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!
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.
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.
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.