Update: I tried another touchstone, and my phone is charging without any apparent issues! Next, I’m going to litter my house with touchstones, and maybe embed one in my keyboard at work.

My Droid Bionic is pretty battery hungry, so I keep it plugged in most of the day while I’m at work. I’m tired of dealing with wires on my desk and forgetting to plug them in, so I decided to try inductive charging. Motorola makes an inductive charging system for the Bionic, but that would run me around $100, and I hack things.

Inspired by [Ryan Rix][] and Will Stone’s [article][], I thought I’d try to modify my phone to work with a Palm Touchstone charger. [Ryan Rix]: https://twitter.com/#!/rrrrrrrix [article]: http://uselesspuzzles.blogspot.com/2011/09/droid-bionic-optimizations-extended-bat.html

I basically needed to connect the receiving coil’s contacts with the inductive charging port built into my phone. To do this, I routed some copper tape to a partially tape-covered piece of foam.

One problem I ran into while doing this is that there is no reliable pinout information available for the four-pin connector on the Bionic. Looking at the last picture in Will’s post, I wrongly assumed that the top pin was +V. One of the comments mentions that the picture might be wrong, and I’m confirming that: The top pin is GND, and the bottom pin is +V. I still have no idea what the center pins do.

For a few minutes after first connecting it, I was afraid I had fried my phone because the mobile data silently turned off.After fixing the polarity and re-enabling data, I placed my phone on the charger and… success! … kind of.

Now, when on the base, my phone toggles rapidly between ‘charging’ and ‘disconnected’. I’ve done some research, and this appears to be a common issue with these mods, as well as stock Pre/Pixi devices. My multimeter and oscilloscope show a fairly consistent 5-5.6V coming from the receiving coils, so I’m not sure what the problem is or how to fix it.

My next step is to try another base. I’ll update this post when/if I find a solution and/or more information. In the meantime, here are a few pics of my mod:

copper tape connector foam adapter


18 December 2012