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Binary Clock Problem

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lclark

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I have built the binary clock from the attached schematic. On my breadboard, it worked great, but after transferring to a pc board, the minutes trigger at 40 seconds instead of 60. The binary counters work as they should...everything seems ok except for that one thing. I have checked my wiring over and over and cannot find any mistakes. Any ideas?
Thanks so much for your time!
 

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lclark said:
I have built the binary clock from the attached schematic. On my breadboard, it worked great, but after transferring to a pc board, the minutes trigger at 40 seconds instead of 60. The binary counters work as they should...everything seems ok except for that one thing. I have checked my wiring over and over and cannot find any mistakes. Any ideas?
Thanks so much for your time!

hi,
I assume you have decoupling capacitors on the +5V rail.?

Also the 74LS93 is a non synchronous counter so you could have a counter 'glitch'. Try a simple RC filter on the input pin of the hours units 7493.
A 100R in series with the input clock and a 4n7 cap from the hours units pin to 0V.

This should eliminate any mis-operation

Lets know how it goes.

EDIT: Added a sketch
 
Last edited:
Thank you so much for the quick reply. I will give it a shot and see how it goes. Thanks again for your help!
 
lclark said:
Thank you so much for the quick reply. I will give it a shot and see how it goes. Thanks again for your help!

hi,
You may have to increase the value of the 4n7, upto 22n0 depends on the width of the glitch.

I suspect the reason it didnt show on the project board is due to the intercapacitance of the plug in contact rows of the project board.
 
I know this is probably a silly question, but I am a beginner. There isn't a difference between 0v and the common ground, is there?
 
It was the decoupling capacitors. Thank you Eric, for taking time to teach me a valuable lesson on how important they are!
 
I built that same clock about 6 months ago and mine still works. Add 0.1uf capacitors to every IC and many across the 5V line and make sure that the crystal is as close to the 4060 and GND as possible. Long wires causes false timings.
 
Actually I found the schematic from one of your posts if I remember right. I added the capacitors and all seems to be working. I am in the process of running it now to make sure the timing is on before I mount it in a case. Thanks for the advice on the crystal...I didn't know that the distance was important.
 
lclark said:
I know this is probably a silly question, but I am a beginner. There isn't a difference between 0v and the common ground, is there?

hi,
This is a very common question.
I prefer to call the 'common' rail thats used as the reference for voltage measurements the '0V' line.
[ that is 'with respect to the 0V line', sometimes shortened to 'wrt'.]
and the 'common ground' point, to refer the point where all the 0V's of the various circuits/pcb's are connected too.

You will find in some circuits that the correct selection of the 'common ground' connection is very important...
especially 'wrt' electrical noise.

Do you follow.?
 
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