Lighting an LED is easy: power and a resistor so you don’t blow out the LED.
Apparently making that LED do something else, like fade in and out, takes something more, like an Arduino microprocessor that supports Pulse Width Modulation (PWM). PWM is basically a method of turning the power on and off rapidly, so the LED in this case appears to fade in and out, or pulse. If you looked at it with a high speed camera, it’d be flashing on and off, each time it came on a bit dimmer. Since this is happening faster than the human eye can detect, it looks like its just fading.
This is all explained in the Arduino PWM Tutorial I followed, which I followed and produced this:
Hurray! I’ve accomplished something a 10 year old can do!
But it was fun…and I’ll do more!
Buy resistors and LEDs!