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'[EE] DIY inductive charging'
2011\11\28@171543 by David

flavicon
face
Hello,

I'm looking at DIY inductive charging, to top up small batteries.
Undecided on the actual battery so far, I'm more interested in the
inductive side for now.  Perhaps an AAA or LIR2032.

I've seen a few pages such as this one:
http://donklipstein.com/samschem.htm#schras4

Has anybody made a small inductive charger that worked?  I would be
interested in any pointers.

Davi

2011\11\28@172918 by Josh Koffman

face picon face
On Mon, Nov 28, 2011 at 5:15 PM, David <spam_OUTlistsTakeThisOuTspamedeca.net> wrote:
> I'm looking at DIY inductive charging, to top up small batteries.
> Undecided on the actual battery so far, I'm more interested in the
> inductive side for now.  Perhaps an AAA or LIR2032.
>
> I've seen a few pages such as this one:
> http://donklipstein.com/samschem.htm#schras4
>
> Has anybody made a small inductive charger that worked?  I would be
> interested in any pointers.

Mouser has an eval kit:

http://www.mouser.com/cymbetcbceval11/

I've never touched it, but maybe you can get some useful info from it.

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

2011\11\28@195352 by RussellMc

face picon face
A major point that is missed in the toothbrush circuit that doesn't
matter so much there but which does in more general applications is
that the receive circuit will get VASTLY more range if it is resonant.
Vastly.
If you can get the two "transformer core halves" in close proximity
then resonance is not absolutely essential, but still a good idea. At
any range you must have resonance for any significant power transfer
at all.

I have many more refs and comments in this area if of enough interest.
I have the MITS metres range PhD paper and refs here somewhere.
And much more.

Excellent advice in Microchip AN710
AN710 Antenna Circuit Design for RFID Applications

              http://ww1.microchip.com/downloads/en/AppNotes/00710c.pdf

______________________


These should open up some mental filters :-) :

_____________

NOT powering but YEE HA !!!!!!!!!!!!!!!!!!!!!!!!!!  (2mm dia, 80
turns, 14 micro wire, fly-flown ... :-) )

Using miniature sensor coils for simultaneous measurement of
orientation and position of small, fast-moving animals
C. Schilstra, J.H. van Hateren *
Department of Neurobiophysics, Uni6ersity of Groningen, Nijenborgh 4,
Groningen, NL-9747 AG, The Netherlands Received 19 January 1998;
accepted 9 March 1999

          http://iwi.eldoc.ub.rug.nl/FILES/root/1998/JNeurscMethSchilstra/1998JNeurosciMethSchilstra.pdf

And:
BLOWFLY FLIGHT AND OPTIC FLOW
I. THORAX KINEMATICS AND FLIGHT DYNAMICS
C. SCHILSTRA AND J. H. VAN HATEREN*
Department of Neurobiophysics, University of Groningen, Nijenborgh 4,
NL-9747 AG Groningen, The Netherlands

            jeb.biologists.org/content/202/11/1491.full.pdf
________________________________


AN710  Antenna Circuit Design for RFID Applications
http://ww1.microchip.com/downloads/en/AppNotes/00710c.pdf


Modeling and Optimization of Printed Spiral Coils in Air, Saline, and
Muscle Tissue Environments
Optimization of Data Coils in a Multiband Wireless Link for
Neuroprosthetic Implantable Devices     RRD Ref6b


http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3171452/pdf/nihms305002.pdf


A Closed Loop Wireless Power Transmission System Using a Commercial
RFID Transceiver for Biomedical Applications

              http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2953772/pdf/nihms235191.pdf


Design and Optimization of a 3-Coil Inductive Link for Efficient
Wireless Power Transmission.
Abstract only - if anyone has a full version I'd love to see it.

         http://www.ncbi.nlm.nih.gov/pubmed/21922034

            ieeexplore.ieee.org/Xplore/login.jsp?url=http%3A%2F%2Fieeexplore.ieee.org%2Fiel5%2F4156126%2F4358093%2F05951804.pdf%3Farnumber%3D5951804&authDecision=-203
Kiani, M.  Jow, U.-M.  Ghovanloo, M.

