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1  Using Arduino / LEDs and Multiplexing / Re: how many volts is needed in one led to turn it on on: August 31, 2011, 10:07:35 pm
Typically the 5mm Red LED uses about 2 volts with 20 mA max current, with the Arduino output at 5 volts then you need to use about a 150 ohm resistor (brown/green/brown) inline with the LED to keep it from burning out.

If your LED specs are different then use the calculator at:

Also, nice article previously posted*
2  Forum 2005-2010 (read only) / Frequently-Asked Questions / Power Supply on: October 14, 2005, 04:06:32 am
I just received the board recently and am wondering what the power supply must be... 12V, 16V?

Thanks for any help*

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