39 ohms is practically a wire
EDIT: In general, what is the preferred method of driving a load needing current limitation from a low impedance source? Particularly when it is a low impedance, low voltage source for which voltage dropout due to something like a diode or resistor means there could be insufficient voltage to accomplish the desired work? Some sort of shunt regulator?
Yeah, I was wondering about a joule thief. So, if I made the capacitor in my original circuit the power source for this:do you think that might have more success?
Or would you have a particular higher efficiency constant-current switching regulator IC that you would recommend?Maybe something like the 756 version of this:http://www.digikey.com/product-detail/en/MAX756CPA%2B/MAX756CPA%2B-ND/1130177 ??