cComega virtual coil

[WM6]

Transfer form TGS thread:

WM6,

Thanks, I missed the graph to check the model. By the way, the computer model is done. I found that the proposal coil design above can not be nulled. The inner TX coil has to be on opposite direction to the outer TX coil. It does not matter. I will explain on some impressive graphics why this model does not work. But it will work on opposite current direction. Also the one third winding factor will very likely not enough to get nulled.

May be I should post the comprehensive results on the coil section to not disturbing the other contributors here. Please make a starting thread and I will post every step consequently. So at the and, we can make a prototype of nulled "Omega-concentric" coil. (How should we name this type of coil?)

Aziz

Aziz, as you say, it is possible that coil can not be nulled, although i am not sure in that. Namely only half of tunning/nulling loop act in opposite direction to outer TX coil, but this is the same in omega coil and there even by full number of TX turns (here only 1/4 to 1/3 of TX turns). On other site, construction of tunning loop is someway "self nulling", influence of this factor i expect to see on EM field presentation in your bright development. Nulling perform during to put near and away of both tunning loop legs.
Repeated sketch of basic idea:

[Aziz]

Hello WM6,

Ok, lets start with the fundamental coil analysis. I recognized, that I should implement in my software also the connection wires between the coils to ensure right understanding. So everybody can then see the correct coil configuration with his exact winding directions. At the moment, this will cause some misunderstandings, even the software computes in right way but not showing this. Also effects of connection wires can be taken into account.

So this will cost me at least one day to implement this feature (changing the coil wire generation functions necessary). But I should invest this time right now. As this is a typical software developing process, only practical situations lead to useable software.

Tuning:
I have obviously misunderstood you. I thought, you increase the flux area of the inner tx coil. To avoid further misunderstandings, the flux area of the coil is the integrated surface area of coil winding. As the inner tx coil is not a true circle (open), the flux area is far less then compared to a circle. A coil that has zero flux area can not induce magnetic fields. There is a minimum flux area needed, to ensure nulling of the inner rx coil.

As a fact, coil configuration can be nulled in two ways:

a) By changing the geometry position of the inner tx coil (flux area constant)
Opening wider the inner tx coil to keep more distance to the inner rx-coil.

b) By changing the flux area of the inner tx coil (geometry changes only for the outer inner tx coil windings).
Stretching/upsetting the outer windings of the inner tx coil.

c) or a combination of both a) and b)

In this way, this type of coils can be easly made and nulled compared to pure concentric coils. As I see the magnetic strength distribution, the original omega coil is more effective than this coil.

More facts on coming days.... to be continued

So I will start coding now..

[Carl-NC]

I don't see how this coil can possibly work. The nulling portion has parallel wires with current flowing in opposite directions, so the magnetic fields will cancel. It will have very little effect on the RX coil.

- Carl

[Aziz]

Yes, as I mentioned on the TGS-Topic, nulling is not possible on the coil configuration seen above. Only the following coil configuration is possible, to get nulled (see below).

[Aziz]

I have corrected the connection of the coils. So any misunderstandings should be avoided.

[WM6]

I have corrected the connection of the coils. So any misunderstandings should be avoided.

OK, thank you, Aziz. Not fully the same as i thought (e.g. how to put thru tunning loop only 1/4 of TX flux), but you can apply only simplified derivate i know. Nulling was planned as you stated in paragraph a.). Let see what is output of your excellent comp simulation.

Theoretically i fully agree with Carl about functionality of tunning loop design (i mentioned "self nulling"), but practice sometimes not support exclusively theoretical approach of clear parameters. Maybe Azizs application put out another view that is for us still invisible at present.

[WM6]

Yes, as I mentioned on the TGS-Topic, nulling is not possible on the coil configuration seen above. Only the following coil configuration is possible, to get nulled (see below).

Yes, and probably to get additional field strength to TX coil too. Thank you for your efforts on corrections.

[Qiaozhi]

I also fail to understand how this could possibly act as a nulling coil.
In the standard omega configuration the TX coil is looped back on itself and overlaps the RX coil. This allows the residual TX signal present in the RX coil to be cancelled. The RX coil can then be mechanically adjusted up or down to find the correct nulling point. In your proposed configuration, it is more like a crippled concentric coil.

[Aziz]

I need some feedback:

- What diameter should the TX1 coil (bigger transmit coil) have?
My suggestion: 9 or 10 inch

- Diameter relation factor of TX2I(inner)/TX1?
My suggestion: 1/3, 1/2 or 2/3

Other factors such as N-TX2/N-TX1 (relation factor number of turns for TX1 to TX2), Radius RX, Radius TX2O depends on the ability to balance.

