in this tutorial, I am going to show you how to build a seven-segment clock

Step 1: COMPONENTS

4* common anode seven segment displays https://amzn.to/3aDfwtP
Arduino UNO https://amzn.to/2VXJOlO
3 push buttons https://amzn.to/2KxexB8
Ds1307 rtc module https://amzn.to/2zmkG0p
Common PCB https://amzn.to/3cPaNXP
2*leds https://amzn.to/2VSgkWB

Step 2: Cicuit Diagram

As the name indicates seven segment displays has 7 segments. each segment is a single led and all the 7 LEDs connected together with a common pin that may be a common positive or a common negative and arranged in a specific style.

A typical 7 segment display has 10 pins arranged in top and bottom each of middle pins are common pins

And others are to control corresponding seven segments

Step 3: Setting the Displays

we have 4 displays that is totals of 4*8=32 pins to control this our Arduino doesn't have 32 pins so how to do this. yes, multiplexing...
so we connect all segments together that is segment A of 4 displays together, segment B of all displays together and soo on ... now we have 7 common segment pins and 4 common anode pins that is total 11 pins yes our Arduino has 11 pins .by using multiplexing lets control 4 displays with 11 pins instead of 32