74192 project problem.

MrCarlos said:

Hello Codeman

What I understand from your original message is you're trying to make a 4-digit digital clock in 24-hour mode.
Therefore only it has two digits for the hours and two for the minutes.

Let me see if we agree:
The counters for the minutes should count from 00, 01, 02, . .10, 11, 12, 13, . . . 57, 58, 59, 00.
The counters for the hours should count from 00, 01, 02, . . . 10, 11, 12, 13, . . . 20, 21, 22, 23, 00.
Right ?

So you need to detect when the counter of the tens of minutes reaches 6 and in that instant reset both counters to 00.
This can be accomplished with a 2-input AND gate connected to the connectors named MQ20 and MQ40. Because: 20 + 40 = 60.

Using the same technique we can say that when the counters, for hours, reaching 24 You'll have to reset them to 00.
This can be accomplished with a 2-input AND gate connected to the connectors named HQ4 and HQ20. Because: 4 + 20 = 24.

Surely you know where to connect the outputs of these AND gates, right?

No pull-down resistor is required. Gates bring the same effect inside.

Carefully analyze the circuit shown in .PDF document I am enclosing you.

I hope you have, in your design, the current limiting resistors for each segment of each display.
And also you have a logical, appropriate level, applied to the inputs you are not using of the IC's.

Click to expand...