[LINK] Some shocking news about wireless electricity

[Adam Todd]

At 06:46 PM 10/06/2007, Glen Turner wrote:
>On Sun, 2007-06-10 at 16:23 +1000, Adam Todd wrote:
>
> > >Then there's the inherent inefficiencies in electronics, and in 
> transforming
> > >one form of energy to another.
> >
> > Agree.  As I detailed in my own example.
>
>Hi Adam,
>
>Oh dear. A electromagnetic field in a wire versus in free space isn't
>"transforming one form of energy to another". Both are electromagnetic.

Glen, I agree, that was from Stewart, but his view is somewhat valid, 
it's all still inefficient.  To convert from 12 volt to 24 volt, one 
needs to drain the 12 volt battery faster, so why not design the 
device to run off 12 volts in the first place?

Then there is the drop from 12 volt to 3.6, 5, 6, 9 volts.  Great, 
it's cheap and easy.  But it has a cost, and sure the old "3 volt 
over" rule doesn't so much apply today as regulators aren't used as 
much, now with efficient switch mode, but there is still a cost.

>In fact, inductive coupling is efficient. Plugpack rectification and
>DC current over thin wires has its own losses and I feel comfortable
>that you could build an inductive charging system with less
>loss. Particularly since the source is a medium voltage AC.

We're assuming it's AC!  Although, we've also got to assume that the 
light bulb was running AC given it was described as a 60 Watt bulb 
:)  Then again, maybe it's just a DC energy saver type bulb.  We 
don't know the facts of the test and example.

We do know the theory, and it's not new, not innovative and not original.

>The problem is that the size and weight required for the inductive
>coils to be efficient is incompatible with the desired handheld form
>for phones, iPods, etc.

This is nearly true.  I use very small inductive coupling for 
transmitters.  Although the power output is very small, the input is 
quite high.  I don't have space for hundreds of windings of coil on 
surface mount microsized boards.

>It is possible that some very clever engineering might see possibilities
>where others have not.

True, as I said in my original comments - I don't have the bottomless 
pity of money to throw into development of such a concept, which is 
why I left it off at a 5W source giving a 300 mW output.  Mind you, I 
can have 30 or 40 of these  transfer modules within range.  That 
doesn't seem to be a limiting factor.  One does not" absorb the 
energy from others, unlike running a very long run of LEDs on a cable :)

>But more likely this is a classic situation where
>a prototype will have excellent performance (being able to be any size
>and shape) but the result will never be suitable for a product.

Very likely.  However, given that most things radiate some kind of 
energy signature, one need only tune into that signal.  Admittedly, a 
1.6 GHz cpu output, isn't really helpful :)  But there is still a 
readable signal up to several meters away.

Now if my mobile could simply absorb that signal, even if tiny, 
that's better than nothing.

You commonly see Solar charges for your car being sold.  They retail 
for around $30, plug onto your battery and that's it.  All it does is 
provide a floating charge, enough to keep the battery topped up all 
the time, the charge is the difference between the battery's natural 
(and cars electronics standby) power consumption and what the cell 
produces.  Don't try and power anything off it though!

> > Yes well, as I said, 5 Watts to power a 300 mW transmitter :)
>
>A poor example because you are trying to modulate the outgoing signal,
>so the amplifying transistors need to be constrained to their linear
>regions rather than their more efficient but non-linear regions
>[simplifying hugely here but the point holds for the more detailed
>explanation].

Yes I guess that's a factor I hadn't considered, given that I wasn't 
trying to charge batteries or power a Laptop from the inductive radiation!

>What it comes down to is the coupling between the input and output
>coils. Have these people come up with a physical design that will
>allow a small device to have an transformer-grade coupling between
>the charger and the device.

I wonder if one needs coils at all?  There are so many other ways of 
inductive coupling.  Maybe they have used pezio devices?  I know I've 
had a brief experiment with the idea, but typically available devices 
aren't for output, rather than input and extremely inefficient.

