LEDs generate very little heat, relatively speaking. A much higher percentage of the electrical energy is going directly to generating light, which cuts down the electricity demands considerably. Per watt, LEDs output more lumens or quantities of visible light than regular incandescent bulbs.
Light emitting diodes have a higher luminous efficacy how efficiently electricity is converted to visible light than incandescents — a watt incandescent bulb can generate between lumens, but you can get the same output from a LED bulb using only watts. And that same LED bulb can last 25, hours, but the watt incandescent is only likely to light up for about 1, hours.
In other words, one LED bulb can last as long as 21 watt incandescent bulbs burned consecutively [source: EarthEasy ]. Until recently, LEDs were too expensive to use for most lighting applications because they're built around advanced semiconductor material.
The price of semiconductor devices plummeted after the year , however, making LEDs a more cost-effective lighting option for a wide range of situations. Several companies have begun selling LED light bulbs designed to compete with incandescent and compact fluorescents that promise to deliver long lives of bright light and amazing energy efficiency. In this article, we'll examine the technology behind these ubiquitous blinkers, illuminating some cool principles of electricity and light in the process.
A diode is the simplest sort of semiconductor device. Broadly speaking, a semiconductor is a material with a varying ability to conduct electrical current. Most semiconductors are made of a poor conductor that has had impurities atoms of another material added to it. The process of adding impurities is called doping. In pure aluminum-gallium-arsenide, all of the atoms bond perfectly with their neighbors, leaving no free electrons negatively charged particles to conduct electric current.
In doped material, additional atoms change the balance, either adding free electrons or creating holes where electrons can go. Either of these alterations make the material more conductive. A semiconductor with extra electrons is called N-type material , since it has extra negatively charged particles. In N-type material, free electrons move from a negatively charged area to a positively charged area.
A semiconductor with extra holes is called P-type material , since it effectively has extra positively charged particles. Electrons can jump from hole to hole, moving from a negatively charged area to a positively charged area. As a result, the holes themselves appear to move from a positively charged area to a negatively charged area. A diode consists of a section of N-type material bonded to a section of P-type material, with electrodes on each end.
This arrangement conducts electricity in only one direction. When no voltage is applied to the diode, electrons from the N-type material fill holes from the P-type material along the junction between the layers, forming a depletion zone. In a depletion zone , the semiconductor material is returned to its original insulating state — all of the holes are filled, so there are no free electrons or empty spaces for electrons, and electricity can't flow.
To get rid of the depletion zone, you have to get electrons moving from the N-type area to the P-type area and holes moving in the reverse direction. To do this, you connect the N-type side of the diode to the negative end of a circuit and the P-type side to the positive end.
The free electrons in the N-type material are repelled by the negative electrode and drawn to the positive electrode. The holes in the P-type material move the other way. When the voltage difference between the electrodes is high enough, the electrons in the depletion zone are boosted out of their holes and begin moving freely again. The depletion zone disappears, and charge moves across the diode.
If you try to run current the other way, with the P-type side connected to the negative end of the circuit and the N-type side connected to the positive end, current will not flow. The negative electrons in the N-type material are attracted to the positive electrode.
The positive holes in the P-type material are attracted to the negative electrode. No current flows across the junction because the holes and the electrons are each moving in the wrong direction. The depletion zone increases. See How Semiconductors Work for more information on the entire process. An electrical current passes through a microchip, which illuminates the tiny light sources we call LEDs and the result is visible light.
To prevent performance issues, the heat LEDs produce is absorbed into a heat sink. The useful life of LED lighting products is defined differently than that of other light sources, such as incandescent or compact fluorescent lighting CFL. LEDs are incorporated into bulbs and fixtures for general lighting applications. Small in size, LEDs provide unique design opportunities.
Some LED bulb solutions may physically resemble familiar light bulbs and better match the appearance of traditional light bulbs. LEDs offer a tremendous opportunity for innovation in lighting form factors and fit a wider breadth of applications than traditional lighting technologies. Some forms of this electromagnetic radiation can take the form of visible light, which humans can perceive via sight. There is an almost inexhaustible supply of applications for LED lights, some of which have already been realized and others that are currently being implemented.
Within the world of electronics LED lights are used in traffic lights, screen displays, computers, brake lights and any other application which requires a bright, inexpensive and long-lasting light.
They also are used in the burgeoning field of photonic textiles and as a source of light in places where high temperatures cannot be tolerated. Indeed, LED lights are one of the most important technologies in contemporary electronic products and many such products would be impossible without them.
A legal clerk and law school student at The Thomas M. But for those who are unfamiliar with modern lighting options like LEDs, making the switch to a new style of light bulb can seem like a daunting prospect. Understanding what LEDs are and how they work can ease the process of finding the right bulb and switching to energy efficient lighting. Keep reading to learn more.
To answer that question, we have to get a bit scientific. All diodes emit photons particles of electromagnetic energy , but only certain types of diodes emit that electromagnetic energy as light instead of heat.
A light emitting diode is a type of solid-state lighting SSL technology, meaning that it emits light from a piece of solid matter.
In this case, that piece of solid matter is a two-lead semiconductor Semiconductor A semiconductor is a material capable of conducting an electric current. Two-lead means that there are two semiconductor materials. An LED is capable of generating light because of the arrangement of the two semiconductor materials located between its electrodes:. Connecting the N-type semiconductor to the negative electrode and the P-type semiconductor to the positive electrode activates the electrons so they can flow across the junction from the negative to the positive layer.
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