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Author Topic: The bifilar pancake coil at its resonant frequency  (Read 567736 times)

itsu

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Re: The bifilar pancake coil at its resonant frequency
« Reply #990 on: April 17, 2017, 10:21:10 PM »
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?


Yes,   working on that too, need another pickup coil first.

Perhaps thats the secret of the TBP coil right there  :o

Itsu

Magluvin

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Re: The bifilar pancake coil at its resonant frequency
« Reply #991 on: April 17, 2017, 10:25:52 PM »
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

Are you testing each area with the hall in the proper orientation as shown below for each section of coil?  Im just showing half for illustration. I left the hall diagrams at the top incase you want to show otherwise you can plug them in.

Because if you are going around the outer edge with the hall in the same orientation as it is above the flat side, then you will show less flux strength at the outer edge because the hall is 90 deg of the flux.


Mags

TinselKoala

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Re: The bifilar pancake coil at its resonant frequency
« Reply #992 on: April 17, 2017, 10:35:31 PM »
The "red" and "blue" assignments are incorrect!

Hold the Hall sensor parallel to the plane of the disk and travel all around the disc's edge, keeping to the plane of the disk. You will see that the polarity does not flip, as it would if the colors were correct.

synchro1

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Re: The bifilar pancake coil at its resonant frequency
« Reply #993 on: April 17, 2017, 10:36:18 PM »
@Tinselkoala,

Here's another Amos and Andy explanation below:


"The "negative" sign on your ammeters is there to show you which way the current is flowing, not to indicate the existence of your imaginary current".

Negative current is positive current moving backwards.

You admit to switching current direction, but you object to calling the reversal a reversal of polarity.

itsu

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Re: The bifilar pancake coil at its resonant frequency
« Reply #994 on: April 17, 2017, 10:39:34 PM »
Quote
Are you testing each area with the hall in the proper orientation as shown below for each section of coil?  Im just showing half for illustration. I left the hall diagrams at the top incase you want to show otherwise you can plug them in.

Because if you are going around the outer edge with the hall in the same orientation as it is above the flat side, then you will show less flux strength at the outer edge because the hall is 90 deg of the flux.


Mags

Ok,  i see what you mean,  no i just sweep from one side to the other in a straight line.
When doing it your way, i have the most strength in the center at the hole, not at the edges.

If you can combine the drawing from post #1014  (http://overunity.com/17186/the-bifilar-pancake-coil-at-its-resonant-frequency/msg504697/#msg504697) with the below
one, you might get the picture.


Itsu

TinselKoala

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Re: The bifilar pancake coil at its resonant frequency
« Reply #995 on: April 17, 2017, 10:55:12 PM »
Ok,  i see what you mean,  no i just sweep from one side to the other in a straight line.
When doing it your way, i have the most strength in the center at the hole, not at the edges.

Sure, because the field lines "bunch up" near the center hole, but must spread out around the edge. Just like winding a toroid with wire: the wire is close together and bunches up in the center hole but spreads out at the outside. There are the same "number" of lines at center and at edge, so they must be further apart at the edge, resulting in a lower field strength across the area of the sensor (fewer lines cross the sensor plane, flux density is less).

Quote

If you can combine the drawing from post #1014  (http://overunity.com/17186/the-bifilar-pancake-coil-at-its-resonant-frequency/msg504697/#msg504697) with the below
one, you might get the picture.


Itsu

The colors are wrong and should be removed.

Coloring the side view that way implies that the Top view looks like this:  But I hope it is obvious that this "color assignment"  is incorrect.

itsu

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Re: The bifilar pancake coil at its resonant frequency
« Reply #996 on: April 17, 2017, 11:14:05 PM »
Off course that can not be correct, but still my hall sensor detects opposite fields when skimming the surface of the disk from left to right or top to bottom.

I think how MH have explained it is correct.

Itsu

TinselKoala

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Re: The bifilar pancake coil at its resonant frequency
« Reply #997 on: April 17, 2017, 11:21:42 PM »
@Tinselkoala,

Here's another Amos and Andy explanation below:


"The "negative" sign on your ammeters is there to show you which way the current is flowing, not to indicate the existence of your imaginary current".

