Originally posted by ZEITFREI Tech 07/05/2023

Light Emitting Diodes, or LEDs, are ubiquitous in our daily lives, from the tiny indicator lights on our electronic devices to the bright headlights on our cars. But what makes an LED emit light, and how does it differ from other light sources? This article, based on an informative video tutorial, will delve into the science behind LEDs, their working principles, and their various applications.

The Principle of LEDs

LEDs and diodes work on the same principle. They both consist of a semiconductor material sandwiched between electrical connectors. Both emit photons, but only LEDs emit photons in the range visible to humans, which is when the photon has a wavelength of around 400 to 700 nanometers. We perceive different colors depending on the wavelength of the photon in this range.

LEDs vs. Traditional Incandescent Lights

Unlike traditional incandescent lights, which generate a lot of heat, LEDs produce very little heat. Incandescent lights work by heating a filament until it glows, whereas LEDs emit light when a voltage is applied across them, causing electrons to combine with holes and release photons in the process. This makes LEDs much more energy-efficient than incandescent lights.

Different Types of LEDs

LEDs come in various shapes, colors, and sizes for different applications. The most common type is the 5mm through-hole LED, which can be inserted into test boards or soldered into printed circuit boards. Surface Mount Device (SMD) LEDs are smaller and are soldered directly onto circuit boards, allowing for more compact designs. High-powered LEDs, which are essentially many LEDs packed tightly together, are often used for torches and floodlights.

LED Polarity and Color

LEDs only illuminate when the anode lead is connected to the positive and the cathode to the negative. The longest lead of the LED is the anode, and one side of the LED’s case has a flat edge, indicating the cathode side. The color of the light emitted by an LED is determined by the material inside the semiconductor layer, not the color of the case.

Special LEDs

There are also special types of LEDs, such as blinking LEDs, which turn on and off automatically at a certain frequency, and bi-directional LEDs, which can change between two colors. RGB LEDs have three separate LEDs inside (red, green, and blue) and can be controlled to emit any color light.

LEDs and Resistors

To prevent an LED from being destroyed by too much current, a resistor is used to reduce the current of electrons. The resistor removes energy from the circuit, turning it into heat. The brightness of an LED can be controlled by varying the current, but if the current is too high, the LED will be destroyed. This is why LED drivers are used in light bulbs and dedicated units powering strip lighting.

Conclusion

LEDs are a fascinating piece of technology that have revolutionized the way we light up our world. They are energy-efficient, versatile, and can be found in a wide range of applications. Understanding how they work not only gives us a greater appreciation for these tiny devices but also opens up possibilities for their use in new and innovative ways.