color mixing with colored Poly-c tubes?

[reno]

hey all.

not sure if this is the right spot for this but has anyone tried to achieve a nice purple using a blue led and red polyc tube or contrary-wise a red led and blue polyc tube. tried to find something on it but i didnt come up with anything. thanks!

[Jedi-Loreen]

It doesn't work. You can't mix colors that way with LEDs.

Unlike ink or paint, which is additive, colored light is subtractive. When you use a filter (like a colored polycarbonate tube would be), you're removing all the other light waves that something like a white LED has, and just allowing the lightwaves of the color you want to come through.

If you try to use a red filter on a blue LED, you're going to get a very dim blade that might look a little bit purple, but the red tube isn't going to let much light out in the blue wavelengths. Similar questions like this have been asked before.

Since they haven't come up with a way to make true purple in a single die high powered LED, the best way is always going to be an RGB (or other multi-die LEDs that have red and blue dies) and mixing the red and blue. Usually with some value of resistor on the red, depending on the make of LED, because it will over-power the blue LED.

You can always try it, but I think you're going to be disappointed.

[reno]

thanks that makes sense. i always get good results mixing my rgbs (thanks to excellent tcss tutorials) but just had to see.

[Ripper]

I make a red blade from a purple led, in a red tube. That's my way of going Sith every now and again.

[thejedilestat]

a V3 blue Mokototsai string and a red tube mite work but it may still be verry dim as Jedi-Loreen stated with a single luxIII led. but ya never know so if you feel up to it give it a try i dont think it has ben done.

[Skottsaber]

Right, Ripper. That is possible because in your purple you have blue and red. Putting a red blade (or filter) on your saber is going to just let the red portion through. If you were to put a blue blade on it you'd only let the blue portion through.

[Darth Magnus.]

Why don't you get a RGB LED? you can use an arduino mini as your driver (there about $12 of ebay) and you can have any color you want.

[Skottsaber]

While that is an idea (although I would use a PIC personally :p ) I would take into consideration whether the OP has the skill/knowledge to build and program an LED driver system using the arduino.
Especially if he was looking for an easier solution using colored blades instead...

[Rhyen Skytracker]

You can just get a RGB LED and resistor the red more than the blue. The typical resistor range for purple is to resistor the red LED 2 to 10 ohms more than the blue LED. Each LED and set up will be different and the shade of purple you like is a personal preference. You will just have to try out different resistors to find the shade you like.

[Darth Magnus.]

Good point, probably just easier to do as Rhyen said.