Everything about led lights - NYMCC Message Board

Members Login

Post Info

TOPIC: Everything about led lights

Tonys57chevy

Moderator

Status: Offline

Posts: 2150

Date: Aug 23, 2009

Everything about led lights	Permalink Closed

Everything about led lights What are LEDs? LEDs are solid-state semi-conductor devices that convert electrical energy directly into light. LED "cold" generation of light leads to high efficacy because most of the energy radiates within the visible spectrum. LEDs can be extremely small and durable and also provide longer lamp life than other sources The manufacturing process of LEDs is known as epitaxy, in which crystalline layers of different semiconductor material are grown on top of one another. Advances in epitaxial crystal growth processes have enabled the use of LED materials for colors that previously could not be made with high enough purity and structural precision Recent breakthroughs in the technique of chemical vapor deposition from metal organic precursors enable the cost-effective production of nitrides of the group III-metals from the periodic table including aluminum gallium indium nitrides. Highly efficient InGaN blue LEDs result from this process. About 30 percent of the light generated inside the chip makes it way out of the brightest LEDs. Semiconductor materials have very high indices of refraction and can trap a great deal of light when configured in a square chip. An epoxy encapsulant around the LED chip reduces the refractive index mismatch and allows more light to be emitted. For some LEDs, the light escaping the chip (extraction efficiency) can be 4 percent or lower. Transparent substrates and thick semiconductor layers increase the extraction efficiency. Making LED chips more spherical, which is now not practical for mass production, could also significantly increase extraction efficiency How to produce LED light To produce LED light, you must first connect two conductive crystals of varying characteristics together. Both crystals have active electrons. In one crystal the electrons “orbit” normally at a high energy level, and the other crystal always “orbit” low. When a certain amount of voltage is applied to the conjoined crystals, the electrons are then forced to move across the area between the two crystals. Now, if the flow movement is right, electrons in the higher up crystal flow into the crystal that is lower and must have to begin orbiting at the lower level of energy. As the electrons come down to a lower energy level, they emit light. What the naked eye sees as light, the frequency of light becomes determined by the difference in energy levels amongst the two crystals. By manifesting different types of crystals with varying kinds of energy levels, many colors can be created. Crystals with seemingly similar levels of energy, make low-energy photons of red light or even infrared light. With a huge difference in energy levels, green light can be produced. An even greater energy creation can create blue light. More Home Decor: Electric tankless water heaters Use only the water you need heated. No longer will you have to pay to keep the water heated when no one is using it. Stainless cabinet pulls The stainless steel pull is a very attractive and easy to clean piece of hardware. Get a great buy here at this site. Unique shower curtains Change the look of your bathroom with a new shower curtain. We carry many unique designs. Cabinet door hinges Hinges can change the way your room looks. For those homeowners that want a rustic feel try buying heavy looking hinges or black hinges. Indoor table fountains The sound of water flowing adds a sense of relaxation to any home or room. Wood burning fireplace inserts The soft glow of a fire not only sets a relaxing mood in the home but it will also help keep your home warm. Butcher block kitchen islands A kitchen island will help the flow of your kitchen. Use a kitchen island to make working in your kitchen easier. Queen comforter sets Comfortable and quirky queen comforter sets. Electric fireplace logs More styles and designs at competitive prices. Buying an electric fireplace logs here will save you money. Bathroom wall mirrors will add a stylish touch to any bathroom. Find all kinds of different wall mirrors for your bathroom. Why even use it ? LED or Light Emitting Diode’s are diodes that give off light. LED light transports electricity into light in the absolute most efficient way. LED bulbs transfer 100% of the energy into light versus an incandescent light bulb which only transfers 10-20% of the energy into light. LED’s have made large improvements since the 1970’s, the biggest problem currently, is the price of LED’s. Where the electrons get the energy ? What place did the electrons get the energy needed to emit light you might ask? And how do they get to a much higher energy state in order to enter into the n-type crystal? Lets see, for the battery to shove electrons through the LED, it had to have supplied an electrical attraction of forces to the electrons in the crystal. To apply a force of electrons to the crystal, it had to apply some sort of force to the electrons in the negative wire. This pinches all of the electrons on the bare surface of the negative wire together, which raises the voltage of the whole wire. (Take this as an example. If the electrons were like