I have noticed an increase this kind of device recently. I seem to remember
from when I played with this that its main issue was loss. IE there is no
way to closely couple the windings enough to transfer enough power to make
it worthwhile. so has there been some revolution here, or is it just some
kind of clever marketing of power wasting rubbish?
I mean, induction hobs could be repurposed as battery chargers using a
plastic plate with a winding inside?

I was thinking about eye great leccy in bathrooms debate.
One other odd thing is that Kitchens have power sockets and water and
nobody seems to worry about that, and yes people do get killed due to this
aspect due to accidents like power cables dropping into sinks or dodgy
cowboy practices in fitted kitchens.
Brian

--
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This newsgroup posting comes to you directly from...
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On 27/01/2017 09:11, Brian Gaff wrote:
I have noticed an increase this kind of device recently. I seem to remember
from when I played with this that its main issue was loss. IE there is no
way to closely couple the windings enough to transfer enough power to make
it worthwhile. so has there been some revolution here, or is it just some
kind of clever marketing of power wasting rubbish?

I've no experience of these, but like you I would think them to be
pretty inefficient. But it only needs a few watts to charge a mobile
phone, so if the charger takes ten times that from the mains would
anyone care? The energy loss would, presumably, just warm the room up a
bit.

I mean, induction hobs could be repurposed as battery chargers using a
plastic plate with a winding inside?

I think you've got a great idea there - hope you patented it before
giving the idea away.

I was thinking about eye great leccy in bathrooms debate.
One other odd thing is that Kitchens have power sockets and water and
nobody seems to worry about that, and yes people do get killed due to this
aspect due to accidents like power cables dropping into sinks or dodgy
cowboy practices in fitted kitchens.

The argument that I've seen is that in a bathroom you might be wet all
over, so the risk is larger. I'm not convinced by this: in a kitchen
you often have both hands wet, and in the event that you touched one
hand on a live wire and the other on say a tap you might get a serious
jolt.


--
Clive Page

Brian Gaff wrote

I have noticed an increase this kind of device recently. I seem to
remember from when I played with this that its main issue was loss. IE
there is no way to closely couple the windings enough to transfer enough
power to make it worthwhile.

Hasn’t been like that for a long time now. If it was ever true.

so has there been some revolution here,

Nope, it was always viable.

or is it just some kind of clever marketing of power wasting rubbish?

Nope, it works fine for lower powered devices like phones, toothbrushes etc.

I mean, induction hobs could be repurposed as battery chargers using a
plastic plate with a winding inside?

Makes more sense to get a dedicated battery charger.

I was thinking about eye great leccy in bathrooms debate.

That’s one of the reasons it was seen with toothbrushes early.

One other odd thing is that Kitchens have power sockets and water and
nobody seems to worry about that,

Because you have to be really stupid to get killed in that situation.

and yes people do get killed due to this aspect due to accidents like
power cables dropping into sinks

Almost no one ever does.

or dodgy cowboy practices in fitted kitchens.

On 27/01/2017 09:11, Brian Gaff wrote:
I have noticed an increase this kind of device recently. I seem to remember
from when I played with this that its main issue was loss. IE there is no
way to closely couple the windings enough to transfer enough power to make
it worthwhile. so has there been some revolution here, or is it just some
kind of clever marketing of power wasting rubbish?

It is a bit inbetween. Very useful for things like toothbrushes where
water could get in the works. Mainly good for modest power.

I mean, induction hobs could be repurposed as battery chargers using a
plastic plate with a winding inside?

Not easily since they would almost certainly see the load as abnormal.

A decent review on the chipsets and pros and con of inductive and
resonant coupled wireless charging is online he

http://www.digikey.co.uk/en/articles...eless-charging

There is no free lunch. A wire will always be more efficient.

--
Regards,
Martin Brown

Martin Brown wrote:

A wire will always be more efficient.

