need blue LED for PC case

[**DONOTDELETE**]

Hey guys,
I'm looking to setup a internal case light for my computer, and instead of cold cathode tubes, I was hoping to use LEDs. I'd like to use blue LEDs, but red or yellow or even green would work too. I'd like it to be fairly bright.

It is running off of my power supply, directly, so I guess it can be either 5V or 12V.

I have been told:
"all blue LEDs
require a forward voltage of 3.6 volts with a 20mA current running through
them. So 3x LEDs require 10.8 volts.

So the resistor has to drop the voltage around 1.2 volts and control the
current running to the LEDs to 20mA. That works out to a 60 ohm resistor."

I'm not sure if I understand all of this, but if you fine people could help me light up the inside of my case with LED's... I'd appreciate it.

Thanks,
-greg
[email protected]

 

[The_LED_Museum]

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by greg:
It is running off of my power supply, directly, so I guess it can be either 5V or 12V.

I have been told:
"all blue LEDs
require a forward voltage of 3.6 volts with a 20mA current running through
them. So 3x LEDs require 10.8 volts.

So the resistor has to drop the voltage around 1.2 volts and control the
current running to the LEDs to 20mA.<HR></BLOCKQUOTE>

Well, that's certainly one way to do it.
Personally, I just parallel the LEDs and let them suckle off the +5 volt line, because in most computers, the +5 volt rail has the ability to supply substantially more current than the +12 rail. But putting them on the +12 volt line does slightly reduce the chance of permanently damaging your system if you screw up, because fewer critical components on the motherboard use it. It is normally used mostly for disk drive & CD-ROM motors and for cooling fans.

I'd say just hook them up in a way that suits your needs & abilities best. There's nothing at all wrong with putting three LEDs in series plus resistor on your +12V.

Just be sure every string of 3 LEDs you add has its own resistor, and don't overload your power supply's +12V current rating. 5 strings of 3 LEDs each will consume an extra 0.1 amp off your +12V line; or about half as much power as an ordinary 12 volt computer fan.

 

[**DONOTDELETE**]

so!
which do you recommend? And how do I physically hoow a resistor up to the series of leds?
Also, what blue leds should I "go for"?
thanks for the help.