Hello everyone..I'm designing a digital clock using 7490 ic, 7447 ic and seven segment displays..I've completed the seconds and minutes portion...This clock is to be built in a 12 hr format....I couldn't figure out how to display 1 after 12 because it resets to zero...I have to display 1 after 12 and not 0. So, how do I do this? Hope you got the question...Also, I'm thinking of adding an alarm facility too..Any ideas regarding this?

 

hi Bruce,
Welcome to AAC.
Do you have a circuit diagram you could post.?
E

 

hi Bruce,
Welcome to AAC.
Do you have a circuit diagram you could post.?
E

 

Before trying to fix the problem on the reset, I would re-evaluate the component values R1,R2 and C2 on the 555 clock circuit. C2 is especially large at 1000uf. Better choice is C2 10uf , R1 50K pot and 47K for R2.
SG

 

I'm designing a digital clock using 7490 ic, 7447 ic and seven segment displays..

Is this homework?

 

Careful Dennis, the last time I asked that question the guy about blew a fuse.
SG

 

hi Bruce,
Further to the query in post #5, is this Homework or a College assignment.
E

 

Dont think you can do the hours with 74x90. Take a look at the datasheet with 74x190.

Allen

 

hi,
The 74LS92 is also a divide by 12.
E

 

Regarding the use of 74LS92;

@dl324 said "I had never used that part, so I wired it up in a simulator. Unless I made a wiring mistake, it has an odd count sequence: 0,1,2,4,5,6." in another thread...

https://forum.allaboutcircuits.com/threads/60-mod-stopwatch-having-problems-in-recycling.154949/

Would that affect the output of how the "Hours" is displayed?

Allen

 

hi absf,
Thanks for the feedback on the 74LS192, just tried a LTS sim with a 74HCT192, also getting divide by 6.??
I will look later ,see if I can work out the problem.
E

 

The 74LS92 is also a divide by 12.

Thanks for the feedback on the 74LS192, just tried a LTS sim with a 74HCT192, also getting divide by 6.??

You started out talking about 74LS92 and then continue the discussion with 74*192. These are not equivalent counters. 74LS92 is divide by 2, 6, or 12. 74*192 is a BCD counter.

 

hi D.
Thanks for the heads up, my error.
E