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Introduction 

Published date: 30/04/2016

In this  guide I will show you how to make a simple - two digit - countdown timer by using the Arduino uno board and 7 segment displays.

We will be able to set the timer in our program sketch by changing the value of one variable. We will use two digit seven segment displays, so the maximum countdown time will be 99 seconds. When the timer will be equal with zero, we will hear an buzzer tone.

Here you can find more info and one simple Arduino tutorial with 7 segment display​.

So, let's get started!

What you will need - Hardware

For this project we will need:

• Arduino uno
• breadboard
• 2 digits 7 segment displays*
• buzzer
• some breadboard cables

(*you can use common cathode or common anode type)

The Circuit 

The connections are pretty easy, see the above image with the breadboard circuit schematic.

(if you want you can connect one 220 Ohm resistor to each pin - except "CC" or "CA")

The Code

Here's the code, embedded using Codebender!

Try downloading the Codebender plugin and clicking on the "Run on Arduino" button to program your Arduino board with this sketch. And that's it, you've programmed your Arduino board directly from your browser! It's really amazing.

• numOfDigits = 2 We have two digits 7 segment display.
• digitPins [numOfDigits] = {3,4} CC or CA pins of them connected to Arduino pin 3 and 4.
• disp.setDutyCycle(50) Control brightness of the display - "50" is 50% of led brightness.
• disp.write(number) Print a number from 0 to 99 (because we have two digits)

If you want to change the timer just click the "Edit" button and change the value of "timer" variable. Value must be bigger of zero and lower (or equal) of 99.
(if you have common anode 7 seg display type just delete the line 24 "disp.setCommonCathode();")

Note: If you will not use the Codebender IDE for programming your Arduino board you will need to manual install the SevenSeg library in your Arduino IDE. Where to find it? Search the web, don't ask me... Or just use the easy and simple way of Codebender.

Well done!

That's it! You have successfully completed this guide and now you have your own simple Arduino countdown timer. If you want to restart the timer, just press the reset button.
​I hope you liked this, let me know in the comments!