Timed LED Signal

A complete first Arduino build with official REES52 video guidance, a checked wiring diagram, working code, build steps and a troubleshooting path.

1. 1Disconnect USB power and place the LED on the breadboard.
2. 2Connect D9 through a 220 ohm resistor to the LED anode.
3. 3Connect the LED cathode to GND and verify polarity.
4. 4Upload the sketch, record three cycles and change both delay values.

const int ledPin = 9;

void setup() {
  pinMode(ledPin, OUTPUT);
}

void loop() {
  digitalWrite(ledPin, HIGH);
  delay(500);
  digitalWrite(ledPin, LOW);
  delay(500);
}

• If the LED is dark, reverse it only after disconnecting power.
• If upload fails, check the selected board, port and data-capable USB cable.
• If brightness is unstable, inspect the resistor and common ground connections.