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Author Topic: The bifilar pancake coil at its resonant frequency  (Read 254055 times)

Offline itsu

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Re: The bifilar pancake coil at its resonant frequency
« Reply #975 on: April 17, 2017, 04:14:42 PM »
Behold:

This is a one-minute sweep of frequency between 10 kHz to 500 kHz of one of my TBF pancakes. (661 uH, FR = 273.2 kHz, distributed capacitance calculated as approx. 513 pF)

The Yellow trace is the voltage across a 9.4 ohm, 1 percent, noninductive precision resistor pair (2 x 4.7 ohm in "opposite series"), connected as you describe. It behaves just as you predict for the parallel LC circuit, with the minimum voltage across the resistor occurring at the resonant frequency of 273.2 kHz.

Very nice TK,

To compare, here is my 10 second sweep of frequency between 10 kHz to 500 kHz of my TBF pancake. (528uH, FR = 307kHz, distributed capacitance calculated as approx. 509 pF)

Using the same method, so measuring across a 10 Ohm resistor (yellow)


Itsu

Free Energy | searching for free energy and discussing free energy


Offline synchro1

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Re: The bifilar pancake coil at its resonant frequency
« Reply #976 on: April 17, 2017, 05:07:50 PM »
@Tinselkoala

Any reference to beat off cream by me would translate into German as"Schlag".

Offline Magluvin

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Re: The bifilar pancake coil at its resonant frequency
« Reply #977 on: April 17, 2017, 05:22:10 PM »
@Tinselkoala

Any reference to beat off cream by me would translate into German as"Schlag".

Hmm. You are still stuck in crap mode.  Sorry. I give 3 strikes, then you are out. As soon as I figure out how to do it cuz you will be the first I have booted.
Apparently you wanted this, so it will be done today.

mags

Free Energy | searching for free energy and discussing free energy

Re: The bifilar pancake coil at its resonant frequency
« Reply #977 on: April 17, 2017, 05:22:10 PM »
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Offline itsu

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Re: The bifilar pancake coil at its resonant frequency
« Reply #978 on: April 17, 2017, 05:45:06 PM »
Using a hall sensor i tried to chart the magnetic field of my TBP coil using 4V DC (1.5A).
The compass shows the field to mainly come from the center, the hall sensor more clearly shows this.

Video here:  https://www.youtube.com/watch?v=F9-vtR6KGZ0


The rough sketch shown below shows what i think the magnetic field looks like according to my measurements.


Itsu

Offline MileHigh

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Re: The bifilar pancake coil at its resonant frequency
« Reply #979 on: April 17, 2017, 06:15:38 PM »
Itsu:

Nice to see that you did the frequency sweep and got similar results to TK.  It makes you ponder the Tesla patent where the statement is that the bifilar pancake coil is modeled as a series LC circuit.  Perhaps with larger "industrial scale" coils they start to look like series LC circuits and not parallel LC circuits at the main self-resonant frequency.

With respect to your magnetic field diagram, the more your shape deviates away from something regular like a conventional bar magnet, the less useful the concepts of "North" and "South" are.  The real essence of the magnetic field is to determine its direction and "follow the loop" so you know where it's going.  Knowing the magnitude is nice also but perhaps of secondary importance.

Please see the attached diagram showing the magnetic field around a pancake coil.  As you can see, you had your Hall sensor in the wrong orientation or plane, in order to track where it was going and follow the loop of the magnetic field.  Sure you can nominally say that over the top of the center axis of the coil is "North" and under the bottom of the center axis of the coil is "South" also.

If you look down on a flat pancake coil along the axis of the coil, as you can imagine the magnetic field on the top half of the coil will look like radial spokes of a wheel going from say the center towards the outer edge, and the magnetic field below the coil will look like radial spokes of a wheel going from the outer edge towards the center.

MileHigh

Free Energy | searching for free energy and discussing free energy

Re: The bifilar pancake coil at its resonant frequency
« Reply #979 on: April 17, 2017, 06:15:38 PM »
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Offline MileHigh

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Re: The bifilar pancake coil at its resonant frequency
« Reply #980 on: April 17, 2017, 06:37:12 PM »
Some people have trouble visualizing magnetic fields and this clip might help:

https://www.youtube.com/watch?v=4c6fRmyh4q8

Look at how he slices a solenoid coil and analyzes a series of current-carrying conductors all in a line.  Look at the magnetic field subtended by each wire and see where the cancellation and addition is between the wires.  Just forget about both sets of wires in the slice of the solenoid coil and just focus on the magnetic field produced by one set of wires.

