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Author Topic: What happens in a pulsed coil?  (Read 19061 times)
Posts: 30

« on: March 22, 2011, 01:03:48 PM »


OK, I posted some questions at and will post it here as well and I will post on the second post of this new thread I will put answers to these questions that were so kindly offered by @members there. I will leave this for another day or so to see if there are more answers then I will expand on these questions.

Reply #1087 on: March 21, 2011, 11:11:24 PM


I have some questions to ask you guys on what really happens when you pulse a coil.

Ok, you have a power supply positive (P) connected to a first side of a coil (C1). The coil has a center tap (CT) and the other coil end C2 is connected to one side of a momentary switch (S1) that is normally open and the other side of the switch (S2) is connected to to the power supply negative (N). So in simple short form, this set-up would look like......
Simple enough, so here are three first questions.

1) With the switch open, if you put your volt meter on S1 and S2, what is the polarity of S1?

2) When the switch is closed what happens to the polarity you identified at S1 or asked another way, where does the polarity you identified at S1 go? I mean, if there is a polarity there that exists, then if it is now longer there, it has to go somewhere. It cannot just disappear. So........

3) When the switch is open again, where does the polarity of S1 come from to be again at its landed position?

Oh, I forgot, the coil has a 2" diameter single layer of 250 turns of 24 awg magwire. The diameter and number of turns is irrelevant (it could be a straight piece of wire) but I want to give you something that really had a wide spread between input and output.

I invite everyone to answer this question, both from the more classical EEers here and from the less classical OUers.

Please do not expand further then this set-up. Stay focused on these three questions. Take your time, this is not a race. What we need to talk about is exactly confined to these limits, and then, if things go well, we can move forward from there.

I know this is off topic but what is the topic of this thread anyways.

Last thing. When I ask about polarity, I mean positive or negative and not north and south.


Posts: 30

« Reply #1 on: March 22, 2011, 01:06:16 PM »

Replies to the questions.


Reply #1088 on: Today at 03:13:00 AM

Hey Watts

If the pos meter lead is on s1 and the neg meter lead is on s2, and the switch is open, s1 would be identified as positive in reference to s2. ;]

Seems like a loaded question, considering the post hints to a test of sorts. If we were still referencing from s2, and well knowing that the switch has some resistance, s1 can still be measured and considered positive in reference to s2. ;]

Well, I dont think I have ever heard of this description as to the positive, or negative as being something that moves around as if it were a ball or object.  But as I see it, if we opened the switch, with the meters leads in place as before, once the field collapse settles from its oscillation, the posititve would still be s1 with reference to s2.

All answered as to how i understood the question.  ;]

Nothing is off topic here, for a long time now. ;]  its Titos lounge.




Reply #1089 on: Today at 11:17:04 AM

Hi Wattsup,

1) and 2)   I agree with Mags.  Notice to 2): polarity remains the same as in 1) but voltage amplitude gets down to the microVolt or mV range (to that of the voltage drop across the switch).

3) Suppose your 'polarity meter' is a scope,  then you could see the opposite polarity voltage spike on S1 wrt S2 what the collapsing field in your coil creates. And then the polarity returns to power supply positive as stated in 1).




Reply #1094 on: March 25, 2011, 09:35:24 PM

hi Watts

interesting questions

this is my take on it:
(assuming v. high impedance DVM!)

1) Switch open;
   initial DVM reading at S1, relative to S2: +V Volts

2) Switch *closing* (< 0.1 second);
    any 'switch-bounce' present is likely to cause a few high voltage spikes as current starts to flow thro' coil then interrupts, giving high 'coil field-collapse' voltage ;

   Switch closed (> few seconds);
   steady-state DVM reading at S1, relative to S2:  +N uVolts
  {where N = ((Rsw)/(Rsw + Rcoil)) x V;
   Rsw probably a few milliohms, Rcoil probably a few hundred milliohms,
  so steady voltage on S1 wrt S2 of the order of around +1mV?}

3) Switch opens;

this is where it can get funky!

depending on voltage V, inductance L, & switch air gap,
then you *could* get sparking across S1-S2 inside switch

