Electronics > Beginners
74HC390: Ripple Counter is Counting Rubbish
trophosphere:
--- Quote from: Henry Petroski ---Failure is central to engineering. Every single calculation that an engineer makes is a failure calculation. Successful engineering is all about understanding how things break or fail.
--- End quote ---
wilfred:
--- Quote from: Darkwing on May 02, 2019, 12:24:33 pm ---Wow, Dave, that's so amazing! I'm glad that I finally was able to contribute to the EEVBlog with my stupid questions. :D
--- End quote ---
Not only was the question not stupid you asked it very well. If more people took a leaf from your book forum questions would get better answers. :-+
Putting in a bit of effort to describe the problem really makes people feel their effort helping will be worth it.
Brumby:
I'll add my voice to the "not a stupid question" chorus!
In fact, some of the most stupid questions are the ones that didn't get asked.
--- Quote from: wilfred on May 03, 2019, 05:44:36 am ---Putting in a bit of effort to describe the problem really makes people feel their effort helping will be worth it.
--- End quote ---
Very true. It demonstrates the question (and the person putting it) are fair dinkum.
LateLesley:
i'll add to the "not a stupid question" crowd. I was once told, "The only stupid question, is one you already know the answer to."
As for the problem, I wonder if we are actually seeing intended behaviour?
If we follow the sequence :-
Q3 Q2 Q1 Q0
0 - 0 0 0 0
1 - 0 0 0 1
2 - 0 0 1 0
3 - 0 0 1 1
4 - 0 1 0 0
5 - 0 1 0 1
6 - 0 1 1 0
7 - 0 1 1 1
8 - 1 0 0 0
9 - 1 0 0 1
10 - this is where it resets to 0, as it''s a decade counter.
So as you can see Q1 Q2 and Q3 won't divide into perfect square waves, as there times when they are off for longer. like Q1 for 8,9,0,1 it will be off, giving a longer gap in the waveform. The same applies to Q2, it's off for 6 counts, but on for 4. So I would actually count out each step, and see if you are seeing intended behaviour for that chip.
NivagSwerdna:
The rabbit hole goes deep... http://www.ti.com/lit/an/sdya009c/sdya009c.pdf Section 5 has a nice table of the different families wrt rise times and how mixing them can ruin your day.
And there is always more than one way to skin a cat... Either a counter with a Schmitt input trigger input or.....
.. an opto with an inbuilt Schmitt trigger output e.g. H11L1M or NTE3090 ?
When is DaveCadCon? I'll buy a ticket. Nice to see FUNdament Friday's are back. Great video.
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