This project is explaining how to create yourself a 6 digits 7 segments clock with AVR microcontroller

Step 1: Prepare the Parts for This Project

We need to prepare a parts for this project,

6x 7 Segments Common Anode

6x PNP transistors for driver, I used 2N3906

6x 1K 1/WW resistors

1x Module ATMEGA128

1x NTC resistor 10K

1x 10K resistor 1/4W

2x Push button for adjusting the hour and minute


1x Atmel studio

Step 2: The Segment Code

I have written the segment code for this project,

Please have a look on the picture in this step....

That's how I drive each seven segment with PNP transistor, it's cheap but more than enough for driving 8 segments

Step 3: The Firmware and MCU Selection

You're going to need at least 15 I/O from your MCU for this project,

In my case I used ATMEGA128, but you can use ATTiny2313,ATMEGA8,ATMEGA16 and others family of AVR 8-bits

I'm using interrupt and timer to increase second, you can upgrade to a calendar as well if you one, quite simple and straight forward.

Hex file is included if you want to use ATMEGA128

Here's the setup for my timer and ISR :

{ seconds++;

if(seconds == 60) {

seconds = 0;

minutes++; }

if(minutes == 60)

{ minutes = 0; hours++; }

if(hours > 23) hours = 0; }

Step 4: The Demo in Video

Let's watch this clock working on video

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