Remote Robot Arm

const int RED = 2;

const int YELLOW = 3;

const int GREEN = 4;

void setup() {

  pinMode(RED, OUTPUT);

  pinMode(YELLOW, OUTPUT);

  pinMode(GREEN, OUTPUT);

  // Explicitly force all LEDs to OFF at startup

  digitalWrite(RED, LOW);

  digitalWrite(YELLOW, LOW);

  digitalWrite(GREEN, LOW);

}

void loop() {

  // 1. RED ONLY

  digitalWrite(RED, HIGH);

  digitalWrite(YELLOW, LOW);

  digitalWrite(GREEN, LOW);

  delay(3000);

  // 2. RED + YELLOW

  digitalWrite(RED, HIGH);

  digitalWrite(YELLOW, HIGH);

  digitalWrite(GREEN, LOW);

  delay(1000);

  // 3. GREEN ONLY

  digitalWrite(RED, LOW);

  digitalWrite(YELLOW, LOW);

  digitalWrite(GREEN, HIGH);

  delay(3000);

  // 4. YELLOW ONLY

  digitalWrite(RED, LOW);

  digitalWrite(YELLOW, HIGH);

  digitalWrite(GREEN, LOW);

  delay(1200);

}

const int RED = 2;

const int YELLOW = 3;

const int GREEN = 4;

const int BUTTON = 12; // Pedestrian button

void setup() {

  pinMode(RED, OUTPUT);

  pinMode(YELLOW, OUTPUT);

  pinMode(GREEN, OUTPUT);

  // CRITICAL: Use INPUT_PULLUP to prevent the pin from floating

  // This means the button reads HIGH when NOT pressed, and LOW when pressed.

  pinMode(BUTTON, INPUT_PULLUP);

  // Initialization: Start with Green ON

  digitalWrite(RED, LOW);

  digitalWrite(YELLOW, LOW);

  digitalWrite(GREEN, HIGH);

}

void loop() {

  // Check if button is pressed (Reads LOW because of INPUT_PULLUP)

  if (digitalRead(BUTTON) == HIGH) {

    // Optional: Add a 1-second delay so the light doesn't change instantly

    delay(1000);

    // 1. YELLOW (Warn cars)

    digitalWrite(GREEN, LOW);

    digitalWrite(YELLOW, HIGH);

    delay(2000);

    // 2. RED (Pedestrians cross)

    digitalWrite(YELLOW, LOW);

    digitalWrite(RED, HIGH);

    delay(5000); // 5 seconds to cross

    // 3. RED + YELLOW (Swedish rule: Prepare to go)

    digitalWrite(YELLOW, HIGH);

    delay(1000);

    // 4. GREEN (Back to idle)

    digitalWrite(RED, LOW);

    digitalWrite(YELLOW, LOW);

    digitalWrite(GREEN, HIGH);

    // ANTI-SPAM: Give cars at least 5 seconds to drive

    // before allowing another pedestrian to trigger the light

    delay(5000);

  }

  // No "else" statement needed here because the loop will just repeat

  // and the LEDs will stay in the state they were last left (Green ON).

}

• Do you dare to cross the street controlled by the traffic lights system built by you?

• What to consider to make a safety-critical program like traffic lights?

• What could cause faults or unstability?

  • Electrical noise?

  • Perdestrains spaming pressing?