12 Hour TTL Clock





Introduction: 12 Hour TTL Clock

About: I really like tearing things apart to discover how they work. I can even put them back together (most of the time). I have an Associates degree in Electronics Enginering and a Bachelors in Information syste...
This was the final project for my Digital 2 class it was so well received that I thought I would share it. To begin the project I created the circuit virtually. By starting this way I was able to work a lot of the kinks out of my design while also making sure to use only the parts that I had in my kit.

Step 1: Gather Your Parts

Parts List:
1. 555
2. 7408 AND gate
3. 7447 BCD to decimal decoder
4. 74LS90 Decade counter
5. 74LS93 Counter
6. 74LS76 JK flip flop
7. 331 resistor chip
8. 104 capacitor, 1µf cap, and a 10µf cap
9. (2) 503 potentiometers
10. 10K potentiometer
11. (6)or (3 dual) seven segment displays (common anode)

Step 2: Minutes and Seconds

 I began with a 555 timer set up with three potentiometers, two are for the actual timing of the circuit and the third is in parallel with the 503 to allow the time to be set. The seconds and the minute’s portion of the circuit are identical so wiring these were straight forward. The 1’s of seconds receives the clock signal at the 74LS90 (Decade counter) it counts 0-9 then clocks a 74LS93 for the 10’s of seconds. The 93 is set to count 0-5 by running two of the outputs B and C through a 7408 AND gate which resets the IC on the sixth clock pulse and triggers the 74LS90 in the minute’s section of the circuit.

Step 3: Hours

The hours portion of the circuit while using the same components as both the seconds and the minutes is a little more challenging (Logically anyway). The first hours digit needs to count 1-9 then 0-2. This can be accomplished by tying pins 3, 6, and 7 to the output of the AND gate. By doing this it allows for a normal count 1-9 but when the second hours digit is a 1 these two high signals along with the B output on the 90 trigger the reset and clock starts over at 1:00.

Step 4: Run It

You can now impress all your friends with this very large and time comsummig project just like I have



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    26 Discussions

    Hello! I find this project really interesting, and I would like to build it too. Can you please send a clear schematic of the device to my e-mail? My e-mail is : szaniszloricsi@gmail.com -Thanks!

    Its a really cool project

    i want to make one too...great job

    Please send me a copy of your circuit diagram with the complete parts list.


    Please send me a copy of your circuit diagram with the complete parts list.

    Hi my friend can you please send me the schematics??


    christantoangga1@gmail.com . My email sir

    Sir please can you give me the schematics for my final task school sir.. pleasee..

    sir is that a home-made trainer.....and please make the pic. clear so that i can see the PICS. clearly....thank you???

    can you please send me the schematics??

    Please send me a copy of your circuit diagram with the complete parts list. I would like to make this with my son. Thanks


    please send me a copy of your circuit diagram !! help me !!

    gmail : tanphat250394@gmail.com

    thank you very much

    please send me a copy of your circuit diagram !!

    help me !!

    yahoomail :: vincentgonzales372@yahoo.com

    the list of materials is not complete...

    what diode did you use?

    what value of resistor if I can't buy anywhere the 331 resistor chip?

    what is 503 and 205 in the picture? is 503 really a potentiometer but it looks like a ceramic resistor?

    also, in the schematic you provided there is the 3 input and gate which is 74ls11 if i'm not mistaken but you didn't include it in the list...

    the schem you provided is blurred, can't read the labels of each component clearly....

    i hope you would reply immediately ^^ i have read other comments saying it is working and I want to make it to but there are some missing information in your post. Thanks in advance :D

    does it can set the clock time?

    Sir please send me the clear circuit. I have to submit my project report ..... please Sir My Email id is: Almurshid5@gmail.com

    plz send me circuit diagram for 12 Hour TTL clock
    my email

    It is not as accurate as a real clock it loses appox. .68 sec a day which doesn't sound like much but over a large period of time say a week or a month the lose is significant.

    good day sir! can i have a copy of your pdf without having PRO ACCOUNT please.. ill be using it as a references in our on going project.. thanks

    1 reply

    I no longer have a copy of it. But if you do a internet search for a diagram you should find one easily.Sorry