leds

[nooblark]

where is best place to buy leds (i think i saw em 10 cents each on all electronics.. dunno if thats cheap.. i want a assorted colored amount just in case i wanan change colors.. and any sites for replacing them on fans, and normal cases (pics help )

*edit* whats the differance between the v and mm of em too

[Spartan]

Go down about 20 or so posts and look at Designers thread. I have bought alot of LED's from Radio Shack for work.

-Spartan

[nooblark]

well that thread dind't help much, he was just telling you about it, not how.. i want a standard fan replacement and/or case (power switch and stuff) and whats the differance between 3 and 5mm (whats each one for) and the v? im obviously new modding, so hook me up with detialed stuff if u can

thanks
-noob

[Designer]

OK, just to clarify things a bit.

Normally LED's come in two sizes that are commonly used they are 3mm and 5mm.
What you get is your preference (obviously depends if your replacing an existing one), but check with the electronics company's catalogue as standard LED's require a low forward current (IF) and voltage,

Standard LED's are normally around 2V forward voltage (VF) and 30mA (milliAmps) forward current (IF), if your planning on fitting LED's into a PC you'll need a series resistor to reduce the forward current and voltage to a suitable level to prevent the LED burning out (although you can buy LEDs with an integral series resistor for 12V operation but the range is somewhat limited),

Anyway, with the values VF and IF you can calculate the value of the series resistor you will need with Ohms law which is V=I*R so if you transpose that formula to R=V/I where R=resistance in Ohms, V=voltage and I=current (in amps)

So say for example your LED has an IF of 30ma (0.03A) and the voltage of the LED is 2V but your running it from 12V (normally used in a PC) then:


Subtract the LED forward voltage VF from the supply voltage

so 12V - 2V = 10V

and the IF (forward current is 30ma or 0.03A) then

R = V / I ........ so ......... 10V / 0.03A = 333.3 ohms

Then select the nearest matching resistor value to this (better to go up rather than down).

Sorry to go off on a maths bit there but you'll need to do that to work out the value.

A 1/4 Watt resistor (low cost metal film type) is suitable to use.


Hope this is of some use to you Nooblark,

PS- Fan LED's are normally 3mm,

and the Anode (Vs +) is normally the shorter led and the Cathode (gnd) is normally the longer leg.

Beware, don't assume all led's have the same forward voltages and currents (different colours are often different)

Regards D

[Designer]

Here's a site Tin Canary suggested in another thread:

http://www.hitechleds.com/

They may be able to help you out a bit.