Zordon

So i have a school project where i have to build a digital clock using 7490's i have already built the seconds and minutes part but i am kind of confused on how to handle the 24 hour counter. current the circuit below will count to 29 and reset to zero. i want it to reach 23 and reset.

LEFT seven segment display Most significant digit

RODALCO

Schema attached of two times 7490 IC's to decode 00 to 23 and reset to 00 again for a 24 hour clock.

Hope it helps you with your clock

Regards, Raymond

Attached Images

DSC01829.JPG (118.9 KB, 43 views)

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RODALCO

Or use two times 7490 IC's and a 7400 to divide the 24.

You have an option available to drive a date counter if you wish.

Attached Images

DSC01830.JPG (123.1 KB, 20 views)

__________________
There are more ways to get to Rome.

Electricity, Electric clocks, Meters and Trains are great.

Diver300

The design with the NAND gates seems a bit pointless, compared to the design without. The 7490 has an AND gate on the reset line, so it seems sensible to use it when it helps, like in the first design you posted.