[sdiy] Issue with CD4024 Ripple Counter

David G Dixon dixon at mail.ubc.ca
Sun Sep 19 22:42:07 CEST 2021


I tried replacing the diode on the output of the comparator with a 10k
resistor, and I disconnected the 10k resistor leading to the inverting
circuit, so that the 4024 Clock pin sees a current-limited full +/-
comparator output (at the low current, the input protection diode should
protect against the negative voltages -- I've happily done this many times
with CMOS chips).  Again, BCN worked fine and BE didn't work.

Then I put a 1M resistor between the + and out pins of the comparator to
give some hysteresis.  Now the BE chip clocked.  However, when I clocked it
with the manual momentary switch, it clocked on both pressing the switch
down and releasing it back up.  Again, the BCN chip worked perfectly under
all conditions.

I also put the diode back in but left the hysteresis resistor in -- same
result.

So, neither the diode nor the lack of hysteresis is the sole cause of the
problem, and changing them both does not result in a fully operational
solution with the BE chips.

I gotta say, at this point I'm pretty flummoxed.  At least I was able to
source about 100 of the through-hole MC14024 chips from some dude in
Germany, so hopefully that will carry me through this build.  It also looks
like I can find some CD4024BCN chips here and there, but the BE are the only
through-hole chip still in active production.  Why would they be so
different?




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