                http://lib.bioinfo.pl/pmid:21922034



An Inductively Powered Scalable 32-Channel Wireless Neural Recording
System-on-a-Chip for Neuroscience Applications.
       
        http://lib.bioinfo.pl/pmid/journal/Dig%20Tech%20Pap%20IEEE%20Int%20Solid%20State%20Circuits%20Conf


A TRANSCEIVER FOR DIRECT PHASE MEASUREMENT MAGNETIC INDUCTION TOMOGRAPHY

            http://www.dtic.mil/cgi-bin/GetTRDoc?Location=U2&doc=GetTRDoc.pdf&AD=ADA411517


NON-CONTACT MEASUREMENT OF THE ELECTRICAL IMPEDANCE OF BIOLOGICAL TISSUE

          http://www.dtic.mil/cgi-bin/GetTRDoc?Location=U2&doc=GetTRDoc.pdf&AD=ADA409909



No prizes for guessing what I've been looking at lately :-)


          Russell McMahon
          Applied Technology ltd
          New Zealand



On 29 November 2011 11:15, David <.....listsKILLspamspam@spam@edeca.net> wrote:
{Quote hidden}

>

2011\11\29@041519 by David

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Quoting Josh Koffman <joshybearspamKILLspamgmail.com>:
> On Mon, Nov 28, 2011 at 5:15 PM, David <.....listsKILLspamspam.....edeca.net> wrote:
>> I'm looking at DIY inductive charging, to top up small batteries.
>> Undecided on the actual battery so far, I'm more interested in the
>> inductive side for now.  Perhaps an AAA or LIR2032.
>>
>> I've seen a few pages such as this one:
>> http://donklipstein.com/samschem.htm#schras4
>>
>> Has anybody made a small inductive charger that worked?  I would be
>> interested in any pointers.
>
> Mouser has an eval kit:
>
> http://www.mouser.com/cymbetcbceval11/
>
> I've never touched it, but maybe you can get some useful info from it.

That's really interesting, thanks.  Even the block diagram is useful.

David

2011\11\29@043251 by David

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Quoting RussellMc <EraseMEapptechnzspam_OUTspamTakeThisOuTgmail.com>:

> A major point that is missed in the toothbrush circuit that doesn't
> matter so much there but which does in more general applications is
> that the receive circuit will get VASTLY more range if it is resonant.

It surprises me that the toothbrush ones aren't resonant at all.  Even  the basic circuits I've seen suggest making them resonant.

> Excellent advice in Microchip AN710
> AN710 Antenna Circuit Design for RFID Applications
>
>                http://ww1.microchip.com/downloads/en/AppNotes/00710c.pdf

Great application note.  Maths is not a strong point, but I'll have a  good read and see what I make of it.

I am more interested in the toothbrush/"power mat" style close  charging than distance.  Perhaps I can find an old toothbrush to  dismantle too :)

Thanks,

Davi


'[EE] DIY inductive charging'
2012\02\20@021309 by IVP
face picon face
If I were to use (strong rare earth) magnets as the cores, would that
significantly increase power transfer ? I've recently discovered an
application where transfer of 20-30mA (@ 4-ish volts, ~100mW)
across about 6mm of air would be just super. Or is permanent
magnetism a no-no ?

I've noticed that some of the inductors/coils I've pulled from boards
are wound on magnets, whilst some are magnetic (presumably soft
iron like power transformer cores) and others are ferrite

Reading pages like this to get some ideas

http://en.wikipedia.org/wiki/Resonant_inductive_coupling

Not too worried about efficiency. The primary could be driven to
any necessarily high voltage at high frequency with an SMPS I

2012\02\20@032810 by RussellMc

face picon face
> If I were to use (strong rare earth) magnets as the cores, would that
> significantly increase power transfer ?

