Ian Dunn
I've added a PDF of the schematic diagram of this project. If you'd like to build it on a breadboard, it should work.
Here's how it works:
Clocks were pretty simple when it was just numbers on a dial and a motor turning the hands. Keeping time with digital logic is pretty complicated!
Here's how I did it:
A 32.768khz crystal feeds it's output into a 4060 14 stage binary ripple counter. This divides the crystal's output down to 2 hz. This 2hz wave is fed to a 4027 flip flop to get a 1HZ signal that is fed to the seconds ones stage.
The seconds ones stage counts to ten, then resets to zero and advances the seconds tens. The seconds tens counts to 5 then resets to zero and advances the minutes ones. The minutes count up the same as the seconds, and advance the hours when the count reaches 60. The hours count up from 1, and reset to 1 when the hours reach 13. Resetting to 1 not 0 and counting to 12 is a little tricky. To do this I used an and gate that resets when the hours are 13. To reset to 1 instead of zero I offset the LED's on the hours segment by one. So instead of the one LED being connected to the one output on the 4017, it's connected to zero.
Marek Więcek
Mario Gianota
sjm4306
Dave Ehnebuske
How about making the PCB 100 x 100 to take advantage of the offers from the various PCB manufacturers, or sizing it to suit photo frames that it could be mounted in ?
As a kit then through hole will be more popular but look awful unless the chips are on the front, a SMT version would look tidy with the chips on the back and would sell more if the chips were pre soldered, JLCPCB are currently offering a free setup for SMT assembly :)