12-hour digital alarm clock using ttls

Thread Starter


Joined Feb 8, 2011
I'm currently working on a digital alarm clock project. Programmable ICs are not allowed. I'm planning to use only TTLs because it's all I have and all I can get. My problem is that I don't know how to force the clock to display 12:00 instead of 00:00. I also have no idea how to implement an alarm that can be set and reset, as with the time. Can anyone provide some insight? Thanks. I have my schematic attached.



Joined Nov 12, 2008
Hi bobon721,

This thread may offer some insight:


Just look up 7400 series equivalent ICs for the CD4000 series ICs if needed.

What are you using to provide the one second clock signal?

I can offer help with a schematic and troubleshooting an actual circuit, not so much for a simulation though. In your schematic however, I notice you have a 50MHz clock signal going into the seconds counter (U2). This should be 1Hz if you're trying to simulate a clock.