This is very similar to a pancake coil where you take that concept and rotate the slice of wires around an axis to get a pancake coil but in this case with current-carrying wires that are in concentric circles.  Obviously when you go from concentric circles to a spiral the magnetic field stays essentially the same.

Offline itsu

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Re: The bifilar pancake coil at its resonant frequency
« Reply #981 on: April 17, 2017, 09:13:40 PM »

Thanks Milehigh,

So when looking at the magnetic field of the pancake coil i should turn my hall sensor 90°, then skim the surface.

I did that and now the magnetic field follows a more realistic path, as we have a gradual increase and decrease from
the outside inwards, then flipping polarity in the middle and again increasing / decreasing.

See drawing on how i imagin that field now.

Itsu

Free Energy | searching for free energy and discussing free energy

Re: The bifilar pancake coil at its resonant frequency
« Reply #981 on: April 17, 2017, 09:13:40 PM »
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Offline MileHigh

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Re: The bifilar pancake coil at its resonant frequency
« Reply #982 on: April 17, 2017, 09:48:14 PM »
Itsu:

I changed and annotated your drawing.  Note that I define north and south areas above and below the hole in the pancake coil.  If you just look at that 3D volume area, it somewhat resembles what would be taking place in a bar magnet.

I am not comfortable with your concept of defining the upper and lower halves of the left and right lobes,  as "North" or "South."  It's all somewhat of a grey area that is hard to define.   It becomes a question of an "observer" and "perceived magnetic field direction."

I will annotate another image to show you what I mean.

A related question is, "Where is the 'North' and 'South' for a long straight current-carrying wire?"   This is an example of where the concept of "North" and "South" breaks down.

MileHigh

Offline Magluvin

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Re: The bifilar pancake coil at its resonant frequency
« Reply #983 on: April 17, 2017, 09:52:13 PM »
Thanks Milehigh,

So when looking at the magnetic field of the pancake coil i should turn my hall sensor 90°, then skim the surface.

I did that and now the magnetic field follows a more realistic path, as we have a gradual increase and decrease from
the outside inwards, then flipping polarity in the middle and again increasing / decreasing.

See drawing on how i imagin that field now.

Itsu

Hey Itsu

Im sure you are using analog hall sensors. Where the outer perimeter of the blue and read bubbles of field, is that perimeter where the hall does not register any longer? Just wondering. Also, does the hall register higher around the outer edge of the coil than on the flat sides? In Teslas transmitter and receiver diagram he shows another 2 turn winding at the outer perimeter of the pancakes for the transmitter and receiver, where the outer winding is the primary on the transmitter and the outer winding is the sec on the receiver. So it would be interesting if there is a concentration of flux at the outer edge of the pancake as that may be the reason for placement of that 2 turn coil in relation to the pancake as he shows, of which is one of my tests on the list.

Thanks for showing

Mags

Free Energy | searching for free energy and discussing free energy

Re: The bifilar pancake coil at its resonant frequency
« Reply #983 on: April 17, 2017, 09:52:13 PM »
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Offline Magluvin

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Re: The bifilar pancake coil at its resonant frequency
« Reply #984 on: April 17, 2017, 09:56:33 PM »
Itsu:



I am not comfortable with your concept of defining the upper and lower halves of the left and right lobes,  as "North" or "South."  It's all somewhat of a grey area that is hard to define.   It becomes a question of an "observer" and "perceived magnetic field direction."


MileHigh

I was seeing that also. But if he just went across from the far left of the coil to the far right, without flipping the hall 180 in the middle, then that is what he recorded. Make sense?  So just one half can be mirrored and all is correct

Mags

Offline itsu

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Re: The bifilar pancake coil at its resonant frequency
« Reply #985 on: April 17, 2017, 10:00:38 PM »
Itsu:

I changed and annotated your drawing.  Note that I define north and south areas above and below the hole in the pancake coil.  If you just look at that 3D volume area, it somewhat resembles what would be taking place in a bar magnet.

