🔌 Node.js – GPIO & Hardware Control Projects: Blink, Button, & LED Effects

🧲 Introduction – Control Raspberry Pi Hardware Using Node.js GPIO

Node.js isn’t just for servers—it also shines in hardware control on Raspberry Pi! Thanks to GPIO libraries like onoff and rpi-gpio, you can interact with LEDs, buttons, and other components using simple JavaScript. These beginner-friendly projects let you bring real-world electronics to life with Node.js.

🎯 In this guide, you’ll learn:

• How to blink an LED using Node.js
• How to read input from a pushbutton
• How to create a flowing LED (Knight Rider) effect

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📘 Topics Covered

🔹 Project	📖 Description
💡 Node.js – Blinking LED	Turn an LED on and off at intervals using GPIO
🛎️ Node.js – LED + Pushbutton	Trigger an LED with a physical pushbutton
🎇 Node.js – Flowing LEDs	Light up multiple LEDs in sequence to create a visual effect

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💡 Node.js – Blinking LED

🔹 Hardware Required

• 1 x Raspberry Pi (any model with GPIO)
• 1 x LED
• 1 x 220Ω resistor
• Breadboard and jumper wires

🔹 Circuit

Connect:

• LED anode (long leg) → GPIO 17 via resistor
• LED cathode (short leg) → GND

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🔹 Code (blink-led.js)

const Gpio = require('onoff').Gpio;
const led = new Gpio(17, 'out');

let isOn = 0;

setInterval(() => {
  isOn = isOn ^ 1; // Toggle
  led.writeSync(isOn);
  console.log("LED is", isOn ? "ON" : "OFF");
}, 1000);

// Graceful exit
process.on('SIGINT', () => {
  led.writeSync(0);
  led.unexport();
  console.log('LED Off, Exiting...');
  process.exit();
});

🧪 Output (Terminal):

LED is ON
LED is OFF
LED is ON
...

✅ LED blinks every 1 second.

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🛎️ Node.js – LED + Pushbutton

🔹 Hardware Required

• 1 x Pushbutton
• 1 x LED
• 1 x 220Ω resistor
• Breadboard + jumper wires

🔹 Circuit

• Button between GPIO 4 and GND
• LED between GPIO 17 and GND via resistor

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🔹 Code (led-button.js)

const Gpio = require('onoff').Gpio;
const led = new Gpio(17, 'out');
const button = new Gpio(4, 'in', 'both');

button.watch((err, value) => {
  if (err) throw err;
  led.writeSync(value);
  console.log("Button state:", value);
});

// Graceful exit
process.on('SIGINT', () => {
  led.writeSync(0);
  led.unexport();
  button.unexport();
  console.log('Clean exit.');
  process.exit();
});

🧪 Output (Terminal):

Button state: 1
Button state: 0

✅ LED lights up when the button is pressed.

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🎇 Node.js – Flowing LEDs

🔹 Hardware Required

• 4–8 LEDs
• Resistors (220Ω)
• Jumper wires
• Connect GPIO 17 to GPIO 20 (or more)

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🔹 Code (flowing-leds.js)

const Gpio = require('onoff').Gpio;
const pins = [17, 18, 19, 20];
const leds = pins.map(pin => new Gpio(pin, 'out'));

let index = 0;
setInterval(() => {
  leds.forEach(led => led.writeSync(0)); // Turn all off
  leds[index].writeSync(1); // Turn one on
  index = (index + 1) % leds.length;
}, 300);

// Cleanup
process.on('SIGINT', () => {
  leds.forEach(led => {
    led.writeSync(0);
    led.unexport();
  });
  console.log('LED Flow Stopped.');
  process.exit();
});

🧪 Output:

LEDs light one after another in a flowing pattern

✅ Visual LED wave effect like Knight Rider or progress bar.

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📌 Summary – Recap & Next Steps

Node.js brings event-driven control to Raspberry Pi GPIO with easy, readable JavaScript. Whether it’s blinking a light or responding to a button, the GPIO pins allow Node.js to interact with the real world.

🔍 Key Takeaways:

• Use the onoff library to interact with GPIO on Raspberry Pi
• Always clean up GPIO on exit to avoid pin lockups
• Blinking LEDs and reading buttons are the foundation of robotics
• Flowing LEDs teach iteration and visual feedback control

⚙️ Real-World Uses:

• Smart light systems
• Security buttons and motion triggers
• LED progress indicators
• Teaching kids IoT basics through visual effects

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❓ Frequently Asked Questions

❓ How do I install the onoff library?
✅ Run:

npm install onoff

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❓ Do I need to run the Node.js script as sudo?
✅ Yes, to access GPIO:

sudo node blink-led.js

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❓ What happens if I don’t unexport the pins?
✅ Pins may remain in use, preventing further access. Always call unexport() on exit.

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❓ Can I control other hardware like buzzers or motors?
✅ Yes! Any digital component (on/off) can be controlled via GPIO, including buzzers, relays, and motor drivers.

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