True, but the convenience of inductive charging often outweighs that, my
previous two phones (Nexus 4 and 5) had wireless charging, I had a
charging pad on my bedside table, and a magnetic charging dock in the car.

My phone is typically going to be left by the bed overnight, so it could
trickle charge over many hours rather than one for all it matters, and
in the car it could provide sufficient power to use it in satnav mode
without draining the battery, just by 'throwing' the phone at the dock.

I was quite annoyed that the Nexus 5X didn't have wireless charging, so
didn't buy one ... until I put the Nexus 5 through the washing machine!

"Brian Gaff" wrote in message
news
I have noticed an increase this kind of device recently. I seem to remember
from when I played with this that its main issue was loss. IE there is no
way to closely couple the windings enough to transfer enough power to make
it worthwhile. so has there been some revolution here, or is it just some
kind of clever marketing of power wasting rubbish?
I mean, induction hobs could be repurposed as battery chargers using a
plastic plate with a winding inside?

I was thinking about eye great leccy in bathrooms debate.
One other odd thing is that Kitchens have power sockets and water and
nobody seems to worry about that, and yes people do get killed due to this
aspect due to accidents like power cables dropping into sinks or dodgy
cowboy practices in fitted kitchens.
Brian

--
----- -
This newsgroup posting comes to you directly from...
The Sofa of Brian Gaff...

Blind user, so no pictures please!
I can't see the difficulty. If the item to be charged is not in the field of
the charging winding, the latter will act as an inductance without any more
loss than a transformer with unconnected secondary in a wired charger.
--
Dave W

"Brian Gaff" wrote in message news

I have noticed an increase this kind of device recently. I seem to remember
from when I played with this that its main issue was loss. IE there is no
way to closely couple the windings enough to transfer enough power to make
it worthwhile. so has there been some revolution here, or is it just some
kind of clever marketing of power wasting rubbish?
I mean, induction hobs could be repurposed as battery chargers using a
plastic plate with a winding inside?

I was thinking about eye great leccy in bathrooms debate.
One other odd thing is that Kitchens have power sockets and water and
nobody seems to worry about that, and yes people do get killed due to this
aspect due to accidents like power cables dropping into sinks or dodgy
cowboy practices in fitted kitchens.
Brian


So if you have a wacking great 132 kV mega amps pylon line crossing your
property, how large a tuned circuit resonating at 50 Hz do you need to pull
significant (and undetected) power your way

Andrew

On 27/01/2017 13:13, Andrew Mawson wrote:
"Brian Gaff" wrote in message news

I was thinking about eye great leccy in bathrooms debate.
One other odd thing is that Kitchens have power sockets and water and
nobody seems to worry about that, and yes people do get killed due to
this aspect due to accidents like power cables dropping into sinks or
dodgy cowboy practices in fitted kitchens.
Brian


So if you have a wacking great 132 kV mega amps pylon line crossing your
property, how large a tuned circuit resonating at 50 Hz do you need to
pull significant (and undetected) power your way

A fluoro tube lamp stood on end will do nicely.

There was a case once in the dim and distant past where there were
allotments around a MW transmitter and some enterprising radio Ham built
a circuit to heat his greenhouse from it. This was OK until he built
ones for others and the resonant load affected the transmitter.

--
Regards,
Martin Brown

Martin Brown wrote:
On 27/01/2017 13:13, Andrew Mawson wrote:
"Brian Gaff" wrote in message news

I was thinking about eye great leccy in bathrooms debate.
One other odd thing is that Kitchens have power sockets and water and
nobody seems to worry about that, and yes people do get killed due to
this aspect due to accidents like power cables dropping into sinks or
dodgy cowboy practices in fitted kitchens.
Brian


So if you have a wacking great 132 kV mega amps pylon line crossing your
property, how large a tuned circuit resonating at 50 Hz do you need to
pull significant (and undetected) power your way

A fluoro tube lamp stood on end will do nicely.

