LED Display digital clock project

[Dido]

Hello,

I want to make myself a digital clock using LED displays as readout, I`ve been searching for some schematics of clocks, there are lots of such in the internet, but I still couldn`t find a reliable one. I don`t want to use a microcontroller, I want the clock to be made with CMOS or TTL IC`s. I found a German website where I found lots of digital clock circuits http://pitts-electronics-home.de/electron/schpluhr.htm

I want to make the circuit Schaltplan einer 6 stelligen LED Digitaluhr mit CMOS- IC's,
I have a few questions about this circuit, as it will use a 555 timer what accuracy should I expect?, Is this circuit going to work?

 

[AN920]

It won't be accurate, and you will have to correct the time daily! Use on of the designs that has a crystal reference. Watch type crystals are common and cheap.

 

[Dido]

AN920, thanks for your comment 

I decided to build the second circuit the one using a crystal oscillator, I have got another question, I think that I will need a frequency counter in order to adjust the trimmer capacitor to the right value, what`s the use of SA in this circuit:

I can`t understand the table drawn in the bottom of the picture. What are the two CD4040 for?

 

[AN920]

The circuit have different clock settings for fast and ultra fast setting as well. There is one setting for normal run mode that uses the 1Hz output. For calibrating the crystal frequency a frequency counter will be handy. The 4040 is just dividers.

You don't need to have all the settings. Just run, set and reset will do