Where to find ferrite for coils.

[TrickyNekro]

Hello guys,

I have that simple question. I'm playing around ultrasonic transceivers and need a coil to build the oscillation circuit.

But an air coil would be too big for my needs so I need a high frequency able core like ferrite. I'll try Ebay, but I'm posting
just to see if you already have something in mind.

The oscillation will be at 40kHz.


Thanks in advance,

Best Regards, Lefteris
Greece

[waltr]

There are distributors of magnetics in Europe.
Check the following makers and look for a distributor, then call to see if you can get samples.

Philips
Ferroxcube
Fair Rite
Magnetics Inc
Epcos

We have gotten samples shipped to the USA from Poland.

For limited selections some to the electronics part houses should have stock.

[Soeren]

Hi,

I'm playing around ultrasonic transceivers and need a coil to build the oscillation circuit.

But an air coil would be too big for my needs so I need a high frequency able core like ferrite. I'll try Ebay, but I'm posting
just to see if you already have something in mind.

The oscillation will be at 40kHz.

40kHz isn't considered HF, so almost any core will work (although some ferrites are better suited to higher frequencies (eg. a couple of MHz).

What kind of core are you after  (toroid, potcore or something else)?
A potcore will probably be the easiest to wind, if you need lots of turns - how large an inductance do you need?

Even winding the coil on a ferrite slab (or a piece of same) from an AM radio will reduce the size

If you can find an epoxy glued core in something trashed, cut the wires if possible and boil it in water for around 20 minutes to soften the epoxy (it becomes soft like hot caramel or cold syrup) and pull it apart with pliers (Careful: Hot when boiled, as it says om some TV-dinners).
(Don't use a pot used for food tough, epoxy is bad in that respect).


The page  Ultrasonic Transducers, Generating, detecting & processing ultrasonic signals may be of some help with the US in general.

[TrickyNekro]

Thanks for the suggestion waltr, I'll be searching right away.

To Soeren:

Hi,
40kHz isn't considered HF, so almost any core will work (although some ferrites are better suited to higher frequencies (eg. a couple of MHz).

Yes, But I think most iron cores won't work at these frequencies. And I think steel cores won't either.
These kinda of cores are better suited for very low frequencies, like the mains.

What kind of core are you after  (toroid, potcore or something else)?
A potcore will probably be the easiest to wind, if you need lots of turns - how large an inductance do you need?

Anything that will work, toroids must be having the lower magnetic loses due to shape,
But I was thinking of a rod at first. Like the old radio antennas.

I want to build an oscillation circuit, to get some nice voltage to the transducer. Based on calculations, the transducer behaves
like a capacitive load of 4nF. So I need a coil that is 4mH.
If I use an air core of about 10mm diameter then I would need more than 200 windings to get the inductance needed. And that's
an overkill cause I'm aiming to build a compact module, when I finish prototyping.

Even winding the coil on a ferrite slab (or a piece of same) from an AM radio will reduce the size

Quite though of the same, but calculations may be a little more difficult, not that I'll have any problem with them.
Darn, the physics I study all these years

The page  Ultrasonic Transducers, Generating, detecting & processing ultrasonic signals may be of some help with the US in general.

Thanks for the suggestion, every little bit comes in handy. But anyways, my Uni already has many white papers to cover than need.