Babel Buster Network Gateways: Big Features. Small Price.
EMAIL INTERVIEW Stuart Berjansky & Ken Sinclair
Mr. Berjansky is a member of the Federal Energy Management Advisory Committee (FEMAC), the government agency charged with charting the direction for achievement of Federal energy management goals. Involved in the lighting industry for more than 14 years, Mr. Berjansky has work for and with lamp manufacturers and energy service companies to promote the use of environmentally friendly and energy-efficient lamps. He has conducted both lighting audits and full building energy audits for many government agencies, including the GSA, US Army, and US Navy. Additionally, he assisted in the development of the Energy Star Buildings Upgrade Manual lighting section and conducted full building energy audits of EPA laboratories.
Mr. Berjansky has held also lighting design positions has designed lighting for a wide range of market segments, including commercial, industrial, and retail. A Certified Energy Manager (CEM), Mr. Berjanksy is also a member of both the Illuminating Engineering Society (IES) and the Association of Energy Engineers (AEE).
Stuart Berjansky, Product
Advance Transformer Co.
Digital Addressable Lighting Interface Protocol
Sinclair: We know DALI stands for Digital Addressable Lighting Interface, but what exactly does that mean?
Berjansky: Lighting control manufacturers each utilize their own proprietary protocol. Some protocols have been open to anyone while most remain closely held. In an effort to standardize lighting control protocol, many European manufacturers joined the DALI activity group. In Europe, the DALI protocol is described in the fluorescent ballast standard IEC 60929 under Annex E.
The DALI protocol is based upon digital signals versus analog signals. Typically, lighting controls utilize analog signals, which utilize analogous waveforms to transmit signals. Digital signals are made up of a series of 1's and 0's that provide the control information. With digital signals, ballasts become individually addressable compared to analog systems where only circuits are addressable. Additionally, DALI allows for bi-directional communication between the ballast and control. DALI also brings the capability of broadcast messaging to ballasts.
Sinclair: So is the DALI protocol for the ballasts only?
Berjansky: When the DALI protocol was developed, it was aimed at the receiver of the signal and not the sender. To a great degree, the intelligence in a DALI system resides in the ballast. A DALI ballast will operate from any manufacturer's DALI signal. However, while different manufacturers' control units may send out DALI signals, these different control units cannot communicate with one another in all likelihood. Currently there is no DALI equivalent for the control industry. However, both the Illuminating Engineering Society (IES) and NEMA are working on establishing a DALI control protocol.
Sinclair: Aren't there already digital control systems?
Berjansky: Yes, but DALI is the first to be openly adopted by the entire industry. Many manufacturers, both ballast and control, have developed digital controls. These protocols fall into one of two categories: proprietary or open. Many companies utilized proprietary protocols in order to maintain an edge in the marketplace. After all, if you had a product that sold well, would you want to give your competition a chance to duplicate your work? Although some companies had developed protocols and offered them free-of-charge on the open market, these have not panned out for various reasons. Because no single company developed the DALI protocol, its acceptance in the marketplace has been less controversial and more widely embraced. Since DALI is a large step forward for the lighting industry - an industry that typically moves at a glacial pace - the jump to a standard protocol that is also digital is truly revolutionary.
Sinclair: "Revolutionary" is quite a bold statement - what makes it revolutionary?
Berjansky: In addition to being able to control individual ballasts, which in itself is revolutionary, DALI requires no special wiring of data cables and no hardwired control groups. Grouping of lights and flexible control of those groups can be accomplished onsite after the lighting has been installed. The lighting can be addressed and grouped through various methods such as personal computers, infrared remotes, wallbox scene controllers and PDA's. These control methods allow for easy initial installation and later reconfiguration - and an extremely simple and intelligent interface with Building Management Systems.
Sinclair: What do you mean by an "intelligent" interface with Building Management Systems? Isn't it simply a "lights on/lights off" communication?
Berjansky: No, it's far more - and this is what building automation designers and contractors should really take note of. Certainly, the BMS can be used for central overrides such as timed on/off switching or dimming - but a DALI system can add valuable extra flexibility through its feedback of lighting system information to the BMS, automatically identifying failed lamps and ballasts and allowing central monitoring of ballast power and dimming levels. Traditionally, a lighting system that is tied into the BMS is done through a gateway that allows only basic control with no feedback.
Case in point: how would you be able to properly maintain the HVAC system in a large commercial building if you couldn't see from the BMS how your mechanical systems were operating? This is comparable to today's lighting systems, where all you really have is one-way communication. With DALI's two-way communication, building managers will know when a lamp is out without receiving a phone call from an irate tenant - or could reduce peak electrical demand on extremely hot days (after all, lighting accounts for about 40% of connected electrical load in most office buildings).
Sinclair: You've mentioned several times "individually addressable" ballasts - does this mean that dimming levels for each ballast can be varied?
Berjansky: Yes. Every single ballast can be programmed differently to dim or turn off in response to ambient light, occupancy, time of day, or different pre-set lighting scenes to accommodate multiple and changing uses of the room. The building manager or other assigned individual may modify the lighting program to accommodate space needs. Again, the lights may be dimmed for aesthetics or energy conservation. If utilized with ambient light sensors, then a lumen maintenance system may be implemented. In this system, light levels are continuously varying in order to provide a fixed light level on the task.
Sinclair: There can be different scenes for one room? What's the point?
Berjansky: Yes. Each ballast can belong to as many as 16 groups, and lighting scenes can be created by setting individual lighting levels for the individual ballasts or groups. 16 scenes can be stored for each user. A good example is a school gymnasium, used for daytime and evening sports events as well as special events such as concerts. Say there's one wall that is predominantly windows. Daylight harvesting can be done to maintain constant light levels for daytime activities - plus saving energy to boot; a different scene might be programmed for evening sports activities; yet another scene for concerts when you want mainly stage lighting; and yet another scene for cleaning.
Sinclair: Okay, so walk us through a typical scenario of a DALI connection to a BMS.
Berjansky: Each DALI system can control up to 64 ballasts, each of which is individually addressable. Via a DALI loop, ballasts are connected with standard building wire to a DALI controller, which can be connected to other controllers for centralized control of larger areas. The DALI system can then be either a stand-alone subsystem or a pure subsystem to the Building Management System. In the stand-alone scenario, only the most important information will be sent to the BMS. With a pure subsystem, the DALI system communicates bi-directionally via a gateway or transmitter and is an integral piece of the BMS. The gateway is connected to the low-voltage DALI cables on one side and to the BMS network bus on the other.
Sinclair: This sounds like something only applicable to new installations.
Berjansky: Not at all. Assuming an existing analog system, simply replacing existing standard 0-10V ballasts with DALI ballasts plus a lighting controller provides a switch-free interface with feedback of lighting system information to the BMS - adding new flexibility to a BMS.
Sinclair: So what's the catch? Higher installation costs?
Berjansky: Actually, installation is much easier and less costly. Standard wiring is used. Less homeruns to the electric panel are required. There is no hardwired power circuit control. The plug-and-play system capability provides full compatibility of DALI-compliant products from various manufacturers. Again, it's extremely easy to connect with a Building Management System for ultimate control and automation.
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