If  NO  spark occurs then the stored energy in the coil tries to dissipate any way it can, which since the switch is open & no current is arcing across it, the energy would probably dissipate in the form of an oscillation between the inductance of the coil and its self-capacitance (however small)

the DVM probably couldn't respond quickly enough to give a sensible reading but a scope might show you an initial high positive 'kick', followed by a decreasing sine wave, at S1, relative to S2, at the resonant frequency of the coil/self-capacitance, with the amplitude decaying away, offset at +V

If there IS sparking across the switch, then current will continue to flow in the same direction  thro' the switch due to coil-field collapse, but because the coil changes from storing to generating current the voltage polarity across the coil reverses and the S1 voltage rises sharply, much greater than +V

so, there will probably be an initial (very fast) high positive spike of voltage on S1, relative to S2, until the spike voltage reaches the break-down voltage of air for the switch gap-length

then the spark will extinguish when the energy has decreased enough that the voltage can't support a spark across the gap, at which point the remaining energy would dissipate as above, with a smaller decreasing sine wave offset at +V

...but, hey - what do i know?!?  ;o)

come on then Watts - spill the beans, man

all the best


« Last Edit: March 30, 2011, 01:35:41 AM by wattsup » Logged
Posts: 30

« Reply #2 on: March 30, 2011, 01:39:30 AM »

Wow. I have been preparing this for several days now (with a very long post) going through several levels of logic, etc., and now realize I should not post this the way it is and risk being misunderstood or even opening up a pretty crazy Pandoras' box.

If you think real carefully on those three questions, especially #2 and what I am specifically asking, it really reaches so far that I am not prepared to put it into words before I have the actual evidence through a proper experimental process.

So I decided to just put up the following animation without any comment at this time. If guys want to mull this over, please do, otherwise please use your time better on the bench.

Anyways, here is an animation, crude and slow so you can see what I think is happening in the coil.


* coil-pulse-anim1.gif (342.92 KB, 474x316 - viewed 1774 times.)
« Last Edit: March 08, 2015, 02:34:33 PM by wattsup » Logged
Posts: 30

« Reply #3 on: March 30, 2011, 02:47:15 AM »

(This is part of the post I had prepared. I am putting it here to not bog up guys at OU.)

OK, so far your answers are the superficial ones that anyone would expect. But if you really analyze these three questions deeper, you will realize some things you have maybe never thought about. This is not an absolute, but a query into what exactly happens in a coil under the mentioned conditions. I am not trying to teach you guys anythings. Actually this is more me asking you guys what could be wrong with this reasoning. Maybe if I understand this better it will orient the way I make and use my next coil set-ups.

Just also please know that the following in my opinion from observations of pulsing coils. Someone with the proper EE credentials may eventually provide some tests or experiments with the best measurement equipment and protocol to show the following to be the true case of pulsing coils. I am already going out on a limb here so please don't be to hard on me. All I ask is for you to please think hard before you respond.

OK, so here we go with how I interpret these questions and what is going on.

1) Polarity of S2 when the switch is open. So P enters the coil as if the coil was a straight piece of wire so yes, it goes to C1 through to C2 so S2 is positive. We know by this that the positive potential has in fact reached the end of the coil and the negative is coming from the N to S2 and is just waiting there for a connection. So the positive fills the coil and is available at S2. In the open state the total coil maintains a positive pre-bias. There is no resistance effect that makes the voltage get lower and lower as it goes through the coil and is available at the connection point.

2) My question #2 is "When the switch closes what happens to the positive at S2? Where does it go?" I did not ask what polarity is a S2, just where the polarity at S2 in the open state goes when S1 and S2 are connected.

OK. Let's first ask ourselves what happens to the coil after it is energized and holds its energized state? We all know this is standard basic stuff. The positive in the first half of the coil will produce a field polarity and the negative in the second half of the coil will produce the opposite field polarity. I am stating them as field polarity to signify the north and south fields you all have seen with a compass, so this simply is the irrefutable condition of the coil when energized. OK, so you have a positive half going up to the center tap and a negative half going after the center tap.

Now let's go back to my specific question. "When the switch is closed what happens to the polarity you identified at S2 or asked another way, where does the polarity you identified at S2 go?"

