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grommeteer 2nd January 2013 11:56 AM

Opinions on Qi, wireless charging of mobile phones etc.
With the new Nokia Lumia and the JBL Powerup I read more and more about wireless charging and the Qi standard.
It seems that in a few years we will all have our little (5W to 10W) inductive transmitters in the living room and in all kinds of public places.
I was not able to find out which freuquency they will be using.
The idea seems to be to have the transmitter running 24/7 with a moderate standby consumption and energy transfer only taking place when a receiver (coil) is placed in the near field.
How many new power plants will we need to power all these standby consumers?
What happens if I place some metal structure in the near field? Say, a wrist watch or a can of beverage? Eddy currents?
"People with pacemakers please do not enter this café. We have have alternating magnetic fields in here."
When is the first vinyl fan going to complain that his phono pre picks up some strange signals?

grommeteer 2nd January 2013 12:05 PM

Operating frequency is 112kHz to 205kHz. So not very far from the audio band.
Parasitic objects can be detected by the transmitter. A cell-phone will communicate with the transmitter when charged. If energy is lost (due to a metal object) and no comms are established, the transmitter will switch off again.

DF96 2nd January 2013 12:43 PM

You probably won't get much energy transfer unless the 'receiver' is resonant, so accidental transfer is unlikely. However, it still seems an inefficient way to charge a battery. People will happily pay for convenience, whatever the energy/financial/ecological cost.

Like everything else we encounter, the electromagnetic spectrum is being steadily polluted by humans and so is rendered less useful than it otherwise could be.

grommeteer 2nd January 2013 02:23 PM

It is interesting how the manage to steal energy from the resonant tank in the receiver. TI are making chips.

firechief 2nd January 2013 03:56 PM

A similar prototype application I worked on involved the charging of batteries inside the human body. These powered a Left Ventricular Assist Device or LVAD that took over part of the function of the human heart. The introduction of any wires into a body results in a serious problem of infection so the designed used low frequency AC charging. Personally I dont like the idea of having batteries in my chest but money was being spent to on the idea. Go figure.

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