Presentation on theme: "LED stands for Light Emitting Diode This is how they work…"— Presentation transcript:
1LED stands for Light Emitting Diode This is how they work… What is an LED?LED stands for Light Emitting DiodeThis is how they work…(see next page)
2How Diodes workA diode allows an electric current to flow in one direction, but blocks it in the opposite direction, much like an electronic version of a check valve.
3How Light Emitting Diodes work A Light Emitting Diode emits light when an electric current passes through it.Basically, LED's are tiny light sources that fit easily into an electrical circuit.
4Why get light from LEDs?They are illuminated solely by the movement of electrons in a very small piece of semiconductor material inside them referred to in the “LED world” as a die.They don't have a filament to burn out, and they don't get especially hot.
5How are LEDs made?These dies, the main component in LEDs, are processed in wafer form similar to silicon-integrated circuits, and broken out into individual dice or chips.Chip size for visible signal LEDs generally fall in the range of 0.18mm square to 0.36mm square (smaller than a pin head). High power LEDs for lighting are yet larger.
6Internals of a Blue LEDWhite visible light starts with a die that emits blue light (It’s coated with Indium gallium nitride, causing the blue coloring)The basic LED structure consists of the die, a lead frame where the die is actually placed, and the encapsulation epoxy, which surrounds and protects the die and disperses the light (see left).
7What about a White LED?To create White light, a coating of phosphor is placed on the die.The recess in the anvil is shaped to project the radiated light forward.The die's top contact is wire bonded to the other lead frame terminal, the post, to complete the circuit.
8So, how do you get white light? As current flows, the die would normally produce blue light. But in this case another color is emitted as determined by the precise amount of phosphor applied to the die. That phosphor fluoresces to achieve a near-white lightThat white light is sorted to colors like warm white, white and cool white and assembled in quantities in tubes.
9These LEDs are mounted on printed circuit boards in shatter-resistant Polycarbonate tubes… …with proper electrical contacts they are designed to replacefluorescentlamps!
10How long do LEDs last?LEDs have a mean time between failures usually in the range of 100,000 to over 1,000,000 hours. But, this is a long time for continuous operation, considering that a year is 8784 hours at most. *Temper this with application, added circuitry and housing. In practice, the useful measure of LED lifetime is its half-life. When the light output falls off to half the original, an LED is deemed to have reached the end of its life* Based on life decay model, series lifetime can reach hr and hr under test condition of 20mA, 25 C and 60%RH.
11How do fluorescent tubes work? Electricity flowing from electrode to electrode in fluorescent lamps produce a charge causing electrons to travel through the argon gas-filled tube. This energy vaporizes liquid mercury inside the tube which in turn releases ultraviolet (UV) photons.The ultraviolet light is transformed into visible light by the phosphors on the inside of the tube. In doing so, about 80% of the energy used is released as heat not light and, in a warm climate, that increases your air conditioning costs.
13Some facts about fluorescent tubes Require inefficient, expensive ballastsGenerate higher utility billsSignificantly shorter life than LEDsPoor performance in cold environmentsRequire immediate replacement, or have wasted life from group relampingWhen broken, you have glass shards contaminated with mercuryCan sound noisy and flicker as they ageDimming is too expensive to be practical
14Benefits of LED Lites Long life (50,000 hrs). 60% savings in your lighting energy bill.No humming/no buzzing.Do not generate significant heat.Not affected by vibration.No toxic components, no disposal costs.Do not attract insects.Efficient in cold temperatures.
15What savings can I expect? A building operating 12 hours a day can usually pay back the cost of the lamps in electrical savings within 24 months. The balance of the life of the lamps (7-8 years) can show savings of 60% or more over previous expenditures. Dollar amounts are dependent on the number of fixtures and local power rates.A savings calculator is available. Merely plug in figures found in a lighting survey of your building.
16How about even more savings? Dimming LED Lites (controlLED Lites) provide even more savings.controlLED Lites can operate from a variety of control signals.They can controlled by occupancy or light level sensors and be connected to existing building automation systems.