Mod idea: inductive charging from Palm Touchstone kit
 

Check out this mod done on an HTC Evo:

http://www.goodandevo.net/2010/06/ho...s-charger.html

It should be possible to do the same mod on other phones including the N900. I don't have any use for inductive charging myself, but I thought I'd mention it and see if anyone's interested.

Re: Mod idea: inductive charging from Palm Touchstone kit
 

I have a touchstone kit already for my Pre. Ive thought about trying this, but I'm too afraid to be the guinea pig. Seems pretty simple after reading some of these blogs though, which makes me wonder whats taking the powermat people so long to come out with some stock sized back plates.

Re: Mod idea: inductive charging from Palm Touchstone kit
 

I might just have to do that -- I got the oversize Mugen battery (with extended back cover) during the first iteration, where the camera etc. didn't work. Since they sent us all two of the new covers after they fixed the issues, I've got a spare to mod on.

Of course, the other thing that comes to mind is USB host -- if one routes the USB contacts out to the back, there should be just enough room in the Mugen case for a simultaneous charging and USB setup, with power from either the touchstone, or through the N900's USB port with an obsolete USB charger (the ones with no connection on D+/D-). Might even squeeze in a USB hub, and multiple mini connectors. I wonder what current the touchstone delivers...

Re: Mod idea: inductive charging from Palm Touchstone kit
 

My buddy gave me his bricked Pre, complete with Touchstone stuff. I've been thinking about trying it, but I do enjoy being able to easily swap the spare battery. And I was really REALLY hoping not to have to solder.

Re: Mod idea: inductive charging from Palm Touchstone kit
 

Odd coincidence that this thread got bumped just when I was going to hunt it down. Thanks, Descalzo! :)

My N900 just took one too many power-cable-assisted dives to the floor yesterday, and now has an IV, if you will, piggy-backed into the battery contacts, and running to my hobby charger.

After my post above, I looked into it, and there's really not room for all the cool stuff I mentioned above. But now that I need a charging system fix anyway, I'm going to attempt the touchstone mod instead of or in addition to soldering the port back down.

So I'm off to buy the hardware; will report back when I get the mod done.

Re: Mod idea: inductive charging from Palm Touchstone kit
 

Subscribed!

Re: Mod idea: inductive charging from Palm Touchstone kit
 

I'll be keeping an eye here as well. A while back I picked up two touchstone back covers, and a touchstone base when Radioshack had them on clearance, I think ~$20.

It looked like it would be difficult to get the coil and circuit board to fit in the stock N900 cover, and I haven't had time to play with it since.

Re: Mod idea: inductive charging from Palm Touchstone kit
 

Update: There's now a standard for inductive charging:

http://www.energizer.com/inductive/w...explained.aspx

Energizer makes some nice kits. You could buy a door for say, the Blackberry, put its guts into the N900 and have a standard inductive charging solution. Now that these things have been standardized, inductive charging is a much more appealing idea.

Re: Mod idea: inductive charging from Palm Touchstone kit
 

Mod accomplished!
Pics and detailed description to follow in a bit.

Since the USB port lifted the VBUS trace off the board, and I couldn't locate VBUS anywhere else (except, per the schematics, under one of the EMI covers which I'm not keen to cut into), I am unable to use the N900's USB charging abilities. I had to add a separate 5V Li-ion charging circuit, wired to the battery connector and the Pre circuit. The circuit I used is a fixed 720mA current, so it won't even maintain the battery constant in real heavy use, but it should be adequate for practical use. (I've only had it back together for an hour, so...)

The N900, with its extrafat battery, is a bit heavier than the Pre, but it still hangs on the touchstone in either portrait or landscape, no trouble.

Now I've got to either locate my camera, or maybe borrow a friends iPhone (*spit*) to document it. Will post back.

Re: Mod idea: inductive charging from Palm Touchstone kit
 

Alright, here's pictures. (Click through to flickr for bigger versions + a few more shots.)

http://farm6.static.flickr.com/5029/...649a43b252.jpg

You'll note there's several places I've cut some plastic off one thing or another.

http://farm6.static.flickr.com/5300/...bdd41fa64f.jpg
The battery's the most critical -- that shiny metal foil there is the Li-ion polymer cell, bare and exposed to the world. If you damage it while cutting the plastic housing, your battery could quite literally go up in flames then or more likely at a later date, taking your N900 and pocket with it. Also, it's now susceptible to damage if you carry it loose in your pocket, so I can't recommend this mod at all if you routinely swap out batteries instead of charging.

Also, there's a PCB just inside one edge of the battery (far side in that picture, bottom side as installed in the N900) -- you don't want to cut into that either, though it'll more likely result in simple doesn't-work than fireworks..

But you need that room (well, a good chunk of it -- I cut a wider panel than I needed to save exact measuring) to clear the circuit from the Pre cover, so...
What I did is very carefully cut a 45 degree bevel along both short edges of the panel, gradually deepening it until you break through. You can see the remains of that bevel on both the near side and far side, above. Once you've got a clear slit to the interior of the battery, you can see how thick the plastic housing is -- that gives you the knowledge to cut almost through with a hobby knife (or razor-sharp pocketknife), without going clear through and risking damage to the Li-poly cell. Then using a knife with a straight or (better) slightly convex back, you can cut outward through the remaining plastic, taking care not to let the tip score the Li-poly cell.

