“Light-emitting diodes (LEDs) have revolutionized indoor and outdoor lighting. This solid-state lighting (SSL) technology, with its superior efficiency, controllability, color spectrum, thermal performance, and unique form factor, is making the venerable Edison incandescent light bulb (as well as fluorescent, metal halide, or sodium vapor) obsolete. Most new interior and exterior designs and upgrades to existing designs now consider LEDs first. Still, designers have to be careful. At the same time of rapid innovation, there are also some hidden dangers, such as non-standard connection and end-user solution mismatch, which can cause negative customer experience.
Light-emitting diodes (LEDs) have revolutionized indoor and outdoor lighting. This solid-state lighting (SSL) technology, with its superior efficiency, controllability, color spectrum, thermal performance, and unique form factor, is making the venerable Edison incandescent light bulb (as well as fluorescent, metal halide, or sodium vapor) obsolete. Most new interior and exterior designs and upgrades to existing designs now consider LEDs first. Still, designers have to be careful. At the same time of rapid innovation, there are also some hidden dangers, such as non-standard connection and end-user solution mismatch, which can cause negative customer experience.
It’s not just the light source itself that it revolutionizes. For example, LED lighting is also changing the design and shape of connectors and their fixtures (called luminaires), which are a necessary part of any lighting system, and they do not accept AC line Voltage, but lower DC voltages , the typical current is usually between 3 amperes (A) and 7 A. In addition, LED lighting systems are often part of a control network supporting the Digital Addressable Lighting Interface (DALI) and Zhaga industry standards, and provide smart, energy-efficient, high-performance lighting as a key part of a smart home or office.
Therefore, it is the engineer’s responsibility to become familiar with these standards and their reflection in real-world connectors before proceeding with LED lighting system designs, as new designs are emerging rapidly.
This article briefly reviews why LEDs are so ubiquitous, then introduces and describes the two connectivity standards to ensure interoperability, rapid development, and easy deployment of smart LED designs. Finally, Amphenol ICC’s connectors are introduced, and the use of these connectors is outlined as a practical representation of the relevant standards and their applications.
Why are LEDs so popular
There are a number of factors that have contributed to the development of LEDs as lighting sources:
Lower costs drive higher yields, which in turn drive lower costs and higher yields
Basic reliability and lifetime enhancement of LEDs as light sources
Circuit improvements, mainly power improvements to drive these LEDs
The use of smart controls and even network I/O increases the convenience of LED control
Improvement in optical output quality characterized by color temperature (Kelvin) and color rendering index (CRI)
Government incentives, standards and mandates to improve lighting efficiency to save energy (lighting is estimated to account for 15% to 20% of total energy consumption)
Development of industry and government standards that ensure interoperability between LED light sources and compatibility with smart controllers.
The last point is especially important. An important size category of traditional incandescent light bulbs is the “E26” 26 millimeter (mm) diameter Edison screw bulb, which is used almost universally in residential settings in the United States and many other countries (Figure 1), and is being replaced by LED and fluorescent bulbs replaced, but to a lesser extent. Of course there are other sizes, such as the E12 base, but the E26 is by far the most widely used.
Of course, standardizing on a single base and socket reduces costs. The same technology has also led to a variety of bulb shapes, power levels, and other attributes built around this foundation, while reducing the worry of long-term replacement of burnt bulbs. Earlier generations of LED bulbs used E26 bases for compatibility with existing sockets, allowing users to get used to LED lighting. These E26 LED bulbs are still widely sold, and since there are countless such sockets in use today, the replacement process will take a long time.
However, LEDs differ significantly in current, voltage (DC) and power consumption compared to incandescent bulbs, which are typically powered using 120/240 volts AC. Also, E26 socket leads tend to have larger screw terminals, which are not ideal for powering LED light sources (Figure 2). Therefore, in order for LEDs to reach their full potential from the system level to the physical connection level, new standards and connector types are required.
Recognizing the need for a modern lighting interface standard, the Digital Lighting Interface Alliance (DiiA) developed the DALI standard.
DALI standard redefines lighting connectivity
DALI is a proprietary protocol for digital lighting control that enables easy installation of robust, scalable and flexible lighting networks (Figure 3). The first version, DALI-1, is more suitable for digital control, configuration and query of fluorescent lamp ballasts, with less consideration for LEDs. It replaces the simple, unidirectional, broadcast-style operation of existing 0/1 to 10 volt analog control methods.
