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2021-01-18, 13:42:15
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Author Topic: Smudge proposed NMR experiment replication.  (Read 20661 times)

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So physically different (mirrored) from the first one?
No, because the coil can be flipped around to make a bucking field. These pancake coils essentially do not have a direction and a hot/cold side because reversing their connections or flipping their sides predominantly changes the direction of the H-field generated by them.

Practically, some of the turns of these coils cross "above" and some other turns cross "below" the former. The idea of the mirror or side flip is for the "above turns" to mesh with the "below turns" of the 2nd pancake, so that the axial distance between the two pancake coils remains as constant as possible.
« Last Edit: 2020-10-17, 01:41:46 by verpies »
   

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Right, so only the crossing scheme will be different from the first coil.


Started to build a second former using 1mm fishing line etc. to create the 2th pancake coil.


I moved the part about the defective Manson SPS4900 PS to a new thread here:  https://www.overunityresearch.com/index.php?topic=3960.msg84636#msg84636


Itsu
« Last Edit: 2020-10-08, 00:10:34 by Itsu »
   

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I finished my 2th, spaced, weave 1 pancake coil (left) which is mirrored compared to the right coil.

16.14uH @ 100KHz compared to 16.17uH for the first one.

Itsu 
   

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I finished my 2nd spaced, weave 1 pancake coil (left) which is mirrored compared to the right coil.

16.14uH @ 100KHz compared to 16.17uH for the first one.
So you don't need to flip it and you've got the first point from the list below, behind you.

So the next steps are:
1) build another pancake to create a bucking H-field when connected in parallel and to minimize the E-field occuring between the two pancake coils.
2) wind the toroidal coil with the same winding technique as the pancake coils in order to avoid circumferential induction in it (this is the major contributor to the H-field crosstalk).
3) surround the toroidal coil with a grounded E-field (only!) shield as described here in order to minimize the E-field crosstalk.
   

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Quote
2) wind the toroidal coil with the same winding technique as the pancake coils in order to avoid circumferential induction in it (this is the major contributor to the H-field crosstalk).

Mammoth task requiring lots of patience...........
   

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Mammoth task requiring lots of patience...........
I know, I've done it but I put some gaps between the turns (like with the pancakes) so it goes faster.
   

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Finally finished the weaved coil around the watertube.

Litz wire
Fres = 34MHz
L= 11uH @ 100KHz
R= 0.4 Ohm

Now looking into screening it.

Itsu
   

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Posts: 1913
Finally finished the weaved coil around the watertube.

Litz wire
Fres = 34MHz
L= 11uH @ 100KHz
R= 0.4 Ohm
That's a high Fres, but that's good.

What S21 do you get for the circumferential induction with a loop of the same diameter, like on the picture below?
How does that compare to the previous coil construction, when the distance is kept the same.?
   

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I made some S11 measurements of this weaved tube coil, see screenshot below.
Seems my Fres from yesterday (34MHz with FG /scope) was on a harmonic.


Problem again with the S21 measurements is the calibration.
I tried some setups, but non showed any sensible data (to me).

Itsu
   

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I made an S21 calibration using a SOL and for thru a short between port 1 and port 2, then inserted the single loop to port 1 and the tube coil to port 2.

Below are some S21 measurements with a distance of 2cm between coils.

Itsu
 
   

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How does that S21 compare to the toroidal coil of the old construction ?
   

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Well, i have to check the old data as i rewound it using the spaced weaved litz wire.

Itsu
   

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It seems i never made such measurements on the old toroidal coil.

I can make similar toroidal coil on a spare tube and redo that measurement....

Itsu
   

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I made a new toroidal coil on a spare tube similar as the old toroidal coil and used the same setup as the new weaved spaced tube coil, see screenshot of the same data.

Itsu
   

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If you look at the two superimposed |S21| graphs (at the same scale) then the difference in the circumferential current induction is significant between the old toroidal construction and the new. This induction is the major contributor to the undesirable crosstalk.  The reminder appears to be of capacitive nature since it increases with frequency.

   

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Great, so your weaved construction method payed off to minimize the crosstalk.

And screening it, will further decrease it.

