Inductances etc..

[WM6]

Otherwise i know my deal; trial&error and lot of trivial things to do!

You are experienced developer, but coils are neverending story and lifelong challenge for all of us.

Coils do not allow free simplification. I am sure you knov by experience that calculating 1 turn inductance from 10 turns are not valid by simple multiplication 1 turn inductance for 100 turns. Here is catch which required huge lab test to overcome (formulas) simplification to usable reality (and at the end new simplified formulas).

[ivconic]

I always wanted to know how is made at major manufacturers. Nobody so far exlained that here, on these forums. How come?
Ok...i do not ask for delicate details, but would be good to see generally how is done.

[Mustafa]

I always wanted to know how is made at major manufacturers.

Hi ivconic,
Watch this video http://www.garrett.com/media/how_its..._its_made.html

Garrett Metal Detectors featured on
"How It's Made" episode on Science Channel

[ivconic]

Ahahahahah! Dear friend! I know that! I know how is "made" as manufactured!
I reffered "how is made" to how is projected, calculated, planned!
Anyway thanks!

[Qiaozhi]

"...Also, when the TX coil and nulling coil are in series, the inductances add. They do not subtract..."

I agree. But i measured different than that? I just bought brand new inductance meter. The inductances add when in serie in same direction. But when in oposite direction than it seems the inductances are giving something else? (Keep in mind that those 2 inductances are sharing same former, one on 21cm and another on 15cm diamms)
I can involve effort and by using trial and error method to achieve to make this one cc coil for TGSL. But it is not what i am up to. I don't exactly need one cc coil for TGSL. I need understanding and clarifications about inductance relations when connected in serie; in same and in oposite directions. A method. Proper and accurate method. That's what i need.
Cheers!

OK - I can confirm that you are not going mad.

The total inductance does depend on whether the coils are in phase or anti-phase, and whether they have some mutual coupling. When the coils are in anti-phase the total inductance will be reduced.

The interaction between the coils is complex, and that's why I suggested having the 5Kg hammer standing by.

There is no easy solution, except taking your best guess, and then using an iterative process (i.e. trial and error) to arrive at the correct number of turns. Even then, nulling a homemade concentric coil is not simple.

[ivconic]

OK - I can confirm that you are not going mad.

The total inductance does depend on whether the coils are in phase or anti-phase, and whether they have some mutual coupling. When the coils are in anti-phase the total inductance will be reduced.

The interaction between the coils is complex, and that's why I suggested having the 5Kg hammer standing by.

There is no easy solution, except taking your best guess, and then using an iterative process (i.e. trial and error) to arrive at the correct number of turns. Even then, nulling a homemade concentric coil is not simple.

Oh, i am mad alright! No worrys!
5kg hammer is also here...waiting!
....
Term,terms,term! I miss proper terms in my English, to express what exactly i want! Now you reminded me on "phase" and "anti phase" terms! I looked up exactly for those terms today!
However...now you understand what i wanted to ask. Excellent!

So... 2 coils, same axis, same plan, you may say same former holder (one coil is 15cm and another 21cm as on posted photo).
Wired in serie, in phase - giving one inductance,
Wired in serie, in antiphase - giving another inductance!
So...we already know that Cancel coil must be in antiphase with TX coil (case when Cancel coil is part of TX coil).
Knowing this...and on given example (where we have 6mH as desireable inductance) ;
how to approx calculate relation (inductance/inductance, no.of turns/no.of turns) of Tx and Cancel coil?
It is pretty awkward...it is tough!
At the same time i must maintain 6mh for LC tank at TGSL and at the same time i must make Cancel coil to cancel TX coil influence on RX coil.
.... withouth knowing any proper calculation....!
It will probably need me to make 8-9mH TX coil and than to add on it antiphase Cancel coil and to finally adjust 6mH inductance, right?
So i did it. Like i posted at my first post on this page. And got terrible results!
5.5 volts residual voltage at RX coil !!!
What is problem - inproper relation between TX and Cancel turns in that setup! I alredy know that. I am awared of that.
So finally, that's why i started this thread to ask about any infos. Must be some calculation which defines proper relation between TX and Cancel coils?
I am also awared that areas covered by TX and RX are playing here important role too.
If TX diammeter was twice the RX diammeter than i could use simple equation and get approx relation in no. of turns between TX and RX. But here at this specific case TX is 21cm and RX is 15cm. Also here i already have known TX inductance to "hunt" for, while making TX and Cancel coils...
Tough task!

