I am building a clock using 74161 chips and I feel like I'm pretty far along. I have the seconds and minutes displays working, but I'm stuck on the hours display. The seconds and minutes reset after 59, but I'm having a little trouble getting the hours to roll over. I want the max to be 12 instead of 23. If anyone could help, I'd appreciate it. Thanks

 

The logic to roll over 12 to 01 is really what I'm stuck on. I can't seem to figure out how to roll over from 9 to 0 then 2 to 0.

 

Hello,

Bill_Marsden did create this thread some time ago:
Digital Clock Block Diagram

Basicaly you should detect the 13 to load the counters again with 01.

Bertus

 

I saw that diagram, but I guess it just doesn't make sense to me. I have this so far
http://img72.imageshack.us/img72/1808/clock1a.jpg

 

I almost finished it. I almost have everything working. I got all the times going and rolling over fine, but I am now having trouble setting the time. I have two switches. One sets minutes and one sets hours. The hours set fine, but when I try to set the minutes, it cycles through the ones place and goes into hex before binary. so it goes from 0-9 then a-f and back to 0. If someone could look at my schematic and help me out or something here is a link. I'm not sure if the colors all show up or not, but I can post another in a different color scheme. Thanks
http://img33.imageshack.us/img33/93/clockbuggin.jpg

 

I have the decoders in the schematic, but aren't using them because I got frustrated having to connect them all, so I just skipped a step and used decoded displays for the schematic purpose. My real one is going to use them, so I thought I'd just throw them on the schematic.
If you can't see the yellow lines, it's not a big deal. That is just the 5v power line.

 

Bill Bowden's Hobby Circuits

72 LED Clock