I ordered the standard
LED Module from Ultra Sabers (Adegan Silver, if that matters) in the electronics section under "Build Your Own Lightsaber". I just assumed you knew I was talking about that one.
For starters, never assume anything. Yes, I could have guessed you were using one of the LEDs that Ultra Sabers sells, but you could easily be running an LED from a different source. And, actually, the color is probably the most important bit of information you could have provided. White LEDs have a forward voltage of 3.1 or 3.15 volts, depending on whether it's a Cree or a Rebel Star. (the difference is negligible) And, they run at 1000mA Now, I'm assuming you're running the 4AAA battery setup. AAA batteries are 1.5 volts, therefore you get 6 volts with four of them. Armed with that information, you can calculate the resistor you need. There's a simple equation to figure this out.
R=V/A (Resistance = Volts / Amps)
So, 6 volts - 3.1 (to be safe) volts is 2.9. 1000mA = 1 amp, so you divide 2.9 by 1 and it comes back out to 2.9. So, you need a 2.9 Ohm resistor. For wattage, you can go with a 3 or a 5 watt resistor, since that's basically just the heat dissipation of the resistor.
Now, does that mean that's what Ultra Sabers uses? I don't know, I don't have a white (silver) LED saber. I just used a simple calculation to figure out what it will probably run on. Resistors aren't an exact science. For example, your forward voltage (3.1v) is a variable number. It's not necessarily going to consistently run at that voltage.
For the build I did recently, I used a royal blue Rebel Star LED that says it runs at 3.2 volts. I'm using a 2.7 Ohm resistor and it's working just fine.
Anyway, that's what I have. Take it or leave it. You can wait for someone who has an Adegan Silver stunt or saber with Obsidian Lite that feels like taking it apart to weigh in if you want. (Obsidian premium sound uses a buck puck, so that won't help)