Negative current is positive current moving backwards.

You admit to switching current direction, but you object to calling the reversal a reversal of polarity.

Someday, if you live long enough, you might learn to stop misrepresenting and redefining what others say, but I doubt it.

Current has no polarity. Voltage has _relative_ polarity. Current is the flow of charge and always flows from higher potential to lower potential.

You are getting all twisted up with yourself, you can't even get your own definitions to be consistent.


And I note, and preserve for the record, the further childish insult contained in your post.  How is your personal vendetta against me coming along? 

TinselKoala

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Re: The bifilar pancake coil at its resonant frequency
« Reply #998 on: April 17, 2017, 11:23:42 PM »
Off course that can not be correct, but still my hall sensor detects opposite fields when skimming the surface of the disk from left to right or top to bottom.

I think how MH have explained it is correct.

Itsu

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.

Magluvin

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Re: The bifilar pancake coil at its resonant frequency
« Reply #999 on: April 17, 2017, 11:29:12 PM »
Off course that can not be correct, but still my hall sensor detects opposite fields when skimming the surface of the disk from left to right or top to bottom.

I think how MH have explained it is correct.

Itsu

Well if you face the hall inline with the fields as he has shown you should have higher flux readings than you have observed because the hall is still facing left and right when you bring it around the outer edge. So in my example imagine starting at the top where it says North in your drawing and as you move to the left toward the outer edge of the coil, the hall should be rotated as you move it so that by the time you are at the outer edge the hall will have turned 90deg, and then another 90deg once it is on the South marked side below.  If you can, try it and see if the outer edge is stronger than if it was with the hall the way you did it before. Just for giggles.

I will be doing the same tests but as I have described

Mags

Magluvin

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Re: The bifilar pancake coil at its resonant frequency
« Reply #1000 on: April 17, 2017, 11:33:06 PM »
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.

Well if he faces the hall around the edge, the hall face will be 90 out from the flux and read neutral, as long as it is kept steady, no?  Shouldnt the face of the hall be perpendicular to the face of the coil on the outer edge??

Mags

TinselKoala

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Re: The bifilar pancake coil at its resonant frequency
« Reply #1001 on: April 18, 2017, 12:21:20 AM »
Well if he faces the hall around the edge, the hall face will be 90 out from the flux and read neutral, as long as it is kept steady, no?  Shouldnt the face of the hall be perpendicular to the face of the coil on the outer edge??

Mags

Perhaps you are misunderstanding me or I am not being sufficiently clear. In my face-on drawing, the lines of flux around the disk edge will be straight up or down (into or out of the plane of the "paper") depending on the current direction. The Hall sensor should be held in the plane of the disk,  not at right angles to it.

Just like in your picture, except scan around the edge, remaining flat in the disk plane, instead of scanning along the _lines_ along the radius of the disk.

tinman

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Re: The bifilar pancake coil at its resonant frequency
« Reply #1002 on: April 18, 2017, 10:14:25 AM »
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

I have asked this question many time's,and never got an answer--so i'll ask again
What are the arrow suppose to show?--what is flowing out one end of a PM,and into the other?
If nothing,then why the arrows?.


My two cent's worth
The arrows are wrong,and misguiding/misleading,and cause only confusion to most that look at magnetic field's,and see these arrows.
Most take this as some sort of flow direction,which is wrong.


Brad

tinman

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Re: The bifilar pancake coil at its resonant frequency
« Reply #1003 on: April 18, 2017, 10:23:22 AM »
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?

I also posted on that effect,where the voltage across the sniffer/pickup coil,was in phase with the voltage across the bifilar coil,and not the current through it.

Brad

tinman

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Re: The bifilar pancake coil at its resonant frequency
« Reply #1004 on: April 18, 2017, 10:26:14 AM »


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?

TK

Are you able to power a small load(E.G an LED) from a pickup coil(secondary) placed on top of the BPC,without it effecting this zero voltage across your CVR.?


Brad