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Controlling LEDs

Controlling LEDs
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Controlling LEDs Technical white paper May 2014 Ethan Biery Thomas Shearer Roland Ledyard Dan Perkins Manny Feris

1 Abstract Ten years ago, Light Emitting Diodes (LEDs) were used primarily in niche applications as status indicators, and in exit signs. Today, they’re designed into nearly every lighting application from street lights to stairwells. However, owners, contractors, engineers and designers do not always know how to control LEDs or they have had a negative experience. Additionally, the fast-moving state of the LED lighting industry means there is a lot of risk that needs to be managed throughout a job. This white paper provides: An overview of LEDs and types of LED products Advantages and...

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You can either switch or dim LEDs, depending on the use of the space. If dimming is preferred important considerations include: • Dimming range of LED products (100 to 20% vs. 100 to 1%) • Dimming performance and expectations (smooth, continuous, flicker-free) • LED fixture and driver standards • Dimmer standards • LED driver features • Minimum and maximum loads for LED drivers and controls There are many control options when it comes to LEDs, with the most common options being: • Two-wire forward phase • Two-wire reverse phase • EcoSystem® digital • DALI digital Once...

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When the unabsorbed blue light mixes with the other colors of light it creates what your eye perceives as “white” light. The choice of blue LED and yellow phosphor, and the method of placing the phosphor, creates hundreds of colors of “white” due to differences in color temperature and CRI (Color Rendering Index). A single LED chip is mounted with other chips, in many different forms, to create LED modules (also known as LED Arrays, LED Engines, or LED Tapes). 3.2 Types of LED products There are two distinct types of LED lighting: the LED lamp (also called a LEDi or retrofit lamp) and the...

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3.3 LED Drivers LED chips are inherently low-voltage devices that need additional electronic components to convert the line-voltage 120/220/277 V power to the low voltage needed for the LEDs. These electronics may also interpret control signals and dim the LEDs accordingly. These devices are referred to as LED drivers. LEDs are powered by one of two different types of drivers. LED driver outputs may be constant voltage (usually 12 V or 24 V) or constant current (e.g. 350mA, 700mA or 1050mA). It is the fixture manufacturer that chooses the driver type and configuration to match the...

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devices or modules, while others can be configured to operate most commonly available LEDs. Generally, it is up to the fixture manufacturer to specify the proper driver type to be used. The selection of an appropriate driver is not limited to just making sure it matches the LED module being used. The driver is the primary component that determines the best-possible dimming capabilities of the LED lamp or fixture. Furthermore, the LED driver is one source of potential failure for the LED fixture. The long-life benefits of LEDs are significantly reduced if the driver is not specifically...

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Higher cost: High Brightness LEDs, necessary for general illumination, are expensive but dropping in price. They also require electronic drivers to convert conventional AC voltage to discrete DC voltages for the LED modules. Color and color rendering: LEDs vary widely in apparent color (Color Temperature) and how they affect the color of objects and people in the space (Color Rendition). Color stability over time is another potential limitation. Control-compatibility challenges: Due to the wide range of LED-based lighting product types, not all LED lamps are dimmable, and the ones that can...

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Dimming LEDs offers many other benefits common to other lighting, including: Space Flexibility: Dimming control systems provide for space flexibility—what may be an office space today could easily be converted into a call center tomorrow; or a gymnasium can be used as a theater or cafeteria just by adding dimming control for the lighting. Your home and your workplace should be designed to complement your needs. As your needs change throughout the day, your lighting should adapt as well; bright enough to read a book, but dim enough for computer use. Whether you are at home or at work,...

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(e.g., 20 percent measured light equals 45 percent perceived light). The equation for determining perceived light is the square root of the measured light percentage (e.g. V0.20 = 0.45). As the designer or the end-user, you need to select the dimming range of your fixture or lamp that will be suitable for your application. A product that dims to 20 percent measured light (45 percent perceived) may be the energy-saving solution necessary for the daylight harvesting strategy needed in an office, but 20% dimming wouldn’t make sense in an Audio/Visual media room where 1% dimming is expected....

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5.3 Dimming performance and expectations The public’s experience with incandescent dimming is that it is smooth and continuous. Specifically, any change in the control (dimmer) position should be reflected by an equal change in light level— there should be no abrupt changes in light level as the light source is being dimmed. Each manufacturer defines dimming in a different way, but the end user expects that the dimming will not be distracting or have noticeable, irregular changes in light. Even more important is eliminating flicker in the dimming range. Flicker is the unexpected modulation...

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5.4 LED Fixture and driver standards Certification by a Nationally Recognized Testing Lab (NRTL), such as Underwriters Laboratories (UL), CSA, or Intertek, is an important aspect of ensuring the safety of any product, and LED luminaires are no different. Such certifications confirm that a fixture has passed standardized tests and establishes that a product should not present any unexpected hazard upon installation. Many types of products are components that have been tested to a particular safety standard, but are intended to be installed as part of a larger, finished assembly. These...

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