[sdiy] Issue with CD4024 Ripple Counter

Roman Sowa modular at go2.pl
Mon Sep 20 10:08:47 CEST 2021


Hi Dave,
thanks for detailed description of the circuit. I see a few pitfalls in 
there, but let's leave it for now, you've got a ton of replies already.
Don't be so hard on those poor digital, or should I say logic circuits, 
they want to be loved as much as their analog brothers and sisters, and 
now they are sorry you called them F stupid S.

I've heard an interesting story, probably it was here on this list, 
about logic chips manufacture. Making sequenctial circuit, meaning 
anything edge controlled, is a work of art. And during early days of IC 
making they had a hard time make them work they way they worked on 
paper. A lot was depending on silicon manufacturing process itself. They 
finally mastered it but at some point a guy, who was responsible for 
doping process, oven profiles and so on, was off to retirement or to 
other company, can't remember Then the next batch of the same ICs they 
made all refused to work. So they designed revised version of the 
silicon die, adding something here and there, most probably to tweak the 
timing, and they were back in the game.

Roman

W dniu 2021-09-17 o 18:47, David G Dixon pisze:
> Hi Roman,
> 
> I have a debouncing LPF on the switch, and it is currently 1k and 2.2nF.  I
> started with 1k and 10nF, and that gave me only intermittent clocking of the
> CD4024.  I removed the cap and also replaced it with 100pF, and that gave me
> clocking on both the down and up of the switch (both edges).  2.2nF at least
> gave me reliable clocking, but on the wrong edge.  The signal from the
> switch and/or the input clock signal goes through the LPF (the input jack
> has a 10k resistor and the switch has a 1k resistor, so that the switch
> signal overtakes the jack) which are both dropped to ground through the
> 2.2nF cap, then they go to an opamp comparator with a threshold voltage of
> +2V.  The comparator output is normally at +V but switches to -V when the
> clock input signal rises above +2V.  With this arrangement, I can clock my
> ASR with any LFO signal or envelope or gate, or really anything handy.  The
> output of the comparator goes through a 1N4148 diode to eliminate the
> negative output, is dropped through a 100k resistor to ground and then goes
> into the 4024 clock input.
> 
> Both the switch and the jack reliably clock the CD4024 on the positive
> transition.  I can understand that the clock signal (which is coming from a
> comparator) may be too slow to clock the counter.  What I don't understand
> is why the counter would, instead, reliably clock on the wrong transition.
> It's stupid.  Digital electronics are stupid, which is why I typically
> confine myself to analog.  I don't have the patience for all the stupid
> arbitrary rules around digital devices, or the stupid coding.  F all that
> stupid S!  That's what I say (but when I say it, I include the uck and the
> hit).
> 
> I see on the MC14024B datasheet that that device has been designed to accept
> even quite slow clock transitions, so I'm assuming that this is the reason
> why it works better.  I'll just go with it.
> 
> 
> 
> 
> -----Original Message-----
> From: Roman Sowa [mailto:modular at go2.pl]
> Sent: Friday, September 17, 2021 1:51 AM
> To: synth-diy at synth-diy.org; dixon at mail.ubc.ca
> Subject: Re: [sdiy] Issue with CD4024 Ripple Counter
> 
> [CAUTION: Non-UBC Email]
> 
> Try to experiment with slew rate of input signal. Feed it with the fastest
> edges clock pulse you can get, say 20ns rise time. And decouple the supply
> pins of the chip generously.
> If that does not help, tell me what crack you smoke, would love to try that
> too.
> 
> Roman
> 
> W dniu 2021-09-17 o 05:57, David G Dixon via Synth-diy pisze:
>> Hey SDIY Team,
>> I've got a device that uses a 4024 ripple counter.  The datasheet says
>> that it advances on the negative transition of the clock.  All mine
>> (CD4024BE) are advancing on the positive transition of the clock.
>> However, I tried an MC14024BCP and it worked properly.
>> Am I smoking crack?  Why are my CD4024s behaving opposite to the
>> datasheet, but the MC14024 is behaving as per the datasheet?  What is
>> it that I don't know about these devices?
>> Cheers,
>> Dave Dixon
>>
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