In this tutorial-based article, we are going to learn how to make an Arduino countdown timer.

Hardware Required

Software Required

Stopwatch vs Countdown timer

  • A stopwatch is used to measure the time taken to complete a particular task whereas a countdown timer is a predetermined timer to complete a certain task. 
  • A stopwatch moves forward and shows the time elapsed whereas a countdown timer moves backward and eventually reaches zero.
  • Examples of countdown timers include microwave timers, tv timers, etc.
  • Examples of stopwatches are when they are used in different kinds of races to measure how much time each player took.

Circuit Diagram

  • The circuit diagram for this project is pretty self-explanatory. The LCD Display pins are connected to the Arduino digital pins 2 till 7. The power and GND pins are connected to 5V and GND pins on Arduino.
  • For lighting the 100-ohm resistor is connected to the positive terminal of the LCD.
  • The 4 push buttons are connected to the pins A0 to A3 and the negative terminals of all buttons are connected to the GND pin. These pushbuttons perform a specific function when pressed.
  • The piezo buzzer is connected to the Arduino digital pin D9. 

The working concept of the countdown timer

  • The working concept of this project consists of 4 main components. 
  • Firstly, the pushbuttons have four different functions. The first button has a START/STOP function. Pressing this button once will start the time. Long pressing it will stop the timer. 
  • The second and third button is for INCREMENT and the third button is for DECREMENT while setting the timer. 
  • The fourth button is the SET button which is used to set and save time. 

Arduino Code


  • Upload the code. 
  • Power the circuit on it will display 00:01:00 (HH:MM: SS). This means by default 1 minute is set on the timer. 
  • Pressing the SET button will ask you to set the minutes first. You can choose anywhere from 0 to 59.
  • Pressing it again will ask you to set the hours. You can set this anywhere from 0 to 23.
  • Pressing the START button will start the timer. When the timer reaches zero, the buzzer will start beeping. 

Now your Arduino countdown timer is ready for use.