but I was wondering.
I know how to calculate what resistor is needed to drop current to an LED if the source voltage is higher than that of the LED with the supply - (led voltage) divided by the required current. But my Voltage source is the same as the LED needs, thing is its a 1 watt LED (at 3.6 volts) but instead of drawing the full 270 mAmps I only want to to draw about 150, how would I go about working that out or what is the resistor I would need for it?

Thanks in advance.

 

Are you saying you have a 3.6V supply and your LED has a 3.6V forward voltage?

 

It is not possible to calculate the resistance required without knowing the I-V characteristics of the LED (which is non-linear).

Do this experimentally by trying different values of resistances until you get the desired effect.

Let us know your results.

 

It is not possible to calculate the resistance required without knowing the I-V characteristics of the LED (which is non-linear).

Do this experimentally by trying different values of resistances until you get the desired effect.

Let us know your results.

It's a 3.6 volt, 1 watt LED (about 0.270 amp)
so yeah I see what you're saying. I'll just mess around ^^ thanks

 

Are you saying you have a 3.6V supply and your LED has a 3.6V forward voltage?

yep

 

yep

Then you will need to step up the voltage. Google "Joule thief" and you will find many such circuits.

 

To reduce the current through the LED you need to reduce the voltage applied to the LED. A resistor would do that or any of a myriad of other possibilities.