Arrive + touchstone ?

onemadrssn

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Feb 24, 2011
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I have noticed many of the users here are former webOSers. I know I miss the touchstone charger and I am sure I am not alone.

So, is anyone up to the task? Ready to take the plunge, risk bricking your phone, and being the first one to take a soldering iron to your Arrive?

It has been done with the EVO: How to mod HTC EVO 4G to work with Palm Touchstone wireless charger
and a few other phones. (I believe I once saw a forum post talking about someone who did it to their LG Optimus S)

I am a Mechanical Engineer by degree, although I work in software now for a consumer electronics company. I do have experience with circuits, electronics, and certainly have soldered my way out of a problem before. However I am not confident enough in my abilities to take that risk with my shiney new phone.

What I gather is that the touchstone coil (from the back cover of a pre or pixi) outputs a USB standard 5V .5A (or 2.5W) of power and all one needs to do is find the positive and negative USB power in on the Arrive circuit and solder in wires thin/flat enough to fit while also having enough gauge for that sort of current flow without heating up too much connecting the touchstone coil to the arrive charging circuit.
 
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onemadrssn

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I should add, I am willing to donate a touchstone back cover to someone willing to experiment. Is anyone willing to donate a touchstone puck for the cause?
 

Matts4313

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I think I have 3 touchstones and 2 backs laying around. The idea of it was cooler than the real life uses in my case. If someone pays for shipping they can have them.
 

onemadrssn

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Question (that I should probably know the answer to): Does inductive charging work through a metal barrier? The barrier in this case being the what I assume to be an aluminum battery cover. On the Pre, Pixi, and EVO the battery cover is plastic.

Edit: After speaking for an EE colleague, we decided that it will probably work as aluminum is not a ferrous/magnetic metal and in our case is also pretty thin. That being said, efficiency might take a hit as attenuation though aluminum is higher than through plastic; the question is by how much? The closest example I can think of is how the iPad's antennas are always behind a plastic strip rather than being put behind the aluminum body.

This might be more complex than I thought...
 
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uptempo777

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+1 I concur! I have a bunch of Touchstones from my Palm Pre and I love using it! You don't have to fumble with the cord into the microUSB and it just sits there waiting for you to take it on the go.

Please make this happen.
 

wellsmanfu

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Look up the directions for the mod someone came up with to get the touchstone to work on the Evo. I can't remember the site, but it was something like good and evo or something like that.

It takes some doing and will definitely void any warranty, but it might be possible. At least there you should see detailed instructions for the modifications and soldering that you'll have to do.
 

Honis

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Question (that I should probably know the answer to): Does inductive charging work through a metal barrier? The barrier in this case being the what I assume to be an aluminum battery cover. On the Pre, Pixi, and EVO the battery cover is plastic.

Edit: After speaking for an EE colleague, we decided that it will probably work as aluminum is not a ferrous/magnetic metal and in our case is also pretty thin. That being said, efficiency might take a hit as attenuation though aluminum is higher than through plastic; the question is by how much? The closest example I can think of is how the iPad's antennas are always behind a plastic strip rather than being put behind the aluminum body.

This might be more complex than I thought...

Aluminum will block electromagnetic waves (a dual layer of aluminum foil is a pretty cheap Faraday cage for low power EM waves).

I only had my arrive for 3 days and was thinking about this the whole 3 days. I have a list of parts and steps but I realized there may be a flaw in them. I was planning on soldering the inductor to the USB +5v and GND pins. Now I'm worried about what would happen when the USB cable is plugged in now that there's a huge inductor Frankenstein'd into the circuit. Besides increasing the current draw on the USB port it would be generating a magnetic field. What would the new current draw be? Can the inductor handle the load or will it burn out? Would the magnetic field be safe or screw with signal gains?
 

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