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Why is my blue LED so dim?

A

Akira13

Senior member
I just got a pair of tailed blue 5mm (3V) LED's. I installed them, and the one I used for my HD indicator works great (super bright), but the one I used for the power indicator is really dim (can't really tell that it's on, but it is). I thought it was the LED itself, but when I switched the two around, the result was the same: the LED connected to my power indicator is dim. I re-attached the original green LED to the mobo, and that was as bright as ever. Does anyone know what's going on? (I tried connecting the ground to both ground sockets, and neither changed the brightness).
 
If you have an ohmeter (sp?) check the voltage running through the LEDs when they're powered. I tested mine today, and they're only putting out 2.1v. Where did you get your LEDs, and what brand are they? I've heard the RS ones are okay, but that you can do MUCH better. RS ones are 2600mcd (brightness), but you could get up to 6000mcd.

Good luck 🙂
 
I got my LED's from frozencpu, so they're not branded or anything. I'm not sure how bright they're supposed to be. Unfortunately I don't have an ohmmeter. Maybe it's about time I invested in a digital multimeter or something.
 
An alternative to plugging the LED into the mobo is to just plug it into the 5v or 12v rail of the PSU with an appropriate resistor, usually 330ohm or 470ohm respectively. And a digital multimeter is definately worth investing in, a $15-20 one should be good enough for most needs.
 
5V rail and resistors huh? Looks like I'm gonna have to use some of the stuff I learned in Physics. Too bad I just couldn't get it to work (read: be bright) with the mobo headers. Thanks everyone, and if anyone has any more ideas, please let me know.
 
In a flash of inspiration, I decided to plug the LED into the turbo led header on my mobo (I didn't know that these things used turbo anymore). Low and behold, the LED now lights up bright as day. If anyone knows any reason why this is a bad idea, please let me know (anything from, "oh no, that'll overheat" to "your PC will implode into a quantum singularity, thus causing a cataclysm of universal proportions"). My thanks to everyone here!
 
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