Luminous Link

1st place · TECHSCAPE 2024 department exhibition

Unlock a door
with light.

Luminous Link is a Li-Fi smart lock. Your phone flashes a PIN as pulses of light, an Arduino reads them through a light sensor, and a solenoid bolt slides open. No Wi-Fi or Bluetooth signal that can be picked up through a wall.

Transmitter your phone
Send via

Receiver virtual lock · PIN 2024

Waiting for light

PIN · 16 bitschecksum
Signal
preamble sets the timing short = 0 · long = 1 checksum

How it works

  1. 01

    Encode

    The PIN becomes 16 bits plus a 4-bit checksum. Each bit is a flash: short for 0, long for 1.

  2. 02

    Flash

    A long preamble comes first. The lock measures it to learn the speed, so a fast screen and a slow torch both work.

  3. 03

    Unlock

    The Arduino times every pulse, checks the checksum and PIN, then drives the solenoid through a MOSFET. Three wrong PINs lock it for 30 seconds.

Hardware

Arduino Uno / Nano
decoder & control
LDR module (LM393)
D8 · light sensor
IRF730 MOSFET
D12 · switches the 12 V lock
12 V solenoid lock
the bolt
Green / red LED
D6 / D11 · open, closed
Buzzer
D4 · feedback & alarm
The Luminous Link prototype: a wooden door frame with a solenoid bolt, Arduino and breadboard wiring
The prototype that took 1st place at TECHSCAPE 2024, my first engineering project