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**Rumcajs** · 05-09-2012, 08:31 PM

Originally posted by bklein View Post

Something work-related but coil-related too:
I'm about to look at wireless power using a TI dev kit (bqTesla) and see this diagram on the wireless power site: http://www.wirelesspowerconsortium.c...ctiveness.html
They recommend a copper plate shield and show it totally shielding the alternate side of it. I'm contemplating placing circuitry on this alternate side that cannot tolerate magnetic fields. So what are the options and recommendations for this shield? Is copper best? Iron/steel/aluminum bad?
You guys might like just looking into this technology as they have dedicated TX and RX chips with squarewave drive 1-5-210kHZ and a communication link on top of it. We could perhaps use this for our purposes in some way or another... Their TX unit uses a litz wire coil. The Rx coil is a parallel two wire spiral.
If you guys have any ideas on how to improve efficiency (coil ideas?) let me know!

Hi bklein,

It is difficult to ensure proper contact with the aluminum foil and the wire between, such as contact failure can often turn a lot of detectors in use. When using copper foil has no such problem.

Copper foil is mined from the old monitor data cable cable shield. Sometimes found an aluminum foil, sometimes found an copper galvanized alu foil, and sometimes galvanized iron sheet of copper foil it. The latter is not good, check the magnet.

As this board has on several occasions it was dealing in ferrous metal (iron, cast iron, nickel sprays, cobalt, manganese & Co.) is NO good for detector shielding.

Returning to the cited article: Wireless battery charging is about.
The Fig 3rd. is not from 1-5-210kH, but from 10kHz to 1MHz.

THIS TECHNOLOGY IS THE REAL ENVIRONMENTAL DESTRUCTION! Do not have enough electric smog of human life behind?
More recent time, with an germanium diode the radio signals easy be detected. That was the end ... and not only the transmitters due to the termination, but the electromagnetic garbage, pollution.
What hey write from the biological effects of electromagnetic waves?
How many watts / square cm?
Beautiful New World... for the functional idiots.

So in the detector very good for copper, but aluminum foil is cheaper ...

Good hunting

Rumcajs

**Tepco** · 05-09-2012, 09:47 PM

The shielding added under the primary and above the secondary is important for the safe operation of wireless power transfer. Without shielding, following problems may occur:

the magnetic field may interfere with the device or other objects;
it may cause battery heating
it may circulate current in metallic parts

MD coils are not magnetically shielded! You cannot magnetically shield something that use magnetic field for it’s primary purpose. MD shielding is against electric field, must not interfere with magnetic.

**bklein** · 05-10-2012, 01:19 AM

I had a typo on the frequency range. Should say 95-210khz.
Although this is marketed as "wireless power" it is really just an air core transformer system. It has a discovery mode so that it doesn't sit there and send at full power. Even then the power output is managed to match the demand from the target side.

I am a little intrigued by this copper shield diagram. Let's say I make a copper disk that I place over the top of our MD coil. How does that affect the behavior of the coil? Would it make it faster, more efficient, more powerful, - or just the opposite in all cases?

I am also interested in the communication scheme. The RX side modulates the load demand for sending data to the TX - the TX primary side sees the variation in coil voltage as data. Is this dependant upon a very controlled physical/electrical relationship between the TX and RX modules or could we see the same thing on our PI MD's if we were to look for voltage variances in the MD "on" pulse amplitudes?

**lari** · 05-10-2012, 10:09 AM

greeting
Long ago I did a coil with a copper shield, gave better results than aluminum foil about 20 posto.sada these tapes have no more.

**Rumcajs** · 05-10-2012, 11:14 AM

Hi,

the wireless power transmission is an interesting theme, and big business, therefore it is the future... where is an human is only problem.

Sorry, i m not an fanatic green, only an (i think

) realist man.

The ideas and reklam says:

http://t2.gstatic.com/images?q=tbn:A...lLP5qwkJRna_Bz

and the realities:

http://cdn.zath.co.uk/wp-content/upl...s-charging.jpg

http://www.wirelesspowerconsortium.c...nto-space.html

,,...The figure shows that for a receiver size which would fit a mobile device (loop diameter 0.04 m to 0.1 m) the power transmission must stay below 2 mW to 30 mW in order not to harm any person. This is about two orders of magnitude too low for general power applications...,,

It is cool! 30mW received power is good for charging the laptops or/and wireless phones? hehe...

Currently buying between 2-60W transmitters, see:

http://www.chiptexpro.com/index.php?...products_id=42

It is the future.

Tepco: You are right. It is true.

Good hunting

Rumcajs

**bklein** · 05-10-2012, 02:44 PM

Lari,
I am asking about the effects of the TX coil being covered only on the top side by a copper disk and how it affects TX characteristics. I am not asking about shielding effectiveness of metal shields on RX coils. Look at the diagram I targeted and see how the magnetic flux is shunted across the copper sheet.

Rumcajs,
Yes - interesting statement in the wc link about safety.
So how do MD's play out in this regard? Are you in the wrong hobby?
Refuse to go through airport scanners?
2 MRI's and still alive here.

Seriously though, I don't much think the concept will fly - right now anyway. Too expensive for high volume products and you have to have a charging dock for focused power transfer. For the multiple coil approach, movement of the device will result in temporary loss of power, which could affect operation of the device at the time.

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Copper as shield (wireless power)?

Copper as shield (wireless power)?

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