CMOS clock, 2nd build

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7 years 3 months ago - 7 years 3 months ago #5287 by wise65vw
Alright, so after I got the IN-14 monster up and running fairly well, I decided to make another with less complication and aggravation. So, I decided to use CMOS 4017's and MPAS42's in the new one, which willrun six IN-4's. I am planning to make this a a gift for a relative who has an extensive background in electronics and personally introduced me to it years ago.
(schematic attached at bottom)
This is merely a rough schematic, as I'm still fiddling with component values and the AM/PM flip-flop setup. Suggestions are always appreciated, though. The Reset circuit is actually an idea I got from another Nixie clock builder whose plans are online, so I take no credit for it. I drew up the 1:00 reset circuit in class before seeing his version online.

The smoke means its working
Last edit: 7 years 3 months ago by wise65vw.

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7 years 3 months ago - 7 years 3 months ago #5288 by wise65vw
Replied by wise65vw on topic Re: CMOS clock, 2nd build
Okay, so I shrunk the schematic down. Hopefully it is still legible when zoomed in on.

The smoke means its working
Attachments:
Last edit: 7 years 3 months ago by wise65vw.

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7 years 3 months ago #5289 by Jeff
Replied by Jeff on topic Re: CMOS clock, 2nd build
Gosh, it looks like a more complicated way to build a clock using Mike's original clock circuit .

Both set switches could benefit from a series resistor in place of the 4148 blocking rectifier(s), and then only a cap would be required for switch debouce (remove the unneeded pullup).

I see you already understand the issue with the hours counter. Looks like a runner.

Regards, Jeff

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7 years 3 months ago #5290 by wise65vw
Replied by wise65vw on topic Re: CMOS clock, 2nd build
Thanks for the advice. I tried doodling four different 1:00 reset designs, until I remembered how my TTL clock was set up to advance all of the numbers forward. Having the output in decimal format made things easy.

The smoke means its working

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7 years 3 months ago #5292 by Ty_Eeberfest
Unless I'm missing something (always a possibility) the "carry" from 10-seconds to minutes, and from 10-minutes to hours (carries where there are set switches involved) aren't going to work as drawn. The pull-ups on the set switches hold the CLK line high. The inter-stage 1N4148s are oriented such that the carry output of the previous stage can drive CLK high. So how does CLK ever go LOW??

Continuing along this train of thought, shouldn't your Set buttons be switching +5 rather than ground?

Keep in mind that unlike the 7490s of your last design these 4017s count on low to high transition of the CLK line.

Look into it later when the dust is clearing off the crater.

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7 years 3 months ago #5293 by Ty_Eeberfest
Also note that the Carry outputs are high for count = 0 thru 4, not just a pulse at rollover. This will wreak havoc with the set buttons. I have a hunch this is why Mike Harrison's 4017 clock uses a totally different setting scheme!

Look into it later when the dust is clearing off the crater.

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