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Toroid core

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transistor495

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I've taken a number of toroid cores out of SMPS's used for desktop computers. My questions is how to know that whether they're powdered iron cores or ferrite cores or something else?

I assume those SMPS's are switched at something 15KHz or like that. So they would be just iron cores? They shows conductivity on surface using DMM test. I hope ferrite cores won't conduct. Also I'm aware of that the cores will be polished with non conductive coating. I've removed that before testing.

I want to use them for 10.7MHz FM IF stages and discriminator stages. Is that sufficient for this purpose? Please enlighten me.
 
There are more types of ferrite and iron dust used in inductor cores that you can shake a stick at!

At a quick guess, it would be safe to assume that the SMPS toroids would be unusable at 10.7Mhz.

Unidentified toroid core are just that, UROs! (Unidentified Round Objects).

Unless you have equipment to make measurements of inductance and Q (Loss Resistance), you are wasting your time.

How do I know? I have been there, torn my hair out when things that should work did not.

JimB
 
Most modern switchers run between 80kHz and 1.5MHz.
 
I assume those SMPS's are switched at something 15KHz or like that. So they would be just iron cores? They shows conductivity on surface using DMM test. I hope ferrite cores won't conduct. Also I'm aware of that the cores will be polished with non conductive coating. I've removed that before testing.
Ferrites are conductive. They just have a much higher resistance than an iron core.
 
Ferrites are conductive. They just have a much higher resistance than an iron core.

sure you are not thinking of nickel cores? ferrite, by definition, is ceramic and might as well be an insulator. this is an advantage since it does not require laminations to prevent parasitic currents in the core.

as opposed to some wound and enamaled toroids made of nickel sheet rolled into the toroid form.

dan
 
After having a look at amidoncorp website, I believe those are not ferrite toroids( almost sure ). So I've to go in search of ferrite ones.
 
In my experience ferrite is conductive, albeit very poorly.

It's fine to treat it as an insulator, except at high voltages.
 
Put a ferrite core on a magnet and see what happens... you might reconsider them being an "insulator".
 
Whether conductive or not I'm too much specific about my application...so I had a look at amidoncorp website and found 67 material toroids might be excellent for my application. Local availability of same spec.s is searching on.
 
Put a ferrite core on a magnet and see what happens... you might reconsider them being an "insulator".

What do you mean?

Something can be magnetic and still be an electrical insulator.
 
Something can be magnetic and still be an electrical insulator.

Really... how about an example?

What is true is that not all conductive materials are magnetic i.e. aluminum.
 
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Really... how about an example?

What is true is that not all conductive materials are magnetic i.e. aluminum.

You've got me there.

Well there's no strong link between electrical conductivity and magnetism, for example ferrite is a very poor conductor (much worse than most metals) yet it's very magnetic.
 
Look at Micrometals powdered iron 18 material mix... could right, it's recomended for DC chokes ≥50KHz and green/red coloring.

**broken link removed**
 
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