Magnets won't help. (Unless you have an oxygen free copper over-unity
crystal dongle, alas).

> I've recently discovered an
> application where transfer of 20-30mA (@ 4-ish volts, ~100mW)
> across about 6mm of air would be just super. Or is permanent
> magnetism a no-no ?

PM is relatively irrelevant. If you had a permeable core that could
saturate then PM will make it saturate sooner on one side of the AC
cycle but that's unlikely to have any/much relevance in this
application.

That power over that air gap is "easy enough" [tm] as long as coil
area is unconstrained.
Without delving into tables etc I'd guesstimate that a coil over 6mm
diameter would do that easily at acceptable Q and that a few times
larger would do so with aplomb and/or abandon.

Resonance - series or parallel, is essential for any sort of distance
at sensible efficincies.

There are many tables / graphs / formulae available and I can dredge
up off disk or point you to them if you don't find enough on web.

I have previously cited the superb  Microchip app note AN710  "Antenna
Circuit Design for RFID Applications"


>From my Stack Exchange RFID answer here
<http://electronics.stackexchange.com/questions/26740/rfid-tags-orientation-issue-how-to-fix/26743#26743>

see

RFID coils usually line in a single plane - ie they are essentially 2D
on shape but will hav 3D thickness.

An extremely good guide to RFID aerial design is given in
Microchip application note AN710 [
Antenna Circuit Design for RFID
Applications](http://ww1.microchip.com/downloads/en/AppNotes/00710c.pdf)

-  (Maintenance page
[here](http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&nodeId=1824&appnote=en011776)
)

Also liable to be of significant assistance is
Microchip AN680 [
microID® 13.56 MHz RFID System Design
Guide](http://ww1.microchip.com/downloads/en/DeviceDoc/21299E.pdf)

____________________

Two "loop" aerials which are essentially 2D in shape will have a very
distinct null when aligned orthogonally (ie at right angles). If the
fixed antenna is on a flexible substrate then simply bending it in a
curve will reduce the tendency to form sharp nulls, but will also
reduce the peak response when the aerials are optimally aligned. In
this application optimal alignment is unlikely to be important.

_________


Phliips app note - 2D focus [mifare
®  (14443A) 13.56 MHz RFID Proximity
Antenna](http://www.nxp.com/documents/application_note/AN78010.pdf) -
2002


__________________

Coupling -

If the master and slave (= transmit-receive coil and tag) coils are
flat coils that are essentially 2D with some thickness, then

Optimum coupling occurs when

- their planes are parallel,

- they are on the same central axis and

- close together.

You will get decreased coupling if you move them

- further apart along the central axis (planes still parallel)

OR

- if you slide one across its plane in any direction so they are not
on the same axis

OR

- if you rotate one around  its X and/or Y axis

OR

-  Any combination of the above three.

**If** the plane of your tag **coil** is almost perpendicular  to the
plane of your "pickup" coil you have near worst case orientation.
ie the magnetic field vector is at right angles to the plane of the
coil so to maximally couple the two coils the sens and receive coils
need to be parallel.


{Quote hidden}

     Russell McMahon

2012\02\20@145054 by Denny Esterline

picon face
There's an Energizer powermat charger "demo set" available at Walmart for
~$30:
http://www.walmart.com/ip/Energizer-Flat-Panel-2X-Induction-Charger-Wii-Wii/12510641


-Denn

2012\02\20@151126 by Neil Cherry

flavicon
face
On 02/20/2012 02:50 PM, Denny Esterline wrote:
> There's an Energizer powermat charger "demo set" available at Walmart for
> ~$30:
> http://www.walmart.com/ip/Energizer-Flat-Panel-2X-Induction-Charger-Wii-Wii/12510641

I've really got to wonder what the transfer efficiency is for one of those things.

