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 Post subject: Determining the Mix/type of an Unknown Toroid
PostPosted: Jul Mon 10, 2017 11:35 pm 
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Howdy Folks,

I have a lot of unknown toroids that I've stripped out of scrounged gear over the years, but have no idea how to determine the characteristics of these things. For instance, can you look at a toroid and determine that it's made from a ferrous material or powdered iron? I know that some of them are color-coded, but the ones I'm talking about have no markings whatsoever. Maybe there is a way to determine their makeup electrically, or maybe there makeup can be determined by how they're being used in a specific application?

73,

Randy AB5NI

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 Post subject: Re: Determining the Mix/type of an Unknown Toroid
PostPosted: Jul Tue 11, 2017 1:36 am 
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You can't even trust the color coded ones, because different manufacturers use their own color code, and they're not the same.

If you can remember what the toroid came out of, and the frequency it was operating at, then that will give some indication of what it might be suitable for.

If you've lost track of its application, then the best bet is to measure the permeability and use that as a guide. The lower the permeability, the higher the operating frequency, generally.

Here's a short blurb on measuring toroid permeability:
http://electronbunker.ca/DLpublic/Toroi ... bility.pdf


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 Post subject: Re: Determining the Mix/type of an Unknown Toroid
PostPosted: Jul Tue 11, 2017 4:39 am 
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Howdy Bob,

BobWeaver wrote:
You can't even trust the color coded ones, because different manufacturers use their own color code, and they're not the same.


One would think there would be an ANSI standard on such things. "Evidently not." to quote Mr. Olivander :D.

Quote:
If you can remember what the toroid came out of, and the frequency it was operating at, then that will give some indication of what it might be suitable for.


Fortunately, most of them are still in place in the circuitry they're being used in, Bob. A few are loose and hanging about, but not many.

Quote:
If you've lost track of its application, then the best bet is to measure the permeability and use that as a guide. The lower the permeability, the higher the operating frequency, generally.

Here's a short blurb on measuring toroid permeability:
http://electronbunker.ca/DLpublic/Toroi ... bility.pdf


Great, and thank you very much for this info. I'm also going to check out Amidon's site, and I'm also thinking that the amateur handbook will have some info on this as well.

73,

Randy AB5NI

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 Post subject: Re: Determining the Mix/type of an Unknown Toroid
PostPosted: Nov Sat 11, 2017 8:38 am 
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As a suggestion, you don't need to know the ferrite material, what you need is to know is if it works at your frequency range of interest.
Permeability measurement is covered in a link in another post.

Checking frequency range will be more dependant on what test equipment you have/want to use.
Think about a set-up for sweaping an if amp, (but it will just be the core with input and output link windings.
Also, sweaping is unnecessary, a hand tuned rf gen and a vtvm with rf probe can do it.

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 Post subject: Re: Determining the Mix/type of an Unknown Toroid
PostPosted: Nov Sat 11, 2017 2:55 pm 
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This one is easy.....need 3 bits of data:
---cost of new toroid core
---time required to test N old ones to find what you need
---value of your time

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 Post subject: Re: Determining the Mix/type of an Unknown Toroid
PostPosted: Nov Sun 12, 2017 1:50 am 
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pixellany wrote:
This one is easy.....need 3 bits of data:
---cost of new toroid core
---time required to test N old ones to find what you need
---value of your time

We have a winner!

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 Post subject: Re: Determining the Mix/type of an Unknown Toroid
PostPosted: Nov Sun 12, 2017 4:20 am 
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Location: Perrysburg, OH, U.S.A.
You can always use most any toroid to make a Joule Thief light: http://www.instructables.com/id/Make-a-Joule-Thief/

I've made a couple of them and they do work. I use AA cells removed from things where they're too used up to work. Most things will stop working when a battery runs down to maybe 1 volt or a little less, but the Joule Thief will work until the voltage drops below the base emitter voltage to turn the transistor on, about 0.7 volts or so. I've got a couple using batteries that would no longer power a transistor radio that have worked in intermittent use for a few months now.

John

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