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I'd like to power a bright LED (1W or 3W) connecting it onto a power source of my computer, directly on the motherboard. I think about using either a fan connector or directly the ATX Power supply. But I don't find any information about how to do that well on the net.

I will have to use a resistance, a led, some wires and perhaps a power switch, and probably some cooling stiff for the LED and the resistance. But what about what-to-do and what-not-to-do about such a DIY stuff ? I mean, what may I connect onto what, what must I take care about, ... ?

examples : the fan connector has 3 pins. My LED has 2 pins...
Making such a connection may damage the motherboard ? What may I do to prevent this ? What about the voltages and power ?

I was starting this with confidence, but not finding anyone that talks about that on the net makes me a litlle be scared.

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  • \$\begingroup\$ Cooling stuff for the LED...how powerful of a LED are you talking here? Datasheet? \$\endgroup\$
    – dext0rb
    Commented May 31, 2013 at 16:24
  • \$\begingroup\$ whats the spec of LED you are using \$\endgroup\$
    – yogece
    Commented May 31, 2013 at 16:44
  • \$\begingroup\$ @dext0rb : I'm talking about a 1W - 3W led \$\endgroup\$
    – Oliver
    Commented May 31, 2013 at 23:11
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    \$\begingroup\$ The motherboard expects "fans" at FAN connectors as it may control the speed using PWM as configured in the BIOS. So your LEDs may not have a constant brightness all the time. Also, You may damage PCB traces if you drive LEDs that take larger current than your fans. \$\endgroup\$ Commented Feb 8, 2014 at 6:50

2 Answers 2

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There is nothing special about a computer when it comes to leds. You can power directly off the ATX supply (Either 12V, 5V, 3.3V) or from the fan connector (12V). Just add an appropriate resistor and you are done. You need to apply the same led calculations as anything else:

$$Resistance = \frac{Source\,Voltage - LED\,Forward\,Voltage\,Drop}{Desired\,Current}$$

The Fan connectors have three pins, one for 12v, one for Ground, and one for Tach/Speed Sensing. Fan connector symbol

Since you mentioned cooling, are you talking about 1W or higher LEDs? The same still applies. You could use the fan connector for both a cooling fan, as well as the led power source.

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  • \$\begingroup\$ does fan connector has short circuit/current limiting feature? if not then he may have to add current limiting circuit or Fuse am i right? \$\endgroup\$
    – yogece
    Commented May 31, 2013 at 16:43
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    \$\begingroup\$ @yogece a resistor is a current limiting feature. \$\endgroup\$
    – Passerby
    Commented May 31, 2013 at 17:09
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    \$\begingroup\$ You might want to mention that the power supply needs to actually be able to handle the LED current since many machines are designed without much power overhead. For a normal LED it's obviously not an issue, but mentioning "bright" and the bit about cooling, I'd pay attention to how much extra load this LED is given the higher current requirements of high-brightness LEDs. \$\endgroup\$ Commented May 31, 2013 at 18:07
  • \$\begingroup\$ I'm talking about a 1W - 3W led \$\endgroup\$
    – Oliver
    Commented May 31, 2013 at 23:08
  • \$\begingroup\$ A computer's PSU should be able to provide the necessary current no problem. \$\endgroup\$
    – BlueBuddy
    Commented Feb 7, 2014 at 19:04
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Many computers will have an extra 4-pin Molex connector providing 5v and 12v coming from the power supply. This would be a great way to power to a LED. No need to worry about drawing too much current from fan connectors, etc. Usually both 5v and 12v rails can supply several amps. Look at your PSU sticker for details. See http://en.m.wikipedia.org/wiki/Molex_connector (8981 series)

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    \$\begingroup\$ You can even get splitters if you dont have enough free cpnnectors. Just make sure thr psu can handle the total load. \$\endgroup\$ Commented Feb 8, 2014 at 4:02
  • \$\begingroup\$ OP is asking to power LED from motherboard internal connectors. \$\endgroup\$ Commented Feb 9, 2014 at 20:27
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    \$\begingroup\$ @ChetanBhargava I think about using either a fan connector or ** directly the ATX Power supply.** \$\endgroup\$
    – Passerby
    Commented Feb 9, 2014 at 22:37

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