Light–Emitting Diodes

LEDs are manufactured in various forms and sizes. The shape they take largely depends on how they are meant to be used. Some LEDs are connected in strips or strings, and some form a grid, while others are individual bulbs.

LEDs utilize electroluminescence, discovered by British scientists in 1907. They observed that Silicon Carbide (SiC) emitted visible light when electricity was passed through it. Despite this discovery, the first working LED was created in 1927 by Russian inventor Oleg Losev.

The colors that LEDs emit depend on the material used. In 1961, LEDs only emitted infrared light, part of the electromagnetic frequency that is invisible to the human eye. LEDs capable of emitting visible red light came shortly afterward.

LEDs today come in all shapes and sizes. They are brighter than earlier designs and use less power. Because the actual light emitters are small, a casing typically encloses LEDs to shape the light and provide protection against the environment.

LEDs are a type of diode, a semiconductor device that only allows current to pass through 1 way. When electricity is passed through the diode, the excited electrons release their energy as photons, which are light. 

Depending on the material used, emissions of different colors are produced.

Unlike traditional incandescent light bulbs, LEDs use specially constructed diodes that are designed to emit light when a current passes through them. A diode consists of a P-N junction, which emits photons when a current is passed through it. 

Simple circuits require batteries to supply the voltage, resistors to limit the current, and LEDs. LEDs are semiconductors, so they only work when current is flowing through them from the anode to the cathode. If reversed, LEDs will not illuminate.

For different color outputs, the diode uses different semiconductor materials. For example, red LEDs are often made with Gallium Phosphide, green with Indium Gallium Nitride, and blue with Zinc Selenide. Combining these 3 primary colors makes additional colors.

LEDs are used all around us all the time. Especially in urban environments, we can see them everywhere, once the sun sets. They are often arranged in a large grid and controlled by a computer to form big billboard displays. 

To form a large display, tens or hundreds of thousands of LEDs are used. Looking closer, we see that the screen is made up of red, green, and blue LEDs. Combined at different intensities, they can create every color possible.

LEDs are used for the illumination of buildings as well as traffic lights, and street lights. They use very little power compared to incandescent bulbs, which makes them ideal for signage.

The extensive use of LEDs for nighttime illumination and advertisement can result in light pollution in large cities. This causes disruption to ecosystem habitats, wastes electrical energy, and makes stars in the night sky less visible. 

In the short 50 years that LEDs have been sold commercially, they have taken over the lighting industry. Due to their compact size, low power consumption, and durability compared to incandescent light bulbs, LEDs can now be found everywhere.

How many uses of LED can you see in this house?

Because LCD screens found in TVs and computer screens don’t produce any light on their own, a backlight is needed to illuminate the display. Most newer displays use LEDs for the backlight.

Excellent as a source for interior lighting, LEDs are found inside houses, offices, and stores. They last much longer in comparison to typical light bulbs and do not produce as much heat.

LEDs are perfect replacements as headlights and taillights for cars. They can better withstand harsh environments and wide temperature fluctuations. LEDs also don’t mind being turned on and off repeatedly, a requirement for signal lights! 

The 7-segment display on the digital alarm clock is one of the earliest implementations of LEDs. By turning individual segments of the display on and off, we can show different numbers.

A camera phone uses a white LED for its flash. It provides a bright burst of light without draining the battery too much, and it can also function as the phone’s flashlight.