(Apologies if I'm being long-winded here, but Li-poly safety is a serious matter. Yes, if you don't follow my instructions, but are reasonably careful about it, there's a fair chance everything will be fine, but I did it the safest way I know how, and I can't recommend anything less. We have few enough Maemo fans out there already, no need burning some of us up, right? :))

http://farm6.static.flickr.com/5227/...abd2db79c8.jpg
Also, you need a couple notches in the connector region of the battery to clear your wires leading up from the + and - terminals -- you can see those in this end view. I just made a couple 90 degree V-notches the width of the terminal slot, and beveled the top out a bit. You might get by with less (or maybe no notching) if you use fine enough wires, but why waste precious power heating up wires...

http://farm6.static.flickr.com/5267/...678f0066f0.jpg
Of course, the other side of those wires will interfere with the cover -- I beveled the relevant region at about 30 degrees, seems to work OK.

Here you can also see how the Pre cover's guts fit in the Mugen cover. Yes, I got it a little crooked. :o The edges are curled up some (and could be trimmed, if desired, since they don't really stick well enough to sustain that curvature) but the coil, PCB, and magnet targets all fit on the flat section. No comments on my ugly solder job, please. I was trying to minimize heat so I didn't melt
anything plastic, let's pretend that's a good excuse. ;)

Now you can't tell from the pictures, but the soldered joints in the lid are lower than the adjacent raised section of the decal (covers the power-handling PCB), so they don't short out on the battery. However, I put insulating tape on the battery anyway, just to be safe -- removed for the photos, but you know what kapton tape looks like. Might put an extra strip over the solder joints in the cover, too, just to be doubly safe (and to hide my shameful soldering).

The free-floating PCB is a 720mA USB Li-ion battery charging circuit. It goes pretty much where it is, just pushed up at an angle between the end of the battery, the radiused part of the cover, and the N900 body. It's pretty close, but it does fit (even before I notched the corner to make it less hassle). I could probably trim a bit off the sides if it didn't. Right now it's floating, which only increases the hassle of assembly, but after I've run a few days shakedown, I'll be gluing/epoxying it in place. It's got a charging LED on the far side, too, so maybe a hole in the cover + clear epoxy. I used a tiny connector (don't know the exact type) used for R/C batteries to allow complete disassembly, but there's enough room for a Berg strip or similar, and you could even hardwire it with the same routing -- as you can see, there's enough slack to get it this far open.

And here's a closeup of the wire routing around the battery -- nothing special.
http://farm6.static.flickr.com/5092/...7b434e8a00.jpg

Oh, I neglected to get a picture of it, but I doubt the iPhone (*spit*)would have done very good anyway... the charging wires are just soldered straight to the side of the blade contacts of the N900, as far back as possible. This is probably doable without dismantling the N900, given a skilled technician with a fine-tipped iron, but I already had the N900's main board removed from the housing to work on the USB port.

As for charging characteristics -- like I said, only had it for a couple hours. But it should charge fastest with the N900 off (obviously...), and take about 5 hours (from dead) in that case. Should be no problem charging overnight with the tablet running, and should more-or-less keep up or get ahead with normal usage. Won't be as fast as the ~1A charger that ships with it, but faster than charging from a computer's USB port.

And that's it -- world's first inductively-charged N900. :cool:

Re: Mod idea: inductive charging from Palm Touchstone kit
 

Benson, would you mind also showing a closeup of the solder points without the battery in? I am interested in doing the same mod, seeing how great yours turned out =D

Re: Mod idea: inductive charging from Palm Touchstone kit
 

Hi Benson,

I know this is an old post, but would you mind commenting on how has it been working all this time?
I wonder if I can do this but with the normal cover and battery, I don't want to make it any thicker.
Also, if you could share more pictures, with the phone closed, charging, etc, that would be nice.

Re: Mod idea: inductive charging from Palm Touchstone kit
 

I ordered a touchstone kit and have the Mugen cover and one of the double Scud packs. I am hoping to make mine with metal contacts rather than a wire between the battery cover and the phone.
I am not finding the Mugen covers on eBay anymore though and am not sure where to find them for my wife's N900.

Re: Mod idea: inductive charging from Palm Touchstone kit
 

I am having a problem finding a Li-Po charger circuit like Benson uses in the diagrams upthread . Anyone have any good ideas?
Would some USB to 3.7v battery charger be good?
What voltage comes out of the Palm Touchstone module, I assume near 5v? How much amperage will it supply?
User Benson has gone the way of many TMO users since 2011 so I can't ask him.

Re: Mod idea: inductive charging from Palm Touchstone kit
 

So I have the Mugen back, a Palm Touchstone back and the touchstone base. I still need to get the battery charge regulator so I can solder down to the battery contacts. In my testing I think I will be able to use this with a double Scud battery pack without cutting the battery case.

