Can LEDs be driven directly from a voltage source?
It is not recommended to apply a direct voltage source to an LED without a current limiting resistor or an LED Driver (BuckPuck).
A slight change in Vf will cause a large change in If. This can result in a possible over-drive condition, thus reducing the life and/or reliability of the LED. Even if over-drive conditions are not reached, large variations in If will result in significant luminous intensity variation. The preferred method of operating from a voltage source is via an LED Driver to limit the current flow through the LED.
How will high junction temps affect high-power LEDs?
The amount of light emitted by the LED lamp diminishes as junction temperature rises. This is because of an increase in the recombination of holes and electrons that make no contribution to light emission. Additionally, the failure rate of semiconductor devices is greatly accelerated as operating temperatures increase.
What are Lumens?
Lumens measures how much light is produced as measured at the light source.
How do I convert mcd to lumens?
1000mcd approximately equal to 1 lumen
How long will my LED Last?
The lifetime of an LED bulb is determined by estimating the point in time when the light emits 70% of its original lumen output. For example, an LED bulb with a rating of 50,000 hours and 300 lumens will emit approximately 210 lumens at the 50,000th hour of operation. Keep in mind that LEDs do not burn out, so the lifetime is potentially significantly longer than itâ€™s rating. Your light will keep shining well after itâ€™s rated lifetime.
What is inside an LED-based lighting system?
Basic components are:
What is an LED?
An LED-or Light Emitting Diode-is a semiconductor electronic component. Diodes are commonly used in all sorts of electronic circuits and allow current to pass in only one direction. Very specific semiconductor compounds are used to make LEDs which have distinct characteristics of emitting a certain color of light when current passes through them.
High-Power LED Tail-Light How To:
Lambertian Radiation Pattern?
Lambertian LEDs (sometimes called 'high dome' LEDs) have a high hemispherical dome that project a wider beam pattern of 140 degrees without any loss of light intensity. They produce an even distribution of light in all directions.
Batwing Radiation Pattern?
Batwing Luxeons (sometimes called 'low dome' LEDs) have a clear resin dome with a nearly flat top surface. Batwings project a flatter, forward distributed light designed to evenly fill an illuminated surface.
Side Emitting Radiation Pattern?
Just like the name suggest, side emitting LEDs project most of the generated light sideways. This produces a toroid of light that is useful for lighting large opaque surface areas. Side emitting LEDs are commonly used in flashlights with a reflector that directs the light forward.
Who invented the LED?
Nick Holonyak, 75, invented the LED (light emitting diode) in the 1960s. He has finally been given an inventor's award for his achievement. NicK was presented the Lemelson-MIT Prize, a $500,000 award given to top inventors by American academic institution, MIT.
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For a good roundup of all the popular LEDs and LED devices out there, check out The LED Museum.