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Author Topic: The bifilar pancake coil at its resonant frequency  (Read 567716 times)

itsu

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Re: The bifilar pancake coil at its resonant frequency
« Reply #1005 on: April 18, 2017, 10:38:04 AM »
Yes, it is, and if you do the test I recommended, scanning all around the edge of the coil with the hall sensor in the plane of the coil, you will see no opposite fields, the lines will always go through the sensor in the same direction.

TK,   Mags,


its not that easy to scan the coil like you mention as the probe connected to the hall and the disk shape of the coil prevents easy access around the wires.
 
I will try later today, but i do not expect nice results, perhaps Mag's will be able to better show his results.


Itsu

itsu

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Re: The bifilar pancake coil at its resonant frequency
« Reply #1006 on: April 18, 2017, 10:45:46 AM »

Quote
Quote from: MileHigh on April 16, 2017, 04:07:28 PM<blockquote>Yes it's a strange question because it was a discussion about Magluvin's mistaken belief that "since a series bifilar coil can look like the wire resistance only, then I can pulse a series bifilar coil and get an instant magnetic field without having to energize the inductor."  It wasn't about the bandwidth-limited square wave excitation that you see in Conrad's clip.
</blockquote>


Hi MileHigh,

Well, it is true that Conrad's function generator happened to produce a distorted square wave instead of a beefy brick wall wave form at the 4 MHz frequency involved but nevertheless it was already far from a sine wave, close to "imitate" a switching waveform, do not you think?

For me, this is not an explanation,  and I do not think what Magluvin wrote is a mistaken belief, I agree with him.

Obviously, the claims have to be proved by measurements and hopefully it is taking place in this thread.

Gyula


going back to this part in the thread for a moment, as i tried a similar setup as in Conrads video to show the resonance, especially when driving with a square wave signal.
As my TBP coil has a much lower resonance frequency (307KHz compared to Conrads 8.5MHz) i had to change the 1pF cap (was blocking my signal) to 10pF.

The video here:  https://www.youtube.com/watch?v=oeHswSGwneg&t=196s

It shows various square wave signals when driving the TBP coil and the influence it has on the resonance frequency.


Itsu

MileHigh

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Re: The bifilar pancake coil at its resonant frequency
« Reply #1007 on: April 18, 2017, 05:51:46 PM »
TK,   Mags,

its not that easy to scan the coil like you mention as the probe connected to the hall and the disk shape of the coil prevents easy access around the wires.
 
I will try later today, but i do not expect nice results, perhaps Mag's will be able to better show his results.

Itsu

In looking at your "TBP coil resonance 1" clip I can see how you have access to the left and right sides of the coil sitting in the CD case with your Hall sensor so you can do the measurement there.  You don't have to scan around the full 360 degrees of the edge of the coil.  The whole thing is symmetrical so there is no need to make more than a single measurement.

MileHigh

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Re: The bifilar pancake coil at its resonant frequency
« Reply #1008 on: April 18, 2017, 06:02:36 PM »
going back to this part in the thread for a moment, as i tried a similar setup as in Conrads video to show the resonance, especially when driving with a square wave signal.
As my TBP coil has a much lower resonance frequency (307KHz compared to Conrads 8.5MHz) i had to change the 1pF cap (was blocking my signal) to 10pF.

The video here:  https://www.youtube.com/watch?v=oeHswSGwneg&t=196s

It shows various square wave signals when driving the TBP coil and the influence it has on the resonance frequency.

Itsu

Another great clip like usual Itsu.  The subject of breaking up a square wave into the sum of a bunch of sine waves at different frequencies is a challenging topic to understand for people with no background in this subject matter.  The short answer is that one of the sine waves in the frequency spectrum of the square wave is at the resonant frequency of the coil, and it's only that particular frequency that makes the coil resonate.

And that is why when you are looking for resonance or just to see how a circuit responds to a frequency sweep, you never use a square wave.  Multiple different square wave frequencies will make an LC resonator like the TBP coil resonate at its resonant frequency.  That can cause errors where you think the "wrong" square wave frequency is telling you the resonant frequency of the device under test.

