What is a Light Emitting Diode (LED)?

A Light Emitting Diode (LED) is a semiconductor device that emits light when an electric current passes through it. Unlike traditional incandescent bulbs that produce light by heating a filament, LEDs generate light through a process called electroluminescence—making them significantly more efficient, durable, and versatile.

How LEDs Work

At the heart of an LED is a semiconductor chip made from materials like gallium arsenide (GaAs), gallium phosphide (GaP), or gallium nitride (GaN). When voltage is applied across the LED's terminals, electrons move through the semiconductor material and recombine with electron holes, releasing energy in the form of photons—visible light.

The color of the light depends on the energy band gap of the semiconductor material:

• Red LEDs: Typically use aluminum gallium arsenide (AlGaAs)
• Green LEDs: Often use aluminum gallium phosphide (AlGaP)
• Blue LEDs: Utilize indium gallium nitride (InGaN)
• White LEDs: Usually combine a blue LED with a yellow phosphor coating

Key Characteristics of LEDs

Polarity: LEDs are polarized components with an anode (positive, longer lead) and cathode (negative, shorter lead). They only conduct current in one direction.

Forward Voltage (Vf): The minimum voltage required for the LED to emit light, typically 1.8-3.3V depending on color.

Forward Current (If): The operating current, usually 20mA for standard 5mm LEDs, though high-power variants can handle much more.

Luminous Intensity: Measured in millicandelas (mcd), indicating brightness output.

Viewing Angle: The cone of light emission, ranging from narrow (15°) to wide (120°+).

What's Possible with LEDs?

LEDs have revolutionized lighting and electronics due to their unique properties:

Lighting Applications

• General illumination: Home and commercial lighting with 80-90% energy savings
• Automotive: Headlights, taillights, and interior lighting
• Display technology: Screens, billboards, and signage
• Architectural lighting: Accent lighting, facades, and decorative installations

Electronics & Indicators

• Status indicators: Power, activity, and error signals on devices
• Seven-segment displays: Numeric readouts
• Optocouplers: Electrical isolation in circuits
• Infrared communication: Remote controls and data transmission

Creative & Interactive Projects

• RGB color mixing: Millions of colors from three LEDs
• Addressable LED strips: Individually controlled pixels (WS2812B, APA102)
• POV displays: Persistence of vision effects
• Wearable electronics: Illuminated clothing and accessories
• Plant growth lighting: Optimized spectrum for photosynthesis

Conclusion

LEDs are fundamental building blocks in modern electronics, offering unmatched efficiency, longevity, and control possibilities. Understanding their electrical characteristics and proper current limiting is essential for any electronics project. This simple brightness control circuit introduces core concepts—analog input, PWM output, and component interfacing—that form the foundation for more complex LED applications like addressable strips, matrix displays, and sophisticated lighting systems.

Whether you're building indicators for a custom device, creating ambient lighting, or exploring interactive art installations, mastering LED control opens up endless creative and practical possibilities in your maker journey.