Turned on by Dali

In the beginning, lighting designs were one of a kind, and little concern was given to the concept of control. When lighting control systems finally developed, the first systems to appear were mainly intended to provide lighting designers with a wider range of aesthetic choices and building occupants, with greater comfort.

04/01/2003


In the beginning, lighting designs were one of a kind, and little concern was given to the concept of control. When lighting control systems finally developed, the first systems to appear were mainly intended to provide lighting designers with a wider range of aesthetic choices and building occupants, with greater comfort.

But as energy concerns grew, new lighting control systems developed to provide ever-increasing efficiency. Most of these systems are proprietary, which means a lighting specifier has to choose a total package from a single supplier.

But now, there's Digital Addressable Lighting Interface (DALI), an interoperable control protocol that is specific to lighting and promises to improve both the specification and operation of lighting systems. (For a brief history of the DALI protocol, see "DALI's Roots," opposite page.) Several installations have already demonstrated that digital can offer greater lighting control and flexibility than analog controls.

Protocol, not product

It must be emphasized that DALI is not a product. Rather, it is a protocol—a set of rules. The current DALI protocol covers electrical characteristics, commands to ballasts and status information from ballasts. There are efforts currently underway to expand the DALI protocol to include control devices as well.

Here, the focus will be a discussion of the DALI protocol with respect to its four major components: power connections, lamp response, control interface and command set.

The DALI protocol specifies a logarithmic dimming curve with 254 steps. Mathematically, this is a 2.8% change per step. The low end of the curve is 0.1% for incandescent lamps, 1% for linear fluorescent lamps and 3% for compact fluorescent lamps. Note that this is lamp arc power, not lamp lumen output.

The intent of the DALI protocol is to provide a digital signal that is low in cost and simple to implement, immune to interference, and interchangeable among different manufacturers.

Electrical parameters

Ballasts conforming to the DALI protocol are programmed at the factory to go to full-light output upon initial application of voltage to the ballast. They are also programmed to go to a preset level upon loss of the DALI signal voltage. These light level settings may be changed during the commissioning process. Ballast manufacturers are also providing universal input voltage (115-volt to 300-volt, 50-Hz to 60-Hz), high power factor, low total harmonic distortion and transient voltage protection, even though these features are not DALI requirements.

The DALI protocol prescribes the "0" bit as zero volts DC (+/- 4.5 volts) and the "1" bit as 16 volts DC (9.5 volts to 22.5 volts), and further states that there shall be no more than a 2-volt drop between the power supply and the furthest device, either ballast or controller. The DALI signal wires—sometimes referred to as a loop or bus—are not to exceed 300 m (1,000 ft.) between the DALI power supply and the furthest ballast or control device. These requirements may necessitate a voltage drop calculation, if small gauge wires are anticipated for the DALI signal wiring.

The DALI terminals of a ballast can draw a maximum two milliamps (mA) of current during the idle or receiving state. Some control devices can draw as much as 15 mA in the idle state. During its query response state, a controller or ballast must be able to sink up to 250 mA of current when it is sending a "0" bit.

Hence, the DALI protocol limits the maximum power output of a DALI-compliant power supply to 250 mA. The designer must be cognizant when designing DALI systems not to exceed 250 mA for the combined DALI current of ballasts and control devices on any DALI bus.

The DALI signal is sent at 1,200 bits per second. Compare this relatively slow speed with Ethernet, the speed of which can be 100 million bits per second. It is this 16-volt, slow-speed control signal that provides immunity to power-line noise and other interferences. The slow speed is not noticeable to the occupants, because a whole group of ballasts react simultaneously in response to a group command.

The DALI signal media consists of two wires. These wires need not be twisted or shielded, and even though a DC voltage is used, the DALI connections to ballasts and controllers are not polarity-sensitive. Furthermore, an end-of-line resistor is not required. The DALI protocol allows for a free topology: i.e., the wires may be installed in a chain, star or tree arrangement.

DALI wires may be installed as Class 1 or Class 2 systems. This makes it possible to install the DALI bus wires along with the line-voltage wires in the branch circuit conduit or even to use a five-wire prefabricated wiring assembly. Or, the DALI bus wire may be installed totally independent of the line-voltage wiring.

If any portion of a DALI bus uses a Class 1 wiring method, then the whole DALI bus must be installed using Class 1 wiring. For example, if the DALI bus is installed in the same conduit with line-voltage wiring, then the whole DALI bus must be wired as Class 1. Simply stated, Class 1 wires may be installed with line-voltage wires, and Class 2 wires must not be installed with line-voltage wires. Any approved line-voltage wiring method is acceptable. One must be aware that unlike the ballasts, not all control units are currently dual-listed as Class 1 and Class 2; some are Class 2 only.

