Silly basic question but I can't think of the answer. I know how to turn an LED on and off by coding digitalWrite(ledPin, HIGH); or digitalWrite(ledPin, LOW); when attached to say pin 10. How do I turn the LEDs on and off if they have a different power source? I will need to power them with some …

LED control when using different power source

Pauly January 27, 2010, 2:22am 4

Thanks.
What type of transistor would I need ?
Something like this NPN 2N3904 from Sparkfun?

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