5V power buck power supply for bicycle use
February 14, 2012
It has to digest a wide range of input voltages, and it has to be efficient enough to deliver 2.5 watts of power.
This version has several flaws (spec’d wrong buck diode, holes were not large enough; needed to bias D+ and D- to make iDevices happy about charging), but with some tinkering, it works (tested with iPod Classic and Nano). Further research needed to figure out why it won’t charge my Motorola phone. Further research: mini-USB is a 5-pin connector, and pin #X (they call it that) is shorted to pin 2 and connector to pin 4 (GND) with a 200k resistor. For now, I will just buy a cable that claims to work for this purpose.