A DALI system requires more than just DALI ballasts. Power supply and control units are also needed. The power supply must supply approximately 16 volts DC, with no more than 250 mA of short-circuit current. Typical control units are scene selector with four or five buttons. Some control units offer means for manual dimming. There are even units that provide daylight harvesting via photosensor input and that respond to occupancy sensors.

The simplest DALI wiring configuration could be just as basic as a household doorbell circuit—with a power supply, controller and actuator—applicable to a single conference room or an executive office.

One ballast maker also has a custom gateway that provides two-way signal conversion between DALI and RS232 and supplies the required 16-volt DC power. This same manufacturer provides a software tool for use with a PDA, which via an RS232 cable provides an easy method of commissioning the components on the DALI bus with their addresses, scenes, groups and other program settings. There is also commissioning software for laptop computers that provides even more features. These also plug into the DALI routers via an RS232 cable.

Wall-box DALI controllers are available with the programming software tool built in as firmware. Thus, through a combination of button pushing, the ballasts on that DALI bus can be programmed with addresses, scenes and groups. A separate PDA or computer is not required when using these controllers.

Another DALI option is a cabinet that contains up to eight DALI-to-RS232 gateways, low-voltage power transformer and an eight port RS232-to-Ethernet gateway.

Thus far, what has been described is the general system configuration. But at the heart of DALI are its digital commands.

Bits and bytes

The DALI digital packet structure for commands to a ballast consists of one start bit, eight address bits (first byte), eight data/command bits (second byte), and two stop bits. For the majority of commands, the first byte identifies which address or group is to use the data or perform the command contained in the second byte. If the first seven bits of the first byte are all "ones," then this is considered a broadcast message, and all ballasts on the DALI bus will perform the command given in the second byte. For information coming from the ballast, the digital packet structure consists of one start bit, eight data bits (one byte) and two stop bits. (See "Control Interface: Bits and Bytes," below, for a depiction of this digital packet structure.)

The DALI protocol assumes that there is only one device sending a command at any one time, and while the currently published protocol does not require checking for simultaneous commands, all major manufacturers of DALI control devices presently include collision detection and avoidance in their products in order to eliminate communication errors. Ballasts do not need this capability, because they only respond to a query on an individual basis.

The current DALI command set is for ballasts. There are more than 100 commands defined, and the protocol structure provides for many more future commands yet to be defined. (For a list of the more common commands and query responses, see "DALI Ballast Commands and Device Types" at right). The commands provide the ability to program, control and monitor the status of ballasts.

DALI programming

Six bits of the first byte in a DALI packet are used for addressing individual ballasts, and thus, there can be up to 64 ballasts or addressable devices. These six bits allow up to 64 unique addresses for ballasts or actuator devices on a DALI bus.

However, ballasts are not assigned an address when they leave the factory. The address is assigned during the commissioning process.

In commissioning, a software tool initiates the addressing process by commanding each ballast to generate a 24-bit (3-byte) random number. The software tool then polls these random numbers and sorts them in numerical sequence. It then assigns address "0" to the ballast with the lowest random number, address 1 to the ballast with the next lowest random number and so on up to address 63. An alternate addressing technique is to manually disconnect the lamp from its ballast. The software will find this ballast and assign it the next address number. Also, the software tool has a routine that allows the reassignment of a ballast address to an unused address.

Each DALI bus can support up to 16 individual groups, and software can assign ballasts to groups. Also, each of the ballast may belong to any or all of the 16 groups.

Moreover, each ballast can have as many as 16 preset scene levels. The software tool can assign levels to each of the scenes in each ballast or to all the ballasts in a particular group.

Building lighting network

In order to fully appreciate the DALI protocol and related products, a look at how it's use in a real building system is instructive. In Figure 4 (p. 54), a server connects to the Ethernet, which connects to the DALI gateways. The server contains software for programming the DALI devices, time-of-day scheduling controls, lamp/ballast maintenance reporting, demand limiting, and energy monitoring. The Ethernet network also connects to the computers at the individual occupant workstations. These computers can be loaded with a DALI icon that allows occupants direct control over the luminaires assigned to them.

Figure 5 (at right) shows the traditional wiring method for a conference room with eight lighting zones and one local scene controller. Figure 6 shows the same conference room using the DALI wiring method. The DALI system has a single home run to the electric closet, as opposed to nine home runs for the traditional lighting control system. Furthermore, there is only one DALI gateway in the electric closet, compared with eight dimmer modules and a controller in the electric closet for the conventional system. The result is a lower installed cost to the owner.

