user28786: I have 3 LEDs powered by an Arduino; each LED has its own flash rate.
Now I want it to be powered by an external 12V power source and still have the flashing function of the Arduino?

user16673: Use a N-channel MOSFET, wire load to drain pin, source to (common) ground, and place a 1 kilo-ohm resistor in series with your arduino pins. Bear in mind that MOSFETs respond to voltage, not milliamps, on the gate - get one that responds well to 5V logic.

28786: <p>I have 3 LEDs powered by an Arduino; each LED has its own flash rate.</p>

<p>Now I want it to be powered by an external 12V power source and still have the flashing function of the Arduino?</p>
 16673: <p>Use a N-channel MOSFET, wire load to drain pin, source to (common) ground, and place a 1 kilo-ohm resistor in series with your arduino pins. Bear in mind that MOSFETs respond to voltage, not milliamps, on the gate - get one that responds well to 5V logic.</p>
