Project: Digital Clock built with 7490 Decade Counters and a Hacked Quartz Clock

Thread Starter

BlackCow

Joined May 11, 2009
65
Thanks jgessling for giving me the idea of hacking a quartz analog clock for my 1 second time base.

Video of the clock.

The time is kept by six 7490 decade counters. The 1 Hz clock is pulsed into a 7490 wired up as a mod 10 counter (for seconds 0-9). The output of the mod 10 counter is pulsed into a 7490 wired as a mod 6 counter (for seconds 0-5). That circuit is then duplicated for the minutes (0-59). The hours are then counted by two 7490s wired up as a mod 24 counter. (0-23).

The tens of seconds are displayed by 3 LEDs in binary. The 7 segment displays are driven by four 4511 BCD-to-7 segment decoders. I needed thirty-three 100 Ohm resistors in total for all the displays and LEDs.

My blog post.
 

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Wendy

Joined Mar 24, 2008
21,906
It would be preferable to move the docs to this site. We have had extensive bad experiences with the other, just pack them in a zip file, they should fit in this site.
 

Thread Starter

BlackCow

Joined May 11, 2009
65
It would be preferable to move the docs to this site. We have had extensive bad experiences with the other, just pack them in a zip file, they should fit in this site.
Yeah I was having trouble attaching the schematic as a pdf. Zipping it worked fine, thanks.
 

Bill B

Joined Nov 29, 2009
61
Very nicely done. I made one using 7490 decade counters as well only mine is a 12 hour with seconds and I used a 74190 programmable decade counter, a 74191 programmable 4-bit counter, and a flip flop for the hours.
 
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