LED Flasher Circuit using RGB LED

Introduction

This LED flasher circuit is a simple and effective way to understand the basics of transistor switching, RC time delays, and how RGB LEDs can be used creatively. Unlike regular LED blinkers, this circuit integrates an RGB LED (LED2) not only for colorful visual output but also as a functional component that helps control the blinking behavior of another LED (LED1). It uses a 2N3904 NPN transistor, a few resistors, and a capacitor to form a compact timing circuit that alternates between ON and OFF states. This circuit is perfect for hobbyists and beginners looking to explore how capacitors and transistors can be combined for blinking effects without using any IC like NE555.

Component Details

S.No	Component Name	Value	Quantity
1	Power Supply	6V DC	1
2	Resistor	1kΩ	1
3	Resistor	10kΩ	1
4	Resistor	4.7kΩ	1
5	Capacitor	100µF / 25V	1
6	Transistor	2N3904 (NPN)	1
7	LED1 (Flasher)	Standard Red	1
8	LED2 (Helper)	RGB LED	1
9	Connecting wires & breadboard	—	As needed

2N3904 Pinout

Circuit Diagram

Circuit Explanation

This LED flasher circuit uses a basic RC timing mechanism and a transistor switch to turn LED1 ON and OFF. Here’s how it works in detail:

Power Supply Stage:

A 6V DC source powers the entire circuit.
The positive terminal is connected to both LED1 and LED2 in separate branches.

Timing & Control:

The 100µF capacitor and resistors (10kΩ and 4.7kΩ) form a timing network.
Initially, the capacitor starts charging via the 10kΩ resistor.
As it charges, it gradually increases the base voltage of the 2N3904 transistor.

Switching Action:

When the base-emitter voltage of the transistor reaches around 0.7V, the transistor turns ON.
This creates a current path from LED1 → capacitor → transistor emitter → ground, causing LED1 to light up.

Role of RGB LED (LED2):

While LED1 is ON, the RGB LED acts as a reactive load.
Its internal switching (between Red, Green, and Blue chips) affects the voltage drop and feedback in the circuit.
This helps discharge the capacitor faster, turning OFF the transistor after a short time.
The cycle repeats as the capacitor charges again.

In short:

LED2 (RGB) plays a vital role by modulating the current path, influencing the switching behavior of the transistor, and helping LED1 blink continuously.