In short, the DALI protocol provides a cost-competitive, interoperable lighting control system with interchangeable, plug-and-play components from various manufacturers. Benefits include:

  • Lower initial cost to the owner due to simplified wiring, assuming that the decision has already been made to install dimming ballasts.

  • Lower level of maintenance effort for the facility manager due to status reports on lamps and ballasts.

  • Greater flexibility for the lighting designer due to software programming.

  • Lower energy costs to the owner due to reduced power consumption.

  • Greater individual control for users.

Although DALI is still new, use of the system is on the increase, with more than 80 installations and more than 10,000 DALI ballasts in the United States as of March 2003.

Further, one can anticipate additional improvements in the near future, giving DALI a sustainable competitive advantage over currently available lighting control systems.


Author Information

Mr. Miller has more than 25 years of experience designing lighting and electrical systems, including control systems for office lighting, daylight harvesting and HVAC. He will be presenting seminars on the topics of LEED certification and DALI at the Lightfair International show, to be held at the Javits Center in New York City, May 6 through 8.


DALI's Roots

DALI was born in Europe. The Austrian firm Tridonic and others developed the digital serial interface ballast in 1991. By 1998, a consortium of European lighting equipment manufacturers had developed the Digital Addressable Lighting Interface. The original concept was to license the DALI protocol to other manufacturers, but the royalties were eventually dropped in order to gain widespread acceptance.

Eventually, the full DALI protocol was developed in the mid-1990s by a committee within the International Electrotechnical Commission (IEC). It was a compromise between those IEC members who wanted to expand DALI's capabilities—they were looking for new markets—and those members who wanted to limit DALI's capabilities because they did not want it to compete with their products.

In the United States, the National Electrical Manufacturers Association's Controls Council on Wiring Devices, Controls and Ballasts, which serves as NEMA's liaison with the IEC, established a DALI subcommittee in 2000. That same year, NEMA asked the Controls Committee of the Illuminating Engineering Society of North America (IESNA) to comment on the proposed DALI protocol. DALI was formally adopted by IEC as Standard EN60929, Annex E & G, in the summer of 2002.

The German Electrical and Electronic Manufacturers' Association (ZVEI), Division Luminaires, has established a trade association, DALI-AG, to promote the DALI protocol and related products. As of March 2003, there were 26 members, including the following: Johnson Controls, Milwaukee; Lightolier, Fall River, Mass.; Lutron, Coopersburg, Pa.; and Universal Lighting Technologies, Nashville, Tenn. European members include: Osram in Germany; Philips in The Netherlands; and Tridonic in Austria. The DALI-AG organization can be reached at

DALI's Roots

DALI was born in Europe. The Austrian firm Tridonic and others developed the digital serial interface ballast in 1991. By 1998, a consortium of European lighting equipment manufacturers had developed the Digital Addressable Lighting Interface. The original concept was to license the DALI protocol to other manufacturers, but the royalties were eventually dropped in order to gain widespread acceptance.

Eventually, the full DALI protocol was developed in the mid-1990s by a committee within the International Electrotechnical Commission (IEC). It was a compromise between those IEC members who wanted to expand DALI's capabilities—they were looking for new markets—and those members who wanted to limit DALI's capabilities because they did not want it to compete with their products.

In the United States, the National Electrical Manufacturers Association's Controls Council on Wiring Devices, Controls and Ballasts, which serves as NEMA's liaison with the IEC, established a DALI subcommittee in 2000. That same year, NEMA asked the Controls Committee of the Illuminating Engineering Society of North America (IESNA) to comment on the proposed DALI protocol. DALI was formally adopted by IEC as Standard EN60929, Annex E & G, in the summer of 2002.

The German Electrical and Electronic Manufacturers' Association (ZVEI), Division Luminaires, has established a trade association, DALI-AG, to promote the DALI protocol and related products. As of March 2003, there were 26 members, including the following: Johnson Controls, Milwaukee; Lightolier, Fall River, Mass.; Lutron, Coopersburg, Pa.; and Universal Lighting Technologies, Nashville, Tenn. European members include: Osram in Germany; Philips in The Netherlands; and Tridonic in Austria. The DALI-AG organization can be reached at

DALI's Roots

DALI was born in Europe. The Austrian firm Tridonic and others developed the digital serial interface ballast in 1991. By 1998, a consortium of European lighting equipment manufacturers had developed the Digital Addressable Lighting Interface. The original concept was to license the DALI protocol to other manufacturers, but the royalties were eventually dropped in order to gain widespread acceptance.