-- Linux Home Automation         Neil Cherry       ncherryspamspam_OUTlinuxha.com
http://www.linuxha.com/                         Main site
http://linuxha.blogspot.com/                    My HA Blog
Author of:            Linux Smart Homes For Dummie

2012\02\20@154316 by YES NOPE9

flavicon
face
Am I correct that for $30 I get a "charger pad" and two rechargeable battery packs..... ?
Would the battery pack power anything of the correct voltage ?  So maybe it can be used for other electronics ?
What does the Wii use voltage-wise ?
gus


> On Feb 20, 2012, at 12:50 PM, Denny Esterline wrote:
>
> There's an Energizer powermat charger "demo set" available at Walmart for
> ~$30:
> www.walmart.com/ip/Energizer-Flat-Panel-2X-Induction-Charger-Wii-Wii/12510641
>
>
> -Denny

2012\02\20@160044 by YES NOPE9

flavicon
face
I found a  video and the two battery packs appear to have two batteries of unknown type.
http://www.youtube.com/watch?v=uuZCSDVuujA
Nintendo does recommend Nickel Metal Hydride (NiMH) Rechargeable Batteries for the remote. ( 1.25 V )
gus

> On Feb 20, 2012, at 12:50 PM, Denny Esterline wrote:
>
> There's an Energizer powermat charger "demo set" available at Walmart for
> ~$30:
> www.walmart.com/ip/Energizer-Flat-Panel-2X-Induction-Charger-Wii-Wii/12510641
>
>
> -Denny

2012\02\20@172219 by IVP

face picon face
> Microchip app note AN710

I have that and will go through it. Was the magnet question I needed
an answer to. Only occurred to me because I happened to be working
with a Hall Effect sensor and used a small magnet as a flux concentrator,
leading me to wonder if that would also 'focus' an electro-magnetic field

> **If** the plane of your tag **coil** is almost perpendicular to the
> plane of your "pickup" coil you have near worst case orientation

Fortunately, although moving, the Tx-Rx can be in a fixed, optimised,
spatial relationship as they move together, coupled magnetically, hence
another reason to ask

(Magnets. Always with the magnets

2012\02\20@174326 by RussellMc

face picon face
On 21 February 2012 09:11, Neil Cherry <@spam@ncherryKILLspamspamlinuxha.com> wrote:

> On 02/20/2012 02:50 PM, Denny Esterline wrote:
> > There's an Energizer powermat charger "demo set" available at Walmart for
> > ~$30:
> >
> http://www.walmart.com/ip/Energizer-Flat-Panel-2X-Induction-Charger-Wii-Wii/12510641
>
> > I've really got to wonder what the transfer efficiency is for one of
> those things.
>
> There really is very little to the basic system.
Amp turns into resonant coil.
Well coupled resonant pickup.
Vout is set by the voltage you choose to use  as long as you take out less
energy than available,. within reason.

I have a dual XBox battery inductive charger that I got from ?Sparkfun? .
I looked at it to see if it seemed to do anything radical and it was about
as expected.
Efficiency should be in the 50-80% efficiency range without undue care and
the inductive power transfer foundation (proper name escapes me and rushing
....) are talking about over 90% for their better configurations.

Over 90% very doable if gap small and dimensions free.
Charts available.
See Microchip AN I cited to start.
I can provide quite a few refs ...



           Russell


-

2012\02\20@174533 by John Gardner

picon face
....Magnets. Always with the magnets

Keep wearing 'em, Joe...  :

2012\02\20@181152 by RussellMc

face picon face
>> ...Magnets. Always with the magnets

> Keep wearing 'em, Joe...  :)

mumetal foil does better than tinfoil, but it's much more expensive.


R

2012\02\20@212316 by Denny Esterline

picon face
The Wii remotes are designed for two AA batteries, these are a "brick" that
fits in the same space and has some other parts to them. Obviously
including the inductive pickup, also some strong magnets that help position
the controller on the mat. Not sure if the magnet is involved in either the
inductive charge loop or the controller sensing.

