I have to connect lines that which is disconnected. Due day is tomorrow I filled half already but I'm not sure I'm correct. So I erased mine.
Timer have to start 3:00 to 0:00 and buzzer bips at 0:00.
Help me

 

If you are counting secs from 555 then you need a 12 bit counter. Preset it to 300
then decode 0 to hit the buzzer.

Since counter is 4 bit elements it has to have cascade connections to function as 12 bit.

So how do you do this ?


Regards, Dana.