What voltage are my case LEDs?

[downhiller80]

I want to replce the standard LED on my case with a brilliant blue one.

What voltage do I need to get? I just ripped out the existing onee to see what it is but it hasn't any markings on it.

Seb

 

[lenjack]

mobo's are so complex, maybe you should leave this as is.

 

[downhiller80]

anyone?

 

[Rain Man]

I bought some blue LEDs from Radio Shack (part # 900-8005), and they work fine - a bit too bright though, so you may want to add a current limiting resistor, unless you want it to be that bright.

 

[Mark R]

Any LED will do.

A blue LED will draw less current when connected to the mobo than a non-blue one. You may however, find that 'super-bright' ones look bad because they are too bright.

 

[downhiller80]

I can't imagine them being too bright but I guess I'll find out for myself.

I've got an Inwin 500 and infront of the LED is a triangular piece of plastic which dulls the LED a bit. I'm gonna try painting all but the top edge with reflective silver paint and see if I can get the light to be cast up the bezel. I think it'll look coo.

Seb

 

[downhiller80]

can anyone tell me what voltage the m/b supplies to the power LED??

Seb

 

[cgclausen]

I think I have just what you are looking for, ther is an article over at virtualhideout.net about how to change your case LCD, I read it and forgot the number but it tells you about what your voltage is. Give it a read it will help I'm sure. http://www.virtualhideout.net/guides/case_leds/index.shtml

 

[downhiller80]

Brilliant stuff. Thanx.

Seb

 

[Dramor]

I thought all LED(atleast Generic) were made to run on about 1.2V, I think thats from my basic electronics classes but who can remember old times heh. Any LEd should work on it, just dont go over 5v to a LED or you take a chance of having the top shoot off. Some can handle upto 9v heh the memories of shooting LED across the class ;p. But times could ahve changed

 

[Rain Man]

The motherboard supplies +5V to the LEDs. Most blue LEDs have a voltage drop of >5V. The ones I bought from Radio Shack are 3-4V. I think Digikey also has some that are 3-4V.

 

[downhiller80]

In the virtual hideout link given to me above it says they're typically 2v?

Seb

 

[SillyBoy]

I have sucessfully hooked up three blue leds from radio shack. They are a little bright, so you may want to use a resistor with them. Other than that, they work fine, nothing burned out etc. etc. (BP6 mobo)

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[SillyBoy]

BTW, most motherboards supply 5v to leds, but I believe that most leds are spec'd for less than 5v. The worst that could happen is that you'll burn out the led and you have to get a new one ($2.00??).

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[Mark R]

The important thing to remember about LEDs is that you don't supply them with a recommended voltage like you do a light bulb - you supply them with recommended current

The easiest way of thinking about supplying an LED with power is to imagine the LED subtracting voltage from the circuit - the LED voltage drop.

Here's a simple problem:

You have a 5 V power supply, a red LED with 1.6 V drop[1], and a resistor. The recommended max current for the LED is 0.02 A.

The LED does not limit the current on its own. If you connect it direct to the power supply, it would be like connecting a short circuit across a (5-1.6 = 3.4 V) supply, and the LED would blow. You need the resistor to limit the current - in this case at least 3.4/0.02 = 170 ohms. This resistor is included on the motherboard.

Now, let's say you change the LED for a blue LED with a 3.5 V drop. The resistor is unchanged. What happens to the current? It will be considerably less than the original setup - sufficient to provide a reasonable light output but with no risk of burning out motherboard, or LED.

[1] LED voltage drop is dependant on colour. Red typically have the lowest at between 1.2-1.6. Green and yellow are slightly at 1.6 - 2.0 V. Blue (and white) are dramatically higher at between 3.4 - 4.0 V.

 

[downhiller80]

Excellent stuff Mark!

I actually should know all this since I'm doing a degree in physics and have just done solid state but I guess I forgot it all . . .

Seb