Back-EMF Manifesto - A Key, hidden in plain Sight.

[tinman]

 author=dieter link=topic=17611.msg517059#msg517059 date=1519398260]

This isn't so much about you being wrong, but much more about a somewhat pathetic attitude to jump in and call people idiots, "proofing" that every word they say is wrong while diverging from the thread subject.

When i referred to !idiots!,i was referring to those that post web pages full of garbage.

I have not diverged from the subject--which is Back-EMF Manifesto -->something you continue to mix up with inductive kickback,which it is not.

[Magluvin]

Here is where I am with the various 'emf's' we are discussing.....

For some strange reason, going to electronics at a vo-tech school 10th through 12th grade, and then 2 years at Electronic institute of Pittsburgh, all back in the early 80s, I had gotten the impression that the currents produced in the coil after taking away the input were reverse currents, never really thinking or even getting close to considering the FE ideas back then of such presented on this and other sites. We didnt cover that in votech with solenoids, relays and switching supplies. We didnt really do much in the supply area in Pittsburg either. Just solenoids and relays using snubbers to dissipate the coils self developed emf's when power was taken away. It was strange in a way that I was sure that it was a reverse current that the diodes were redirecting back into the coils, for reasons that the HV developed could harm a driving transistor or other sensitive circuitry. If they had conveyed the ideals properly and I just had it wrong, well I have to assume that it was the words flyback and back/counter/reverse emf that jilted me. Naturally they might have some influence, as we have seen over the years here, including me, on the idea that the currents out of the coil were reversed when power is taken away. All the "we would want to keep these hv potentials from feeding 'back' into the circuit" etc, etc. Had me going until around 10yrs ago and I was in utter shock to find out and test otherwise. Maybe it was that I didnt grip the importance of thinking on electron flow all the time in this game and just put more effort into + and - and paying attn to voltage/current limits and such in circuits. It wasnt really until I was jolted by actual facts that it is now a first and foremost thing to be concerned with in all electrical/electronic things that I en devour in to now, for the last 10 years. Either schools were just that bad at getting us to be on the the 'first and foremosts", or I was just a 'you big dummy', as Fred Sanford says. But over the last 10 years, I have seen many many many others that seemed to be in the same position and train of thought that I was in. MANY!. I mean how can this be with sooo many others also? Are, or were we all just big dummy's? Why is it that soo many have the idea that the currents out of the coil are reverse of what was being put in? Fly'back'? Reverse emf? back emf? Even 'counter' emf???  Even well knowing that a diode would only conduct with the neg potential at the cathode and positive at the anode and still not seeing the kind of simple puzzle that the circuit of the coil and snubber and input circuit represent. I cant remember all the exact details of the learning sessions on the use of snubbers on relay and solenoid coils, but I do recollect that we didnt stick with that subject much longer than to just understand that the diode was necessary to protect other circuitry the coil was involved with from the hv potential of the coils when input was disengaged from the coil and then we moved on. Switching supplies and dc to dc converters were most likely just coming into play in the 80s to blend in as common electronics knowledge then, as I dont recall any of that really. Or, I just didnt take a lot of interest in it and just did what I did to pass the grade. I dunno.  But I was definitely in the belief that the output of the coils was a reverse flow of currents compared to the input.

I didnt get into doing anything really with electronics other than my own things till I was 26. Job at vcr/electronics repair shop. Bout 7 years and then car audio got me hooked. Like I got good at fixing car amps, with switching supplies, and vcrs had them also, but it never dawned on me as to visualizing the current flow in the operations of these circuits, but I knew how to fix them, thinking I fully understood them. Like I understood polarities and specs for transistors, diodes, caps. I understood ratios of step up and down transformers and the like, but never went as deep into it all till I came here and was corrected. I argued it at first and for some time. And searching for the truth forced me into a position of having to look deeper to find out what was what. But now I know.

