A Small String Of Decorative Flashing Lights Using Arduino

This project implements a dynamic decorative lighting display controlled by an Arduino Uno board. The system utilizes digital output pins from the microcontroller to sequence a string of 9 to 18 LEDs. Because an Arduino Uno's digital pins have limited output current capacity—and driving numerous LEDs simultaneously exceeds safe per-pin and total microcontroller current limits—the circuit incorporates discrete NPN transistors (labeled T1 through T9 for the 18-LED variant) acting as electronic switches. When the Arduino sends a control signal to a transistor's base, it allows a larger current to flow from the power supply through the LED string. Current-limiting resistors (R1 through R9) are placed in series with the LEDs to drop excess voltage and maintain safe operating currents through each semiconductor, preventing burnout. The entire circuit is assembled on a breadboard or custom PCB using connecting wires, drawing power via a USB cable. The Arduino IDE is used to write, compile, and upload custom firmware to the Uno's microcontroller, executing programmatic loops and timing delays that dictate the flashing patterns, chasing sequences, and decorative animations displayed across the LED string.