dboisvert

Im attempting to wire led's to my case fan...

I ran into a minor issue (hopefully)

When plugging the led's into the psu, 2 of the LED's flash very quickly and the other two do nothing at all. Then the psu powers down...

Im assuming there is a short in the two that are not turning on?

G|F.E.A.D|Killa

how do you have them wired,they should be in series

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radodrill

I'm assuming that you connected each LED directly to the +12V supply; this would have instantly burned out the LED.

Typically LEDs use 1.8V or 3.2V, so you'll need a combination of LEDs and resistors to get them to work right.

If you have the datasheet (or specs) for the LEDs and how may you want to install on the fan I can tell you how they have to be wired.

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dboisvert

I am using 4 LED's, each have a 470ohm resistor on the positive (longer leg) and the shorter leg is the ground.

The leds are 1.8 - 2.2v Blue leds at 30mA

radodrill

Somewhere your numbers don't quite jive

(12V-1.8V) / 0.03A = 373.33 ohm resistor for a single LED

or

(12V - 4 * 1.8V) / 0.03A = 160 ohm for a single resistor and 4 LEDs in series.


Also, do you have pics of the wiring?

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dboisvert

I know that its a bit overkill on the resistors, but they were free and its only going to dim them a little bit, and it will prolong the life of the leds... thats why I used 470ohm

Could the led legs touching cause the short?

CattleRustler

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radodrill

You do not want to use a way over sized (current limiting) resistor as that can cause the LED to not illuminate at all since the resistor would limit the current to be well below the operating range of the LED. You're best advised to select the resistor that's closest in size to the design resistance.


If they are uninsulated, most definitely. I personally use heatshrink around all my joints; and if you don't have that available, you should at least use some electrical tape.


BTW, the LED momentarily flashing very brightly that you stated in the OP is a surefire sign that the LED has been burned out.

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dboisvert

Alright, well I spent most of last night working on the fans, found my problem and pulled a noob mistake because I was in a hurry... I forgot to insulate the legs. So I got 2 out of 3 fans working now...

The 3rd fan is all wired up and I am running into some weird problems...

The leds all light up and stay on for a long while (they work) when I connect their individual molex connector to my test psu. As soon as I hook up the Fan it shorts and the PSU shuts off. The fan also works fine by itself, and when I plug in the leds it does the same thing...

There are 2 molex connectors one for the LED and one for the fan (if I wasnt clear)

radodrill

Got any pics of the wiring? As long as they're properly wired in parallel there shouldn't be any problems, that is unless you're somehow overloading the PSU.

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