Do you remember where the tutorial is?
Trying to find it. That thread died long ago. Anyway, this link is very useful.
http://led.linear1.org/led.wiz Use this for your arc reactor, repulsors, and pepper's ghost eyes.
It will print a diagram and how many resistors and what kind you need.
For example, you want 12 LEDs for your arc reactor.
Put this and it will print a diagram and how many resistors you need.
Source of voltage: 9 (battery)
Diode forward voltage (color of LED): 2.0
diode forward current mA: 20 (either 3mm or 5mm LED)
number of LEDs in your array: 12
This is my rubbish diagram for pepper's ghost
[/URL] Uploaded with
ImageShack.us[/IMG]
You can buy a roll of reflective sheet at online store. Home depot carries acrylic sheets for your lens.
Can get more simple than that, can it?