Unwinding my inductor to obtain lower inductance - 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 2nd January 2004, 12:48 PM   #1
michael is offline michael  Australia
diyAudio Member
 
Join Date: Sep 2003
Location: Adelaide Hills
Send a message via MSN to michael
Default Unwinding my inductor to obtain lower inductance

i needed a 0.25mH inductor and all that was available was a 0.22 and a 3.3mH, i bought the 0.33 because i thought that i could unwind it until i reached 0.25mH.
Can someone tell me how i many winds till i get to 0.25 or another way of getting there without spending $60 on an inductance meter.
  Reply With Quote
Old 2nd January 2004, 02:29 PM   #2
sreten is offline sreten  United Kingdom
diyAudio Member
 
Join Date: Nov 2003
Location: Brighton UK
Details in this article :

http://sound.westhost.com/lr-passive.htm

sreten.
  Reply With Quote
Old 2nd January 2004, 04:27 PM   #3
Ron E is offline Ron E  United States
diyAudio Member
 
Ron E's Avatar
 
Join Date: Jun 2002
Location: USA, MN
Firstly, the 0.22 is just on the verge of being close enough, and may work ok, depending on what type of circuit it is going into.

To unwind the other one...realize that inductance is approximately proportional to the number of turns squared:
1) Count the number of turns in the 0.33mH coil - call it N.
( - just multiply the number of layers by the number of turns per layer)
2) calculate 0.25/.33=((N-T)/N)^2
rearrange to: T=N*(1-sqrt(0.25/0.33))

T is the number of turns you must remove.

BTW, the above only works for air cored inductors, AFAIK.
__________________
Our species needs, and deserves, a citizenry with minds wide awake and a basic understanding of how the world works. --Carl Sagan
Armaments, universal debt, and planned obsolescence--those are the three pillars of Western prosperity. —Aldous Huxley
  Reply With Quote
Old 2nd January 2004, 08:19 PM   #4
michael is offline michael  Australia
diyAudio Member
 
Join Date: Sep 2003
Location: Adelaide Hills
Send a message via MSN to michael
thanks guys
  Reply With Quote
Old 3rd January 2004, 03:22 AM   #5
michael is offline michael  Australia
diyAudio Member
 
Join Date: Sep 2003
Location: Adelaide Hills
Send a message via MSN to michael
okay im about to unwind the inductor and i want to check if im working it out right, firstly what is an aircored inductor???
secondly i worked that formula and it gave me 16.6 as the T value so now i unwind a single row as there are 16 winds per row. and there are 8 rows. am i doing this right?
  Reply With Quote
Old 3rd January 2004, 03:33 AM   #6
tool49 is offline tool49  Canada
diyAudio Member
 
tool49's Avatar
 
Join Date: Apr 2003
Location: Montreal
Aircore simply means that their is no conductive material in the center of the bobbin. I calculated the same thing as you, so my guess is that you are doing it right!

Sébastien
  Reply With Quote
Old 3rd January 2004, 03:46 AM   #7
michael is offline michael  Australia
diyAudio Member
 
Join Date: Sep 2003
Location: Adelaide Hills
Send a message via MSN to michael
okay thanks for the reply, 1 row is now unwound, now i still need the rest of the drivers so that i can do some real testing...grrrrr damn couriers taking a christmas break still
  Reply With Quote
Old 4th January 2004, 10:00 AM   #8
Nardis is offline Nardis  United Kingdom
diyAudio Member
 
Join Date: Aug 2003
Location: London
I just had the same problem.
I measured the size of the bobbin and counted the number of turns. Then I used the online calculators at http://www.colomar.com/Shavano/inductor_info.html
and http://lalena.com/audio/calculator/inductor/
to work out the lengths of the wire in the value I had and the value I wanted, then unreeled the difference in length.
  Reply With Quote
Old 5th January 2004, 09:59 AM   #9
michael is offline michael  Australia
diyAudio Member
 
Join Date: Sep 2003
Location: Adelaide Hills
Send a message via MSN to michael
we so need an inductance meter, perhaps if i do a big project where i need to adjust numerous inductors i will buy one.
  Reply With Quote
Old 5th January 2004, 10:58 AM   #10
diyAudio Member
 
Join Date: May 2002
Location: Switzerland
Have you got a frequency counter and a sinewavegenerator ? If so you could easily measure the inductance-change by building a parallel resonant circuit by adding a capacitor ?

Regards

Charles
  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
Unwinding a steel laminate core inductor? Formula? AudioLapDance Parts 1 18th February 2009 02:27 AM
unwinding a 1mh. steel laminate inductor into .8mh, good idea or not? marchel Multi-Way 17 20th February 2008 09:44 AM
Lower rails for lower impedance? 95Honda Solid State 7 19th December 2007 09:59 AM
unwinding inductor chainenoble Multi-Way 2 31st January 2007 10:29 AM
Unwinding o-core trafo to lower voltage - what´s the trick ? Groundloops Everything Else 8 14th August 2005 07:57 PM


New To Site? Need Help?

All times are GMT. The time now is 11:23 AM.


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