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Topic: LED - resistor & current relations (Read 2 times) previous topic - next topic

cmd1024

Apr 01, 2012, 06:53 pm Last Edit: Apr 02, 2012, 05:08 pm by cmd1024 Reason: 1
Hello,

I am often using LEDs as many of you. I noticed that LEDs are operating very well without burning out even if i do not add any resistor. But when I read any information about them, it is written almost everywhere that series resistor is a must to use, otherwise LED will burn out instantly.

The point is LEDs are not burning out at all in 5V in the absence of a resistor.

Do they have extra resistance inside? If so why everybody still uses resistors in series with them?

It may sound weird but, i really couldn't find any information about this fact.

Best,

zoomkat

I voted for the first one. Hope this helps!
Consider the daffodil. And while you're doing that, I'll be over here, looking through your stuff.   8)

dxw00d

The resistor is not there to protect the LED, it's there to protect the Arduino.

cmd1024

dx.... I am talking about the information is not matching the experiments. Look what is written about LEDs:

"So it's vital to stay within the limits of the LED. If you would attach an LED to a 5 Volt power supply directly, you would burn it instantly. The high current would destroy the pn-gate. That's the point where the current limiting resistor comes in."

This is not true or not complete. LEDs are ok with 5V without any resistor.

pluggy

Depends where the 5V is coming from, if its from a digital pin on the arduino, the gate on the processor is acting as the current limiter.  You're too tight to buy resistors ?

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