Ferrite rod, side by side or in line - Page 4

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Re: Ferrite rod, side by side or in line
On Monday, October 15, 2018 at 7:31:04 AM UTC+2, Jasen Betts wrote:
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I am looking for about 3-5 US cents cost

Re: Ferrite rod, side by side or in line
On Sunday, October 14, 2018 at 7:18:48 PM UTC-4, Klaus Kragelund wrote:
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Huh, that was going to be my suggestion.  Two e-cores or something.  

Maybe someone makes them bonded to some metal that can be soldered down?  

George H.  
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Re: Ferrite rod, side by side or in line
On Monday, October 15, 2018 at 10:45:06 AM UTC-4, George Herold wrote:
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Or some clip?  
http://ferroxcube.home.pl/prod/assets/plane_fr.pdf

(random search for planar e-cores)
GH
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Re: Ferrite rod, side by side or in line

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Buy a troid ferrite and slice it in half, place the barrier between (use  
Nomex at 1500V / mil)  I would not go any higher than a 5 mil gap as  
that is actually ten mils with the dual break.  Coupling will occuur,  
but not much. power transfer capability will suffer as that gap  
increases.  The toroid encapsulates the flux circuit and gives you the  
best chance of the most efficient method for this.

  You could use laminated stack toroid halves if the frequency is low  
enough.

  There is also a way to assemble laminate stacks with insulator sheets  
between each layer that would allow the construction of a pair of  
windings with high isolation between them.

  As that gap increases, your "transformer" transforms into a sniffer  
and capacity to make power moves toward nil.

Re: Ferrite rod, side by side or in line
On Monday, October 15, 2018 at 2:28:16 AM UTC+2, snipped-for-privacy@decadence.org wrote:
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I need to bridge a 3mm gap, so no can do

By the way, using coreless spiral PCB transformer, I have about 60% efficiency. But, it's a pain to mount a PCB vertical on another PCB, so the full cost of the solution is high, since production needs special equipment to mount it

Using a standard drumcore, I could come down to 3 cents cost, and no production hassle

Re: Ferrite rod, side by side or in line
snipped-for-privacy@googlegroups.com:

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Then...  power transfer no can do.

  If your application is a wireless charge device, the coupling does work,  
but is very inefficient.

  Good for a toothbrush or cell phone battery, but not so much for a high  
capacity device like motorized vehicles.

  The idea is a reduced carbon footprint, not a larger one.

Re: Ferrite rod, side by side or in line
On Monday, October 15, 2018 at 1:24:05 PM UTC+2, snipped-for-privacy@decadence.org wrote:
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I have it working, just need to reduce cost if possible

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Efficiency about 60% is easy, I think for wireless power at limited supply load that is quite good

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I need < 5W

I don't care, spend your time asking the Chinese or Americans to reduce their carbon footprint, not my small power supply

Re: Ferrite rod, side by side or in line

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By this you mean turns ratio over coupled voltage efficiency?

  I am sure also you are reading it no load.  Efficiency drops severely  
when you actually try to drive a load.

  The key is the complete magnetic circuit.

  Those core half faces are what need to be as close together as possible.  
So those need to be at your 3mm spacing to take your readings and do your  
characterizations from.  

  There are long, flat cores that are pre split and faces polished that  
your windings could go on without much profile height rise.

  Like little sticks of gum with little blocks on the ends.

Re: Ferrite rod, side by side or in line
On Monday, October 15, 2018 at 1:28:48 PM UTC+2, snipped-for-privacy@decadence.org wrote:
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I have a load of about 1W, good efficiency

Cheers

Klaus

Re: Ferrite rod, side by side or in line

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  Then your solution is a pancake flat pot core pair and use hand wound  
"(scatter wound is fine) flat form windings that spiral in and back out.
epoxy stripes lock it in place and the pot core form factor encapsulates  
the stray flux.

  All you need are physical impressions and steps on the mating parts to  
insure that correct alignment ocuurs.

  You can do it core free with the pancake winds, just a lot less  
efficient.  Then misalignments are less a problem and cost goes way  
down.

