[sdiy] Issue with CD4024 Ripple Counter

David G Dixon dixon at mail.ubc.ca
Sat Sep 25 08:37:27 CEST 2021

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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