Magluvin

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Re: The bifilar pancake coil at its resonant frequency
« Reply #1009 on: April 18, 2017, 07:16:18 PM »
In looking at your "TBP coil resonance 1" clip I can see how you have access to the left and right sides of the coil sitting in the CD case with your Hall sensor so you can do the measurement there.  You don't have to scan around the full 360 degrees of the edge of the coil.  The whole thing is symmetrical so there is no need to make more than a single measurement.

Agreed.  I was just thinking if he has the face of the hall on the same plain as the coil throughout the go around, then it is not showing the actual flux density at the edges as compared to the flat areas, though it does explain the red and blue differences as he went around as we have taken notice of.

Mags

Magluvin

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Re: The bifilar pancake coil at its resonant frequency
« Reply #1010 on: April 18, 2017, 08:51:08 PM »
Ok. I just had someone ask me about what I have said and I should clear that up.....

When I said there may be an instantaneous mag field when we apply input to the bifi due to neutralizing self inductance as tesla describes, I should have included the resistance that would be part of that RC time in the statement of which would kill the use of the word instantaneous.

But that is not to say that if Tesla is correct that we could not get a much faster charge to the capacitance if the resistance is very low and the self inductance delay of currents were neutralized.  The neutralization of self inductance claim is what we should be looking at as it is the claim.  Im under the strong assumption that the neutralization is in effect when we first introduce dc current to the coil, not at resonance.  If it were at resonance, then we wouldnt have resonance because the self inductance is said to be neutralized due to the capacity magnifying effect of the particular winding scheme. We need L and C for resonance. If one is not there then no ringy dingy. So when is it that the self inductance is neutralized as he claims? It must be at initial input or pulse that Tesla is thinking of.

Thinking deeper, if the claim is true, how does the coils capacitance neutralize the self induction? Does it happen due to charges developing between turns, and those charges affect the self induction between turns? Like some guys here that say it is not flux cutting that causes induction, but it is E field, sooo, where is their beef with that idea??? ;) ;D

Like say if the capacitance of the bifi coil or even a regular coil of the same where we had a V meter between every turn, a meter that magically did not affect the circuit in any way, and the coils were 100t and we apply 100v, how long after the input is applied should we see max voltage between each turn pair? Is it instantaineous that every meter would read the same voltage division between each turn? Instantaneous? Or would resistance produce a delay in full charge for each segment vs the time the input was applied? And then further, if the resistance was the only opposition to each turn pair reaching max fraction of the input, and then current begins to flow as self inductance allows, would this not be a no brainer?  Lets say we only read the 2 adjacent turns just in the middle of the coil, when we apply input, will we read 1v between the 2 turns immediately? Or would one say out of the blue that the voltage between those 2 turns wont reach 1v until max current and mag field??? I dont think so.

So the charge in the capacity between turns happens before current is affected by the inductance, and to say there is no current to charge the capacity would be wrong in my opinion, and experience.  Lets say I could wind a coil as we have done with 1uf of capacitance, would current have to flow to charge that capacitance?
If not, then have we charged that capacitance for free and if we disconnect the input at the moment the charge is there, no current happened, then the thing has been energized for free? ???   Na, Im thinking current flowed till the capacity is fully charged and then the self induction stops further flow and slowly lets current reach peak as we know it from there on..

Thats my story samson simpson.  ;)   Think on that.




In a normal coil, there just may be the same effect but it is sooo tiny that if we dont look for it closely we may not notice, as the capacity in the normal coil will have only a tiny fraction of the input applied and further more, the actual capacitance is tiny. But as I said before that tiny capacitance becomes less insignificant when the potential of that same tiny capacity is at a much greater level. So the initial bump that may be there when measuring a normal coil when we first apply dc is most likely tiny as said before and very short lived. But it just might be there. Just a theory based on Teslas claim.  But Im thinking that the bifi will have a bigger more noticeable bump. Im thinking on how to look at that. Would it be a pulse train that the scope will sync to or just a one shot input and can I get my scope to react to the one shot and hold. anyway....


I see the bifi as a series LC for the soul reason of if it were parallel then the cap would accept the input and not through the coil, but a series LC would. And a regular series LC has no way of neutralizing the self inductance. So Tesla says that the coils internal capacitance is responsible for the neutralization of the self inductance.

Mags

Magluvin

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Re: The bifilar pancake coil at its resonant frequency
« Reply #1011 on: April 18, 2017, 09:55:19 PM »
If we have a 10,000 turn bifilar inductor, it should be pretty high in inductance. It should take longer for current from dc to get to max than most coils we have experienced.

