Palm Touchstone Charger Teardown



Teardowns provide a look inside a device and should not be used as disassembly instructions.

In this teardown, we will show you the innards of Palm's slick induction based Touchstone Charging Kit for the Pre.

Edit Step 1 Palm Touchstone Charger Teardown  ¶ 

Image #1

Edit Step 1 Palm Touchstone Charger Teardown  ¶ 

  • The Palm Pre can be recharged in two fashions:

    • Wired Micro USB, included with the phone and rather lame.

    • Or the super-cool Touchstone wireless inductance charging system, which will set you back a measly $69.99

  • The Touchstone charger utilizes magnetic inductance, or electric current produced through a loop of wire in the presence of a magnetic field, to charge its internal battery wirelessly.

  • The beautifully designed packaging includes:

    • Touchstone charging dock.

    • Touchstone back cover.

    • User guides and warranty information.

Edit Step 2  ¶ 

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Edit Step 2  ¶ 

  • Weighing in at a portly 118 grams, the Touchstone dock makes a great paperweight.

  • And it's so pretty!

  • Palm has attached pretty chrome dots to show you which cable plugs in where.

  • The underside of the dock is nearly covered in a doughnut of foam tape. Don't stick it to a veneer table!

  • The AC adapter has a detachable plug, presumably allowing for connectivity in foreign countries.

Edit Step 3  ¶ 

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Edit Step 3  ¶ 

  • Side-by-side view of the Touchstone back and the standard Pre rear panel.

  • The Touchstone rear panel has a matte finish, probably to reduce visible wear from constant contact with the dock.

  • The outline of the induction loop (large circle) is visible on the inside of the Touchstone rear panel. The current produced by induction flows into the Pre via two gold plated pressure contacts.

  • The four small circles are magnets that align the Pre to the Touchstone dock, similar to the way Best Buy's iPod displays always align the iPod right side up.

Edit Step 4  ¶ 

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Edit Step 4  ¶ 

  • The inductor charging base assembly.

  • The new Palm Touchstone wireless charger works on the principle of resonant induction. When you move a magnetic field near a coil of wire, it induces a current in the wire.

  • Taking advantage of this principle, the Touchstone creates an electrical coupling between two coils of wire that are not physically connected. It does this with a primary coil of wire in the base unit which transmits energy to the secondary coil of wire in the phone via a magnetic field.

Edit Step 5  ¶ 

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Edit Step 5  ¶ 

  • The Touchstone rear panel includes a secondary induction coil.

  • The magnetic field generated by the base unit turns on and off rapidly, generating a magnetic pulse that is carefully tuned to the dimensions of the wire coil inside the phone. This oscillating magnetic field induces a current inside the phone, allowing the battery to be charged.

  • Similar technology is used to transmit power to some battery-operated toothbrushes, razors, etc.

  • This explanation is an oversimplification of a very specific field of electrical engineering.

  • You'll note that the location of the induction coil is in the center of the device, well away from the antennas that line the perimeter of the phone.

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Comments Comments are onturn off

I asked this as an "ask a question" but this seems more appropriate as a comment; is this charger Qi compatible? With all the upcoming phones that suppor the Qi wireless charging standard it would be amazing to get these chargers for $5-$10.

Adam Wroblaski, · Reply

That's not foam tape! That's the material that's based on gecko feet, the stuff you can mount even on glass without leaving a mark.

bluemonq, · Reply

The "foam tape" might be the first implementation of carbon nanotubes technology that mimics the minute hairs that allow geckos to cling to vertical surfaces.



blueness, · Reply

Blueness, can you give me a source for that information about the Touchstone's base? It certainly does grip nicely.

Kyle Wiens, · Reply

A link refering to palm saying the base would use that technology:

deeceefar2, · Reply

Quote from deeceefar2:

A link refering to palm saying the base would use that technology:

Also a link to VP of design mentioning the tech in a youtube linked interview at 2:25s :

deeceefar2, · Reply

I wonder how efficient this is compared to the normal charger - is it Energy Star rated?

DNN, · Reply

Your wrong about the "foam tape". It isn't that new. It's Micro-Suction® (registered in 2003). It's still cool but not what "deeceefar2" says it is. Most importantly, clean it with scotch tape or a wet rag if it looses it's suction. It doesn't stick when wet.

bbazookajoe, · Reply

I really like the charger kit with the magnetic. This palm pre touchstone charging kit is really useful and unique, it uses no wires to charge up the palm pre. I purchased it on this site.

gearheadz234, · Reply

Quote from bluemonq:

That's not foam tape! That's the material that's based on gecko feet, the stuff you can mount even on glass without leaving a mark.

Geeko tape is polyamide not carbon nano tubes. baesystems own the patent and rights to geeko tape. one of if not 'the' longest patent applications ever. something like over 170 pages.

orp12, · Reply

The four small circles are iron peaces that align together witht four magnets in the Touchstone dock the Pre to this, similar to the ....

(Magnets in the cover would catch everything made of iron in your pockets :):) )

Very good job, both the PRE and the Stone!!

Regards, Martin, Switzerland

Martin, · Reply

How is the base held on? Rivets? Screws?

I have read that only the Pre USB cables wold work with this base, but it looks like with a little modification that can be changed.

Onedee, · Reply

Quote from Onedee:

How is the base held on? Rivets? Screws?

I have read that only the Pre USB cables wold work with this base, but it looks like with a little modification that can be changed.

The bottom of the base is held in place by three screws. To open it, peel back the foam tape donut on the bottom and unscrew the three screws. The base should come apart from the rest of the charger fairly easily once the screws are removed.

Miroslav Djuric, · Reply

Can the position of the primary inductance coild be altered without damaging it once you have the unit open?

I ask in reference to the common problem that these have when the Pre is 100% charged, where it chimes on and off of the "charging" mode. Slightly separating the phone from the Touchstone (with a paper towel or a piece of fabric) solves the problem, but if you could push the coil farther away in the base, that would be a more elegant solution.

Rich, · Reply

To emulate the Touchstone base I made a coil (20 turns) out of wire and drove 10Vpp sinewave into it.

I probed the output of the coil inside the Pre backcover and it showed ~6Vpp sinwave induced (it peaks around 400kHz). However the two contacts that connect to the phone itself still show 0V. Looks like the circuit (that takes coil AC voltage and turns it into DC) inside the back cover expects higher amplitude. Anyone knows what amplitude it expects?

Anyone knows what frequency and Voltage the back-cover expects before it outputs a charging voltage to the Pre?

Hardgnd, · Reply

Any idea who makes the chipset and materials for the phone portion of the inductive charger?

Sparky, · Reply

Can anyone tell me how to incorporate this technology into an existing product I am going to modify?

Christian Rogers, · Reply

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