24hr Digital alarm clock


Joined Jan 27, 2019
Welcome to AAC.

Unfortunately, your question is unclear.

What to you mean by "use an RTC to program it"?
Why do you think the time format (24 hour) affects the answer to the question?
What exactly do you envision the "24 hour clock" to be when it is complete?
Why are you designing this?

More information will help a lot in helping you.


Joined Mar 31, 2012
Is it possible to design a 24 hour clock without having to use an RTC to program it?
The devil is in the details.

If this clock is going to be powered from the mains (i.e., plugged into the wall), then it can be designed to be very simple and will keep excellent time by counting the cycles of the mains frequency. Until, of course, it has a power disruption. At that point, you have to reset the time once the power is restored. But, hey, that's how most plug-in clocks are, anyway. You can add some additional complexity to let it continue keeping time during a power outage using a battery backup. The time keeping won't be great during that interval, but if the interval is short, you probably won't notice too much. To go beyond that, you will need to have some way for the clock to access time information itself and there are four ways that come to mind -- WWV or WWVB (if you are in the U.S.) or a similar radio signal that is broadcast in your area, getting time information from a GPS signal, getting time information from a cellular network, or querying an Internet time server.

So it really depends on what it is that you really need/want.