Post by thread:[EE] Neat Charging Mechanism

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. ____________________________________________

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 ____________________________________________

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_OUTbyronTakeThisOuTcc.gatech.edu> wrote: {Quote hidden}> 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. ____________________________________________

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/ ____________________________________________

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}>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. >_____________________________________________

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 <.....adampicKILLspam@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. ____________________________________________

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}

> 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. ____________________________________________

> 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. ____________________________________________

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/ ____________________________________________

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}>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 > > ____________________________________________

> 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. ____________________________________________

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 ____________________________________________

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 ____________________________________________

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.hordKILLspamgmail.com> wrote: {Quote hidden}> > 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. > > > ______________________________________________

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}

> 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 ____________________________________________