24 hour clock using 74HC393, 74LS247...

[andyy07]

Hi everyone.
I have just finished my clock project, without using a microcontroller, only discrete chips, and I want to share it with you...

It uses 74HC393 for the counters, 6 74LS247 for the decoders (I used those because they have 6 and 9 tails and a ripple blanking input), 74HC08 to condition the counts 0>59>0 and 0>23>0, 74LS14 for debouncing the set buttons, 4060 oscillator using a 32768Hz crystal and a 7474 to get it down to 1Hz.

In the schematic are shown some VQE 14/24 displays but one can use anything that has common anode, I've only used VQE24 for the seconds, the hours and minutes are some bigger ones that I've recovered from some thrown away board. Instead of the 330 ohm resistors, I've used some 220 ohm ones.

Cheers...

 

[ronsimpson]

good job!

 

[Rahul G]

could you please upload your block diagram and why have you used a couple of 1n4148 gates?

 

[RODALCO]

Very nice work, I build a few TTL clock's 25 years ago, still works and used 7447 IC's but added extra 7408 And gates to create the tails for the sixes and nines.

 

[schmitt trigger]

First of all; congratulations!

Building a project utilizing basic building blocks gives you an insight on how these circuits work that a software solution does not provide.

And good looking too! I like the fact that seconds are implemented with smaller digits.

 

[alec_t]

Nice one!
Out of curiosity, what is the total current draw?