Last night I installed the voltage divider assembly into the Dension cradle. I thought I had some fine soldering tools but my smallest Metcal iron tip looks like a Louisville Slugger next to the 30 pin cock connector pins. It took some steady hands (which apparently I don’t have either), and some good diffuse light to make these connections. I used a strand of silver plated copper wire to make the connections, and a piece of the full stranded wire to make the power connection to the voltage divider assembly.
It would have been a little less kludgy to make a new circuit board with the proper resistor divider traces on the board, but I’m not sure that I can make a boar with traces fine enough to reliably fit the connector. I am also concerned that I couldn’t get the connector off the existing board without damaging it. So this is the result. It seems to work quite well at this point.
The next step is to step down the power coming into the cradle from 12(ish) volts to 5 volts. A linear regulator doing this job would be dumping more power into heat than it provides to the iPhone for charging, which not only may overload the factory head unit, also requires the linear regulator be heat sunk somewhere. V-Infinity has a really snazzy switching regulator that has an efficiency of about 92%. This means that during full charging, the regulator will only dissipate about 0.2 watts and will not need a heat sink.
Sheldon
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Thanks Sheldon. I took the plunge and made the mod to my Dension ICE-link One, and it’s working successfully. Things I did differently (limited by what I had in my electronics components “junkbox”:
1) Used 3 resistors for the voltage dividers: (5v) – 36k – (2.7V) – 10k – (2.0V) – 33k – (0V) to get voltages of 2.7V and 2.0V which works fine.
2) I used an analog 7805 regulator and replaced the cradle bracket with an aluminium bracket-heatsink. It still runs very hot … I hope it’s going to last. When I find a switching regulator I’ll replace it.
3) I left the 12 volt supply to the firewire circuits on the cradle motherboard, so I can use both my iPod 5G and iPhone 3G on the same cradle (one at a time).
Thanks for your posting! It really helped me a lot, and gave me the confidence to undertate the project.