Open Arduino IDE
Go to Sketch → Include Library → Manage Libraries
In the search box, type DHT sensor library
Find the one by Adafruit and click Install
When asked to install dependencies, click Install All

A library is like a helper toolkit - it gives you ready-made functions so you don't have to write complex code from scratch.

Step 4

Write the Code by opening Arduino UNO

Open Arduino IDE, create a new sketch, and paste this code:

temperature_sensor.ino

// Temperature Sensor - NKDevSpace Tutorial
#include <DHT.h>

#define DHTPIN 2       // Data pin connected to Pin 2
#define DHTTYPE DHT11  // We are using DHT11 sensor

DHT dht(DHTPIN, DHTTYPE);

void setup() {
  Serial.begin(9600);  // Start Serial Monitor at 9600 speed
  dht.begin();         // Start the DHT sensor
  Serial.println("Temperature Sensor Ready!");
}

void loop() {
  delay(2000);  // Wait 2 seconds between readings

  float humidity    = dht.readHumidity();
  float temperature = dht.readTemperature();  // Celsius by default

  // Check if reading failed
  if (isnan(humidity) || isnan(temperature)) {
    Serial.println("Failed to read from DHT sensor!");
    return;
  }

  Serial.print("Temperature: ");
  Serial.print(temperature);
  Serial.println(" °C");

  Serial.print("Humidity: ");
  Serial.print(humidity);
  Serial.println(" %");

  Serial.println("-------------------");
}

Step 5

Code Explanation

Let's understand what each part does in simple words:

#include <DHT.h>

This loads the DHT library we installed. This loads the DHT library required to communicate with the sensor(Think of it like opening a toolbox before starting work).

#define DHTPIN 2

define creates a name for a value. Here we're saying "DHTPIN means pin number 2". This makes the code easier to read and change later.

DHT dht(DHTPIN, DHTTYPE);

This creates a dht object - think of it as telling Arduino "I have a DHT11 sensor connected to pin 2, remember that."

Serial.begin(9600);

This opens a communication channel between Arduino and your computer so we can see the temperature values printed on screen. 9600 is the speed of communication.

dht.readTemperature()

This asks the sensor "what is the current temperature?" and gives back a number in Celsius. The result is stored in the temperature variable.

isnan(temperature)

isnan means "is not a number". If the sensor fails to read, it returns an invalid value. This check prevents printing garbage data.

Step 6

Upload & See Results

Make sure your Arduino Uno is connected to your laptop using a USB cable
If not already selected, set the correct options:
- Go to Tools → Board → Arduino AVR Boards → Arduino Uno
- Go to Tools → Port → COM X(COM 3, COM4, ...) (Arduino Uno)
Click the Upload (→) button in Arduino IDE
Wait until you see the message Done uploading
Open Tools → Serial Monitor (or press Ctrl + Shift + M)
Set the baud rate to 9600 at the bottom right
You should see temperature and humidity values printing every 2 seconds

Try breathing near the sensor. The humidity value should increase, which confirms the sensor is working properly.

Step 7

Try It Yourself - Challenges

Now that it's working, try these to go further:

Add an LED that turns ON when temperature goes above 30°C
Add a buzzer that beeps when temperature is too high
Display temperature on an LCD screen instead of Serial Monitor
Read temperature in Fahrenheit - use dht.readTemperature(true)

Components Needed

Software Required