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Sick of ridiculous KVL infighting
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SiliconWizard:

--- Quote from: dunkemhigh on January 16, 2022, 11:15:47 am ---
--- Quote ---at a basic level you just need to know not to do it
--- End quote ---

I think this is what distinguishes, say, a script kiddy from a programmer. Anyone can follow rules, but knowing why you follow them allows you to apply them properly and appropriately (and, sometimes, not to). As they say, "Rules are for the obedience of fools and the guidance of wise men."

--- End quote ---

Yes. But you'd also be a fool thinking that just because you apply more complex rules, then you're not just following rules, and that you actually understand something. =)
PlainName:
That's a nice scarecrow (aka strawman) with the ever more complex rules :)

All I pointed out was that it's better if you know why a rule is there. You don't need to go down rabbit  holes or have more complex rules, just know why that rule is the rule. For instance, you put a diode across a relay coil as a matter of course. It's a rule. But if you didn't know why it's a rule then you don't understand what your circuit is doing. Sure, it will survive better than if you didn't know the rule was there, but you're just tickboxing. However, knowing why you put the diode there doesn't imply anything about quantum mechanics or the 40 lower layers of sub-rules that might be invocable.

In the specific case of the ground planes, why do you not route over gap? If you don't know and just follow the rules, the probability is that when you need to do it (perhaps you have no choice) you won't be able to choose the least worst way of doing it. Perhaps it doesn't actually matter in this design and having separate planes is more important. Who knows? (Clearly, not the person who unknowingly rule-follows.)
SiliconWizard:

--- Quote from: dunkemhigh on January 16, 2022, 10:26:17 pm ---That's a nice scarecrow (aka strawman) with the ever more complex rules :)
All I pointed out was that it's better if you know why a rule is there. You don't need to go down rabbit  holes or have more complex rules, just know why that rule is the rule. (...)

--- End quote ---

That was just a pinch of humility, which never hurts, and which some seem to be severely lacking here (not talking about you).

But of course, the more you know... the more you know. In a way. =) (Jokes aside, because beyond some point, excessive "knowledge" can actually end up counterproductive.)

Yes, applying rules without understanding them is never a good thing. You should at least understand the basic principles underlying them - which will help applying them wisely.

You don't necessarily need to resort to Maxwell equations  - or the Schrödinger equation  ;D - to design and analyze electronic circuits. The moment you think you do, either you *really* do, or you are probably going to teach physics rather than design things.

Of course knowing why you use some rules while routing PCBs *is* a necessity. But knowing the principles doesn't mean you need to dig ultra deep. When was the last time you used Maxwell equations to route a PCB?

And precisely, I think a good engineer (and admittedly not all are "good") must be good at applying physics. Engineering is applied science. And believe it or not - I'm pretty sure a few will fiercely disagree - good engineers are often better at applying physics than many physicists (at least, those that are theoretical physicists). Experimental physicists are a different matter. I have a deep respect for them (I have for theoretical physicists too, don't get me wrong, it's just that we are talking about applied science here!) Many theoretical physicists are not good at experimental physics. Which is why it's not unusual that the ones having devised sophisticated theories and the ones that have been able to observe them through experiments are different people/teams.

So anyway, just a few random thoughts. My point is, certainly, if you don't understand the underlying principles, you're going to have a tough time, but conversely, just because you perfectly master the underlying principles to the minute details doesn't mean you'll be good at applying them in all circumstances.
nctnico:
In short: engineers apply science; turn applicable theory into something that works in the real world.
Nominal Animal:

--- Quote from: SiliconWizard on January 17, 2022, 12:33:44 am ---And precisely, I think a good engineer (and admittedly not all are "good") must be good at applying physics. Engineering is applied science. And believe it or not - I'm pretty sure a few will fiercely disagree - good engineers are often better at applying physics than many physicists (at least, those that are theoretical physicists). Experimental physicists are a different matter. I have a deep respect for them (I have for theoretical physicists too, don't get me wrong, it's just that we are talking about applied science here!) Many theoretical physicists are not good at experimental physics. Which is why it's not unusual that the ones having devised sophisticated theories and the ones that have been able to observe them through experiments are different people/teams.
--- End quote ---
I agree.  Similar difference exists between mathematicians and physicists, too.  Things like galling have a rather funky causation chain, and are obvious in hindsight, but very, very difficult to predict from the theory alone.  Yet, just about anyone dealing with metal-to-metal sliding contacts knows about galling, and how lubrication helps avoid it.  (Even then, cold welding (in vacuum) was a bit of a surprise when it was discovered in the 1940s.)

Kirchhoff's circuit laws precede Maxwell's equations for classical electromagnetism.  Neither is exactly correct: they are both limited models.  As far as we currently understand, for a full description of electromagnetism, we need to turn to quantum electrodynamics.

QED is also currently used for the most precise simulations of chemistry (including molecular dynamics and materials physics), by only modeling the outermost interacting electrons for each atom.  Even there, because of its calculation-intensive nature, we are limited to cases with at most some tens of thousands of electrons, plus the volume must repeat in every direction (periodic boundary conditions).

Now, mathematically, you do get from QED to Maxwell's equations at the limit of taking the reduced Planck constant to zero, \$\hbar \to 0\$.  This is deceptively simple, because it really does not just mean that we ignore the quantum nature of the universe –– even though there are a lot of highly respected theoretical physicists that will laugh at that and say that of course it does –– because that difference is what produces some of the unexpected effects: just like galling I mentioned before is unexpected to those considering atomically perfect metallic crystalline surfaces sliding against each other, but obvious and easy to explain in hindsight, when you already know it does happen.

(Do remember, that physicists still cannot exactly agree if and why hot water freezes faster than cold water in the exact same conditions.  This is easy to experimentally verify.  I do believe the reason has been found through simulations, and is essentially that heating water will affect the O-H bond length decreasing the heat capacity of the molecule, but when shedding the heat, the bond length shrinks slower than the other degrees of freedom that comprise the heat of the molecule (various vibration modes).   This is why I don't see anything "strange" in arguing whether KVL or Maxwell is correct in some specific situation, because to me, it is normal argument about which imperfect model is better applied since the "correct" one, QED, is too complicated to apply here.  But remember galling: math alone does not say what effects there are if you simply approximate a single constant a bit.  A lot of things go wonky in geometry if you assume e.g. \$\pi = 3.14\$ i.e. rational, for example.)

Full disclosure:  I don't like QED.  I am not a mathematician, and getting my feeble brain to work with QED and the approximations required to work with it (like the Hartree-Fock method) so overwhelms it that I then have no touch with the physical systems I'm trying to work with.  Lagrangian and Hamiltonian mechanics I can just about grok, and I can work with quantum physics in general (since it has a nice definition of observables that keeps me in touch with the actual physical systems I can measure and, uh, observe).  So, I won't be offering much wrt. KVL-vs-Maxwell.  I'm best suited to making the computational tools for others to work with, really.
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