I consider back emf and counter emf and reverse emf to not have anything to do with the coils output when the input is removed. Counter/back/reverse emf is the emf developed in the coil by way of self induction and the cause of the delay from the 'time' the input was applied to the coil, up until the point of max field and max currents reached dictated by the resistance of the coil/circuit.  Cemf, the term I prefer, as it most resembles the 'opposition'(counter) to the input of the coil that makes the coils self induction 'impede' the input during a period of time depending on the inductance value. After truly finding out these things, I made my own terms that I use here at times for the coils current outputs. Field(magnetic) Collapse Currents or even FEMF for Forward EMF. I prefer to call them Collapse Currents as I understand that the opposition(impedance) to input is due to the 'outward' growing magnetic fields of each winding cutting all the other windings, and when the input is taken away, that field collapses inward thus producing forward currents in the coil, opposite of the previous cemf opposition currents developed when the field was initially expanding outward and impeding the input. So yes! Absolutely! When the input is taken away from the coil, the output currents of that coil are forward going currents in reference to the initial input current that was taken away. To me this is ingrained. This is fact. This is real. I can see it in my mind. I see the fields expand and collapse. I see the currents flow in the circuit in my head.

Flyback is a term that was developed to describe the flyback of the trace in a crt of an oscilloscope or a television set. Somehow I suppose that the flyback transformer maybe had some ideological influence on bringing the term to life elsewhere in electronics. But I dont consider it to be an actual term we should use when considering pulsing coils and what and which way the currents flow in the process.

When I truly found that the coils output was actually forward and not reverse, I freaked. I was all up into a conspiracy of it all. I was angry! I thought, 'what was it that they taught me back then? Were they hiding something??? And why?? Was there a secret to FE there??  I mean really if you think about how many others have had the same false conclusions over the years here alone, maybe there was a conspiracy to it all.    But these days I just believe it is just a mass misunderstanding that has/had come about due to the not really knowing what these 'emf' terms mean, along with the toss in of the term flyback, that seems to instill the ideas into peoples heads most likely before they really get into firstly visualizing the electron/current flows and magnetic field expanding and collapsing functions during the circuit operations. Yup. Im nuts. Im seeing things.

I visualize the current flows. I visualize the mag fields building, collapsing and interactions. In 'this business' it is a must. Fixing vcr's, amps, tv's, etc, it is not necessary to visualize that way of such things.  But it is a requirement when developing things and designing parts, coils, semiconductors, OU devices, etc. And here we are.

So people that want to dip their toes in these waters need to dig in and try to get into having those visions of electron/current flows, and magnetic fields, physics of all natures necessary to understand things 'here' and be able to discern whats real and whats fake or even identify others and your own mistakes along the way.

Ok.  Nuff said for me on that today.

Mags

[Magluvin]

And I think Falstads Circuit Sim, which shows current flow in the circuits operations is a great tool for learning to visualize the current flow in circuits.

Mags

[Magluvin]

Now, very quickly as I have a job to work on tonight, below is how I see the way mag fields engage the core of a toroid or any closed loop core and how the fields of a say primary winding on the left side of the core can 'cut' a secondary on the right side of the core. All the action is in the hole of the core, other than leakage on the outer sides. So no, I dont believe that the mag field is only in the core.  The core is only a path material that allows the fields to come together and be able to make sharp turns, etc.  When we look at the field mushroom out of the end of a magnet, those like fields repel and are pushed outwards away from one another. A magnetic core 'helps' to negate or better to say, reduce that like field repulsion that happens outside a magnet or a core and allows the fields to be denser and to bend and turn in the cores path much much easier than when the fields are outside the magnet or core. That is my contention on that subject.

Mags

[Magluvin]

Why is it that soo many have the idea that the currents out of the coil are reverse of what was being put in? Fly'back'? Reverse emf? back emf? Even 'counter' emf??? 

Mags

Woops. Forgot a big one.  Inductive Kick'back'   

Mags