The Ludicrous N900 Powermat Mod
 

Hey there,

at first the usual warnings:

If you do something similar as described in this thread you
- loose the warranty for your device,
- may damage or destroy your device,
- may cause damage to you or your environment,
- might do other dangerous stuff!
If you try to do anything of this you do this on your own responsibility and at your own risk!
There is absolutely no warranty that this will work for you.
Furthermore, there is no warranty that the posted information is correct at all.
Do not blame me if you mess up your device or something else by trying to do this.


That being said, lets go to the fun part:

I made some rather brutal modification to my N900 which allows me to charge it with the Powermat (TM) system.
So far it basically works.
One issue is that the Powermat sender stops charging after some 20 minutes of charging.
I didn't actually measure the time yet.
Though, this works as a very first proof of concept.

I attached some first pictures taken of the device being charged and the modification itself.
I'll add more pictures of the nasty work and inside of the device and also more details of how I did this later on.

Re: The Ludicrous N900 Powermat Mod
 

Oh man... you must put up a warning that there are some very graphical and disturbing images on this thread. :eek: Had to turn away in horror when I saw the second picture of the glorious N900 with it's back cover all... torn up... (shivers) :D

Kudos to you for trying something like this though. :cool:

Re: The Ludicrous N900 Powermat Mod
 

Dude, we are all eager to see further instructions!!!

Re: The Ludicrous N900 Powermat Mod
 

It would be nice if the power mat made the back of the N900 flat, instead of having the camera module sticking out a bit :) nice work so far, keep it up!

Re: The Ludicrous N900 Powermat Mod
 

The horror! But it sure would be nice to either support inductive charging or be able to hot swap a battery.

Re: The Ludicrous N900 Powermat Mod
 

WOW! Super! I would love this. I use an Otter Box on the outside, so removing or mangling the original back isn't that big of an issue if that's all the space it needs! Where are you connecting it internally?

Re: The Ludicrous N900 Powermat Mod
 

Curiously, does this connect directly to the battery or run through the device to the pins before the IC?

Looking forward to seeing the internal pictures.

Re: The Ludicrous N900 Powermat Mod
 

The system banner says "Akku wird geladen" which apparently translates to "battery charging", so I assume he must be charging through the device.

Re: The Ludicrous N900 Powermat Mod
 

Alright... of course all warnings etc. from the initial post apply as well ;)

I connect the whole shebang via USB. Though I am not using the USB port but rather the pads beneath the battery (see the first image).

I took the Powermat receiver of an Iphone 3G Powermat set. You can pretty easily break it off the casing without damaging it. Furthermore, it is internally connected via a flat ribbon cable which detaches easily.
On the second picture you can see where I identified GND and +5V (actually you get something around 5.2V from it). I accidentally fried the first GND soldering pad located next to the +5V pad so I used another GND pad which can be seen in the background.

In the third picture you can see the cabling on the pads beneath the battery. The fourth picture shows the inserted battery and the already modded back-cover including the Powermat receiver and the cabling.

Note: You need to short-circuit +Data and -Data of the USB port in order for the charging to work. Actually I measured something like 2.5 Ohms resistance between these two but short-circuiting also works. For more information see: http://talk.maemo.org/showthread.php...818#post997818
I do this by using a dip switch which connects +Data and -Data.
So when I want to charge via Powermat I have this switch turned on (default for now). One only needs to remember to put this to off if you want to connect via the "normal" USB port. Else you would short-circuit your computers USB port.

Also note that I put a small diode (something above 5V, 40 V or so will do with 1A) between the Powermat +5V and the USB 5V on the N900. The reason for this is to protect the Powermat receiver from the 5V when a USB cable is connected.
I actually don't know if this is needed. I just wanted to make sure I do not fry my receiver the next time when I connect my N900 to my PC via USB.

Well, after this was all setup I simply put the stuff together. Though, on the side where the cables come out from beneath the battery the back cover does not close completely, i.e., there is some opening left. This is no problem for me as I use another cheap silicon case anyway.
As you may have noticed the Powermat receiver nicely aligns with the silicon case. You can see this on the second picture in the first post. You also see the dip switch there.

The whole modding of the back-cover required quite some force. I used a drill to get four holes in and a small saw to cut out a square (smaller than needed). Then I used a cutter knife to carefully increase the created hole to make it fit to the Powermat receiver.
Note: I kept checking the size of the hole each time to ensure I do not cut off to much. I also cut out another small square beneath the camera opening to have a place to put the dip switch and the diode.
Then I used some epoxy glue to attach the receiver to the back-cover. I also used epoxy glue to fixate the dip switch and the diode.
Note: make sure the whole thing works prior to doing this. Also be very careful with this glue stuff as you can easily glue together parts you don't want to be put together permanently, ;) e.g., the back-cover and the main body of the N900.

