Winding your own inductors - Page 2 - diyAudio
Go Back   Home > Forums > Loudspeakers > Multi-Way

Multi-Way Conventional loudspeakers with crossovers

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 21st October 2012, 06:04 PM   #11
oshifis is offline oshifis  Hungary
diyAudio Member
 
Join Date: Mar 2004
Location: Budapest, Hungary
Quote:
Originally Posted by AndrewT View Post
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.
Absolutely true. I used A. N. Thiele's (yes, that Thiele) JAES article "Air-cored Inductors for Audio". If the cross-section is square, and the innner diameter is 2x the coil width, this geometry gives minimum resistance for a target inductance. The formula gives the wire diameter and length, the coil dimensions, but not the number of turns. I made several crossover coils in the mH range, and they all were within 1%...
  Reply With Quote
Old 21st October 2012, 07:17 PM   #12
diyAudio Member
 
James Lehman's Avatar
 
Join Date: Oct 2012
Location: Akron, Ohio USA
Send a message via Skype™ to James Lehman
I have wound quite a few inductors. This is just personal experience, but it worked well for me. I used a wooden dowel with stiff disks epoxy-ed to it to make a spool. I got a long drill bit and drilled from the inside of the spool out through one of the sides to feed the wire into the spool. I made a crank mechanism to wind the coil. I had a block of wood with some pieces of dowel sticking out of it to wrap the wire through to give it drag so I could pull the wire tight onto the spool. When I thought I might have enough wire on the coil to reach my target inductance, I used a razor knife to scrape off just a bit of the enamel so I could test the coil at that point. If it didn't have enough wire on the coil, I'd cover the scrap with some clear plastic box tape and keep winding. When I got to my target inductance, I wrapped the whole inside of the spool with several layers of electrical tape.

Metal by James Lehman ~ Extra Stimulus Inc.

You can measure a coil by putting a known resistance in series with the coil. Calculate the freq at which the coil's impedance and the known resister would be the same. Drop that freq across both the coil and resister in series and measure the AC voltage drop across each part individually. When you measure the same voltage drop, the parts will be the same impedance. You will have hit your inductance value.

I used my computer and sound card to generate sine waves of the right freqs.

You can use the same technique to add caps together to get exactly the right values.

James.

Last edited by James Lehman; 21st October 2012 at 07:24 PM.
  Reply With Quote
Old 22nd October 2012, 08:18 AM   #13
AndrewT is offline AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
Does the "looseness" of the coil affect the inductance?

What type of coil is more sensitive to "looseness" errors?

I suspect that a stretched single layer coil is very insensitive to "looseness" once you have the correct formula.
and the corollary to that, that the ideal "squarish" coil is most sensitive to "looseness".

But the inductance of all coils are extremely sensitive to diameter !!!!!!!!!!
__________________
regards Andrew T.
  Reply With Quote
Old 22nd October 2012, 08:48 AM   #14
AJT is offline AJT  Philippines
diyAudio Moderator
 
AJT's Avatar
 
Join Date: May 2003
Location: Palatiw, Pasig City
how times change, now online calculators do the work for you....

rectangular lets you use traffo bobbins.....
Rectangular Coil Inductance Calculator
Inductance Calculations: Rectangular Loop

circular coils......
Inductance Calculations: Circular Loop
Clemson Vehicular Electronics Laboratory: Inductance Calculations - Circular Loop
RF Inductance Calculator - HAMwaves.com
  Reply With Quote
Old 22nd October 2012, 06:36 PM   #15
diyAudio Member
 
Join Date: Nov 2003
Location: flyover country
I believe the highest inductance per length of wire (for an air core inductor) is where the width equals half the center hole diameter and the cross section is square. It is probably a good idea to overwind by 20% and take turns off incrementally, checking the inductance each time. I've used tape to temporarily hold windings in place while taking breaks, or, alternatively, hot or medium CA glue or epoxy to hold turns in place (the CA acts like a potting compound also, without completely filling interwinding gaps which is probably a good thing dielectric absorption wise) with an electrical, mylar or kapton tape overwrap when finished winding.


I have made removable side disks so that, once 'potted', my inductors are minimum size/volume with them removed. Facing materials that don't stick to the 'potting' compound need be used while winding the inductor with this technique, of course.

I've found PVC pipe caps to make pretty handy center forms as long as they don't have much of a radius at their ends. They're available cheap in a variety of sizes, are strong enough to do the job, and only require a hole to be drilled at their center to enable single screw mounting.

Last edited by thoriated; 22nd October 2012 at 07:00 PM.
  Reply With Quote
Old 25th October 2012, 11:23 PM   #16
diyAudio Member
 
James Lehman's Avatar
 
Join Date: Oct 2012
Location: Akron, Ohio USA
Send a message via Skype™ to James Lehman
Quote:
Originally Posted by AndrewT View Post
Does the "looseness" of the coil affect the inductance?

What type of coil is more sensitive to "looseness" errors?

I suspect that a stretched single layer coil is very insensitive to "looseness" once you have the correct formula.
and the corollary to that, that the ideal "squarish" coil is most sensitive to "looseness".

But the inductance of all coils are extremely sensitive to diameter !!!!!!!!!!
It might make a difference if the coil is in the magnetic field of a speaker magnet. In general, loose windings can move and therefor absorb energy and throw off the value of the inductor.
  Reply With Quote
Old 26th October 2012, 03:23 AM   #17
AJT is offline AJT  Philippines
diyAudio Moderator
 
AJT's Avatar
 
Join Date: May 2003
Location: Palatiw, Pasig City
^yes, we tap the coils on the tv tuners to do re-channeling Japanese tv's....
  Reply With Quote
Old 26th October 2012, 05:42 AM   #18
diyAudio Member
 
Join Date: Feb 2005
Hi Jason,

The specs to wind a choke for 0.24mH out of#14 wire via the linked 'lalene' program, and using a centre diameter starting point of 2" and 1" length (between side cheeks, that is) gives approx 4 layers of 16 turns/layer, and trying to bend a #14 wire into a 2" dia and keeping it under control in a 1" gap without a winding m/c is no joke and is not something you'll want to do twice.

However, if you use 3 parallel wires of #16 wire, much easier (trifilar). For the low mH, and a "better" sound indeed, use enamelled Ohno copper wire.

As Oshifis indicated above (#11) the Theile design is the one for "best" sound but I don't have a link - can send a scan of original article if you want. Low impedance is only 1 of the parameters for a better sounding choke.
__________________
... jh
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Winding Inductors noodle_snacks Multi-Way 40 10th March 2010 12:58 AM
Winding inductors - tips? Tenson Multi-Way 9 13th February 2007 05:04 PM
Winding perfect lay inductors tktran Multi-Way 3 2nd February 2004 05:35 AM
Winding own foil inductors? tpenguin Multi-Way 2 25th December 2003 11:05 AM
Winding inductors for audio.... Lisandro_P Parts 8 31st March 2001 03:36 AM


New To Site? Need Help?

All times are GMT. The time now is 01:53 PM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2