Eventually, the full DALI protocol was developed in the mid-1990s by a committee within the International Electrotechnical Commission (IEC). It was a compromise between those IEC members who wanted to expand DALI's capabilities—they were looking for new markets—and those members who wanted to limit DALI's capabilities because they did not want it to compete with their products.

In the United States, the National Electrical Manufacturers Association's Controls Council on Wiring Devices, Controls and Ballasts, which serves as NEMA's liaison with the IEC, established a DALI subcommittee in 2000. That same year, NEMA asked the Controls Committee of the Illuminating Engineering Society of North America (IESNA) to comment on the proposed DALI protocol. DALI was formally adopted by IEC as Standard EN60929, Annex E & G, in the summer of 2002.

The German Electrical and Electronic Manufacturers' Association (ZVEI), Division Luminaires, has established a trade association, DALI-AG, to promote the DALI protocol and related products. As of March 2003, there were 26 members, including the following: Johnson Controls, Milwaukee; Lightolier, Fall River, Mass.; Lutron, Coopersburg, Pa.; and Universal Lighting Technologies, Nashville, Tenn. European members include: Osram in Germany; Philips in The Netherlands; and Tridonic in Austria. The DALI-AG organization can be reached at

DALI's Roots

DALI was born in Europe. The Austrian firm Tridonic and others developed the digital serial interface ballast in 1991. By 1998, a consortium of European lighting equipment manufacturers had developed the Digital Addressable Lighting Interface. The original concept was to license the DALI protocol to other manufacturers, but the royalties were eventually dropped in order to gain widespread acceptance.

Eventually, the full DALI protocol was developed in the mid-1990s by a committee within the International Electrotechnical Commission (IEC). It was a compromise between those IEC members who wanted to expand DALI's capabilities—they were looking for new markets—and those members who wanted to limit DALI's capabilities because they did not want it to compete with their products.

In the United States, the National Electrical Manufacturers Association's Controls Council on Wiring Devices, Controls and Ballasts, which serves as NEMA's liaison with the IEC, established a DALI subcommittee in 2000. That same year, NEMA asked the Controls Committee of the Illuminating Engineering Society of North America (IESNA) to comment on the proposed DALI protocol. DALI was formally adopted by IEC as Standard EN60929, Annex E & G, in the summer of 2002.

The German Electrical and Electronic Manufacturers' Association (ZVEI), Division Luminaires, has established a trade association, DALI-AG, to promote the DALI protocol and related products. As of March 2003, there were 26 members, including the following: Johnson Controls, Milwaukee; Lightolier, Fall River, Mass.; Lutron, Coopersburg, Pa.; and Universal Lighting Technologies, Nashville, Tenn. European members include: Osram in Germany; Philips in The Netherlands; and Tridonic in Austria. The DALI-AG organization can be reached at

DALI's Roots

DALI was born in Europe. The Austrian firm Tridonic and others developed the digital serial interface ballast in 1991. By 1998, a consortium of European lighting equipment manufacturers had developed the Digital Addressable Lighting Interface. The original concept was to license the DALI protocol to other manufacturers, but the royalties were eventually dropped in order to gain widespread acceptance.

Eventually, the full DALI protocol was developed in the mid-1990s by a committee within the International Electrotechnical Commission (IEC). It was a compromise between those IEC members who wanted to expand DALI's capabilities—they were looking for new markets—and those members who wanted to limit DALI's capabilities because they did not want it to compete with their products.

In the United States, the National Electrical Manufacturers Association's Controls Council on Wiring Devices, Controls and Ballasts, which serves as NEMA's liaison with the IEC, established a DALI subcommittee in 2000. That same year, NEMA asked the Controls Committee of the Illuminating Engineering Society of North America (IESNA) to comment on the proposed DALI protocol. DALI was formally adopted by IEC as Standard EN60929, Annex E & G, in the summer of 2002.

The German Electrical and Electronic Manufacturers' Association (ZVEI), Division Luminaires, has established a trade association, DALI-AG, to promote the DALI protocol and related products. As of March 2003, there were 26 members, including the following: Johnson Controls, Milwaukee; Lightolier, Fall River, Mass.; Lutron, Coopersburg, Pa.; and Universal Lighting Technologies, Nashville, Tenn. European members include: Osram in Germany; Philips in The Netherlands; and Tridonic in Austria. The DALI-AG organization can be reached at

Some Available Lighting Control Systems

Some of the available lighting control systems are listed below. Most of these systems are proprietary, with the following exceptions: Agili-T, which uses the DALI protocol; DMX512, which was developed by the theatrical lighting industry; and IBECS, which was developed by a federally funded national laboratory. In comparison, DALI was developed by a consortium of lighting equipment manufactures and is non-proprietary and royalty-free.

