Originally Posted by
Milton Keynes
Most LED's operate on 1.5V. Running 6V through them without a current limiting resistor runs the risk of burning out the LED. That being said, many LED systems run on 3 to 6V, so my opinion is, it depends on the power requirements of your light.
just to clarify...
the forward voltage of LEDs varies with the color, with longer wavelengths having the lower voltages and shorter wavelengths having higher voltages.
White LEDs, which use phosphors to convert blue light to other colors, tend to have a forward voltage of about 3V.
Dynamos are designed to have a limited current when shorted. As such, they produce a maximum of about 0.5A. If the LED(s) in the headlight are rated for 0.5A, then no other current limiting circuitry is required.
The exception to this is the Velogical bottle dynamo.
Steve in Peoria