[punkky] has been documenting his adventures building digital clocks. They each use six 7-segment LED displays, but he’s been gradually changing how they are built. The first version used a CMOS BCD-to-7-sement latch on each display, which is tied to a PIC16F627a. For the next run, he added multiplexing, so he could drive all the segments using just thirteen pins. He’s posted a final schematic with code and details of how the clock timing actually works.
Pfft :P The PIC is cheating! We had to do it with 74xx logic and a 12VAC transformer alone!
I am projecting a one with only 74xx logic, 555 and discrete components… With ALARM!
Yea seriously… Why do you need a uC for this?
if he really wanted to be cool, he’d use nixie tubes. :P
Not sure on the required gate count, but what about using a CPLD like in one of the previous entries here?
khani3s, how do you plan to implement an alarm? Some type of FSM?
You could do the alarm with some ‘ls85 comparators, a RS flop, and a 555 (or buzzer) for the sound.
If it doesnt need to be battery powered, you could step line voltage down to 5v, clean the wave up with a schmitt trigger, and set up a frequency divider to get a 1pps square wave. The 555 would be easier nvm XD
Thank you for all comments. As I stated in my blog, I built this clock for learning Microcontroller. I’m not looking for an easy way to build a digital clock :)
Alarm might be the next feature to be added.
yeah an alarm would be a good idea.
http://digitalwallclock.biz
We all have to begin somewhere. It is a good learning project. I have made a clock using 74′ series IC, programable counter, keyboard entry, latches for alarm and a comparitor circuit.
I have many PIC’s, basic stamps, Z80 and ….. But I still injoy the extream challange of designing a circuit without any programming…stuff.
Good job!!!