Maybe some electronics guru can explain this, I've read about the resistor drop thing- so we is it I can't use a resistor to drop the 12V from a car battery to 5V so that it can be used to power a GPS or other 5V electronic device? All the schematics I've seen involve using some regulator either a 7805 or something more expensive. Am I misunderstanding something about what the voltage drop means in the context of a resistor?