  Your dollar figure for what you want this to add to the cost of your  
product is very low.  ANY configuration will likely have a higher cost  
than that which you are projecting in this thread.

Re: Ferrite rod, side by side or in line
On Sunday, October 14, 2018 at 6:39:44 PM UTC-4, Klaus Kragelund wrote:
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I take it the barrier is already in place?  The barrier is usually between the coil and the core, no?  

Rick C.  

Re: Ferrite rod, side by side or in line
On Monday, October 15, 2018 at 4:21:48 PM UTC+2, snipped-for-privacy@gmail.com wrote:
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The barrier is between the two coils

Like this:

http://www.efxkits.com/blog/wireless-power-transfer/

Re: Ferrite rod, side by side or in line
On 10/14/18 23:39, Klaus Kragelund wrote:
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The question here is, what is the application ?. If you just need  
isolation (plastic barrier), then there may be better ways of doing
that other than a transformer. If you must use coils, then a flat
pancake coil at each side of the plastic barrier, both tuned to
resonance, sounds like a possible way to go. Also the best way if
you want to transfer power, as in a wireless charger...

Chris


Re: Ferrite rod, side by side or in line
On Monday, October 15, 2018 at 8:11:41 AM UTC-7, Chris wrote:
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In terms of regulatory compliance, a design with half-pot-core
on each side would be somewhat self-shielding, and would
have higher inductance (so you can use lower frequency
and presumably get better Q).   It'd be hard to stack a high
set of flat pancake windings to match a bobbin in half
a  pot core.    Pot cores, though, are likely not a low-cost winner.

It's possible to use a pot core in the power-source side, with pancake
receiver windings, if the economics (one source, many receivers) work.

Pot core halves are brittle; potting or molding would be a good precaution.

Re: Ferrite rod, side by side or in line
On 10/15/18 21:18, whit3rd wrote:
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I was just thinking that a pancake format would maximise transfer area
across the effective 3mm airgap. There's also other considerations, such
as what frequency to use, rfi shielding, though running both coils
at resonance could minimise harmonics. What frequency ?. Guess anything
from 100KHz upwards of 1 or 2 Mhz as a first stab, but it would need
some labwork to see what's feasible in terms of power transfer,
efficiency and any heating effects. Ferrites may help, say, flat sheet
ferrite, would be cheaper that pot cores, where only the larger sizes
could provide a decent transfer area across the gap...

Chris

Re: Ferrite rod, side by side or in line
On Monday, October 15, 2018 at 4:18:30 PM UTC-4, whit3rd wrote:
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Right, I was thinking two (planar) e-cores would be sorta similar.
(Klaus is a clip cheaper than glue?  I have no knowledge of high  
volume stuff, but it's interesting.... maybe you don't have enough
area for a planar thing.)

George h.  

Re: Ferrite rod, side by side or in line
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Why use any shape?  FYI, a ferrite plate on either side of the board, with a  
width:gap ratio around 30:1 has an average permeability of ~10 for planar  
windings.

Still a glue step, but you can buy self-adhesive ferrite plates for EMI  
shielding.  Which is exactly what you're doing here. :)

Tim

--  
Seven Transistor Labs, LLC
Electrical Engineering Consultation and Design
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Re: Ferrite rod, side by side or in line
On Tuesday, October 16, 2018 at 1:45:38 AM UTC-4, Tim Williams wrote:
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OK... I was thinking the little E tabs would help guide the B-Field :^)
Or fit into slots on the pcb.  
Still I don't know how you do anything for $0.03-0.05.  
George H.  

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Re: Ferrite rod, side by side or in line
On Sunday, October 14, 2018 at 8:49:37 AM UTC+2, whit3rd wrote:
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Good point. I will do both, and test in EMC chamber to verify the difference in far field emissions

Re: Ferrite rod, side by side or in line
On 14/10/18 17:49, whit3rd wrote:
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End-to-end, but broad and flat - you need to increase the diameter
from rods up to flat slabs, like pancake coils. Leakage will come
mostly around the periphery, so increasing the diameter means a
higher percentage is far from the periphery.


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