Push Button LED Control – Arduino Nano

🟢 The LED on D5 will blink only while the button on D2 is pressed,
and stay OFF when the button is released.

We’ll keep the same non-blocking (millis-based) blink logic — no delay(), so it runs smoothly.

Circuit

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✅ LED Blinks Only While Button is Pressed

#define LED_PIN     5   // LED connected to D5
#define BUTTON_PIN  2   // Button connected to D2 (one side to GND, using INPUT_PULLUP)

#define BLINK_INTERVAL 500  // LED blink interval (milliseconds)

int led_state = LOW;           // Store current LED state
unsigned long prev_millis = 0; // Store last blink time

void setup() {
  pinMode(LED_PIN, OUTPUT);
  pinMode(BUTTON_PIN, INPUT_PULLUP); // Internal pull-up resistor
  Serial.begin(9600);
}

void loop() {
  // Read button (LOW = pressed, HIGH = released)
  int button_state = digitalRead(BUTTON_PIN);

  if (button_state == LOW) {
    // If button is pressed, blink LED
    unsigned long current_millis = millis();

    if (current_millis - prev_millis >= BLINK_INTERVAL) {
      led_state = (led_state == LOW) ? HIGH : LOW;
      digitalWrite(LED_PIN, led_state);
      prev_millis = current_millis;
    }
  } else {
    // If button is not pressed, turn LED OFF
    digitalWrite(LED_PIN, LOW);
    led_state = LOW;
  }
}

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🧠 How It Works

1. The button pin is set with INPUT_PULLUP, so:
   • Pressed → LOW (0)
   • Released → HIGH (1)
2. When pressed, the code enters the blink section:
   • Uses millis() to toggle LED every 500 ms (non-blocking).
3. When released, LED turns OFF immediately.

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⚙️ Circuit Wiring (same as your setup)

Component	Arduino Pin	Other Connection
LED (Anode +)	D5	Through 220Ω resistor
LED (Cathode −)	GND	—
Push Button	D2	One end to D2
Push Button	GND	Other end to GND

✅ Note: Because we’re using INPUT_PULLUP, button must connect to GND (not 5V).

If your button is already wired to 5V, just change:

pinMode(BUTTON_PIN, INPUT);

and reverse the logic to:

if (button_state == HIGH) { // instead of LOW

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Would you like me to generate a clear circuit diagram (image) for this exact wiring —
LED on D5, button on D2 → GND (for INPUT_PULLUP type)?