OK, before anyone blasts me with the "do your own work speech" let me let you that I'm 33, not in school, and this is a hobby. I already made a working 24 hour clock. (see attached pictures) It came out great. I even etched my own board.

I want to have a go at making a 12 hour version. Rev 2 of my clock will pretty much use the same board and chips (7490's and 7447s) I can get the clock to run in 12 hour mode, but the whole AM/PM LED is bothering me. I was going to add a flip-flop, but I can't for the life of me figure out how to get the LED to stay on when the hours read "12" and then off again 12 hours later.

Anyone have a schematic? I don't want to redo the clock using 7492s since I already have all the 7490s on hand.

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Never mind. I thought I found something, but that wasn't it....

 

Hi Krye,

I don't think I ever built a clock, that makes me the ideal
person to give you some advice on how to build one.

Connect all R9's to gnd, that will make the clock count
instead of displaying six nine's.

QD of U5 and CLKA of U6 are both connected to +5 volt, that's
probably a typo.

The setting for minutes and hours is completely wrong.

And . . . the hours counter will count from 0 to 13 ?????

As I said before, I don't know much about clocks so I could
be wrong.

on1aag.

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Hi,

I built a clock 14 years ago using 4000 series chips. I built it on breadboard and used it as my bedside clock for many years. Never got around to putting it in a proper case (as with a lot of the projects I used to build). It was probably one of the last things I built before abandoning hobby electronics until my resumption very recently.

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Very nice, except that isn't 'breadboard', presumably it's Veroboard? - breadboard is a temporary construction method.

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You're right. It's wrong. It's all wrong! I don't know what I was thinking. I removed the schematic so I can redo it.

 

@krye: The flip flop should be set to toggle on the falling edge of the "1" driver.

 

Maybe like this ?

on1aag.

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That's the basic idea.

 

Cool, thanks

K

 

RODALCO PLS EMAIL ME THE SCHEMATIC DIARGRAM OF DIGITAL CLOCK WITH 555 TIMER pls. ..

sweet_ko2007@yahoo.com

 

Help me guys!!

 

im having problem with my clock hour simulation...my 12:00 time isnt goin back or rather resetting to 00:00...how am i goin to do so..im using ttl gates mainly 7490 & 7492 as seconds mins and hours...nid help..tnx