Arduino LED Project for Beginners

1. Connect the board and select the upload target

Connect the UNO Rev3 to the computer with a USB data cable. In Arduino IDE, choose the UNO board and the port associated with the connected board. Open the built-in Blink example from File → Examples → 01.Basics → Blink.

For this exercise, leave external components disconnected and use the board's built-in LED. The LED_BUILTIN constant identifies the LED pin for the selected board. A power indicator LED is separate from the programmable LED.

2. Upload a short repeating pattern

The following sketch gives the LED two equal phases. The setup function configures the output once. The loop function repeats the on/off pattern. On the UNO Rev3, HIGH turns the built-in LED on and LOW turns it off.

const unsigned long phaseMs = 500;

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

void loop() {
  digitalWrite(LED_BUILTIN, HIGH);
  delay(phaseMs);
  digitalWrite(LED_BUILTIN, LOW);
  delay(phaseMs);
}

• Use Verify to check that the sketch compiles for the selected board.
• Use Upload and wait for the IDE to report completion.
• Observe the programmable LED: each phase is 500 milliseconds, so one full on/off cycle lasts about one second.

3. Change one value and predict the result

Change phaseMs to 1000, upload again and predict the full-cycle duration before observing the LED. Then try 250. The full cycle contains both an on phase and an off phase, so equal phases of 1000 milliseconds produce a cycle of about two seconds.

Next, replace the two delay values with different durations. For example, an on phase of 200 milliseconds and an off phase of 800 milliseconds still makes a cycle of about one second, but the LED spends less of the cycle lit. Record the code values alongside what you observed.

4. Troubleshoot in a fixed order

5. Connect the exercise to robotics

This project introduces a repeating control sequence: configure an output, change its state and observe the effect. A robot adds inputs and actuators, but keeping a small, testable output exercise is still useful when bringing up a new controller.

The delay function pauses the sketch's normal execution. A robot that must read controls and respond continuously needs a more suitable timing approach, such as the official Blink Without Delay example. For a next electronics build, learn about LED polarity and current-limiting resistors before connecting an external LED; use the board's specifications for voltage and current limits.