post #11 of 11
I use mylar primarily because I have access to it.
Scotch tape might work ok as a diffuser. Benefit is you probably already have some. I'd also recommend scuffing up the LED packages with some 400 grit sandpaper. You can even grind down the epoxy casing (the clear part), drill it, or do whatever you like to reduce it's size or to shape the beam. As long as you don't totally overheat the LED chip by grinding to hard and fast, or cut too close to the metal parts inside where the chip resides, there's absolutely no problem.

There is a -12v line available. There's also a 3.3v. Check the ATX pinout.

There is no issue with connecting to a +5v and -12v pin to give 7v potential. This is how most benchtop power supplies (even those converted from ATX PSU's) work.

Some fan controllers reduce voltage by using a variable resistor, or power regulator. As far as "how to hook up a power regulator"... google for the data sheet for the part and it'll tell you what each pin on the part is for, therefore how to hook it up. Generally you wire them to a power source within their specifications (say maybe 5v-15v DC). You have a pin for filtered output voltage. That's obvious. Hook up your device to this pin and the common (ground) pin. Then there's a "voltage adjust" pin. You attach a properly sized (use the data sheet's lookup table) resistor to this pin. The voltage regulator then alters the input voltage and gives out the voltage you need. Some voltage regulators will even ADD voltage by sacrificing current. Theoretically you can use that 12v strip on a USB cable... but will not be able to run more than say a foot of it... because the USB can't supply more current. I've personally never done this, and I'm no electronics expert, but some of this stuff gets pretty easy when you're pointed in the right direction to find the information.