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Just a quick question, I just took apart an old pc and it has a simple power led. It was attached directly to jumpers on the mother board (power led, activity led and hdd led)

Can I use it on the RPi just like that? Or do I need resistors on all the use cases?

I am totally noob at electronics, just wanted to start playing around with GPIO pins.

I was reading a lot of posts, that you should use the resistors to help to protect the board in case you accidentally supply higher current on your end, but if my circuit is just a simple led do I also need to use them?

  • I am jsut thinking that led from the pc is somehow different and so safe to use without resistor, as it was already used on the mb of the pc. – user2917823 Apr 18 '16 at 22:44
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You always need a series resistor. Otherwise the LED will try to draw excessive current. This will be limited to the Pi can provide via its internal circuitry and ultimately won't cause permanent damage, but is inadvisable and would impact on other circuitry.

A LED (depending on colour) has a forward voltage drop of ~2V regardless of current. It will draw more until it pulls the output to this voltage.

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