Digital clock using 74192 ic

Thread Starter


Joined Nov 29, 2019
Hello All,

I'm new to the forum and I'm having trouble with a university project. I am using a 555 timer, six 74192 up/down counter chips, six 7447 displays, three AND gates, and six 7 segment displays to function as a 24 hour clock. I followed the data sheets and diagrams that my professor gave us but the seconds start counting from 60 and when it reaches 70 it restarts back to 60 and I can’t seem to figure out the problem. Here are the data sheets and diagram;


Joined Mar 30, 2015
Have you double and triple checked your wiring? Have you left any inputs floating?

Post a schematic of how you have things connected; meaning trace the wiring on the breadboard and create a schematic from that.


Joined Jul 11, 2016
you likely don't want to pinboard this . . . it likely can be simplified -- but a somewhat "clean switching" for MOD60
sn74x192 - 24h-TEST.png


Joined Aug 1, 2013
Please update your schematic with these features:

1. Keep the function names at each pin inside the rectangles, but add pin numbers outside the rectangles.

2.. Show every pin of every device. This is the only way that we can verify that you have accounted for all possible control pin combinations.

3. Add bubbles (small circles) to the pins that are negative-true. For example, if the Reset input clears the counter when it is low, it should have a bubble.

Separate from that, the 192 is a synchronous counter, but you are cascading them in an asynchronous manner like a ripple counter. This can cause very short incorrect pulses at the outs of the three AND gates. Better to read up on synchronous counters work and how to interconnect them. You still will need the AND gates, but they should act as enable gates for the 555 clock signal into each counter's clock input.