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Hi im having trouble with something which i thought would be simple, but its doesn't seem to be.

i compiled  the blinking test and is it communicating with my arduino.  so i know it is working. however i wanted to switch the current LED with a brighter LED (product code - N20BY Blue LED), i read on some forums that i needed a resistor otherwise it will fuse out, so with that i put the new LED through a breadboard.  so the current circuit is

connected through the breadboard via wires
GRD--> to LED --> to 1kohm resistor -->back to 13pin

but im having difficulty with making the Bright LED turn on

i was trying to mimic this tutorial
http://www.ladyada.net/learn/arduino/lesson3.html

can anyone advise. thanks

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The led is either reversed or 1k is too much. It's got a forward voltage of 3.6V (link), so 1k limits the current to 1.4mA. The led is rated for 30mA max.

R = (supply voltage - forward voltage) / desired current

So I'd test for polarity and later switch to a different resistor to allow for some more current. A value of 100 should give about 14mA.
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sorry im very new to all of this, but does that mean, i could actually use the LED without a resistor?

thanks
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Please don't !

The current grows exponentially once you  pass the on-voltage (link). So either you precisely hit the right spot on the VI curve, or you create SMOKE. LEDs need a current limiting "device", the simplest being a resistor.




« Last Edit: November 02, 2008, 05:37:03 pm by madworm » Logged

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thats fine, i'll just go out and buy one. thanks for the advice
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Doesn't Pin 13 already have a built-in current limiting resistor on it for LEDs?

The rest of the digital pins do not so you will need the appropriate resistors for them but I believe Digital Pin 13 already has a resistor

Please correct me if I'm wrong

smiley
« Last Edit: November 02, 2008, 06:23:46 pm by gnu_linux » Logged

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There is a 1k resistor at pin13, but it only limits the current of the on-board led.
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the new LED that i brought didn't want to work in the PIN13 hence i felt i had to the use the bread board, and it worked somehow. so no worries there smiley-razz
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Obviously it seems to be that the positive and negative are switched around.
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Quote
I believe Digital Pin 13 already has a resistor

It depends on what sort of Arduino you have. I have seen one on the Arduino mini schematics.
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