On Tuesday 17 February 2009, Alexander Mueller wrote: > Hey all, > is anybody out there who is using the FR on longer trips for navigation > and/or geocaching? How did you solve the power problem? > > I would love to have an adapter from my hub generator for the > Freerunner. Should not be too difficult. Something to convert AC to DC > and then maybe some switching thing to getthe right voltage (DC/DC > converter or what). > > Does anybody have a solution or some hints?
I have run a Psion 5 and Garmin GPS from my lightspin generator. I used a bridge of schottky diodes and a capacitor to get DC, and the car PSU to feed them their nominal 6V and 3.3V. The car PSU used ordinary fixed voltage linear regulators. The Psion only starts using external power at 5.5V and this was available above ~12mph with this setup. The lightspin needs another tweak, but that's because it's rather an unusual generator. The voltage characteristics of different dynamos vary somewhat under load, but if you use schottky diodes for the bridge and a low dropout 5V regulator you will probably be ok from fairly low speeds. The schottky diodes have a lower voltage drop than normal rectifier diodes which is the reason to use them in this case. Charging a battery would be a better solution, as someone else suggested, but would be more complicated. to implement well. _______________________________________________ Openmoko community mailing list community@lists.openmoko.org http://lists.openmoko.org/mailman/listinfo/community