My teacher told me to design a 24-hour clock which would display like this (23:59:59), but in the hour position it is displaying (24:00:00), and my teacher said this Is wrong because it becomes a 25-hour format. He suggested that if a 24-hour format is to be designed, the last hour should be (23:59:59). Can someone find my error and help me? This is my circuit

 

It looks like U7 counts 0--->9.
U8 counts 0---->5.
U9 0--->9.
U10 0-->5.
It is hard to see. I think it should.
U11 0--->9, 0--->3 (reload if U11=9 or U12,U11=2,3)
U12 0--->2. (reload if U12,U11=2,3)

 

Why are you using 74LS160 and 74LS161 instead of using all 74LS161?

Why are you using the LOAD control input?

Look up the datasheet to find out how to cascade 74LS160/161 counter ICs.

 

I need your help. Would you like to take a look at my multisim file?

 

Not really. I don't use multisim.

 

Should I use 74LS161 then? Will it be ok after that?

 

or what you think I should do now to get desired results?

 

You could use 74LS160 or 74LS161 or both as in your circuit. But only the first option makes any sense, i.e. use 74LS160 for all.
Look up how to connect two 74LS160 and then redesign your circuit.

So far, nothing that I have suggested is meant to fix your problem. It only simplifies the logic and the design, i.e. don't make life more difficult than what is necessary.

 

Can someone find my error and help me? This is my circuit

It would be helpful if you cleaned up the routing, didn't route wires over labels, and printed to PDF so we don't have deal with the grid.

Something like this would be easier to read:

As I recall, the text looked better on screen, but MultisimBlue no longer runs so I can't check.

This is part of a 24 hour clock that also counted down.