Electronics Introduction to LC Oscillators circa 1974 US Air Force Training Film

For use in our study of Parametric Excitations of Electric Oscillations, Join us at: www.aboveunity.com

[@matyi1656]

This is the kind of education that should have stayed. They made a paralell between something you know and the new knowledge creating these examples. So much easier to absorb the basics this way, and after this you can go to the advanced part and understand that more easily thanks to this. Nowadays they teach you like you already know the basics well and that is where today's education fails.

[@ovalwingnut]

Yes, Maty. You are wise and speak the truth. What has happened to us... it's like most things that actually worked have been forgotten. But not today! I watched it and R a better person 4 it. Cheers

[@Kurt1968]

Man, these old videos are so much better than the modern stuff you see in KZbin. The right cadence, clear English, proper use of visual aids (even using more primitive ones like this are more clear).

[@ovalwingnut]

Y. Who knew are GR8T GR8T GR8T grandfathers were so smart?

[@omsingharjit]

That old way of explanation is rare now days

[@alakani]

Not rare at all, just really expensive now

[@rodericksibelius8472]

Professors scares the students with COMPLEX MATHEMATICAL Physics and STUDENTS quit Engineering. DEMOTIVATIONAL system of education. LOL.

[@jacobvandijk6525]

Yep, I like this old stuff too.

[@thephilosopher7173]

@@alakani Well it is rare because its expensive lol

[@edtruthseeker3337]

I was a USAF Electronics Student. They did have some really good films for training.

[@colin55111]

HOW THE TANK CIRCUIT WORKS An "in-depth" description of how the Tank Circuit delivers the energy from the capacitor to the coil (inductor) and then back to the capacitor. The "secret" of its operation has never been described before and all discussions have glossed-over "how and when and why" the capacitor gets fully discharged before the cycle starts again. Suppose the capacitor is charged and is placed across the inductor. Current will flow into the inductor and produce magnetic lines of force in the core that will cut all the other turns and produce a voltage in these turns that is opposite to the incoming voltage. This means the incoming voltage will see a voltage produced by the inductor that will be as high as 99% of the incoming voltage. This means the incoming voltage will appear as a very small voltage and it will increase the flux lines very slowly. The capacitor will keep supplying current but since the voltage across it is reducing, the current will be reducing and thus the flux will be expanding at a reduced rate. The back voltage produced by the expanding flux depends on the rate of expansion and since this expansion is getting less, the back voltage is reducing. The amazing thing is this: as the voltage of the capacitor decreases, the back voltage decreases and the current increases. I can explain it this way. Suppose you put a 9v battery across the coil, after a short time the flux will be a maximum but it will not be expanding flux and inductor will produce the maximum flux and take the maximum current. When the capacitor is almost fully discharged, the current will be a maximum and because the flux is not expanding, there will be no back voltage. So a point comes when the capacitor has no voltage across it and the inductor produces no voltage. This is the secret to how the oscillator works. Because the inductor has a very small resistance, it only takes a very small voltage to deliver a very high current and produce a very large amount of magnetic flux. But eventually this small voltage cannot maintain the flux and all the voltage and current-capability is taken from the capacitor. At this point in the cycle, the flux cannot be maintained and it starts to collapse. As it collapses, it can only produce a certain amount of current and this current charges the capacitor. In other words the capacitor controls the rate of collapse of the inductor and the voltage across the capacitor gradually increases. In actual fact, the inductor "can and will" produce a very large voltage during a collapse if nothing is connected to it and this is called a fly-back voltage. But since a capacitor is connected, the voltage can only rise as the capacitor allows it to rise. So it rises until the flux has almost fully collapsed and even at this point the collapsing flux is able to produce a voltage much higher than the voltage across the capacitor and that's why it can keep charging the capacitor right up to the point when the flux has almost completely collapsed. That's why the capacitor gets charged to almost the original voltage. Even the tiniest amount of flux will produce a charging voltage. But eventually the flux is zero and the voltage across the capacitor sees the inductor as a very small resistance and it starts to deliver a current. This current produces magnetic flux in all the turns of the winding and each turn produces a back voltage so that the actual magnetizing voltage is very small and thus only a very small current flows to create the second cycle. THE SECRET Here's the reason why the capacitor is able to deliver all its energy to the coil: As the voltage across the capacitor decreases, the coil can only produce a back voltage that is slightly less than the capacitor voltage. That's why the energy keeps flowing from the capacitor to the inductor. It is only when the capacitor cannot deliver any more current, that the circuit starts to change direction. Just before this occurs, the voltage of the capacitor can be very small because the resistance of the inductor comes into play since the back-voltage is very small and it is the back-voltage that turns the resistance of the coil into an inductance. Now we have a very small capacitance voltage being able to deliver a high current into a small resistance to maintain the magnetic field. Only when this voltage finally reduces to almost zero, does the circuit start to change direction. Now, going back in the other direction, why is the inductor able to keep charging the capacitor when it is nearly out of magnetic flux? The reason is this. If the capacitor was not connected, the inductor would be able to produce a very high voltage when the magnetic field is collapsing because the size of the back-voltage depends on the speed of the collapsing field. Even when the inductor is almost out of flux, it can produce a very high voltage when nothing is connected to it. That is: when no capacitor is connected, it will collapse very fast and produce a very high voltage. So, it is the capacitor that is controlling this voltage, BUT it is always slightly higher than the voltage across the capacitor so the charging keeps occurring until the inductor is finally out of flux. Don't forget, when the magnetic field of the inductor is collapsing, the voltage it is producing is in the opposite direction to the original voltage. This means the capacitor gets charged in the opposite direction. In the diagram above, the top rail is the supply rail and the bottom rail is connected to a transistor. If we connect a multimeter or digital CRO to the transistor, we will see the voltage reduce lower than rail voltage during half the cycle and then become higher than rail voltage during the second half of the cycle. This means the effective voltage at this point is TWICE RAIL VOLTAGE. The Tank Circuit can double the supply voltage !!