There was a case once in the dim and distant past where there were
allotments around a MW transmitter and some enterprising radio Ham built
a circuit to heat his greenhouse from it. This was OK until he built
ones for others and the resonant load affected the transmitter.


Urban myth? Just seems improbable to me that you could draw enough power
from a MW radio transmitter to run any sort of heating but I dare so those
who understand these things will put me right. ;-)

Tim



--
Please don't feed the trolls

Well they do, a person in this very borough got killed by it about three
years ago and there are regularly some near misses in the local papers.

In the case of inductive charging perhaps they use an hf ac signal to
increase the efficiency, aas 50 hz is always going to be ineeficient due to
the low frequency.
Brian

--
----- -
This newsgroup posting comes to you directly from...
The Sofa of Brian Gaff...

Blind user, so no pictures please!
"Rod Speed" wrote in message
...
Brian Gaff wrote

I have noticed an increase this kind of device recently. I seem to
remember from when I played with this that its main issue was loss. IE
there is no way to closely couple the windings enough to transfer enough
power to make it worthwhile.

Hasn’t been like that for a long time now. If it was ever true.

so has there been some revolution here,

Nope, it was always viable.

or is it just some kind of clever marketing of power wasting rubbish?

Nope, it works fine for lower powered devices like phones, toothbrushes
etc.

I mean, induction hobs could be repurposed as battery chargers using a
plastic plate with a winding inside?

Makes more sense to get a dedicated battery charger.

I was thinking about eye great leccy in bathrooms debate.

That’s one of the reasons it was seen with toothbrushes early.

One other odd thing is that Kitchens have power sockets and water and
nobody seems to worry about that,

Because you have to be really stupid to get killed in that situation.

and yes people do get killed due to this aspect due to accidents like
power cables dropping into sinks

Almost no one ever does.

or dodgy cowboy practices in fitted kitchens.

On 27/01/2017 14:57, Tim+ wrote:
Urban myth? Just seems improbable to me that you could draw enough power
from a MW radio transmitter to run any sort of heating but I dare so those
who understand these things will put me right. ;-)

http://message.snopes.com/showthread.php?t=9291

On 30/01/2017 23:04, Vir Campestris wrote:
On 27/01/2017 14:57, Tim+ wrote:
Urban myth? Just seems improbable to me that you could draw enough power
from a MW radio transmitter to run any sort of heating but I dare so
those
who understand these things will put me right. ;-)

http://message.snopes.com/showthread.php?t=9291

I tend to disregard snopes.
I know of at least one incident that snopes puts down as an urban myth
that wasn't.
The one of there being rat in KFC.
The shop in west bromwich was fined for serving rat to a customer that
just happened to work for trading standards.
The shop became a fish and chip shop shortly after.

On Friday, 27 January 2017 16:31:37 UTC, Brian Gaff wrote:
Well they do, a person in this very borough got killed by it about three
years ago and there are regularly some near misses in the local papers.

In the case of inductive charging perhaps they use an hf ac signal to
increase the efficiency, aas 50 hz is always going to be ineeficient due to
the low frequency.
Brian


yes they start at about 100KHz for low power and up to 300KHz for higher power.
I think I remmeber a a figure of GHz for charging over a distance.

"whisky-dave" wrote in message
...
On Friday, 27 January 2017 16:31:37 UTC, Brian Gaff wrote:
Well they do, a person in this very borough got killed by it about three
years ago and there are regularly some near misses in the local papers.

In the case of inductive charging perhaps they use an hf ac signal to
increase the efficiency, aas 50 hz is always going to be ineeficient due
to
the low frequency.
Brian


yes they start at about 100KHz for low power and up to 300KHz for higher
power.

I think I remmeber a a figure of GHz for charging over a distance.

Sounds a bit unlikely given that those are microwave frequencys
with the associated health problems with those.

On 27/01/2017 09:11, Brian Gaff wrote:
I have noticed an increase this kind of device recently.

The gf has an inductive charged vibrator.



--
Adam