Alternate Blinking LED Code – NANO

🧩 Circuit Connections (Text Description)

Component	Arduino Nano Pin	Connection Details
LED 1	A3	➜ Connect anode (+) of LED to A3 through a 220Ω resistor. ➜ Connect cathode (–) to GND.
LED 2	A4	➜ Connect anode (+) of LED to A4 through a 220Ω resistor. ➜ Connect cathode (–) to GND.
LED 3	A5	➜ Connect anode (+) of LED to A5 through a 220Ω resistor. ➜ Connect cathode (–) to GND.

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⚙️ Power & Ground

• Arduino Nano 5V pin → powers the circuit.
• Arduino Nano GND pin → common ground for all LED cathodes.

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🪛 Quick Wiring Summary

A3 → 220Ω → LED1 → GND
A4 → 220Ω → LED2 → GND
A5 → 220Ω → LED3 → GND

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✅ Checklist to Verify Your Drawing

• Each LED’s long leg (+) goes to A3 / A4 / A5 via resistor.
• Each LED’s short leg (–) connects to GND.
• All GND points are connected to the Arduino’s GND pin.
• No two LED anodes are shorted together.
• Resistors are in series with LEDs (not parallel).

Circuit

Here’s your updated code that makes the LEDs blink alternately (LED1 ON, LED2 OFF, LED3 ON, then reverse).

// Alternate Blinking LEDs on A3, A4, A5

#define LED1 A3
#define LED2 A4
#define LED3 A5

void setup() {
  pinMode(LED1, OUTPUT);
  pinMode(LED2, OUTPUT);
  pinMode(LED3, OUTPUT);
}

void loop() {
  // Step 1: LED1 and LED3 ON, LED2 OFF
  digitalWrite(LED1, HIGH);
  digitalWrite(LED2, LOW);
  digitalWrite(LED3, HIGH);
  delay(500); // wait half a second

  // Step 2: LED1 and LED3 OFF, LED2 ON
  digitalWrite(LED1, LOW);
  digitalWrite(LED2, HIGH);
  digitalWrite(LED3, LOW);
  delay(500); // wait half a second
}

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⚙️ Working Explanation

1. When the program starts, pins A3, A4, and A5 are set as outputs.
2. Inside the loop:
   • First pattern: LED1 and LED3 turn ON, LED2 turns OFF.
   • After 500 ms, it reverses: LED1 and LED3 OFF, LED2 ON.
3. This keeps alternating forever — giving a chaser-like or alternating effect.