[@manuelvillarreal1021]

just watched "the beauty of LC oscillations" and while the animations were great, I was losing my mind because the direction of the induced emf didn't change at the correct time when the current began to decrease... THANK YOU SOO MUCH !!!

[@mazharkhaliq1971]

Thanks for the knowledge 😊

[@jboy6944]

Sir, you are truly a BOSS! You've somehow explained what I've found difficult for months 💕💕❤❤

[@sachinhrajak1709]

Amazing explaination 👍

[@nusyil]

Great explanations! Thanks!

[@simonlinser8286]

If you want to get the navy (i think its navy) manual on electronics it's pretty cool and actually still relevant for learning stuff, it's readily available for download

[@PaulCrooks-qj6di]

Boy I went to college and didn't understand it like this.

[@surendersingal2192]

Fantastico education on LC circuits n cost added by self resonance damping. Elegant comparison WITH flywheel n paper graphs. Jussojuan surender singal

[@p0k7lm]

solid example !📕🎺📖📚📐✏🔬

[@user-og1ko7fe8q]

Is the current flow direction correct when capacitor discharge? I think the current from the capacitor is clockwise when flip the switch to C.

[@veronicanoordzee6440]

@ 6:50 The coil becomes a voltage-source because the decaying magnetic field acts like a battery! My battery produces voltage, not energy! And so this magnetic field contains no energy. Faraday's law of induction is about changing magnetic fields and ... voltage.

[@Satyaprakash81102]

A battery contains potential energy and similarly an induction coil stores potential energy due to magnetic field generated as a result of applied voltage.

[@arifwahyudiansyah2809]

so how to build regenerative feedback circuit?

[@rockyreynolds739]

What could the motivation be for the one jagoff voting this video down?

[@RapperBC]

He's a jagoff. Nothing can save him.

[@AvantGrade]

maybe he/she wanted the classified version.

[@ubrayj02]

Fell asleep at the helm and forehead hit the thumbs down button in the submarine.

[@greeneblack7330]

this is a russian guy

[@jacobvandijk6525]

Start here: 4:53. Of course, 0.159 = 1 / (2.pi) en.wikipedia.org/wiki/LC_circuit

[@Eligus33]

I watched a lot of these training films and film strips back in 98 before they made everything confusing

[@carlosdeandro7046]

Why the actual explanations isn´t so that didactic ?

[@mazharkhaliq1971]

I have a question 1) if the amplifier is used to strengthen the signal that is restoring the amplitude that is lost due to circuit resistance then why do we need a feedback circuit? Please explain? And if feedback is used to get the same signal frequency and phase, but isn't that the job of the LC circuit won't the LC circuit generate constant frequency signals ?

[@nikiopia]

I believe I can shed some light on your question. To answer your first question, you're right, the amplifier is used to regenerate the energy losses in the LC (oscillator) circuit. The feedback circuit is required because without it, you would simply be amplifying the gradually decaying output from the LC circuit. The feedback circuit is what gives back the LC circuit the energy it loses due to its internal resistances. For your second question, the LC circuit's job is to provide the capability of generating constant frequency/amplitude signals, but without amplifier feedback to recoup loses, the output will decay away over time like the felt pen demo held in place by rubber bands. Hope this helps, cheers.

