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> Epoxy with ferrite powder, Does anyone make such thing?
kender
  Posted: May 16, 2007 07:15 pm
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Colleagues,

Iím looking for an epoxy loaded with ferrite powder. Something that can be cast or molded or overmolded. I realize that such material would have a lower permeability compared to the standard solid ferrite, but high permeability is not required in my application. I normally use pot cores, but there are no small enough pot cores for my present project. Essentially, I want to mold one myself.

Any references, insights and inspirations are greatly appreciated!

Sincerely,
Nick


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tekwiz
Posted: May 16, 2007 07:30 pm
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I am sure there must be, but finding some in small quantities might be a problem. You can always crush some scrap ferrite, sift out the finest powder, & then combine it with the minimum amount of epoxy. This will get you a substance very close to commercial ferrite. How small a core do you need? I have seen transformers smaller than a pencil eraser, & I am sure they come smaller than that. cool.gif


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kender
Posted: May 16, 2007 08:06 pm
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QUOTE (tekwiz @ May 16 2007, 07:30 PM)
How small a core do you need? I have seen transformers smaller than a pencil eraser, & I am sure they come smaller than that. cool.gif

I have looked for the miniature pot cores. The smallest I could find were the 5.8mm ones made by TDK. That's not small enough, and on top of that I couldn't find a place where to buy or sample them. What vendors for miniature pot cores do you know?

I need a core 3.5mm in diameter (half the diamter of a pencil eraser), 1mm deep (depth can be adjusted with grinding... possibly).


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kellys_eye
Posted: May 16, 2007 10:17 pm
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Sounds like a typical surface-mount solution.

I have some SM boards with coils on them of about this size. They came from an old hand-held stock control push-button thingy wiht LCD display.

This is where the ubiquitious junk box comes in handy.


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kender
Posted: May 17, 2007 12:26 am
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QUOTE (kellys_eye @ May 16 2007, 10:17 PM)
Sounds like a typical surface-mount solution.

...but it's not (if you're talking about standard SMT chip inductors in 0402, 0603, 0805, etc). What I really need is a pot core, actually, one half of a pot core.


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tekwiz
Posted: May 17, 2007 06:14 pm
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Do you need the bobbin as well? I will check my junk, I might have one, but the chances of disassembly while keeping the bobbin intact are slim, as you have to heat them to get them apart. cool.gif


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Trouble rather the tiger in his lair, than the sage among his books.
For to you, kings & armies are things mighty & enduring.
To him, mere toys of the moment, to be overturned at the flick of a finger.

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kender
Posted: May 18, 2007 02:21 am
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QUOTE (tekwiz @ May 17 2007, 06:14 PM)
Do you need the bobbin as well? I will check my junk, I might have one, but the chances of disassembly while keeping the bobbin intact are slim, as you have to heat them to get them apart. cool.gif

I don't need a bobbin, becasue I'll use only one half of a pot core, and the bobbin occupies both. If you find miniature pot core small transformers in your junk, could you send me a photo?


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tekwiz
Posted: May 18, 2007 02:25 am
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I looked , & the smallest pot core trafos I have are just over 6mm in dia. Can you use toroids? I have a few that are 4mm in diameter. cool.gif


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kender
Posted: May 18, 2007 02:35 am
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QUOTE (tekwiz @ May 18 2007, 02:25 AM)
I looked , & the smallest pot core trafos I have are just over 6mm in dia. Can you use toroids? I have a few that are 4mm in diameter. cool.gif

Thanks for looking! Although, I need a geometry similar to a pot core. I'll see if a small pot core can be machined out of this stuff: http://www.eccosorb.com/catalog/eccosorb/MF.pdf. The material is designated as "lossy", but at my low frequency the losses might be acceptably small.


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tekwiz
Posted: May 18, 2007 02:41 am
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Interesting material. I'll bet you could make a similar product by loading epoxy with the magnetic toner carrier used in copiers & laser printers. Then you could cast your own net shape. cool.gif


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Trouble rather the tiger in his lair, than the sage among his books.
For to you, kings & armies are things mighty & enduring.
To him, mere toys of the moment, to be overturned at the flick of a finger.

Fortuna favet fortibus.
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