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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!

<p>awesome project ! I liked so much. You have a new follower and a new subscribe o/</p><p>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 https://www.youtube.com/user/AlisooNFreitas to latin public</p><p>Hug!</p>
<p><strong>muito obrigado meu amigo!</strong> I have visited and also subscribed to your wonderful youtube channel. Keep in contact via PM. <em>tchau!</em></p>
<p>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.</p><p>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. </p><p>Speaking of learning, how do you handle the current limmiting on the LEDs? Is the internal resistance of the CD4017 high enough?</p>
<p>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&acute;s about the maximum current CD4017 can source x out. </p>
<p>Oh, right, I didn't noticed that. Thanks</p>
So good to see electronics rather than code being implemented with electronics. I cut my teeth on ttl logic, great project.
<p>Thanks &amp; Greetings!</p>

About This Instructable

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