[@mazharkhaliq1971]

@@nikiopia Ooh okay thank you for the explanation😊

[@user-rq9po2zv4k]

Пояснення дуже дотепне

[@precursortopain8262]

Shouldn't the LC capacitor be a non-polar capacitor?

[@camron695]

I believe it doesn't matter which kind of capacitor you use

[@Satyaprakash81102]

It must be a non polar capacitor. The induced oscillating current is AC. So a polarized capacitor will die. The symbol surprised me.

[@abulfazibrahimov1990]

1000th like

[@itrstt66]

why did the quality equation get inverted at 16:08?

[@Inflec]

Because the first equation for Q was for the series resistance of the circuit. The second equation refers to any *parallel* resistance *across* the circuit, which must be kept at a high value to obtain a satisfactory Q for the L-C combination.

[@felixdiaz4438]

👍

[@itrstt66]

Why doesnt it cancel out in the mic and speaker feedback example? the phase shifting doesnt happen?

[@tobiasgertz7800]

The only waves that will reinforce for a standing wave are 180° out of phase. It's a closed loop system that selects for those conditions. Great question.

[@itrstt66]

@@tobiasgertz7800 thank you for The answer, Im not sure i understand what you mean by "... Selects for those cpnditions...". What does it exaclty means?

[@tobiasgertz7800]

kzbin.info/www/bejne/pYuWaYxmgJ2YY7s Your englishv is good, but you won't need words to understand this one.

[@tobiasgertz7800]

kzbin.info/www/bejne/mZ-rY5-qm7xnbrc

[@tobiasgertz7800]

In the feedback loop the physical soundwaves have a speed through the air and they also have harmonics. There are more than just one fundamental frequency. The one specific frequency that fits inside the physical distance between microphone and amplifier is the one that has the least resistance to the loop and gets amplified. Positive reinforcement happens over and over again rapidly. There is necessarily phase shifting and harmonics in the system. The speaker isn't a perfect sine wave generator, and air isn't a lossless or homogenous medium. It all generated harmonics. One of those harmonics (different but related frequency) will appear as a phase shift.

[@piotrne]

6:05 In those days, did the current flow from minus to plus?

[@abhirajsingh960]

they are not using conventional current they are depicting actual electron flow

[@jakobjensen3424]

Current has always been minus to plus, it's voltage that's from plus to minus.

[@piotrne]

@@jakobjensen3424 No... Current traditionally flows from positive to negative, although electrons flow from negative to positive.

[@jakobjensen3424]

@@piotrne Current traditionally flows from negative to positive. Because current is* electron flow.

[@mikejones-vd3fg]

​@@jakobjensen3424 But in a circle 2 points are both behind and infront of each other , there isnt a front or behind, both points are going toward each other, so technically this explantion doesnt make sense either way? and maybe why my brains starts to hurt when i see a diode in a schematic.

[@good.citizen]

thank you i use a whawha pedal for my fdd.. .

[@cyklop1977]

Zajebiste

[@jongdonglu]

"Unclassified" so this simple piece of information was classified?

[@bsdiceman]

Unclassified just means public. It doesn't necessarily mean it was ever classified.

[@supremeleader5516]

Yes made, today this is simple but at that time hardly someone know about electronics, it can be used against u by ur enemy to obviously you don't want your enemy to be educated as u

[@oakspines7171]

It should have been classified and it was.

[@intheshell35ify]

Well I'm not scared of em anymore.

[@tobiasgertz7800]

Amplifiers oscillate and oscillators amplify.

[@PremSingh-ev4mo]

Wrong current flows from + ve to -ve

[@BTW...]

Wrong.. Deluded That is not the reality of electron flow, which is current flow. If you were taught that, they would have explained that is termed 'conventional flow' thinking and not in accordance to reality.... I call it 'deluded'.

[@Amine-gz7gq]

@@BTW... The problem is to mix up the two conventions: in high school physics lessons, during charging of the capacitor, the direction of the current is from the battery's + terminal to its minus terminal, whereas during discharging, the direction of the current is from the negatively-charged armature to the positively-charged one.

[@two_number_nines]

This video is a swiss cheese of theory needed to explain. While most things aren't completely explained a few details were wrong and the presentation completely failed to demonstrate what it has to demonstrate to the intended audience.