12 Hour digital clock

[Nitori]

Apparently I've faced some problem while simulating the circuit.
The circuit was based on a book for my project.

Current problem faced are:
1. The LED in the middle doesn't blink each second ( Which I think it is suppose to do so.)
2. The minutes display isn't counting even though it is left for a long time. ( I'm not really sure is
the circuit working or not...)
3. Somehow the minutes counts up to 79 minutes and reset back to 00 at 80 minutes. (Done by
pressing switch)

Could anyone tell me what's wrong with the circuit??

View attachment 61241

 

[ronsimpson]

There are many things I do not know.

What software are you using?

"3. Somehow the minutes counts up to 79 minutes and reset back to 00 at 80 minutes. (Done by
pressing switch)" What switch?

Break down the project into small pieces! Look at the output of the LM555 and see if you get a 1hz pulse.

Look at the collector of Q2. Is it "blinking".

Look at the Q outputs of U12 and U13 and see if they are counting.

Test each counter group and see if they are counting.

 

[Nitori]

Current software using Multisim 11.

Still new to the software and the studies so wouldn't know much especially in dividing the parts. ><

The switch I mention is the Switch J2 used to control the minutes section.

I just tested the LM555 output to see the pulse using a frequency counter. Apparently it doesn't show any result. Assuming I used it correctly, it means the LM555 is currently isn't generating any pulse?

The collector Q2 "blinking" is it referring to the LED? if it is referring to the LED then it isn't blinking.

I've only manage to test that the hour is counting correctly by using the switch J3.
For the minutes (U10 & U14) is the part where is counts to 80 then resets to 00.
I couldn't manage to test the seconds (U11 & U15) to see whether it could count correctly. When i connect to a 7-segment display it both (U11 & U15) displayed a weird symbol.

Correct me if I'm wrong. By separating the project into small parts, is it like this? The LM555 , U12 & U13 [Seconds counter] , U10 & U14 [Minutes counter], and the U11 & U15 [Hour counter]

 

[ronsimpson]

I don't know Multisim 11 but:
There is a "scope probe" where you can look at the wave form. The output of the LM555 is like this:
-------____-------------------______------------------______----------


If the hour is counting at all then the LM555 must be working.
For each block (Hour, Minutes, Seconds) they should count. The QA,QB,QC,QD should start out 0,1,2,3,4.......end count,0,1,2,3......
I know there are many ways of looking at points in your project.

QA----____----____----____
QB_______----------______
QC_____________----------

or

QA:QB: 0 1 2 3 4 5 6

or

QA0000111110000001111100000
QB0000000001111111111100000
QC0000000000000000000011111

 

[jbeng]

U14 is resetting itself when it's QD output goes high, which is 8. It should instead reset itself when QB and QC both go high, which is 6. AND signals QB & QC together, feed the output to the reset pin and it should count to 59 and reset.

 

[Nitori]

Oh I see it now. Thx for the tips.
My clock can work correctly now. ^^

 

[ansam]

Hi , I need to design same project 12 hour digital clock can you help me and give me this project .