As you may notice I also cut off some parts of the camera opening. This was necessary as the Powermat receiver is quite big. Though, if you don't cut off too much the camere still works. Even the camera app launches automatically and the pictures still look fine.

Edit: also note that for some, currently unknown, reason the charging just stops after a while.
When you take the phone off the Powermat sender and put it back on the charging continues.
Currently I need to do this about two or three times to get a the N900 fully charged.

Re: The Ludicrous N900 Powermat Mod
 

where can i get theese powermat things??

Re: The Ludicrous N900 Powermat Mod
 

Nice to see more modders in here, good work.
If it had not been for my pretty powerful external/internal charger i would have made wireless charging myself.

But like the fact that you use a stock product and mod it with the N900, just like me, buy one thing, use it for something probably not intended :D

Re: The Ludicrous N900 Powermat Mod
 

http://www.powermateu.com/pm_uk/

They're also on Amazon and ebay.

Re: The Ludicrous N900 Powermat Mod
 

Another thing, if you make a dual mod, with other battery's then the scuds (because of the thickness), you should be able to integrate the powermat receiver module inside the cover, like if you use japod's or polarcell.

Re: The Ludicrous N900 Powermat Mod
 

Been considering something like this since I saw a mod for another phone. On Hackaday.
So, this is from an iPhone powermat. Dont those things need their data lines at certain voltages to charge properly?
If thats the true for the powermat charger, there must be something on the receiver or maybe the back that does the shorting. Any chance of reusing it?

Re: The Ludicrous N900 Powermat Mod
 

Would like to try this, but I'm going though airport security soon and I'm sure all them wires popping out might turn a few heads.

Re: The Ludicrous N900 Powermat Mod
 

Well, dunno about the iphone.
But there is the flat ribbon connector on the powermat receiver which connects to quite some pins of the iphone connector. From what I saw some of these are USB data lines indeed. Though, I have no clue what is happening on that lines. Furthermore, I am not that good in SMD soldering. Another chance to get this done could be to mess with the flat ribbon cable directly. Though, these things are pretty sensitive as well. Anyhow, my version is just a pretty crude, "hacked" together proof of concept. Maybe in some time there will be a better solution.

Edit: the iphone 3G Powermat receiver also has loop-through functionality for USB. So it "should" be possible to use this too instead of using a custom diode and a dip switch like I did.

Heh, yeah, this is also one of my concerns. Well I think I'll have to reactivate an old phone to take with me on the travel. I don't like the idea of some airport security guy pulling apart my N900 and messing with the fragile cabling. ;)

Edit2: or even being pointed at with guns or being thrown at the floor with a knee in my neck... :eek:

Re: The Ludicrous N900 Powermat Mod
 

It seems like the sender and the receiver need to be put very tightly next to each other in order for the charging to work.
I am not sure if it will work "through" that case.
Most probably you would need to also "mod" your otterbox case.

Re: The Ludicrous N900 Powermat Mod
 

Thank you for the warning... I think I will order a set anyway and see what happens. I think I will also order a new back, so I have it, just in case I want to use it without the Otterbox in the future. ;)

I've wanted something like this for a long time, but always got hung up on how to connect it into the system without endangering/blocking the USB port. I plan on putting a micro reed relay (or maybe a low power opto-isolator?) in to short the data pins activated by current from pad itself, so it auto-closes the connection when it's powered by the pad. That should take less than 10-20mA for an opto-isolator...

Thanks so much for this awesome mod and the pictures. I love this phone, and the community around it!

Re: The Ludicrous N900 Powermat Mod
 

Using an opto-isolator seems to work quite well. :) Thanks for that hint. I made an improved mod that uses such an opto-isolator (Optokoppler in German) to short-circuit +Data and -Data. I attached an image of the actual circuit I am currently using.
The diode BY 133 is used to protect the Powermat receiver from the USB +5V voltage and to prevent the opto-isolator being activated when the N900 is attached to a common USB port/charger.
Furthermore, I am now using the receiver part of a Powermat Nintendo DS Lite charger. This one is slightly thicker and requires more manual work in order to being attached to the N900 battery cover. Though it has the benefit that it is not as complicated as the Iphone 3G version and occupies a smaller area. I'll let you know how this one works out...