The standard also includes a broadcast option where, with simple reconfiguration, each DALI device can be assigned an individual address, allowing digital control of individual devices. In addition, DALI devices can be programmed to operate in groups, so that the lighting system can be reconfigured via software, avoiding wiring changes.
The growth of user expectations and the improvement of LED technology have led to the development of the current DALI-2 standard. DALI-2 is not just an industry standard, it is now also a standard of the International Electrotechnical Commission (IEC 62386). DALI-2 adds many new commands and functions. DALI-1 covers only control modes, while DALI-2 covers control devices such as application controllers and input devices (such as sensors), as well as bus power. The focus is on interoperability of products from different vendors and is supported by the DALI-2 certification program to confirm product compliance with the specification (Figure 4).
Like all composite standards, DALI-2 is complex. In short, with a single wire pair as the bus, each device on the DALI network can be addressed individually. The bus is used to provide both signal and power and supports power supplies capable of delivering up to 250 milliamps (mA) at 16 VDC (typical). The standard supports devices powered by AC line or DC power rails.
While extra-low voltage (ELV) is defined in various standards, the IEC defines an ELV device or circuit as one where the potential difference between an electrical conductor and ground does not exceed 50 volts ac or 120 volts dc. The DALI control cable is classified as an ELV device and therefore requires only basic insulation from the AC mains; it can be run with the mains line or a multi-conductor cable that includes the mains line.
Beyond DALI-2: Zhaga spec targets luminaires
Standards like DALI-2 are important, but they only go so far. Defining how to relate the standard to specific applications such as LED lighting and luminaires is beyond its scope. To solve this problem, the International Zhaga Alliance has developed an interface industry specification for components used in LED lamps. The consortium is a member program of the IEEE Industry Standards and Technology Organization, with more than 120 members as of 2019.
Now is the time to understand the difference between lighting equipment and lamps. The Illuminating Engineering Society (IES) Lighting Handbook, ANSI/NEMA Standards, and IEC all use the term “luminaire”. It was added to the National Electrical Code (NEC) handbook in 2002 and is formally defined as “a complete lighting unit consisting of one or more lamps and designed to distribute light, locate and protect lamps, and Components for connecting the lamp to the power supply”. Luminaires include lamps and all parts directly related to the distribution, positioning, and protection of lighting fixtures, excluding supporting parts such as arms, ribs, or rods; fasteners for securing fixtures; control or safety devices; or power conductors . Luminaires come in a variety of forms and are suitable for a variety of occasions, from strictly functional outdoor street lighting to indoor office lighting, or even ‘fashionable’ retail or home lighting.
“Lighting equipment” is not defined in the NEC, and generally refers to anything in the mind of the user, which may include some or all of the following elements: a light tube (bulb), perhaps with a cover, bulb, lens or diffuser, bracket, lamp Pole or light fittings, and other elements.
Officially known as Books, Zhaga specifications address electrical, mechanical, optical, thermal, and communication interfaces and allow for component interoperability. By adhering to the Zhaga specification, designers can ensure that users have components that are interoperable, replaceable or repairable, and that LED luminaires can be upgraded once new technologies emerge after installation.
The Zhaga Book 18 and Book 20 are particularly useful for designers working with LED light fixtures; the former focuses on outdoor designs, while the latter is aimed at indoor applications.
Zhaga Book 18: “Intelligent Interfaces Between Outdoor Luminaires and Sensing/Communication Modules” specifies the power and communication aspects, in addition to the mechanical fit and electrical pinout of the connection system defined in version 1.0. It simplifies the addition of application modules, such as adding sensors and communication nodes to LED luminaires, and ensures plug-and-play interoperability.
Zhaga Book 20: “Intelligent Interface of Indoor Luminaires and Sensing/Communication Modules” defines the intelligent interface of indoor LED luminaires and sensing/communication nodes. This node connects to the LED driver and control system, and typically provides sensor input or enables communication between network components. Nodes can be installed and replaced in the field.
LED lighting has dramatically changed indoor and outdoor lighting for industrial, commercial and residential. It combines a near-perfect combination of energy efficiency, long life and flexibility in luminaire configuration.
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