Digital Clock Block Diagram

Thread Starter

Wendy

Joined Mar 24, 2008
21,848
We seem to be getting a lot of queries about Digital Clocks, so I've drawn up this block diagram to help out. If anyone (especially the mods) can suggest improvements please do.

 

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bertus

Joined Apr 5, 2008
20,048
Hello,

Another clocksource can be a 32768 Hz crystal oscillator
(from an old digital watch for instance)
with a 32768 divider to get the 1 Hz reference for the seconds.

Greetings,
Bertus
 

Thread Starter

Wendy

Joined Mar 24, 2008
21,848
True enough, but what do you think most of the students are being assigned? From what I can tell, these courses are being given as a practical assignment in flip flops and counters.

I didn't realize how wide this diagram wanted to be when I started. :rolleyes:
 

bertus

Joined Apr 5, 2008
20,048
Hello,

With a crystal oscillator you are independend of the line frequency.
You could even make a CMOS version on batteries.
(though the display will take some current when not multiplexed).

Greetings,
Bertus
 

Thread Starter

Wendy

Joined Mar 24, 2008
21,848
I don't think any of these guys are actually building this sucker. If you go through the last 5 or so posts asking for help they come up with "I don't have a clue where to start" or a simple "HELP!". I only wish the clocks I buy used something so good, for the most part they seem to have a poorly adjusted RC oscillator when the power goes out and the battery backup takes over. This really is the commercial standard.

This is meant as a starting point for these guys. If you and I were to build the clock this would be totally unnecessary. Near as I can figure, over half of the old hands would start off with a microcontroller.
 

beenthere

Joined Apr 20, 2004
15,808
The number of counters isn't too bad, but the PCB gets awfully busy if you're just using logic.

I am pretty past it, but I lost interest pretty seriously about the time 8 bit systems went away. But I'm about to glom onto the STK500 and a clock is my first project. Got lotsa LED's for it - gonna track seconds (also stay busy at the drill press for a bit).
 
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