Arduino UNO Tutorial 1 - Flashing LEDThe Arduino UNO already has an led and resistor connected to output pin 13, so we will use that. No other components are required.
You don't have to have a resistor on pin13, but the rest you do. Pin 13 has an led on the board, but you can add one too without a resistor.
QuoteYou don't have to have a resistor on pin13, but the rest you do. Pin 13 has an led on the board, but you can add one too without a resistor.That isn't true (anymore) - an external LED would still need a current limiting resistor. The onboard resistor only applies to the onboard LED (in parallel with pin 13). I understand that early Arduinos had the onboard resistor in series with pin 13 but that hasn't been the case since at least the Diecimila.
I just bought my first Arduino which is an UNO and I haven't done anything with it other than...
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