LED header voltage

[Afro000Dude]

What is the voltage coming from the front led headers for the power and hdd led's? I want to replace the stock led's on my case but I don't know if a resistor is needed or if I could just solder a replacement led right onto the wire that is there. I assume it is a standardized voltage for all motherboards given the variety of cases out there, I just need to know what it is. Thanks!

 

[hasu]

The voltage drop across an led can varry with type. LED is basically a current driven device.
Most of the ordinary RED leds have a forward voltage of about 1.6-1.8 v and it gives full brightness at a forward current of about 10-20mA.

I would assume that your mother board has current limiting resistors built-in into it or it may be working as constant current source. I am assuming that because I have never seen any series current limiting resistors on computer cases which I have used. Though LEDs normally work at a forward current of 10-20mA, it can withstand much more than that - may be 5 times, (though it can potentially tax the mother board). But reversing the polarity of the input can easily damage the LED, especially if the current is not limitted. But in my pc, I have reversed the case LEDs for extended periods of time without damaging the LED.

I think it is safe to solder new LED onto the same wire, if there is a series resistor you can use that also.

Keep in mind that the Blue LED has a much higer voltage drop (around 4.5v), so if you use blue led, the brightness could be low.

see the following links, just for reading: (just search in google you will get lot of useful information)
LED Series Resistance Calculator
Shedding Some Light On LEDs

 

[Afro000Dude]

No, what I was wondering was whether it is giving 12 volts, 3.3 volts, 5 volts? 12 volts would most definitely require a resistor, 5 or 3.3 might not, depending on the led, and assuming it is using one of the standard voltages from the power supply. Anyone know?