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Old 6th August 2001, 07:08 AM   #1
Jason is offline Jason  Australia
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I'm in the process of winding my own crossover inductors, with varying results.

Compared to professionally made inductors of the same gauge and length, they tend to have lower inductance. The tighter packed the coil the better the results, so it seems and would make sense.

I had a look around the web for a coil winding reference/tutorial and didn't find much decent information other than that at http://www.lalena.com/audio/.

I was wondering if anyone had another reference or personal tips and tricks on the subject regards optimum sizing (in this case using 14ga wire and aiming for 0.24mh).

Thanks in advance,

Jason
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Old 6th August 2001, 10:54 PM   #2
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Jason,
Keep in mind that tighter packed means more stray capacitance between the windings, but yes, higher inductance.
The trick about winding inductors is that there are scads of variables. Worse yet, there are no standardized formulas. Sound weird? It's true. I've seen papers comparing five or six formulas and pointing out that the results were inconsistent. (I touched on this briefly in another thread, but didn't feel like making an issue of it; people look in a textbook, find a formula, and assume that it is *the* formula. There's no such thing. Not to mention, you'd think that [seeing as how we're now in the 21st century] we'd have a reliable formula for winding inductors. T'ain't so, unfortunately.)
Anyway, find a book with a formula and wind an inductor, but be prepared to spend a while fine-tuning it. Or drop by http://www.sound.au.com. I believe there's some info in the speaker section about inductors for passive crossovers (note that he also mentions, in passing, problems with inductor formulas).
As far as optimum, generally speaking you want the cross-section of the inductor to be approximately square. It'll be more efficient that way, since the magnetic flux will be more confined.
Broomsticks or other wooden dowels make good cores for transformers. There are plastic coil bobbins for sale, but it's difficult to find the size you need.

Grey
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Old 7th August 2001, 07:13 AM   #3
Vivek is offline Vivek  India
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I too have tried to wind my own inductors. The problem is the wire keeps bouncing back like a spring. I have had a really tough time trying to keep the wound wire in place. Any solutions?
Thanks for any help.
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Old 7th August 2001, 07:22 AM   #4
Jason is offline Jason  Australia
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A hot glue gun did the trick for me, followed by some neat cable ties. The glue can then be easily peeled off.
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Old 7th August 2001, 02:59 PM   #5
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Vivek,
Some people use the packing tape with the fiberglass strings in it, but over time the adhesive tends to dry out and the tape comes loose. It might be a good while-you're-winding solution, though.
Overall, Jason's suggestion about cable ties is the best option short of an actual bobbin.

Grey
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Old 9th August 2001, 05:36 PM   #6
Vivek is offline Vivek  India
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I'll try both. Thanks for the help.
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Old 21st October 2012, 01:37 PM   #7
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Default Inductors

Try freeware Coil Maestro - Coil Maestro - freeware coil/solenoid calculator for designing
Put your drill machine to use for winding and create a tensioning jig so that it does not spring back.
Hope this helps
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Old 21st October 2012, 01:48 PM   #8
AndrewT is offline AndrewT  Scotland
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the highest inductance comes when the coil crossection is nearly square.
This just happens to be the closest packing of the turns in a winding.

If the packing does have that effect of reducing the inductance, then extended coils whether they are single layer or triple layer (leads at opposite ends) will tend to have more inductance than loosely packed coils.

If you want least resistance then the square form of the cross section is important.
Look at your old fashioned VHF coils in radio sets etc. The coils on the former/s are all bunched into squarish packets.

Once one makes the decision to use a long coil rather than a square coil one may find that looseness of packing begins to have a lesser effect on reducing inductance.
i.e. a hand wound single layer coil may be less sensitive to packing ratio, than a mullti-layer coil.
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regards Andrew T.

Last edited by AndrewT; 21st October 2012 at 01:53 PM.
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Old 21st October 2012, 04:43 PM   #9
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You might be interested to read this:- http://www.solen.ca/pdf/solen/stdind.pdf - from Solen on what they call 'perfect lay hexagonal winding'.

Note that there are 2 (at least) types of enamelled solid copper wire out there, annealed copper and 'hard drawn' copper wire, the former being comparatively soft and workable and the latter being quite springy and usually supplied in large loose coils.

Annealed copper wire is often stretched before use to put what is called a 'set' on it, i.e. it becomes straight and a little stiffer due to slight work hardening taking place. The wire is secured at one end and the other end is pulled until a slight give of a few percent is felt. This is usually hand-done by 'feel' and results in neat-looking wire links on PCBs.
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Old 21st October 2012, 05:44 PM   #10
tvrgeek is offline tvrgeek  United States
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I was going to build a gig. But I find the cost of bulk wire to be higher than the cost of a completed coil. Makes no sense.
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