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'[EE] Neat Charging Mechanism'
2004\10\20@195947 by Mike Hord

picon face
My wife and I just bought a Sonicare Elite ultrasonic electric
toothbrush.  Unpacking it, I discovered that the charging unit
and the toothbrush base unit have no charging contacts!

Apparently, the charger works through induction.

Unfortunately, as this is a new item at $120, I doubt my wife
will let me fiddle with it too much, even if I *promise* I can
put it back together.

Mike H.
____________________________________________

2004\10\20@201829 by Byron A Jeff

face picon face
On Wed, Oct 20, 2004 at 06:59:45PM -0500, Mike Hord wrote:
> My wife and I just bought a Sonicare Elite ultrasonic electric
> toothbrush.  Unpacking it, I discovered that the charging unit
> and the toothbrush base unit have no charging contacts!
>
> Apparently, the charger works through induction.
>
> Unfortunately, as this is a new item at $120, I doubt my wife
> will let me fiddle with it too much, even if I *promise* I can
> put it back together.

Not that unusual. Essentially every DC power supply has line isolation
via induction in the transformer. So if you put half the coil in the base
and the other half in the toothbrush, you can transfer power.

Now I'm sure it's not real efficient. However toothbrushes, shavers, and
the like have low duty cycles.

So it's a perfect match then.

BAJ
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2004\10\20@210050 by Jinx

face picon face
> Not that unusual

I had a look at articles like this a couple of months ago

www.auckland.ac.nz/cir_newsevents/index.cfm?action=display_news&news_
id=3817

A friend had asked if it was possible to transfer energy through
a window (her landlord wasn't keen on holes being drilled)

____________________________________________

2004\10\20@230557 by Josh Koffman

face picon face
The Oral-B toothbrushes used to do the same, I don't know if they
still do. Also, there was a startup that aimed to make a mousepad
looking device that would charge electronic devices placed on top of
it, provided they had the right bits inside. Nice idea...however it's
been a few years, I forget the name, and I haven't seen a commercial
product doing that yet so...

Josh
--
A common mistake that people make when trying to design something
completely foolproof is to underestimate the ingenuity of complete
fools.
       -Douglas Adams

On Wed, 20 Oct 2004 20:18:28 -0400, Byron A Jeff <spam_OUTbyronTakeThisOuTspamcc.gatech.edu> wrote:
{Quote hidden}

____________________________________________

2004\10\20@233446 by Herbert Graf

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face
On Wed, 2004-10-20 at 19:59, Mike Hord wrote:
> My wife and I just bought a Sonicare Elite ultrasonic electric
> toothbrush.  Unpacking it, I discovered that the charging unit
> and the toothbrush base unit have no charging contacts!
>
> Apparently, the charger works through induction.

Neat yes, but certainly not new. We used to have an electric toothbrush
about 15 years ago that did the same, I'm sure it goes further back then
that.

The clear benefits is it can be made absolutely waterproof, good in a
bathroom environment! :) TTYL

-----------------------------
Herbert's PIC Stuff:
http://repatch.dyndns.org:8383/pic_stuff/

____________________________________________

2004\10\20@235742 by M. Adam Davis

flavicon
face
Radio electronics had an project quite some time ago that used this
method.  It was a laser pointer (back when the red laser diode was $70 -
for the cheapie) with three nicads and a charging coil.  The charging
base was even simpler.  If there's a lot of interest I can try to find
it and scan the schematic.

-Adam

Mike Hord wrote:

{Quote hidden}

>_____________________________________________

2004\10\21@085147 by Josh Koffman

face picon face
I remember that article! I really wanted to build one...but as you
mentioned, parts were a bit dear. Of course, at that point my skills
aren't what they are now, and I probably would have ruined the diode
anyways.

I really want to do this on a product I've been thinking of. The
"head" of the unit would need to rotate continuously. I've thought
about brushes, but I am worried about the cost/lifetime issue.
Induction would be super sweet, I worry about it interfering with
outside devices though. If I was really clever (which I'm not) I could
make the induction part of the switching power supply. That would
reduce the size of the transfer coils needed, right? Any idea if I
could get reasonable efficiency trying to transfer ~200W of power like
this?

