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Old 7th April 2006, 06:49 PM   #51
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I agree with Magura, 1 inch internal dia is not a good combination, the aspect ratio of a coil has a lot to do with induction. If you start from a bigger core you will find that you can get to the induction you want with fewer turns.

If I were you I would trade some of the Rdc of the coil by a more compact aspect ratio and use say 14 ga wire. The overall eficiency of the coil will be better meaning less turns for the given intuctance you want, so the trade off on Rdc will be less than what you think.

Do you have an inductance bridge John?

When coiling heavy wire I use Masking tape over the fingers I use
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Old 8th April 2006, 06:29 AM   #52
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Default inductor calculator

This is the web page I use to calculate my inductor size. It suggests that a small core uses less copper than a large core. Try out several core sizes for the same mH and tell me what you think. Maybe the software is wrong. I'm a carpenter with a great bunch of audio friends. I trust your judgement.

apassgear, what is an inductor bridge? I appologize for my ignorance. Masking tape, cool idea.

John Inlow

It says "this page cannot be found", which is wrong as the page is right there in front of you. Also, hit the arrow in the upper right hand corner; it takes you to a page loaded with goodies.

www.lalena.com/audio/calculator/inductor/
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Old 8th April 2006, 01:57 PM   #53
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The Lalena calculator have caused me a great deal of trouble. Something doesn't add up, or I'm crap at winding
I use a small DOS based calculator, works real good. I will give you the name of it when I get back home.
I can also give you the dimensions of the coils I made for the purpose, I played a lot with the figures before I chose the final solution. As I told earlier I chose 1.9mm wire, in order to keep the DCR down, I never paid much attention to anything but the electrical properties and the practical issues according to actually winding the coil.

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Old 8th April 2006, 02:39 PM   #54
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Default Thanks, Magura

I've located another calculator on line and it is more in agreement with you. For 80 mH, it suggests 2.45" height with 4.9" radius and 472 turns.


Thanks for offering to share your findings with me.

John
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Old 8th April 2006, 03:23 PM   #55
Magura is offline Magura  Denmark
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Off the top of my head I made my 80mH inductors with 550 turns.
Are you going to wind you own?

Magura
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Old 8th April 2006, 04:24 PM   #56
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John and Magura,

As you, I have also made many coils, air core and cored, I do have an inductance bridge (that serves to measure inductance of course). One can make different aspect ratio coils with the same inductance and they will have different amount of turns using the same Gage wire. Depends also on how tight you pack the wire on the coil. So you can have the 80 mH with 1000 or 478 or whatever turns.

As to my previous point, from John’s link, look at the following results using only 16 gage you get at 80 mH with 3.58 Rdc with only 6.83 pounds of copper, assuming the calculator works well.


Inductance 80.15 mH
DC Resistance 3.58 Ohms
Wire Gauge 16 AWG
Wire Diameter 50.8 mils (1 mil = .001 in)
Coil Length 2 in
Coil Inner Diameter 2 in
Coil Outer Diameter 4.64 in
Average Turn Diameter 3.27 in
Wire Length 874.04 feet
Copper Weight 6.83 pounds
Turns 1022
Levels 25.96
Turns/Level 39.37

16 AWG has 2,583 circular mils, so this coil could work well up to some 2 or even 2.5 Amps on a ventilated surrounding.
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Old 9th April 2006, 02:40 AM   #57
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Default Hi guys,

Magura and appassgear, good to hear from you. Just got home from some volunteer work. Tired, but ever so happy to read your posts.


I will wind my own coils. I'm either going to fabricate a winder, or purchase a small motorized unit. I'm trying to get into the speaker business (I have a design that flat out knocks my socks off) and I'm going to require a winder to wind the chokes in my x-overs.

I have just recently purchased an inductance/capacitance meter to measure inductance.

I'm anxious to wind two large center tapped chokes for my upcoming ZV9-T project. Won't that be a blast. Naturally, I'm anxious to learn as much as possible from you guys.

Many thanks for your time,

John
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Old 9th April 2006, 11:47 AM   #58
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Default coil winder

You won't get far wit a small motorised unit, as you will need a quite powerfull unit to wind 2*1.9mm wire. The best way to do it "low budget" is to use a lathe. I have a winding machine for smaller coils, but I use a lathe for anything over 1mm wire.
All you have to do is to make a rev. counter, such can be purchased as a complete unit, or made of a calculator and a switch. I have chosen the calculator solution, as it can count parts of a rev.

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Old 9th April 2006, 04:52 PM   #59
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Default a lathe...

Now, that's a really good idea! I see that Harbor Freight has them on sale from time to time. I knew I should have purchased one last year.

The revolutions counter sounds terrific. Care to share your design?

Thanks,

John Inlow
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Old 9th April 2006, 06:23 PM   #60
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John,

This is what I use for my DIY work. It has a core shaft where I mount different forms made of wood or solid steel. It has a rev counter attached to the shaft with ¼” rubber hose. Initially it was design with the idea to motorize it but never came to do that. I have work 12 gage wire over rectangular forms, which is more demanding that round forms, not easy though with that heavy wire.
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