📶 Li-Fi Data Transfer System

Wireless light-based communication. Transmit data or audio through modulated visible light using an LED and photodiode.

📋 Overview

Light Fidelity (Li-Fi) is an innovative, high-speed, and secure wireless communication technology that uses visible light waves to transmit data instead of radio frequencies. This project implements a hardware transceiver system.

What you'll learn: Optical signal modulation and demodulation, analog photodiode threshold sensing, operational amplifier filtering, and building optical wireless transmitter/receiver circuits.

Estimated time: 2-3 hours. Difficulty: ⭐⭐⭐⭐ Advanced.

🧩 Components Needed

Component	Specification	Qty	Notes
Arduino Uno R3 (x2)	5V Logic	2	One for transmitter, one for receiver
Solar Panel or Photodiode	Small 5V / BPW34	1	Light receiver
LM358 Op-Amp	Dual channel	1	Amplifies received signals
High-Power White LED	1W / 3.3V	1	Light transmitter
TIP122 Transistor	NPN Darlington	1	Drives high-power LED
Resistors & Capacitors	100uF, 10k, 1k, 220 Ohm	1 set	For filtering circuit

📖 Step-by-Step Tutorial

Assemble Transmitter Circuit

Connect Arduino Pin 3 (PWM/Serial TX) to the base of the TIP122 transistor via a 1k resistor. Wire the high-power LED to the transistor collector with an external power source.

Assemble Receiver Circuit

Wire the photodiode or small solar panel to the non-inverting input of the LM358 operational amplifier to boost the weak optical pulses into a clean 5V square wave.

Establish Communication Protocol

Write a serial transmitter protocol that modulates data by turning the LED on and off at high frequencies (baud rates).

Upload Transmitter Code

Upload the serial packet sender code to the transmitter Arduino, modulating high-speed data bits into light.

Upload Receiver Code

Upload the serial packet decoder code to the receiver Arduino to parse incoming light pulses and reconstruct the sent text.

💡

Keep the transmitter and receiver in a straight line-of-sight path. High ambient room lighting can create signal noise; use a dark tube around the receiver to isolate it.

💻 Code / Configuration

lifi_transfer.ino

INO

// Li-Fi Transmitter Modulation Code - Volt X
int txPin = 3; // Modulating LED pin

void setup() {
  Serial.begin(9600);
  pinMode(txPin, OUTPUT);
}

void loop() {
  if (Serial.available()) {
    char data = Serial.read();
    transmitChar(data);
  }
}

void transmitChar(char c) {
  // Simple bit-bang UART emulation over light
  digitalWrite(txPin, LOW); // Start bit
  delayMicroseconds(104);  // 9600 Baud rate duration
  
  for (int i = 0; i < 8; i++) {
    digitalWrite(txPin, (c & (1 << i)) ? HIGH : LOW);
    delayMicroseconds(104);
  }

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