Connecting case power LED

[javafiend]

Hi all,

How would you connect a case power LED to a motherboard that doesn't have a power LED header?

Thanks!

[Luke122]

Why not just tap into a molex connector for a power source?Then it'll light up when the case is powered.

[javafiend]

I had considered that, but it seems to me that there might be a more elegant way to do it. Would splicing it into the wire for the power button be a viable option?

[Luke122]

I dont think so.. my understanding of the power button is that it momentarily shorts the two terminals, causing the power supply to fire up.

I think it could be easy to splice into the molex connector for the HDD or even the CDrom, and hide the wires along the drive cage to the front of the case. :)

Anyone else have any ideas?

[javafiend]

Hmm... that sounds like a decent idea. Now considering I'm kinda electrically illiterate, what would be a good way to connect the LED to the molex or PSU without removing the motherboard header on the LED?

[Luke122]

I'm not sure of the voltage requirement for the LED you are using.. Just a standard one? I'll throw the meter onto a mobo here after lunch, and let you know what you need for a resistor (if you need one) when you tap into the 5v line on the molex.

As far as how you could tap into it, maybe look for a male-female molex plug for splicing fans inline with components, then just cut the wires for the fan and solder onto a set of pins that you can plug the connector into..? I'll try to sketch something up for you when I get back from lunch. :)

[javafiend]

Cool, thanks!

[Luke122]

OK, so I just pulled 5v off that mobo power LED header, which is the same as the red and black lines on a molex connector.

Since most ultrabright LED's use between 2 and 3.5v, and 20-30ma, you would want a 250ohm resistor. That way the LED will still light up bright enough, but not risk being overdriver (and self destructing).
http://i128.photobucket.com/albums/p176/lukifer122/250resistor.jpg
Image courtesy of Dannyg.com (http://www.dannyg.com/examples/res2/resistor.htm)

SO.. FEAR MY LEET MSPAINT SKILLS!!!1!!one!

http://i128.photobucket.com/albums/p176/lukifer122/splice.jpg

As far as how to connect the wires inside the molex connector, you can drop some solder in there to hold it into the metal pin inside, or just get something like this (http://www.pccasegear.com/prod285.htm), seen here....
http://i128.photobucket.com/albums/p176/lukifer122/3pinto4pinbig.jpg
...and cut the fan connector off the end. Use that, and half the work is done already.

Also, make sure that when you solder the wires to the resistor and the led, use a clip to help dissipate some heat, or else just work FAST. You dont want to overheat the resistor or the LED, as you could damage them. :)

And remember, heatshrink tubing is your friend!