Bar-graph Display Digital Clock

Introduction: Bar-graph Display Digital Clock

About: Music: my profession for over 40 years... Electronics: my beloved hobby always.

CD4017 is a versatile integrated circuit (and its small brother CD4022) and has infinite applications. This digital clock project is made from 8CD4017´s plus a 7812 or 78L12 for supply. Time reference is obtained from the AC line frequency(50-60Hz)and subdivided by the CD4017´s to obtain seconds, minutes and hours. AC line frequency is quite stable and has been used by electric wall clocks for decades. The 4017´s drive LED bar-graph displays directly from its outputs with 1 single current limiting resistor. A microcontroller version of this project would be much simpler to wire... but this is also great fun!

Step 1: Project Overview

Step 2: Circuit Diagram (part 1) & Main Components

IC1: 7812 or 78L12 voltage regulator IC

IC2-IC5: CD4017 cmos decade counter

T1: 12v+12v secondary power transformer. (current requirement is very low)

Step 3: IC2: 50-60Hz to 10 Hz Divider

Step 4: IC2 Line Frequency Selection

connect reset source signal according to your local line frequency

Step 5: IC3: 10Hz in to 1 Hz Out (divide by 10)

Step 6: IC4-IC5: 1Hz in to 1cycle Per Minute Out (divide by 60)

Step 7: Circuit Diagram (part 2) Display

IC6-IC9: CD4017 cmos decade counter

Display: 4x 10 led bar-graph display

SW1-SW2 push-button momentary switch (time set)

Step 8: IC9: Minutes Units (0-9)

Step 9: IC8: Minutes Tens (0-5)

Step 10: IC7: Hours Units (0-9)

Step 11: IC6: Hours Tens (0-2)

Step 12: And Gate Decodes "24" and Resets IC6-IC7 to 0

Step 13: Seconds LED

Led LD1 blinks every second. Use SW1-SW2 to set time.

Step 14: Watch the Video & Subscribe! Thank You!

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    awesome project ! I liked so much. You have a new follower and a new subscribe o/

    How can I do to talk to you? I maked a new channel in english, and I would want to know if you want to be my partner; This is my current channel to latin public



    Reply 5 years ago

    muito obrigado meu amigo! I have visited and also subscribed to your wonderful youtube channel. Keep in contact via PM. tchau!


    6 years ago on Introduction

    Sure you can use a microcontroller - you can use it for almost everything. It wouldn't even need mains ac to run, just a watch crystal.

    But thats not the point. Sometimes it's just good to know how simple things can be, in fact it might be those things I've learned most from.

    Speaking of learning, how do you handle the current limmiting on the LEDs? Is the internal resistance of the CD4017 high enough?


    Reply 6 years ago on Introduction

    Hi! R5 (220 ohm)is the current limiting resistor. It is a single resistor which is common to all led cathodes. With 12v supply minus 2.5v (approx led Vf) current is 40mA. Since 4 leds are on at any time, that gives 10mA per LED. That´s about the maximum current CD4017 can source x out.


    Reply 6 years ago on Introduction

    Oh, right, I didn't noticed that. Thanks


    6 years ago

    So good to see electronics rather than code being implemented with electronics. I cut my teeth on ttl logic, great project.