I have not yet measured any power at the gold contact points on the case but I also have been using an underpowered Nokia 5.7v 800mA charger rather than the Palm wall wart but I do hear pulsed buzzing from the base. I think the Palm USB charger gives 1000mA and something between 5.7v and 6v making compatibility with non palm chargers sketchy. It will not take standard USB power. I get no response at all with my N900 charger plugged into the touchstone base. From several forums it seams that the base does require shorted data cables before it will accept power. I am considering shorting pins 2 and 3 inside the base on the PCB but enough voltage is still a problem.
https://upload.wikimedia.org/wikiped...sb_th1.svg.png

Some other notes is that the polarity is +Positive for the gold contact near the PALM name and X-ed out trash can on the sticker that holds down the coil and -Negative for the gold contact on the cover nearest the impression of the coil on that sticker.
http://www.pocketables.com/images/ol...970b-800wi.jpg

I do not recommend disassembly of the base as there are some spidery wires to a small coil that are easily broken, though carefully cutting the USB port hole on the base open makes using alternate cables easier.

http://www.ifixit.com/Teardown/Palm-...Teardown/810/1

http://www.pocketables.com/2010/06/h...s-charger.html

http://forums.webosnation.com/webos-...tone-dock.html

Re: Mod idea: inductive charging from Palm Touchstone kit
 

Bill of goods for converting 2xN900s:
-2x mugen battery covers, search ebay for extended battery cover N900 not listed as mugen
-2x 450mA USB charger for e-cigarette battery (thanks dr frost dk) to rip battery manager board from
-4x blue scud battery, to make two 3000mA/h double battery packs
-2x Palm Pre cylinder wall wart AC to USB, this is what the base needs and they are now pretty reasonable on ebay/amazon
-2x Palm Touchstone bases, they pretty much require the real palm charger above, the N900 charger is a no go so might as well buy the real deal than save a $2-3 on an incompatible power supply
-2x Palm Pre Touchstone backs, to harvest the coil and circuit board
-Hobby brass, will snip to the right shape to make contacts between door and N900/harvested charge regulator soldered to N900 battery +- poles.

I have one Mugen N900 door with the Palm/Touchstone coil installed, the sticky holding the coil is weak, I might try cleaning the next one with alcohol before sticking the coil down. The magnet is just strong enough to hold the phone down to the charge pedestal. Will see what works when the other touchstone door, batteries, regulators, and Palm wall chargers arrive.

Re: Mod idea: inductive charging from Palm Touchstone kit
 

It is a good idea to use some Scotch double sided sticky tape to pin down the coil and little metal buttons to the sticker that covers them and holds them to the phone battery cover. The clear inner sticky film that comes with the palm cover will probably be ruined in harvesting and you don't want to loose those little 5mm metal buttons which are needed for the magnets on the base to grab your phone and start charging, also your touchstone charger wont stick properly to your Mugen cover unless you do a quick clean off with alcohol and use the double stick tape to get everything attached.

Re: Mod idea: inductive charging from Palm Touchstone kit
 

Just wanted to post an after mod story.
The inductive charging works great especially on my wifes N900 with a broken USB.
The downside is that since I am wired direct to the base of the battery contacts I am bypassing the whole charging system; I often reboot the phone after undocking in the morning to get an accurate battery reading.
I run a double scud battery and I never have problem charging overnight and a few times got 80% from nearly flat after just a few hours.
One big upside to bypassing internal charging logic is I never get the dead battery makes phone unchangeable.
Anyone else using the touchstone system I am curious if the palm 12v jack actually works with the inductive touchstone puck for car charging?

Re: Mod idea: inductive charging from Palm Touchstone kit
 

Does anyone know if it is possible to play with charging scripts so that we could solder directly onto the system board rather than requiring a charging circuit to be crammed under the battery cover along with the inductive loop. Of course we would want to preserve USB host mode and charging.

One crude option is adding a shorting switch to the USB data pads under the battery but this is very inconvenient requiring shutdown, switching, and bootup before the USB port can be used.

Re: Mod idea: inductive charging from Palm Touchstone kit
 

The N900s I had modified with Touchstone have all broken or became corrupted with no option to reflash their USB ports being broken, no fault of the Touchstone mod.
I have decided to go with QI on my next try with our newer N900s since that is now the industry charging standard.
There are inexpensive universal charging adapters which have a flat cable which leaves the battery door and plugs in as a cover-plug for the microUSB port.
I am waiting for the delivery but while there seems to be progress towards enabling charging without shorting the data pins with modified battery scripts and the BME replacement the QI universal receiver and plug will work normally in charging status indication, protect the USB port from dust, and is easily removable when I want to use USB host mode, mass storage, or USB 3G network tethering for my laptop.
for example:
http://www.amazon.com/Universal-Wire...dp/B00I1D4DV0/

Re: Mod idea: inductive charging from Palm Touchstone kit
 

I have posted the steps to installing the new Qi system and modding to work with the N900 here: http://talk.maemo.org/showthread.php...01#post1431701
Includes timed charger script to bypass the USB shorting issue.