The bifilar pancake coil at its resonant frequency

[Magluvin]

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]

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]

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]

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]

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