I am not comfortable with your concept of defining the upper and lower halves of the left and right lobes,  as "North" or "South."  It's all somewhat of a grey area that is hard to define.   It becomes a question of an "observer" and "perceived magnetic field direction."

I will annotate another image to show you what I mean.

A related question is, "Where is the "North" and "South" for a long straight current-carrying wire?   This is an example of where the concept of "North" and "South" breaks down.

MileHigh

yes,  i know what you mean, its more the direction of the magnetic field lines that are detected, not the north or south poles.
My hall sensor detects the arrow direction in your above drawing.

Itsu 

Free Energy | searching for free energy and discussing free energy

Re: The bifilar pancake coil at its resonant frequency
« Reply #985 on: April 17, 2017, 10:00:38 PM »
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Offline itsu

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Re: The bifilar pancake coil at its resonant frequency
« Reply #986 on: April 17, 2017, 10:07:15 PM »
Hey Itsu

Im sure you are using analog hall sensors. Where the outer perimeter of the blue and read bubbles of field, is that perimeter where the hall does not register any longer? Just wondering. Also, does the hall register higher around the outer edge of the coil than on the flat sides? In Teslas transmitter and receiver diagram he shows another 2 turn winding at the outer perimeter of the pancakes for the transmitter and receiver, where the outer winding is the primary on the transmitter and the outer winding is the sec on the receiver. So it would be interesting if there is a concentration of flux at the outer edge of the pancake as that may be the reason for placement of that 2 turn coil in relation to the pancake as he shows, of which is one of my tests on the list.

Thanks for showing

Mags

Hi Mags,

no it is like my (and MH's) drawing above, when skimming from top to bottom (TBP coil vertical like my earlier picture) from the upper edge to the middle hole we see a increase/decrease of strength, same with the next part after the hole (no changing of the Hall sensor) increase / decrease until the lower edge (opposite direction detected)

Hope that is clear   :o


Itsu

Offline TinselKoala

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Re: The bifilar pancake coil at its resonant frequency
« Reply #987 on: April 17, 2017, 10:08:17 PM »
Thanks Milehigh,

So when looking at the magnetic field of the pancake coil i should turn my hall sensor 90°, then skim the surface.

I did that and now the magnetic field follows a more realistic path, as we have a gradual increase and decrease from
the outside inwards, then flipping polarity in the middle and again increasing / decreasing.

See drawing on how i imagin that field now.

Itsu
Very nice result on the frequency scan. Your coil's parameters are very similar to mine, and that's great as our results can be more easily compared.
 
See MH's drawings for how the field "circulates" around the windings and thus around the whole disk, like a big torus or donut in space. With a big enough disk the lines would actually be parallel to the disk surface over much of the disk, only becoming orthogonal at the edge and at the hole.


But what about the results I posted earlier where I show that there is still plenty of induction, hence plenty of alternating magnetic field,  going on even when the current sensing resistor voltage indicates no voltage across the resistor?

Offline MileHigh

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Re: The bifilar pancake coil at its resonant frequency
« Reply #988 on: April 17, 2017, 10:09:20 PM »
In this annotated drawing, the "eye" symbol is the observer, and "North" is "a magnetic field direction coming towards you" and "South" is "a magnetic field direction moving away from you."

It may look strange, but it actually all makes perfect sense.  What is "North" and "South" is a function of the observer's position.

Offline TinselKoala

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Re: The bifilar pancake coil at its resonant frequency
« Reply #989 on: April 17, 2017, 10:17:24 PM »
Quote
A related question is, "Where is the "North" and "South" for a long straight current-carrying wire?   This is an example of where the concept of "North" and "South" breaks down.

Right you are, and out the window with it is the concept of the "Bloch Wall". Generations of children have been fooled by looking at bar magnets painted red on one half and blue on the other half, and iron filings on paper to "map" the lines external to the magnet. Once Oersted figured out how the field actually surrounds a current-carrying wire, and people started cutting up bar magnets into smaller and smaller pieces, the true picture started to emerge. But they still paint bar magnets with colors by halfs,  rather than arrows and circulating lines parallel to the bar internally.

 

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