I haven't studied it much, but the wife has bought several of the
"cheapie" cradle chargers and they've all been absolute trash. Batteries
that wont hold a charge for ten minutes and useless contacts that won't
actually make contact. I finally bought this set for her for Christmas this
year. Haven't had an single issue with them at all.

-Denny

On Mon, Feb 20, 2012 at 1:43 PM, YES NOPE9 <KILLspamyesKILLspamspamnope9.com> wrote:

{Quote hidden}

>

2012\02\21@024947 by IVP

face picon face
> http://ww1.microchip.com/downloads/en/AppNotes/00710c.pdf

AN710 is also part of this package

13.56MHz System Design Guide

http://ww1.microchip.com/downloads/en/devicedoc/21299e.pdf

A 13.56MHz chip like the MCRF450 needs about 130uA to write, and
20uA in normal mode, so that's some idea of what magnitude of power
transfer is required @ > 2.8V

125kHz System Design Guide

http://ww1.microchip.com/downloads/en/devicedoc/51115f.pdf

125kHz MCRF200 is 50uA write, 5uA normal

See also

http://en.wikipedia.org/wiki/Radio-frequency_identification#Miniaturization

2012\02\21@030750 by IVP

face picon face
> If you had a permeable core that could saturate

So, if I understand it (or something, anyway), an air core inductor/
antenna would be preferred, as the intention is to radiate energy,
not lose it in a solid core ?

As for the transfer itself, say I make two identical air-core inductors/
antennae, spatially in parallel. If one is driven resonantly, the other
should be a matching receiver ?

2012\02\21@070335 by RussellMc

face picon face
>> If you had a permeable core that could saturate

> So, if I understand it (or something, anyway), an air core inductor/
> antenna would be preferred, as the intention is to radiate energy,
> not lose it in a solid core ?

Not directly related to what I said.
I was commenting on the effect of a permanent magnet on the system.

The desired result is a coil of adequate Q and this may be achieved
with or without an additional core material BUT most systems which
transfer substantial power do so using a core. This may be ferrite or
may be powdered iron depending on frequency.
The IPT (I'll call them" organisation has various reference coil
designs freely available and the uChip App Note  I have referenced
several times discusses many coil designs.

> As for the transfer itself, say I make two identical air-core inductors/
> antennae, spatially in parallel. If one is driven resonantly, the other
> should be a matching receiver ?

Both should be resonant and at the same frequency. They do not need to
be mechanically identical.

For a TX inductor I used 100 metres of TPS mains wiring driving.
Assume 2 core and drive phase and neutral as a current loop with far
end shorted. Resonate.
Receivers were Ferrite U cores with a winding on cross bar (could have
been anywhere on core) and a resonating capacitor.
In this case TPS had outer sheath removed at desired pickup points and
conductors separated enough for one ferrite leg to fit between. That
was demo only - multi station working system can have conductors
spaced as required.
Your system wants an across air gap transfer so facing flat coils is
better. Look at photos of MIT 2 metre plus transfer to get a 'big
picture' view :-).

FWIW (very little) "my" 1999 US patent is here
<www.wipo.int/patentscope/search/docservicepdf_pct/090063618000d9f7?download>
Please not to blame me for typical patentese and nasty diagrams at
rear and I don't know where the 555 timers came from :-). I did all
the power transfer and signalling stuff. Others did warehousing stuff.


<http://www.sumobrain.com/patents/wipo/Signalling-system-based-inductive-transfer/WO1999050806A1.pdf

2012\02\21@192324 by IVP

face picon face

> <http://www.sumobrain.com/patents/wipo/Signalling-system-based-inductive-transfer/WO1999050806A1.pdf>

Thanks

2012\02\21@193750 by IVP

face picon face
> Both should be resonant and at the same frequency. They do not need to
> be mechanically identical.