water, then the wire would be like a very long trough. The battery serves to pump water into one end of the trough and this makes the level of the water/voltage rise everywhere in the trough.) When the negative wire’s electrons get up to the energy level equaled to the n-type crystal, they begin to flow into the crystal and fall down so-to-speak emitting light as they go. (The analogy just given is however incomplete: at the same instance that the battery pumps up the “water level” of the negative wire to equal the n-type crystal level, it is also minimizing the “water level” of the positive wire so that the low-energy electrons of the p-type crystal could be sucked in the wire.) Light emitting diodes, commonly called LEDs, are real unsung heroes in the electronics world. They do dozens of different jobs and are found in all kinds of devices. Among other things, they form the numbers on digital clocks, transmit information from remote controls, light up watches and tell you when your appliances are turned on. Collected together, they can form images on a jumbo television screen or illuminate a traffic light. Basically, LEDs are just tiny light bulbs that fit easily into an electrical circuit. But unlike ordinary incandescent bulbs, they don't have a filament that will burn out, and they don't get especially hot. They are illuminated solely by the movement of electrons in a semiconductor material, and they last just as long as a standard transistor. In this article, we'll examine the simple principles behind these ubiquitous blinkers, illuminating some cool principles of electricity and light in the process. How Can a Diode Produce Light? Light is a form of energy that can be released by an atom. It is made up of many small particle-like packets that have energy and momentum but no mass. These particles, called photons, are the most basic units of light. Photons are released as a result of moving electrons. In an atom, electrons move in orbitals around the nucleus. Electrons in different orbitals have different amounts of energy. Generally speaking, electrons with greater energy move in orbitals farther away from the nucleus. For an electron to jump from a lower orbital to a higher orbital, something has to boost its energy level. Conversely, an electron releases energy when it drops from a higher orbital to a lower one. This energy is released in the form of a photon. A greater energy drop releases a higher-energy photon, which is characterized by a higher frequency. (Check out How Light Works for a full explanation.) As we saw in the last section, free electrons moving across a diode can fall into empty holes from the P-type layer. This involves a drop from the conduction band to a lower orbital, so the electrons release energy in the form of photons. This happens in any diode, but you can only see the photons when the diode is composed of certain material. The atoms in a standard silicon diode, for example, are arranged in such a way that the electron drops a relatively short distance. As a result, the photon's frequency is so low that it is invisible to the human eye -- it is in the infrared portion of the light spectrum. This isn't necessarily a bad thing, of course: Infrared LEDs are ideal for remote controls, among other things. LEDs are not yet practical for all lighting purposes as they are prone to generating a TON of heat, even more than a light bulb with the same light output. Also while they do not have a filament to burn out, they still do not last forever. They are rated by hours based on duty cycle and how they are driven (current, NOT voltage) There is a few other caveats involved too, which is why they are not yet mainstream and practical. I know as I work with them everyday in our products. Researching LEDs for use in our industrial products is one of many components I research and help choose for use. A majority of LEDs would never stand up to our requirements, only a select few. I also deal with ALL components used in our products from semiconductors of all types to passives (resistors, capacitors, inductoprs and such) to hardware as well. This means I also meet with the engineers and technical experts from the largest suppliers of these products to allow us to design the very best industrial products in the world. While that LED info is very good, it lacks many important details as I suspect that is more sales pitch than true technical information. Not trying to shoot it down Tony, just a heads up that all is not what it seems and it really is not quite that simple. There is no mention of current and how much of a surge or pulse is needed for it to survive so you need to choose carefully based on application. Most also will require some very precise optics (lenses or diffusers) for them to preform as desired. Certain colors will survive better than others so you also need to know exactly what range you need form a color standpoint, color bandwidth is almost as important as maximum current and all affect the duty cycle the LED will be able to survive long term. Way more complicated and technical than most people realize. So, it is unfortunately NOT everything about LED but only the simplified surface info. __________________ Pres. WICKED RIDES car club www.wickedridesnj.com www.wickedmontes.com

Page 1 of 1 sorted by

Create your own FREE Forum
Report Abuse