First project: Blink — the LED blinks

The "Hello World" of electronics — a blinking LED. On the breadboard (solderless board): long LED leg (anode, +) → pin 13 via 220-Ω resistor → short leg (cathode, −) → GND. Without the resistor the LED burns out — like in our circuit lab! Code: setup() runs once — pinMode(13, OUTPUT). loop() runs forever — digitalWrite(13, HIGH) → delay(1000) → LOW → delay. Uploaded — and it blinks once a second.

• ●Long LED leg = plus; short/flat side = minus
• ●The 220-Ω resistor protects the LED — Ohm’s law: I = U/R
• ●Pin 13 already has an onboard LED — blinking works with no circuit at all