I will make such coils easy to build. Even for hobby builder. But remember, these coil types are not efficient, due to local canceling of the magnetic field strength. Anyway, it is same principle of concentric-coils but easy to tune.

Aziz

[Aziz]

Hi Qiaozhi,

I also fail to understand how this could possibly act as a nulling coil.
In the standard omega configuration the TX coil is looped back on itself and overlaps the RX coil. This allows the residual TX signal present in the RX coil to be cancelled. The RX coil can then be mechanically adjusted up or down to find the correct nulling point. In your proposed configuration, it is more like a crippled concentric coil.

The principle of nulling is very easy. The integration surface area of the magnetic field vectors of the flux area of the rx-coil should be zero (zero vector). Then the rx coil is balanced. To achieve this, some regions of the rx-coil has other polarity of the magnetic fields. This can only be done with local canceling of the magnetic fields. The inner TX2I coil does the local canceling. The strength of the magnetic field of the TX2I is defined by the flux area of TX2 and his geometry (position, radius) and the number of turns for winding. This principle is not novel - it is same as concentric coils - but easy to build (this could be novel - do not patent this please! ).

Aziz

[Aziz]

Waiting for input parameters..

Hello,

Ok, the coil software for desired functionality is implemented now. I am still waiting for input from all of you for a particular coil design.

I has been pointed out, that the number of inner TX windings (TX2) should be half of the number of the outer TX (TX1) windings (=N turns). So this can be easily adapted to a particular desired coil inductivity. The TX coil (TX1+TX2) can then be made from only single wire and in one step. First the outer TX1 should be wounded, then wind to inner TX2 and remain winding until the N/2 windings completed. Tuning mode a gives the ability to tune course and mode b the ability for fine tune. For tuning mode a, one can place a plastic screw to enable a more better tuning by moving the inner TX coil ends together or apart.

Following picture shows a cross section of the magnetic strength field:
TX1: Number of turns N = 40
TX2: Number of turns = N/2 = 20
Diameter: ~20 cm (TX1)

Aziz

[Qiaozhi]

Hi Qiaozhi,



The principle of nulling is very easy. The integration surface area of the magnetic field vectors of the flux area of the rx-coil should be zero (zero vector). Then the rx coil is balanced. To achieve this, some regions of the rx-coil has other polarity of the magnetic fields. This can only be done with local canceling of the magnetic fields. The inner TX2I coil does the local canceling. The strength of the magnetic field of the TX2I is defined by the flux area of TX2 and his geometry (position, radius) and the number of turns for winding. This principle is not novel - it is same as concentric coils - but easy to build (this could be novel - do not patent this please! ).

Aziz

When I said "I fail to understand how this could work" - what I was politely trying to say was "this configuration will not work".
The nulling coil needs to be in anti-phase so that it cancels the residual TX signal generated in the RX coil. The proposed configuration will not do that. In fact, it will fail to cancel anything, except itself!
No need to worry about patents.

[WM6]

Hello,

Ok, the coil software for desired functionality is implemented now. I am still waiting for input from all of you for a particular coil design.

I has been pointed out, that the number of inner TX windings (TX2) should be half of the number of the outer TX (TX1) windings (=N turns). So this can be easily adapted to a particular desired coil inductivity. The TX coil (TX1+TX2) can then be made from only single wire and in one step. First the outer TX1 should be wounded, then wind to inner TX2 and remain winding until the N/2 windings completed. Tuning mode a gives the ability to tune course and mode b the ability for fine tune. For tuning mode a, one can place a plastic screw to enable a more better tuning by moving the inner TX coil ends together or apart.

Following picture shows a cross section of the magnetic strength field:
TX1: Number of turns N = 40
TX2: Number of turns = N/2 = 20
Diameter: ~20 cm (TX1)

Aziz

Thank you Aziz seems good this virtual coil to find some virtual treasure.

Now it was tested by me on nulling possibility in real world too. It is hard to reach acceptable nulling by 1/4 of total TX turns loop. So i made some modification (see sketch below). Now tunning loop comprise same number of turns as outer TX coil. I perform tunning by signal generator at 14 KHz and cheap (80€) digital scope (FFT mode): nulling perform easy to entire 0.0 without trouble. Coil showing considerable stability too.

[Aziz]

Hi WM6,

This experiment lead to a real concentric coil but with opened inner tx coil to tune easy. Your next proposal is very similar to a concentric coil. Following magnetic fields strength cross section shows a typical concentric coil. The N-TX1=40, N-TX2=12, RX coil placed ~3 mm above the TX2 coil and has same radius. Typically, RX and TX2 coils are wounded on the same plastic core.

[Aziz]

But I like the standard omega coil. The RX coil "sees" much more magnetic strength in his flux area and nearby it. This can induce more signals compared to a standard concentric coil.

Next picture: Omega coil cross section.