Digital watch

[Nada]

Hi there ,

am Nada electronic engineering student , actually i need to make a digital watch am going to use 7-segment with it's driver and counter 74LS192 , but i have adoubt about the idea shall i nand the output of the couter when it is 59 second and then it'll recount again ??...

waiting for your help

 

[DigiTan]

The NAND reset should get the job done. I'm guessing you're only allowed to use basic logic in this project. You might also need the counter to reset on "60," so the "59" stays visible for a full second. Don't quote me on that one though. :wink: A BCD counter like a 74LS160 could help minimize your reset circuitry if you have on one hand. How many digits are you using total?

 

[tavib]

:twisted:
The simple gates circuit for reseting the counter is not secure in all cases.
Try to figure out what happen if one or more counter bistables is faster than others. This bistables will go to 0 before others perform this step, and your gates detect a diferent than 60 combination so, because the gates are faster than counter, the reset signal will be cutt off before the entire counter is completely reset, and the counter will be not in 0 but in an random state.
To make the reset process secure enough, the reset signal must be susteined long enough to assure entire counter reset.
You can found several ways to make this.

 

[Nada]

am using 6 digits 2 for second , 2 for minutes and other twofor hours