• Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.


Not open for further replies.


New Member

:?: I need a schematic diagram of a digital clock using simple 74xx ICs I'm a college student and i still dont have much knowledge about building a digital clock. I need it for my project in electronics laboratory. Preferably using 7490,7447, and the like....please :oops:

thanks in advance!! :shock:


New Member
one can build a digital clock with a row of 4 or 6 7 segment displays or one can build one with 60 + 12 LED's in a circle, which is it you are interested in?
Your biggest bugbear - if you want the clock battery operated - is the obtaining of a stable frequency from a 1 Mhz crystal or such. All the clock chips with onboard oscillators are not TTL logic.
If you can use the mains frequency as a clock pulse source it is somewhat easier but there's no power off time keeping facility.



Do your own bloody work!


Active Member
Now this one is school work. I hope no one sent him a direct link to one :eek:..

Come on man..

If he did not learn enough in school to build it AND can not work google..

Practice this, "would you like to super size your order?". (I sound like hitech and Hero wants to club him.)


New Member
Hiya! Nice to be back in this forum.

Lol, I didn't thought on1aag referred a link to my thread, how nice yet embarrassing. XD

But yeah, sometimes you have to do it yourself than others do it all for you. I mean, after on1aag gave the rest of the schema, I felt like "damn, I'm relying on others again". But I did studied his schema and figure out how he did it and spent hours on my breadboard. Good thing I didn't get callouses after that, hehehe :D And there's a thing that I've been "trying too hard" figure out how to set the hour hand to 12-hour instead of 24 (our instructor issued us a challenge that if we can figure out to set the clock to 12-hour format instead of 24-hour, we're exempted on a written exam), until I reached the point that it's impossible for a 74LS90 IC. Maybe someone here can, who knows? :D The thing is that I did my what I can, but on my own. :D
Last edited:


New Member
I dare you to harvest a board from an old clock radio and just hand it in.. A guy in my class who couldn't read resistor codes tried to pass off a consumer walkie-talkie as his own..
I gotta give him credit though.. He was stoic, and straight-faced.. Almost like a politician denying something obvious..


New Member
please help me with ma project work am working on LED digital clock and i need your reply urgently because i have to finish it in a month's time


New Member
Well I typed "TTL clock circuit" into a goggle window and the very first listing was:


Talk about students having it easy these days :p Although I suspect that they won't learn much using this approch. :rolleyes: But he only has a month to finish so what is a guy to do :rolleyes:

Just delete the copywrite notice and the header title on each page and you should get an A just for the documentation work you did! Tell him the dog eat the clock but it was working great before that.

Good luck

Last edited:


New Member
digital clock using quartz pulse for 1 second pulse.

I made an experiment to build a digital clock with seven segments display. it consists only hour and minute display ( 4 seven segments ). for 1 Hz oscilator I use the 3v desk clock ( only take its pcb ). but the pulse out is 1/2Hz, so I multiples it with 7490 as divider. Thus for minutes and hours I just use two 7490 and two 7493, for display are four 7447. Unfortunately now I dont find its schematic. Later I will post here.
Not open for further replies.

Latest threads

EE World Online Articles