HACKING AN INDUCTION CHARGER - help me figure out its inner workings

[flx]

Hi y'all!

You may or may not have read about the "wireless" charger for Palm Pre. A few details and some pictures (inside & outside) can be found at iFixit.com

I'm trying to use this thing for charging something else and the problem I ran into is its power saving feature whereas the base only pushes current if the phone is actually on it. Otherwise, it just sends a "presence signal" about once per second. I tried connecting various loads to the output of the secondary coil (the phone part) but I just couldn't trigger the charging mode. On occasion, I am able to enter charging mode by connecting two led's in anti-parallel (I couldn't replicate that when shooting the video) but as soon as I take them away (it gets hot quickly), the whole thing goes back to "normal". While in continuous mode, it puts out exactly 5V.
Here's a short 20 sec video about it. Notice the faint buzz in the background that I'm picking up with that headphone, it goes along with the LED blink.

If anyone has any idea on how this thing works or even just suggestions on what I could try next, I would appreciate it very much!

Base: **broken link removed** Receiver: **broken link removed**

Video: YouTube - MVI_2644.AVI

Thanks!!!

 

[Sceadwian]

Perhaps the receiving unit is actually transmitting a signal briefly to turn on the transmitter? Try using a third coil just as a signal pickup and see if you can figure out what the transmitter and recevier are actualyl doing when they get close together.

 

[flx]

I actually don't have the phone itself, only its back cover. The phone has 2 pins on its backside which make contact with the golden pads (as seen in the picture). Do you think the phone would send some signal through that rectifier / stabilizer PCB back to the coil?

I do think it's more basic than that, otherwise I can't explain how I'm able sometimes to trigger the charger with the right combination of LEDs.

 

[Sceadwian]

Are you able to reproducibly cause the transmitting station to stay on? If not then you're just guessing. So am I.

 

[Mr RB]

Check the data sheet for the SMPS chip that drives the transmit coil. It probably has a nice easy logic level "enable" pin to turn it on and transfer the power.

On the receiver side you only need to identify the rectifier diodes and add a cap after that, you can probably remove half the guff on that receiver PCB.

 

[unclejed613]

TI Contactless Power - TI.com

TI's bqTESLA cordless charging system, development kits are available...

 

[flx]

The March 2010 availability was announced quite some time ago but March is here and nothing showed up as of yet. I signed up for the kit and I hope to get their email soon, though I'm not holding my breath...

 

[unclejed613]

i've noticed that with a lot of interesting silicon. analog devices had a wimax transceiver chip in "to be released soon" status for 4 YEARS, and just changed it to "current production" status only 2 months ago. i was beginning to think the device was vaporware.

 

[flx]

In some cases they are probably waiting for market adoption first, which I think was the case with the WiMax chip you mentioned. By that time, however, others may emerge with competing solutions which will make these early-announced products already late to the party. Sure, in the US, only now has Sprint launched its WiMax network - but wait a sec... whose chips are floating around in the handsets? Wake up, AD!

Same goes for this induction charging. Sure, the Chi standard isn't ready yet but again, by the time it will, mfgs will be using competing chips. It's beyond my comprehension why can't they just follow the path of - say - 802.11N which is still in "draft" phase but the market is full of products.