How long would it take when we apply 100v dc for the capacitance to charge to 50v between each turn, based on what criteria would one need to make that determination?

Mags

Magluvin

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Re: The bifilar pancake coil at its resonant frequency
« Reply #1012 on: April 18, 2017, 10:07:54 PM »
If we have a 10,000 turn bifilar inductor, it should be pretty high in inductance. It should take longer for current from dc to get to max than most coils we have experienced.

How long would it take when we apply 100v dc for the capacitance to charge to 50v between each turn, based on what criteria would one need to make that determination?

Mags

Taking that a bit deeper, if we compared the time it took for the inductor to allow max current from initial input, as to the time it took the capacity to be fully charged to 50v after initial input, could we say that the inductance had any influence on the time it took for the capacity to reach 50v??? ??? ;)

Weird to think about aint it? ;D

Mags

itsu

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Re: The bifilar pancake coil at its resonant frequency
« Reply #1013 on: April 18, 2017, 10:26:18 PM »
In looking at your "TBP coil resonance 1" clip I can see how you have access to the left and right sides of the coil sitting in the CD case with your Hall sensor so you can do the measurement there.  You don't have to scan around the full 360 degrees of the edge of the coil.  The whole thing is symmetrical so there is no need to make more than a single measurement.

I redid my hall sensor measurements, including the edges like mentioned by TK.

Allthough the edges show a minimum negative signal, its all around the coil as far as i could see, so no flipping over.
I used a speaker magnet to compare the results and there we see the same effect that when skimming the magnet/coil
from left to right with the hall sensor at 90° we do see a flip over of the signal on the scope.

Anyway, i think it is all explainable with the field line drawing MH put up earlier.


Video here:  https://www.youtube.com/watch?v=2dxMgjbR90o


Regards Itsu

itsu

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Re: The bifilar pancake coil at its resonant frequency
« Reply #1014 on: April 18, 2017, 10:27:02 PM »
Another great clip like usual Itsu.  The subject of breaking up a square wave into the sum of a bunch of sine waves at different frequencies is a challenging topic to understand for people with no background in this subject matter.  The short answer is that one of the sine waves in the frequency spectrum of the square wave is at the resonant frequency of the coil, and it's only that particular frequency that makes the coil resonate.

And that is why when you are looking for resonance or just to see how a circuit responds to a frequency sweep, you never use a square wave.  Multiple different square wave frequencies will make an LC resonator like the TBP coil resonate at its resonant frequency.  That can cause errors where you think the "wrong" square wave frequency is telling you the resonant frequency of the device under test.

I agree, its a challenging topic, that like you said has to do with the fact that a square wave is made up of all kind of sine waves and will generate odd harmonics.

Itsu

itsu

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Re: The bifilar pancake coil at its resonant frequency
« Reply #1015 on: April 18, 2017, 10:28:32 PM »
How about this magic, MH: 

Here is a scopeshot of the TBF pancake coil (661 uH, FR = 273.2 kHz) being stimulated by a sine wave at the resonant frequency. The Blue trace is the source frequency,  the Yellow trace is the voltage across the current sensing resistor as used in the previous scopeshots connected as MH specified, and the Purple trace is the signal from a "pickup coil" (actually the monofilar pancake, it was the first thing handy to grab) suspended a couple of cm away from the TBF coil. Not connected (but share the common ground of course). It is clearly getting a voltage induced in it. But the current sensing resistor on the TBF coil is showing zero voltage across the resistor, which should mean no current flowing through it. Clearly, the TBF is still generating a magnetic field that alternates at its driven frequency, otherwise it could not induce a voltage in the pickup coil. Right? 

(Inspired by Gyula's questions, thanks!)


Here my results of that same setup (528uH, Fr = 320Khz).

Yellow the flatlined signal across the 10 Ohm resistor.
Blue the input signal from the FG
purple the signal across a coil dangeling 2cm in front of the TBP coil.

Detuning the frequency returns the yellow sine wave signal and leaves the both blue and purple signals the same.

Itsu

Magluvin

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Re: The bifilar pancake coil at its resonant frequency
« Reply #1016 on: April 18, 2017, 10:59:56 PM »

Here my results of that same setup (528uH, Fr = 320Khz).