Josh
--
A common mistake that people make when trying to design something
completely foolproof is to underestimate the ingenuity of complete
fools.
       -Douglas Adams

On Wed, 20 Oct 2004 23:57:16 -0400, M. Adam Davis <.....adampicKILLspamspam@spam@ubasics.com> wrote:
> Radio electronics had an project quite some time ago that used this
> method.  It was a laser pointer (back when the red laser diode was $70 -
> for the cheapie) with three nicads and a charging coil.  The charging
> base was even simpler.  If there's a lot of interest I can try to find
> it and scan the schematic.
____________________________________________

2004\10\21@085357 by Lawrence Lile

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face
You'll find your Sonicare Ultrasonic toothbrush has a PIC in it.  A 12Cxxxx IIRC.

It generates a ~~1MHZ acoutstic pulse on top of the ~~2 khz mechanical oscillation, or thereabouts.  I know this because I had to measure the ultrasonic part of it.  

The induction charger is pretty cool, and simple.  Allows the toothbrush to be completely sealed agaist water and still charge.  You'd have a devil of a time getting it apart since some parts are sonic welded.  I had to cut them apart when I was testing them.  


-- Lawrence Lile, P.E.
Electrical and Electronic Solutions
Project Solutions Companies
http://www.projsolco.com

> {Original Message removed}

2004\10\21@093030 by Jake Anderson

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face
check out the heads in VCR's
they opperate on a simmilar principlle (induction)
perhaps at a lower power level

> {Original Message removed}

2004\10\21@094110 by Mike Hord

picon face
> Now I'm sure it's not real efficient. However toothbrushes, shavers, and
> the like have low duty cycles.
> BAJ

I would expect it's horribly inefficient.  The coil for the charger is below
base, so the coil for the chargee must be in the very bottom of the
handle, which means that the coupling between the two must be kind
of poor.  Nothing I see makes me think there's a lot of electronics or
any kind of ferrous core to the coil in the charger, so I expect its a
60 Hz air/plastic core transformer.

Still, it's a very cool idea.  A good way to transmit the tiny trickle of
power needed to keep the brush working for the 8 minutes a day it
needs to operate.

Mike H.
____________________________________________

2004\10\21@094610 by Mike Hord

picon face
> You'll find your Sonicare Ultrasonic toothbrush has a PIC in it.  A 12Cxxxx IIRC.

Aha!  I knew there was something inherently attractive about it.

> It generates a ~~1MHZ acoutstic pulse on top of the ~~2 khz mechanical
> oscillation, or thereabouts.  I know this because I had to measure the ultrasonic
> part of it.
>
> The induction charger is pretty cool, and simple.  Allows the toothbrush to be completely sealed agaist water and still charge.  You'd have a devil of a time getting it apart since some parts are sonic welded.  I had to cut them apart when I was testing them.

I'll just have to keep an eye open for them at garage sales, then.  Do
you happen
to recall how smart the charging circuit is?  If I leave it in the
charging cradle, will
it slowly kill the NiCad, or is it smart enough to throttle back the
charge current?

Mike H.

> -- Lawrence Lile, P.E.
____________________________________________

2004\10\21@104818 by Herbert Graf

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face
On Thu, 2004-10-21 at 09:41, Mike Hord wrote:
> > Now I'm sure it's not real efficient. However toothbrushes, shavers, and
> > the like have low duty cycles.
> > BAJ
>
> I would expect it's horribly inefficient.  The coil for the charger is below
> base, so the coil for the chargee must be in the very bottom of the
> handle, which means that the coupling between the two must be kind
> of poor.  Nothing I see makes me think there's a lot of electronics or
> any kind of ferrous core to the coil in the charger, so I expect its a
> 60 Hz air/plastic core transformer.

Actually the ones I've taken apart DID have a ferrite core. The little
"post" the headset sets on is actually a ferrite core covered in
plastic. I don't know if the modern ones are built the same way though.
TTYL

-----------------------------
Herbert's PIC Stuff:
http://repatch.dyndns.org:8383/pic_stuff/

____________________________________________

2004\10\21@110700 by M. Adam Davis

flavicon
face
A company I previously worked for used this for dynamic industrial fan
balancing.  The rotating ring had 4 chambers with liquid, opposite
chambers connected by a tube (two tubes).  Each chamber had heaters, and
if you heated one chamber, fluid flowed to the opposite side changing
the balance of the thing.

The heaters required quite a bit of power, and AFAIR they used an
inductive ring to send both power and control signals to the circuitry
located on the rotating assembly.  The fans these things balanced were
usually huge (12 foot diameter) fans used in cement plants and other
processes where the fan would continually build up an unbalanced coating
of some material or another.