Just a thought, what about the speakers in mobile phones.  They have 
a coil.  It could be switched into a mode where the coil simply 
absorbs localised EMF and puts it across a charger circuit.  (No idea 
if this is even practical, ben a long time since I looked at speaker 
coils for production of electricity.)

>If they have, the mechanism will be so novel and so, in retrospect,
>obvious that having seen it you will be able to explain it to people.
>Those people will then whack their forehead for not having thought of
>it themselves.

(smile) No doubt :)

Hey I can generate energy using a hall effect.  But that doesn't mean 
it's going to run a laptop!  Yet alone a light bulb!

>But such ideas are scarce. I can count on the fingers of one hand
>people I know that have had such insights to engineering problems
>and I can count on my fingers and toes the people living that have
>had such insights in their careers.

It's an amazing world Glen.  Even the weirdest ideas in discussions 
lead to innovative solutions.  I know, my wife is not "whizz" at 
computers or electronics, but all to often, something unrelated and 
rather bizar inspires an amazing solution.

>And such ideas being so scarce, you are perfectly entitled to be
>skeptical. I just ask that you get the engineering rationale for
>your skepticism correct.

I'm not skeptical, overall.  I think it's highly likely, given the 
further miniturisation of electronics, and the lower voltages 
required to run devices today, that eventually devices will simply 
run off EMF in the air around them.

Gosh I gulp sometimes when I look at current technology.  What was 10 
years ago powered by 48 volts is now powered by 5 volts.

Mobile phones are a fantastic example.  We use to have to have 12 
volts in cells to transmit 500 meters.  Today, we can do that with a 
3.6 volt battery, a complete high speed CPU, LCD display IN 
COLOUR!  And it's got a TX and RX built in, in fact a couple of them!

No, I can see really radical changes in the future, and hopefully a 
migration to very low voltage devices.

> > Then the idea of turning the TV of instead of Standby no longer is
> > relevant because it's charging the phone, laptop, shaver, watch, pace
> > maker, and other devices :)
>
>That's likely to happen,

Except less and less people are going to have a TV that has an EHT 
coil, radiating screen and a huge transformer in the box!  LCD's have 
switch mode power supplies, are extremely efficient, and emit quite 
little EMF. (In comparison.) And there is NO Radiation from the display!

>but with a computer with Powered USB
>in place of the TV in your example. Unfortunately, there is a
>lot of argument that the standard for Powered USB has been
>stuffed with too many compromises to work in the real world
>and we'll probably need a Powered-2 USB before equipment is
>likely to be acceptable to consumers.

(rofl) Oh, yes, that's no joke.  I over load my USB ports all the 
time.  Everything seems to draw power from the USB and the Firewire 
(there's that amazing low voltage again)

I have a MOTU Ultralite.  Like a Sound Desk - you see at rock 
concerts etc.  It's an 8 Channel input mixer (actually it has FOUR 
independent mixers).  It has 10 outputs.  I can switch any input to 
any combinations of outputs.

But it runs off 5 volts.  It runs off a firewire cable (draining the 
laptop battery of course!  Although I got 4 hours of constant 
recording before the Powerbook battery alert popped up!)

Now this kind of thing was unheard of ten years ago, even 5 years 
ago.  You needed power to drive the DSP's, pre-amps.

My goodness this little baby has TWO phantom power signals that 
delivers +48 volts down the mic cables!  All from a 5 volt supply!

>Powered USB will lead to efficiencies because one large power supply is,
>in practice, more efficient than multiple small power supplies.

True, but we need to make the USB source more efficient and the 
batteries bigger in capacity and smaller in size.

>This isn't so much an electrical argument, as one of the economics
>of consumer sales (manufacturers care about cents in a $30 product
>but in a $700 product will allow more expensive engineering, and
>thus sophistication, and thus efficiency).

True.

But you yourself know, what we had 5, 10, 15, 20 years ago, is just 
laughable comnpared to what we have today.