On Sun, 12 Oct 2014 14:14:53 -0700, Jim Thompson
wrote:

On Sun, 12 Oct 2014 14:03:08 -0700, RobertMacy
wrote:

On Sun, 12 Oct 2014 13:25:32 -0700, Jim Thompson
wrote:

On Sun, 12 Oct 2014 13:17:04 -0700, RobertMacy
wrote:

On Sun, 12 Oct 2014 12:45:29 -0700, Jim Thompson
wrote:

I need a SWAG on this, just to see if it's feasible...

Two inductors (solenoids) with Ferrite cores, each ~5mm in diameter
and separated by ~5mm spacing.

What coupling coefficient might I expect?

(Essentially no load on the "receiving" inductor except natural
losses... and I could tune or not.)

...Jim Thompson

5mm rods, how long? what orientation? end to end? side by side?

audio ferrites? low perm ferrites?

I don't know. What would be best? ~100kHz sinusoidal drive

...Jim Thompson

obviously, best orientation depends on length.

from memory rods usually are 4:1 up to 10:1 aspect ratio rarely longer,
they break pretty easily. surprisingly the aspect ratio determines more
the 'effective' permeability much more than the basic permeability, like
with a 4:1 anything with more than 100 rel perm makes NO difference.

do you have any way to 'close' the magnetic path just a bit? Tuning makes
a BIG difference! on getting a huge voltage out of it.

I can make some 'guesses' or spend some time to look at it in a bit more
detail over night and get back to you with justifications for why do this
versus do that.

Cross talk you can get some good estimates. If this is for a
'communication' at all; we should discuss that a bit too.

This is an RFQ for a slow speed (~100bps) data link "magnetically",
with ~5mm gap.

I'm just wondering feasibility before sticking my neck out.

...Jim Thompson

Data? That can't miss at 5 mm. I've used similar geometries to
transfer enough power to run a microprocessor-based electric meter
*and* send the data back over the same path, more like 25 mm.

Get an assortment of small unshielded drum-core inductors from Digikey
and measure things. Drums have a nice geometry for axial coupling.
Resonating both ends will help keep the power requirement down. 10 to
50 KHz carrier should be fine. You could get volts at the receive
coil.




--

John Larkin Highland Technology, Inc

jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com