Re: The Ludicrous N900 Powermat Mod
 

Excellent! Couldn't find complete pinouts when I did my inductive charging mod, so I added a Li-ion charger to directly charge the battery -- now I can connect to the USB pads and BME can stop being a ****** about low-battery warnings.

Check my version out in my sig, and welcome to the very exclusive inductive-charging club! :)

Re: The Ludicrous N900 Powermat Mod
 

Happy to hint, and thanks for the diagram. Will be handy when I go to add it to my N900. :)

I was looking at that on the powermat site and debating it. I figured it was a little smaller than the iPhone pad, but wasn't sure it had other issues. Thicker sounds like a pain. :P

I've also been looking at various Qi based chargers, which should work the same way. They appear to have a slightly better range, and don't require the mag-lock powermat uses. (Plus, they're an industry standard that several folks are making pad/charger pairs for.) For right now I'm holding off a bit, since I'm over-project-ed as it is. But I do look forward to doing this soon. :)

Re: The Ludicrous N900 Powermat Mod
 

Alright,

the new version works much better than the first one.
With the new receiver the problem of the charging being interrupted after some time is gone now. So far I successfully fully charged my N900 two times.

Though, there is a slight new "issue" the charging process is slower than via a USB connection to a PC right now. Afaik the problem is caused by the forward voltage drop of the diode.

Due to this the voltage on the battery side is smaller than 5V. Actually, the new Powermat receiver (Nintendo DS Lite) I am using supplies about 5.15V. Though, due to the diode in the circuit at the N900 USB side the voltage is lower. I already use Schottky diodes as these have the smallest forward voltage drop.

There are some solutions using a (MOS)FET instead of a diode which should result in a significantly lower voltage drop. Though, I am not that much into electrical engineering topics and didn't try this yet.

I'll keep you updated...

Re: The Ludicrous N900 Powermat Mod
 

Alright,

I tried a solution with a different type of Schottky diode, one using a MOSFET as diode replacement and one connecting the +5V source directly. Neither of these worked. In all attempts the N900 started to charge, though, after some (10 or so) seconds the charging stopped. In some cases I could hear some chirping noise from the device before the charging stopped.
Apparently the BY 133 was a very fortunate choice for this setup. ;)

I also made some pictures of the new receiver and the current setup I am using.
I'll upload the pictures as soon as I manage to get em off the camera. ;)

Re: The Ludicrous N900 Powermat Mod
 

As promised the pictures of the current setup using the Powermat Nintendo DS Lite receiver.

Edit: The Powermat Nintendo DS Lite receiver has a black, adhesive, circular protection foil on the back.
I reuse this foil in my setup as protection as well.
I just mention it here as it is not shown on the pictures.

Re: The Ludicrous N900 Powermat Mod
 

Looks great. How much thickness does it add to the back? That's a major thing for me. (Could we get a photo from the side-on to get an idea?)

Also: I note this back has a lot more room, and isn't carved up. Where did you get your spare back? Most of the places I'm finding that have spare back panels are quite pricey. :(

Re: The Ludicrous N900 Powermat Mod
 

Excuse the late reply... I am very busy at the moment.
With respect to the thickness: the first attempt on this added about 2-3 mm extra. Though, as it got loose I had to take a second try which now probably adds about 4-5 mm (?). Note that this only adds partially to the advertised overall thickness of the N900 as this includes afaik the bump of the camera slider and stand.
Still, this makes the device look even more clunky. But if you happen to like a diy-ish "MacGyver look" you probably wouldn't mind. ;)

Also note that I experience problems with respect to the USB data connection. I didn't notice this earlier as I do not use this pretty often. I don't know if the problems are related to the optocoupler solution or if any USB related parts in the device got damaged. Unfortunately I am currently lacking the time to investigate this further. Charging via USB still works btw. IIRC the USB data connection did work with the first "dip-switch" solution.

Last but not least, if you like messing with your precious device in a similar way, be sure to check out the pretty informative post by joerg_rw at the bottom of the page: http://talk.maemo.org/showthread.php?t=71414&page=2

Edit:
One last note: I do not charge the device unattended, so I can quickly respond in case something goes wrong. Luckily so far I did not encounter such a circumstance.

Re: The Ludicrous N900 Powermat Mod
 

I know this is an old thread but has anyone tried to use the inductive charger back cover from the Palm Pre with the Touchstone ? If you look at the cover the inductive device added to it is quite thin and looks like it would fit right under the cover of the N900. Also, upon closer inspection it appears it simply makes contact at the Palm Pre's existing + and - battery contacts for charging it's battery. Just a thought for whatever its worth.