today more and more smartphones support wireless charging, whether it's out-of-the-box or via an available hardware upgrade (special back cover). but there is no reason why all other USB charged devices shouldn't enjoy the luxury of wireless charging.
in this instructable i'll show you how to add wireless charging capabilities to your smartphone (demonstrated on a Samsung Galaxy S II) or practically any USB charged device (of course i can't guarantee that it'll work on any device but i see no reason it shouldn't, unless there's some other patent or technology preventing it).
Step 1: background and clarifications
*** FOLLOW THESE INSTRUCTIONS AT YOUR OWN RISK ***
take safety precautions and do not do anything you are not certain of.
i cannot be held responsible to any damage you may cause to your device or to yourself !
(now, after i covered my ass, we can begin)
there are a few projects similar to this one on the net. I've drawn ideas from everywhere and incorporated some of my own.
the whole concept and basic design is based on Palm's technology (although there are other manufacturers offering similar solutions). the Touchstone is a Palm charging dock meant for the Palm Pre smartphone, which supports wireless charging via a separately sold back cover.
there are a few wireless charging technologies made by different manufacturers that all rely on the same physical concept but they are not cross-compatible, you cannot mix coils and docks (I've tried).
i will not bore you with the physics behind the concept (although it's quite interesting) and there's nothing i can write that's not already available with more professional descriptions on the net, so if you want you can google "wireless charging" and read all about it.