It is a pretty common first project to use an Arduino (or similar) to blink an LED. Which, of course, brings taunts of: you could have used a 555! You can, of course, also use any sort of oscillator, ...

Back in school, I spent more hours than I can count hunched over an Arduino Uno – blinking LEDs, wiring up sensors, and building clunky robots that barely worked but felt like magic. The Uno was ...