Well since the positive really exists at S2 in the open state, hence is equally present in the first and second halves of the coil, once the switch is closed the positive has to do something. It cannot just disappear and let the negative take over. The only thing I can think of that is happening is the positive is PUSHED BACK into the center tap area where it reaches its point of mutual balance between the positive and negative potentials. Call it a territorial battle where the negative pushes the positive back into its side of the coil center. If this did not happen and that coil only had positive feeding it from entrance to exit, the complete coil would produce only one field polarity. But it does not. The coil produces two field polarities when energized, being a north and a south field polarity. This indicates that when the switch is held closed, the positive is already there in the first half of the coil up to the CT area and from there the negative takes over to produce the other field polarity. So at switch closing the positive gets quickly pushed back into the coil and this is what we see as a "kick" on coil contact. The kick is simply positive being pushed back into the first half area of the coil that already has positive in it and this combines to make the "kick" that all are always talking about. The "kick" is a re-coil of the positive back past the central area where the negative cannot push more. The kick is the result of a single polarity crank.

3) From there we open the switch again and what happens? The second half of the coil is full of negative potential but this connection to the negative potential is severed. At this point the positive rushes back to the end of the coil pushing out the existing negative potential as what we see being an inductive discharge that we see when an inductor is disconnected.

So you see there is a play happening in the coil at open and close of the switch. But when I see this using two compasses near a coil, I have noticed that on connection, the compass play mainly happening in HALF THE COIL. The half that is on the side of the switch is the half that I see the compass moving very fast to show the polarity. This when you have used two compasses and you have to place them so as to negate any adverse reaction from the omnipresent biasing of compasses by the Earths' own magnetic field. The first side positive, then gets a positive kick and then hold positive. The compass action on that side is not as dramatic or energetic as the compass that is on the other side of the coil, which is the pulsed side. This pushes me to wonder if the only part of the coil that can really impart a field movement is hence the second half and not the whole coil. And this pushes me to realize that when you pulse a coil, you are really only using half the coil to do the work you see being done to impart to any other coil. All transformers, wheather AC or DC fed will have this limitation.

Now, we say that when the switch is open, there is a field collapse that returns to the coil and exits at the disconnect point. The best visual would be the Stargate Cloud when the gate opens. That is totally wrong. A field is generated and once it is generated it is now out of the physical confines of the coil itself, (actually I have a differing point there but this talk is on conventionals), so how do you expect the field to return to the coil windings and then follow on to the disconnect point? Try to explain this and you will realize that this is just a way we have been describing these events without analyzing the logic of each movement. The only reason the field is there is because there is an energized coil, so you understand that fields love energized coils, magnets, fire, plasma, etc. How do you expect a field to know where to return? It is like saying when I spray water on the grass, once I shut the valve, some of the water will re-enter the hose. Good luck with that one. So now, I am stuck because the above reasoning then pushes me to conclude that what we call the collapsing field, is simply the positive pushing out the negative to re-claim the totality of the coil at switch open. It is not like Stargate. On off the field is released and the positive reclaims the coil creating the flyback, bemf, or whatever you want to call it.

This applies to all coils that are pulsed on one end. The end that is pulsed produces greater dynamic field movement on that half. The end that is not pulsed is the static end that will always be full of the feed polarity but will not undergo a positive to negative energy shift. If you put a dioded capacitor parallel to C1 and CT. Here you have the positive return as battery feedback. Add an inverse and you have AC.

So in essence, a working coil is really half a coil. The first half is not wasted. It is required to maintain the compressing kick at switch on and again required to produce the re-claiming purge of the other polarity on the switch open.

If you can understand this and use this, then you will start to build coils that can take greater advantage of this movement.

OK, now put the positive on the center tap and put the two coil ends in parallel to S1. This does not change anything since now you have two halves being pulsed and each half will only have half of that active. Hence only two quarters of the coil are active one at each end. Center tap the coil means pick up at the end 1/4 length

Now what does this tell you about the TK device knowing that half the coil is useless if on a core. So you severe the ct and make two coil winds one

Posts: 30

« Reply #4 on: March 30, 2011, 09:52:48 PM »

The following is an extension of the above animation. By adding the two caps and four diodes, this will capture the first spike at connection and the discharge at disconnection.

Notice that the two are connected off the center tap of the pulsed coil. With this type of system, if you wound a pickup coil over the right half of the above coil, it will generate output on that coil. Also the bulb shown does not have to be there. That energy can be returned to the source to achieve very low cost operation.


