Inductor in very big values (500mH, NOT for crossover) - diyAudio
Go Back   Home > Forums > General Interest > Everything Else

Everything Else Anything related to audio / video / electronics etc) BUT remember- we have many new forums where your thread may now fit! .... Parts, Equipment & Tools, Construction Tips, Software Tools......

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 July 2010, 08:27 PM   #1
diyAudio Member
 
gain wire's Avatar
 
Join Date: Nov 2004
Location: NCR
Default Inductor in very big values (500mH, NOT for crossover)

I didn't bother to do a search honestly, because I figured no one would have the answers to both of my questions.
First, I am wondering why it is that it's so difficult to find inductors or chokes over a couple mH anywhere. It seems as though no one makes these. I need something in the area of 200mH to 1H for an LC-based audio filter.

Second, have any of you compared the quality of the budget-friendly LCR meters available on ebay? I want to know why they are so cheap while classic LCR bridges from HP, Fluke and other notable companies remain over 200$.

thank you for your help,

gain-wire
__________________
Trans-directional-servo-logamp non-zerocrossing autogain compressing thingamajig
  Reply With Quote
Old 2nd July 2010, 08:44 PM   #2
diyAudio Member
 
Join Date: Apr 2006
Location: Minnesota
I suggest you use an active filter and eliminate the need for the large inductor.
  Reply With Quote
Old 2nd July 2010, 09:28 PM   #3
expert in tautology
diyAudio Member
 
bear's Avatar
 
Join Date: Apr 2002
Location: New York State USA
The way to get inductors of this size is to use some sort of core, laminated core, like a transformer. You size the core and type and gapped or not depending upon the application. They are sold. The Japanese use them all the time. UTC made them for audio, others did and may still.

The primary and secondary of an ordinary audio transformer can be used as well - depending again on the DC or lack thereof...

The cheap imported "digital meters" basically are oscillators that then coordinate the resulting frequency with an inductance value. The more expensive meters or bridges can deal with other parameters (such as "Q") as
well as measuring at different frequencies and power levels...

I'd look for a nice bridge.

_-_-bear
__________________
_-_-bear
http://www.bearlabs.com -- Btw, I don't actually know anything, FYI -- [...2SJ74 Toshiba bogus asian parts - beware! ]
  Reply With Quote
Old 25th April 2011, 08:43 PM   #4
akis is offline akis  United Kingdom
diyAudio Member
 
Join Date: Jul 2008
Hi

I also want a 500mH coil for an audio circuit. I tried winding my own on a old AM/FM radio ferrite rod which is 12 cm length and 1cm diameter. After I wound almost the 11cm I measured 6.87mH... Almost 80 times less than what I need.

I looked in Farnell and they have a ready made 500mH - not sure if it will work
BOURNS JW MILLER|70F501AF-RC|INDUCTOR, CHOKE | Farnell United Kingdom - but I will get it anyway.

Ideally I would like some sort of heavy-duty ferrite cores where I could wind my own coils to reach 500mH without needing millions of turns. Do you know if any retailers have them?
  Reply With Quote
Old 25th April 2011, 08:57 PM   #5
diyAudio Member
 
Join Date: Jan 2002
Location: Tyrone Ga. U.S.A.
About the cheap LCR meters on ebay. The cheap one I bought sure is handy but
the inductance readings are about 10 to 20% off.
  Reply With Quote
Old 25th April 2011, 09:00 PM   #6
infinia is offline infinia  United States
diyAudio Member
 
infinia's Avatar
 
Join Date: May 2005
Location: Californication
Quote:
I also want a 500mH coil for an audio circuit. I tried winding my own on a old AM/FM radio ferrite rod which is 12 cm length and 1cm diameter. After I wound almost the 11cm I measured 6.87mH... Almost 80 times less than what I need.


a ferrite bar has a very large gap in the magnetic path, so the Al value is low.
get a core catalog 1st and then you will find non-gapped toroids or pot cores or other magnetic stuctures and materials that will give reasonable turns. You must check for the desired Q and also make sure it will meet any linearity targets (ie saturation) over the DC and AC signals present, steady state or under transients from your application.
__________________
like four million tons of hydrogen exploding on the sun
like the whisper of the termites building castles in the dust
  Reply With Quote
Old 25th April 2011, 10:09 PM   #7
DF96 is offline DF96  England
diyAudio Member
 
Join Date: May 2007
Typical ferrite rod inductances will be a few hundred uH for MW and a few mH for LW, depending on how many turns are used. For 500mH you need a ferrite pot core.
  Reply With Quote
Old 26th April 2011, 08:52 AM   #8
akis is offline akis  United Kingdom
diyAudio Member
 
Join Date: Jul 2008
I just discovered farnell have the RM10 ferrite pot and bobbins and have ordered a couple to play with.
  Reply With Quote
Old 26th April 2011, 09:52 AM   #9
diyAudio Member
 
abraxalito's Avatar
 
Join Date: Sep 2007
Location: Hangzhou - Marco Polo's 'most beautiful city'. 700yrs is a long time though...
Blog Entries: 100
Send a message via MSN to abraxalito Send a message via Yahoo to abraxalito Send a message via Skype™ to abraxalito
For an audio circuit, you might be able to get away with a synthetic inductor, otherwise known as a gyrator. With RM10 you'll likely need around 180 turns to reach a value of 500mH as the AL value I found is 16uH/N^2.
__________________
When you design something for other people you don't have as much motivation to make it beyond excellent - Woz
  Reply With Quote
Old 26th April 2011, 10:35 AM   #10
diyAudio Member
 
Join Date: Sep 2004
Location: Napier, Hawkes Bay
Quote:
Originally Posted by gain-wire View Post
I didn't bother to do a search honestly, because I figured no one would have the answers to both of my questions.
First, I am wondering why it is that it's so difficult to find inductors or chokes over a couple mH anywhere. It seems as though no one makes these. I need something in the area of 200mH to 1H for an LC-based audio filter.

Second, have any of you compared the quality of the budget-friendly LCR meters available on ebay? I want to know why they are so cheap while classic LCR bridges from HP, Fluke and other notable companies remain over 200$.

thank you for your help,

gain-wire
Audio Transformers By Cinemag Inc.
  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
Tannoy Eaton Inductor Values & Crossover Advice Thomo Full Range 0 31st October 2009 10:39 PM
D2Audio Inductor Values tripathdude Class D 0 26th September 2009 02:50 AM
Inductor values in crossover? googler Multi-Way 1 3rd August 2005 03:50 PM
Inductor values ? timcow Parts 2 31st July 2004 01:22 PM
help with inductor values on legacy crossover? confused Car Audio 0 14th March 2004 08:10 PM


New To Site? Need Help?

All times are GMT. The time now is 04:38 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