> Your system wants an across air gap transfer so facing flat coils is
> better

Only a little bigger than I want but a very demonstrative demonstration

http://www.youtube.com/watch?v=2ODW-ntPHSU

2012\02\21@195900 by RussellMc

face picon face
Various:


MIT
web.mit.edu/newsoffice/2007/wireless-0607.html
BIG coils :-)

Smaller
http://www.instructables.com/id/Wireless-Power-Transmission-Over-Short-Distances-U/

You Tube
http://www.youtube.com/watch?v=2ODW-ntPHSU

Nissan
http://www.greencarcongress.com/2009/07/nissan-wireless-20090720.html

Images, misc
http://www.google.co.nz/search?q=mit+inductive+power+transfer&hl=en&safe=off&prmd=imvns&source=lnms&tbm=isch&ei=rjpET9bhBYefiQeopuGfAw&sa=X&oi=mode_link&ct=mode&cd=2&ved=0CB4Q_AUoAQ&biw=1536&bih=864

Some value
http://www.youtube.com/watch?v=TIhPayFBE9c&feature=related

http://www.youtube.com/watch?v=Hw1h-cFGxdI&feature=relate

2012\02\21@200905 by IVP

face picon face
> Various:

Thanks. Videos, photos, and their associated schematics are helpful
at this stage to understanding a technical pdf, which I do appreciate
you mentioning (banging my head on) more than onc

2012\02\24@193242 by IVP

face picon face

> Various:

Came across this quite by chance

http://gtresearchnews.gatech.edu/tonguedrive3/

Not big power transfer but an interesting applicatio

2012\02\25@180833 by IVP

face picon face
Re: the video here

http://www.youtube.com/watch?v=2ODW-ntPHSU

I've tried something based on his schematic

http://4hv.org/e107_files/public/1251129162_89_FT1630_through_hole_wireless-schematic.pdf

Works, but I'm wondering about the heat produced, particularly
wrt the health of the FETs (and wastage)

Once the resonant frequency is found, would it be better to
make a proper power driver (sinusoidal or square ?) ?

2012\02\26@183903 by IVP

face picon face
www.youtube.com/watch?v=1V0yRJspOyA

I've made one of these with two 20-turn air coils (0.63mm enamelled
wire), 15mm diameter, transmitter centre-tapped. Standing current is
32mA @ 5V, rises as the receiver is loaded with white LEDs and a
PIC. Good place to start experimenting fro

2012\02\26@215107 by RussellMc

face picon face
Did you resonate them?
MUST be resonant if you care about range and efficiency


 Russell


On 27 February 2012 12:38, IVP <RemoveMEjoecolquittTakeThisOuTspamclear.net.nz> wrote:

> http://www.youtube.com/watch?v=1V0yRJspOyA
>
> I've made one of these with two 20-turn air coils (0.63mm enamelled
> wire), 15mm diameter, transmitter centre-tapped. Standing current is
> 32mA @ 5V, rises as the receiver is loaded with white LEDs and a
> PIC. Good place to start experimenting from
>

2012\02\26@221119 by IVP

face picon face
> Did you resonate them?
> MUST be resonant if you care about range and efficiency

For the quick 'n' easy first version, no. That it worked first time
with a result that would suffice is most encouraging. Separation,
consumption, and transfer are all within what I was looking for.
A second, tuneable, version is under way


'[EE] DIY inductive charging'
2016\01\10@220153 by IVP
face picon face
escribblings,

I've done some experimenting with inductive coupling, mostly of
the light-an-LED sort.

Resonance is the key - matching the frequency to the coils and
having identical coils (ie easiest way to get equal inductance)
does make a difference. I was using simple air coils, which
aren't terribly efficient. Conventional power transformers use
eg iron or ferrite of course which has higher permeability than
air to make a stronger magnetic flux for the secondary to
generate an EMF

https://en.wikipedia.org/wiki/Resonant_inductive_coupling

This page helped

https://sites.google.com/site/ddmcintosh2projects/inductive-charger

The spacing might not be too much of a problem. As you can see
in this video, the fields seem to localised enough to enable the
various "dancing" movements

https://www.youtube.com/watch?v=05gPzM7OJ34

Joe


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