* coil-pulse-2b.jpg (60.5 KB, 555x597 - viewed 1515 times.)
« Last Edit: March 08, 2015, 02:38:25 PM by wattsup » Logged
Posts: 30

« Reply #5 on: April 03, 2011, 02:43:37 AM »

Quote from: the_big_m_in_ok
Reply #1108 on: April 01, 2011, 07:23:35 PM

Regarding posted Reply #1101,
Hadn't there ought to be a high-enough voltage capacitor paralleled with the coil to store a charge for spark gap shorting to the battery?
(I looked and saw that something might be missing.  Otherwise, the circuit is simple and straightforward.) --Lee

Quote from: MrMag
Reply #1109 on: April 02, 2011, 02:21:34 AM

I agree, he won't get any spark across that switch with only the charge that is stored up in the inductor.

That is just to show what is happening inside the coil in slow motion. All that movement would take but a millisecond. What I wanted to show is the action that you see on the scope, the first rise, then the gradual slope resonance, then the negative side discharge. You see it on the scope and I wanted to show it on an animation.

When the coil is open, you have twice as much positive potential in the coil then when it is closed. The negative pushes the positive back into the coil giving the famous kick (waveform flash) that has guys scratching their heads for so long. When the coil opens again the positive now pushes out the negative as the spark onto the negative of the feed supply.

Don't confuse this with a spark gap on a high voltage line. Just think of the coil having high inductance.

The first half of the coil (left half) always stays positive. The second half of the coil (right half) starts positive biased, then gets hit by the negative. I will have to explain this many times. The negative cannot go past the half way point. While it gets there, it is pushing the positive back into the first half and that gives you the kick. When the coil opens, that inductive discharge is the positive rushing back to the end of the coil pushing out the negative potential. That is the field collapse we all imagine. By the way, there is no field collapse. The field is always released. Fields are not trained dogs that obey to the first whistle. Once their reason for sticking around is gone, they leave also. lol

The only part of the coil that is really switching from positive to negative is the second half. This may put some more ideas for TK designs.

In the TK glass unit, there is a small coil with two coils, one on each end wound over it. If you put a positive to a center tap and pulse the negative of the two ends together, the above same logic will mean the two outer quarters are changing from positive to negative. Hence his two over coils one at each end. (See OC1 and OC2 at A below)

Now if you use this half coil static / half coil dynamic into further practice, you can then make what I would call "tri-coils". (See C and D variations with same direct over coil (C) and perpendicular overcoil (D).

A tri-coil is really two coils with half half bifilar wound on one layer. This means let's say 20 winds of one wire, then continue with that wire and a new wire for 20 winds at which point the first coil leaves and the second coil now continues for 20 turns. This will give you half/bi-halves/half or A20(AB20)B20. A tri-coil of two coils. You then wind the secondary (OC1) over the bifilar area.

This may give some of you guys a push to get out of the simple coil wind method and start using this method to increase your output and provide better coupling potentials without the cross bottlenecks that standard coil over coil have to fight against to produce the outputs that you presently see.

Then there is how to use this logic in winding toroidal coils. The idea is always the same. Use the first half of the coil for biasing and the second half of the coil for coupling. The first half would be the outer layer of a two layer discharge coil. The pulsed side would always be the end that is closest to the core. I am convinced that guys that play with the Joule Thief will get higher OU with this type of logic. This also applies to toroidal winds of TPUs, and more. A ring of 2 1/4 turns will have one static turn and one dynamic turn with a little overlap, so you are always better off with the pulsed half be against the coupling line.

The notion that when you pulse a coil, the pulse travels across the coil windings with equal effect is . The main effect will be on the first half of the end that is pulsed and die off through the second half. Yes you will still get a scope reading on the second half but the dynamic movement will only happen on the half that is pulsed.

I am also putting this information up on my new forum that I made recently at etherimpressDOTcom. It is freshly started and is designed for mostly builders that need a quiet place to store their information. The site is fully viewable for guests so there is no favoritism in that regard. It is just that I do not plan on having hundreds of members. I needed to put my own works and theories, etc., all in one place and am offering a place to those that need it.


* toroid-coil-winds1c.jpg (140.65 KB, 492x943 - viewed 1703 times.)

* alt-coils-AtoB-1a.jpg (205.36 KB, 508x2223 - viewed 1745 times.)
« Last Edit: March 08, 2015, 02:40:00 PM by wattsup » Logged
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