There are patents galore covering this technology.  I suspect the main
issues are the fact that the core is split and you need a specially
shaped core to get the best possible, but still low, efficiency.

-Adam

Josh Koffman wrote:

{Quote hidden}

____________________________________________

2004\10\21@112520 by Mike Hord

picon face
> Actually the ones I've taken apart DID have a ferrite core. The little
> "post" the headset sets on is actually a ferrite core covered in
> plastic. I don't know if the modern ones are built the same way though.
>
>
> TTYL

Mine has no headset or post.  Think cylindrical handle which sits in a
a cup.  No evidence that the coil is in the cup, and the base is quite
light and thin.

Still, a neat idea.

Mike H.
____________________________________________

2004\10\21@114356 by Harold Hallikainen

face picon face
An interesting 50/60 Hz transformer that carries a kw or two and has a big
air gap is the Austin Ring Transformer
(http://www.austin-insulators.com/radio/xfmr.html). It's commonly used to
get AC power onto an RF hot tower to drive the lights on a series fed AM
tower. I've always been amazed how they work. You could run a lot of
toothbrushes with one of these!

Harold



--
FCC Rules Online at http://www.hallikainen.com
____________________________________________

2004\10\21@114716 by olin_piclist

face picon face
M. Adam Davis wrote:
> There are patents galore covering this technology.  I suspect the main
> issues are the fact that the core is split and you need a specially
> shaped core to get the best possible, but still low, efficiency.

The maximum energy transfer for the mass and volume may be low due to the
large air gap, but that does not mean efficiency has to be low.

One of our current projects is the follow on to a rotating LED display.  A
picture of the existing product is at
http://www.embedinc.com/olin/eyeball.jpg.  Power is transferred to the
rotating arm via a transformer with rotating secondary.  In this version the
primary is driven directly from wall power.  The new version has a lot more
LEDs and requires 10s of watts.  In that the secondary is chopped at 10s of
KHz and works quite well.  Efficiency is reasonable.


*****************************************************************
Embed Inc, embedded system specialists in Littleton Massachusetts
(978) 742-9014, http://www.embedinc.com
____________________________________________

2004\10\21@121621 by Bob J

picon face
They will work for a 3-4 days using them twice a day without charging.
Hasn't been an issue for me, because it will warn you if the charge
is low and the cradle is the best place for it anyway.  I have one and
my gums seem to be really happy with the Sonicare.  My dentist
recommended it to me.  The thought of wondering if it had a PIC in it
had crossed my mind on many early mornings...

Regards,
Bob

On Thu, 21 Oct 2004 08:41:08 -0500, Mike Hord <mike.hordspamKILLspamgmail.com> wrote:
{Quote hidden}

> ______________________________________________

2004\10\21@125352 by Lawrence Lile

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face
IIRC the charging mechanism is dumb as a post.  The batteries are probably not going to be long lived.  This is, of course, and advantage because you can then take the thing apart, analyze it, pop in some NImH's and use it some more.

-- Lawrence Lile, P.E.
Electrical and Electronic Solutions
Project Solutions Companies
http://www.projsolco.com

> {Original Message removed}

2004\10\21@131235 by John Ferrell

face picon face
> I would expect it's horribly inefficient.  The coil for the charger is
> below
> base, so the coil for the chargee must be in the very bottom of the
> handle, which means that the coupling between the two must be kind
> of poor.  Nothing I see makes me think there's a lot of electronics or
> any kind of ferrous core to the coil in the charger, so I expect its a
> 60 Hz air/plastic core transformer.

If you make the inductors resonant the efficiency will surprise you.
If you raise the frequency, it gets a lot easier to make them resonant.
If you are worried about patent violations, it is highly probable that Tesla
had the necessary patent and it is now public domain...

John Ferrell
http://DixieNC.US


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2004\10\21@143402 by Harold Hallikainen

face picon face
Even if the charger is dumb as a post, my Sonicare has been going for
about 10 years and still works fine. Anyone remember the Seinfeld episode
that concentrated on the Sonicare?

Harold



--
FCC Rules Online at http://www.hallikainen.com
____________________________________________

2004\10\22@011321 by David Schmidt

flavicon
face
Forget who did it, but there's a design to charge electric vehicles using a
'paddle' from a "gas pump" that gets inserted into a rectangular slot in the
electric vehicle - no contacts, all induction.  I believe you can still see
this design being used at Costco at their electric car parking spots.

Dave

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