Agili-T by Lightolier

Centura by Leviton

Digital-MicroWatt by Lutron

DMX512 by USITT

Easylite by Easylite Ballasts and Lighting Systems

Ergolight by Ledalite

GR2400 by Lighting Control and Design

IBECS by Lawrence Berkeley National Lab

NexLight by Northpoint Engineering Co.

PowerLink by Square D Company

SuperDim by Energy Savings Inc

Synergy by Lithonia

DALI Ballast Commands and Device Types

There are currently more than 100 DALI commands. The following are the most commonly used commands.

Commands to Ballast

Off

Fade to level

Step up

Set actual level

Step down

Set power on level

On and step up

Set system failure level

Set max

Set fade time

Step down and off

Set fade rate

Set min

Set scene

Go to max

Go to scene

Go to min

Remove from scene

Up to max

Set group

Down to min

Remove from group

Query from Ballast

Actual level

Scene level

Power on level

Fade time

System failure level

Random address

Max

Version number

Min

Device type

Group assignment

Device Types

Type 0 - Standard (fluorescent)

Type 1 - Emergency lighting

Type 2 - High-intensity discharge lamps

Type 3 - Low-voltage halogen lamps

Type 4 - Line-voltage incandescent lamps

Type 5-255 - Future device types

DALI Ballast Commands and Device Types

There are currently more than 100 DALI commands. The following are the most commonly used commands.

Commands to Ballast

Off

Fade to level

Step up

Set actual level

Step down

Set power on level

On and step up

Set system failure level

Set max

Set fade time

Step down and off

Set fade rate

Set min

Set scene

Go to max

Go to scene

Go to min

Remove from scene

Up to max

Set group

Down to min

Remove from group

Query from Ballast

Actual level

Scene level

Power on level

Fade time

System failure level

Random address

Max

Version number

Min

Device type

Group assignment

Device Types

Type 0 - Standard (fluorescent)

Type 1 - Emergency lighting

Type 2 - High-intensity discharge lamps

Type 3 - Low-voltage halogen lamps

Type 4 - Line-voltage incandescent lamps

Type 5-255 - Future device types

DALI Ballast Commands and Device Types

There are currently more than 100 DALI commands. The following are the most commonly used commands.

Commands to Ballast

Off

Fade to level

Step up

Set actual level

Step down

Set power on level

On and step up

Set system failure level

Set max

Set fade time

Step down and off

Set fade rate

Set min

Set scene

Go to max

Go to scene

Go to min

Remove from scene

Up to max

Set group

Down to min

Remove from group

Query from Ballast

Actual level

Scene level

Power on level

Fade time

System failure level

Random address

Max

Version number

Min

Device type

Group assignment

Device Types

Type 0 - Standard (fluorescent)

Type 1 - Emergency lighting

Type 2 - High-intensity discharge lamps

Type 3 - Low-voltage halogen lamps

Type 4 - Line-voltage incandescent lamps

Type 5-255 - Future device types

DALI Ballast Commands and Device Types

There are currently more than 100 DALI commands. The following are the most commonly used commands.

Commands to Ballast

Off

Fade to level

Step up

Set actual level

Step down

Set power on level

On and step up

Set system failure level

Set max

Set fade time

Step down and off

Set fade rate

Set min

Set scene

Go to max

Go to scene

Go to min

Remove from scene

Up to max

Set group

Down to min

Remove from group

Query from Ballast

Actual level

Scene level

Power on level

Fade time

System failure level

Random address

Max

Version number

Min

Device type

Group assignment

Device Types

Type 0 - Standard (fluorescent)

Type 1 - Emergency lighting

Type 2 - High-intensity discharge lamps

Type 3 - Low-voltage halogen lamps

Type 4 - Line-voltage incandescent lamps

Type 5-255 - Future device types

DALI Ballast Commands and Device Types

There are currently more than 100 DALI commands. The following are the most commonly used commands.

Commands to Ballast

Off

Fade to level

Step up

Set actual level

Step down

Set power on level

On and step up

Set system failure level

Set max

Set fade time

Step down and off

Set fade rate

Set min

Set scene

Go to max

Go to scene

Go to min

Remove from scene

Up to max

Set group

Down to min

Remove from group

Query from Ballast

Actual level

Scene level

Power on level

Fade time

System failure level

Random address

Max

Version number

Min

Device type

Group assignment

Device Types

Type 0 - Standard (fluorescent)

Type 1 - Emergency lighting

Type 2 - High-intensity discharge lamps

Type 3 - Low-voltage halogen lamps

Type 4 - Line-voltage incandescent lamps

Type 5-255 - Future device types



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