[ivconic]

21cm/15cm=1.4

So covered area ratio should be 1.4
For to get 6mH on 21cm former i had to make 104 windings (wire gauge is not measured, but is 0.27mm approx.)

So.. if i divide; 104/1.4=74.xx (this is not accurate...but let's take it as some starting point)

Does this means i should make 74 windings over RX coil (15cm) to form adequate Cancel coil?
But!
I already have 104 windings on 21cm former, giving 6mH. If i connect another 74 windings (made on 15cm former in antiphase) that will disturb 6mH inductance and .....?

[ivconic]

Uh...seems i made mistake!

P=r2Pi

rtx=21/2=10.5
rtx2=10.5*10.5=110.25
Ptx=110.25*3.14=346.185
Ptx=346.185

rrx=15/2=7.5
rrx2=7.5*7.5=56.25
Prx=56.25*3.14=176.625
Prx=176.625

Ptx/Prx=346.185/176.625=1.96

So...area ratio is not 1.4 but 1.96!

[Qiaozhi]

21cm/15cm=1.4

So covered area ratio should be 1.4
For to get 6mH on 21cm former i had to make 104 windings (wire gauge is not measured, but is 0.27mm approx.)

So.. if i divide; 104/1.4=74.xx (this is not accurate...but let's take it as some starting point)

Does this means i should make 74 windings over RX coil (15cm) to form adequate Cancel coil?
But!
I already have 104 windings on 21cm former, giving 6mH. If i connect another 74 windings (made on 15cm former in antiphase) that will disturb 6mH inductance and .....?

Hi Ivconic,

You have an error in your calculation. The area inside a circle is pi*r^2.
Therefore the ratio is 10.5^2 / 7.5^2 = 1.96. In this case we have 104/1.96 = 53 turns.

[Qiaozhi]

Uh...seems i made mistake!

P=r2Pi

rtx=21/2=10.5
rtx2=10.5*10.5=110.25
Ptx=110.25*3.14=346.185
Ptx=346.185

rrx=15/2=7.5
rrx2=7.5*7.5=56.25
Prx=56.25*3.14=176.625
Prx=176.625

Ptx/Prx=346.185/176.625=1.96

So...area ratio is not 1.4 but 1.96!

You noticed the error before I could finish my post!

[ivconic]

Yes i made trivial mistake - i am tired from banging had against the wall, whole day long today...trying to solve this thing!

[ivconic]

So...yes 53 turns, but ONLY if 104 turns for TX are accurate.
But we know that 104 turns already giving 6mH.
Adding 53 turns in antiphase will disturb those 6mH!

[ivconic]

Dog, running in circles, trying to catch own tail - that's how i feel!

[Qiaozhi]

See images below. #1 is for Nulling coil, and #2 is for TX coil, and #3 is for new TX coil.

If the Nulling coil is 1.217mH, then you will need to increase the number of turns on the TX to give a final value of 6.56mH + 1.217mH = 7.777mH.
Note that the original TX coil has a calculated inductance of 6.56mH, whereas the real coil was measured as 6mH. The final value depends very much on how tightly you bind the bundle and on the accuracy of the radius measurement. Any differences will be due to the construction method used and/or tolerances.

It appears that the number of turns on the TX coil must be increased by 9 to 10 turns. At least this should be a good starting point. Also, don't forget that the inductance will change slightly when you add the RX coil ... more chasing of the dog's tail!

[ivconic]

Now you made trivial mistake! Ahahahahah!

Inner radius for TX is 21cm and for RX is 15cm!


Ignore this post!