Yellow the flatlined signal across the 10 Ohm resistor.
Blue the input signal from the FG
purple the signal across a coil dangeling 2cm in front of the TBP coil.

Detuning the frequency returns the yellow sine wave signal and leaves the both blue and purple signals the same.

Itsu

Nice work Its

So where do we go from there? The thread title is what it is.  Not being cynical, just is that it?  Or do we load the sec and see what we get. Or move the second coil right on top of the bifi and see what we get. Would be interesting if it is all just normal transformer action. But for me this is not what I think tesla was intending with his discovery, thats why I didnt include the resonance test in my list of 3 tests.  Here is why..

If you can measure the inductance, resitance and capacitance, does it jive with the result on the test equipment? Are we in the range of res freq calculated? If so, then this is not the way Tesla intended his discovery to be operated, for one reason only..... It doesnt show the 'neutralization of inductance" he describes. If the res freq situation were to show such we wouldnt have a resonant freq because the induction element would be lost. LC with no L. So it is good to show what you guys have shown, as it proves we need to look at it a different way in how we are to achieve his claimed effect. ;D I already knew that and thats why I claimed I wasnt looking for resonance effects earlier in the thead, of which may boot me out of the conversation. :o   But if it is teslas bifilar coil we are looking into, then we should continue on to see what else we can do with this coil in reference to Teslas claims. I believe it is in dc discharge is where we should be heading because I believe that is where we will see his claim come into effect and be able to fully charge the capacitance without influence of inductance and only impeded by resistance. And if someone answers my question on the last page, if they believe that all the pairs of turns are fully charged immediately, by measuring the potential between turns at the time of external input, then we can say good by to the resistance impedance also and the cap gets fully charged without delay. But I think resistance 'may' play a part, but we will see.

Mags

synchro1

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Re: The bifilar pancake coil at its resonant frequency
« Reply #1017 on: April 18, 2017, 11:04:43 PM »
Nice work Its

So where do we go from there? The thread title is what it is.  Not being cynical, just is that it?  Or do we load the sec and see what we get. Or move the second coil right on top of the bifi and see what we get. Would be interesting if it is all just normal transformer action. But for me this is not what I think tesla was intending with his discovery, thats why I didnt include the resonance test in my list of 3 tests.  Here is why..

If you can measure the inductance, resitance and capacitance, does it jive with the result on the test equipment? Are we in the range of res freq calculated? If so, then this is not the way Tesla intended his discovery to be operated, for one reason only..... It doesnt show the 'neutralization of inductance" he describes. If the res freq situation were to show such we wouldnt have a resonant freq because the induction element would be lost. LC with no L. So it is good to show what you guys have shown, as it proves we need to look at it a different way in how were are to achieve his claimed effect. ;D I already knew that and thats why I claimed I wasnt looking for resonance effects earlier in the thead, of which may boot me out of the conversation. :o   But if it is teslas bifilar coil we are looking into, then we should continue on to see what else we can do with this coil in reference to Teslas claims. I believe it is in dc discharge is where we should be heading because I believe that is where we will see his claim come into effect and be able to fully charge the capacitance without influence of inductance and only impeded by resistance. And if someone answers my question on the last page, if they believe that all the pairs of turns are fully charged immediately, by measuring the potential between turns at the time of external input, then we can say good by to the resistance impedance also and the cap gets fully charged without delay. But I think resistance 'may' play a part, but we will see.

Mags

@Mags,

The coil goes past the cancellation phase and accrues "Negative Henries". This factor measures gain in the coil's magnetic field.

Magluvin

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Re: The bifilar pancake coil at its resonant frequency
« Reply #1018 on: April 18, 2017, 11:10:10 PM »
@Mags,

The coil goes past the cancellation phase and accrues "Negative Henries". This factor measures gain in the coil's magnetic field.

What does that all mean man?  That is like, who would understand that statement as a whole?

Mags

synchro1

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Re: The bifilar pancake coil at its resonant frequency
« Reply #1019 on: April 18, 2017, 11:19:42 PM »
What does that all mean man?  That is like, who would understand that statement as a whole?

Mags

The coil field increase factors directly into electrical power units that can be deducted from the input for an accurate COP. A negative Henry is the measure of the coil's magnetic field strength! Joseph Henry's formula of Inductance allows us to measure the field strength in units of negative inductance, and give that an equivalent value in electrical power units.