Itsu
   

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I was trying all sorts of easy screening methods to avoid using verpies his suggested method, but they all failed, so i finally decided to give verpies his idea a shot, see here:
https://www.overunityresearch.com/index.php?topic=3924.msg82938#msg82938

The result looks promising, so now have to apply severall layers of varnish and see if it will hold its shape.

Its 3 layers of magnet wire on a flexible hose.

Itsu
   

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The result looks promising, so now have to apply severall layers of varnish and see if it will hold its shape.
What diameter is this wire?
How long did it take you to wind the 3 layers of this wire?

The diameter of the hose seems a little too small to create an overlap of the 2 hemi-toroids created after the circumferential cuts...but I might be wrong just by looking at the photo.

Varnish the wires first on the surface and cut them later after the varnish dries.
Do not let the varnish soak through the wires so much that it glues them to the hose*, unless you were proactive and wrapped the hose with a saran wrap first (or coated the hose with wax).
Do not use a saw with teeth to cut the wires because teeth will fray them. Use a small and thin abrasive cut-off disk (e.g. for the Dremel tool) or a very very sharp knife.

After separating the Litz Cloth (formed by the varnished wires) from the hose, varnish it again from inside and don't forget about the cut edge, (the one that will be overlapped and not be soldered), so it is varnished in such manner that the exposed ends of the cut wires are not shorted electrically. We do not want to create any conductor loops that will oppose the AC magnetic field.

Note, that some varnishes are more rigid than the others.

* I used a flexible styrofoam rod which completely dissolves in acetone instead of the rubber hose and an epoxide based varnish which is immune to acetone, so I did not have any stiction problems.

   

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Wire is 0.2mm, it toke 20 mins or so to wind once i had the winding rig set up.

I now too think the diameter of the hose is to small, but it was all i had and went with it.

The wire is directly onto the hose, so i will have to see how it comes out.

I expect the inner layer will not be adequately varnished and could cause problems during cutting or lateron, so will see how that goes.

I will use a dremmel cut-off disk.

Many thin layers of varnish will be better than a few thick ones, so will take some time.

Itsu
   

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After 7 layers of varnish i used the dremmel cutting tool to slice it in half.

Getting it loose from the tube was somewhat cumbersome, but doable, some loosened up wires stayed behind, so first thing i did was varnish the inside to fixate it, see picture.

Soldering the outer rings will be the next challence.

Itsu
   

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Soldering the outer rings will be the next challence.
If you want, you can also solder the inner rings instead of the outer rings. The ground connection placement doesn't make much difference for an E-field shield so it is up to you.
Whichever ones you chose, make sure the wires on the opposite rings are not shorted together. You can fray them a little and varnish their ends to isolate them. We do not want Eddy loops anywhere!
   

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Soldering the edges is a mess, the heat melts the varnish before it melts the green solderable coating of the magnet wire causing the half rings to fall apart in multiple pieces.

It smokes and smells like hell and the burned varnish prevents solder from attaching to the exposed copper, see picture.

I can't see how to attach the both halfs together using more solder as the halfs will crumble apart while applying heat.

Not sure this is doable.

Itsu
   

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Soldering the edges is a mess, the heat melts the varnish before it melts the green solderable coating of the magnet wire causing the half rings to fall apart in multiple pieces.
That is a problem indeed.
The epoxide varnish, which I use, does not melt and holds the wires together despite the temperature.  It is the same stuff which is used in PCB soldermasks.
   

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I give up on making a screen for the tube coil.

I tried severall approaches, i sacrificed a kacher/Tesla secondary coil.

The varnish/coating of the magnet/litz wire makes it somehow impossible to solder it again as the solder won't flow and/or stick to the cleaned blank copper.

I used heavy solder irons and normal light ones, but non works.

So untill i find another solution this has to go on the backburner for now.

Itsu
   

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Enjoy your trek through life but leave no tracks
Soldering the edges is a mess, the heat melts the varnish before it melts the green solderable coating of the magnet wire causing the half rings to fall apart in multiple pieces.

It smokes and smells like hell and the burned varnish prevents solder from attaching to the exposed copper, see picture.

I can't see how to attach the both halfs together using more solder as the halfs will crumble apart while applying heat.

Not sure this is doable.

Itsu
Well with ltz wire don't try the back burner it vaporizes the fine copper strands ;) but wife's nail varnish remover works on most things,
   
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