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1  Forum 2005-2010 (read only) / Interfacing / Re: Which resistor for a white LED 3,6V / 75mA ??? on: February 25, 2009, 11:32:37 am
Thanks to all of you guys for your reactivity.
I learned something today  smiley-wink
2  Forum 2005-2010 (read only) / Interfacing / Re: Which resistor for a white LED 3,6V / 75mA ??? on: February 25, 2009, 11:19:10 am
My conclusion.

So, if I use this kind of LED (18 cd @ 3,1V / 20mA - Maxi : 22cd @ 3,6V), I don't need a transistor (below the 40 mA) and can only use 95 ohms resistors.

Am I correct?
3  Forum 2005-2010 (read only) / Interfacing / Re: Which resistor for a white LED 3,6V / 75mA ??? on: February 25, 2009, 11:06:55 am
Okay, thanks.
Last n00b question: what kind of transistor?
4  Forum 2005-2010 (read only) / Interfacing / Re: Which resistor for a white LED 3,6V / 75mA ??? on: February 25, 2009, 10:45:32 am
Thanks for your replies.

My intention was to use this sample by just changing the resistors accordingly to the LED characteristics.

http://arduino.cc/en/Tutorial/Loop

Will it work with this kind of LED and 18 ohms resistors only if I use 5 output pins or do I need a transistor?
5  Forum 2005-2010 (read only) / Interfacing / Which resistor for a white LED 3,6V / 75mA ??? on: February 25, 2009, 07:49:11 am
Hi all,

I need to use 5 white LEDs connected to an Arduino Duemilanove

I'm absolutely new to electronics and have no idea which resistor value I should apply to each LED. Looks like 200 ohms or 270 ohms is fine for the LEDs provided with the starter kit but for the LEDs I intent to buy, I'm not sure. See info below.

• LED Ø 5 mm
• Intensité lumineuse >10cd (10.000mcd)
• 50cd@ 3,6V / 75mA
• Maxi: 50cd @4,2V

If someone could tell me how to calculate that value that would be great.

Thanks,
J
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