[sdiy] Issue with CD4024 Ripple Counter

rrsounds (null) rrsounds at aol.com
Sat Sep 25 10:30:19 CEST 2021


Looking at the board layout as posted, I would suggest that 1), there should be a ground plane layer, and if there isn’t, all areas that are not signal or power should be flooded with ground return copper; 2) Low current fast signals don’t need traces to be particularly thick, but they do need to be direct and sharp-turn-free if possible. 3) Using a plug-board pattern as a design guide is not a particularly good practice. And 4) all bypass (0.1µf) caps need to be as close to the chip as possible, with as short as possible connections to power and grounds, and every chip needs at least one cap for each supply.
I also always include a 10µf tantalum across all power supply inputs. 
David Reaves

Sent from my iPad

> On Sep 25, 2021, at 8:39 AM, David G Dixon via Synth-diy <synth-diy at synth-diy.org> wrote:
> 
> Further to my last posting, I think I understand why the CD4024 was used for
> a 2-bit counter in Ken Stone's original circuit.  Without a schmitt trigger
> on the clock input, the CD4013 dual D flip flop is absolutely unforgiving in
> terms of clock inputs.  So far, I haven't been able to get it to work at all
> with the switch (although it works fine with the signal input).  I figure
> that if I put a pair of CD40106 schmitt triggers in line, then it would be
> OK, but I don't have room on my board for that.
> 
> Hence, it looks as if I am just going to go with the revised version of my
> original circuit, with a TL072 comparator and rectified inverter, and
> CD4024BCN or MC14024B.  After all, it worked perfectly.  The only issue was
> that it didn't work with CD4024BE, but I now believe that this was because
> the batch from which those chips came from is defective (and don't have
> functioning schmitt triggers).  I'll follow the suggestion of someone here
> and replace the rectifier circuit with a diode into a divider into a simple
> inverter, which saves a diode and doesn't sacrifice output impedance.
> 
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