Back to basics for me :D - Page 1
Forum section: electronics / beginners

author: john_edmunds
author_rank: Newbie
timestamp: November 29, 2019, 07:52:43 pm
content: Hi Folks,First post here. An avid watcher of EEVblog (especially the fundementals) I decided recently to start re-learning electronics (sort of) for the first time in since 2000. I have begun making the obligatory Nixie clock using 4000 series logic, but have run into a wall and would appreciate any help.I am using a 4060/4013 combo to feed a 1 hz clock pulse into a 4017 counter. I then cascade these together to give me seconds/ tens of seconds, then minutes/ tens of minutes. Both sets of tens, the number 6 output is tied to the reset line to make sure that it counts from 0-59 in both tens and minutes. This works a treat for both the minutes and seconds, but does not quite work with hours due to the need to count to 12/24.This is where I have become stuck.I had originally used 2 more 4017s, but it can only count to 20. I was toying with a another counter that would trigger a reset when it counts the 2 output a second time, but this would trigger another carry out. This is all becoming a spiralling mess of countersIs there any easy way to either count to 12 or 24 and have it ouput the number onto the nixies or am I barking up the wrong tree.(The nixies are IN-12s with ULN2003A with the +ve rail provided by a 160v boost converter)I can post a screen of my schematic as it stands if this would help.Cheers for any suggestionsJohn

author: PA0PBZ
author_rank: Super Contributor
timestamp: November 29, 2019, 08:04:36 pm
content: Quote from: john_edmunds on November 29, 2019, 07:52:43 pm2 Cascaded 4017's can count to 99, I think your problem is that you have to craft your reset from either 13 or 25 which needs some more logic gates.

author: john_edmunds
author_rank: Newbie
timestamp: November 29, 2019, 08:26:01 pm
content: Thanks for the response.There was a short circuit between my chair and the keyboard. The way I have it set up a the moment it only counts to 20. My apologies, I should have been more specific. Whilst I like the idea of shaving 4 hours off of each day as it means my Birthday will come around quicker and I get to eat more cake, probably not a great idea over all.I was wondering about using a couple of shift registers and shift each time an hour passed, when it hits 12 or 24 hours, use this to trigger a reset, but it seems a bit cack handed and I've not really played with those before so not sure how possible it it.

author: ArthurDent
author_rank: Super Contributor
timestamp: November 29, 2019, 08:40:09 pm
content: As posted above you need some logic gates. For hours you have 2 decades, units and tens. connect a two input AND gate to decode 13 from tens/units and another AND gate to decode 24. have the outputs from these two AND gates go to a SPDT switch to select which mode (12/24) you want and that selected signal can be the reset for hours.

author: john_edmunds
author_rank: Newbie
timestamp: November 29, 2019, 09:07:17 pm
content: Aha.. I see now. I hadn't thought of using logic gates. I still have a lot too learn.Thank you both kindly for your help.I'll go back to the bread board and hook it up, I'll let you know how it all goesCheers.