What Is DALI?

DALI stands for Digital Addressable Lighting Interface. It is a bi-directional communication protocol used to provide control and communication of components in a lighting system. DALI originated in the late 1990s and was defined in IEC 60929. The current (2020) version of DALI is called DALI-2 and is defined in IEC62386.

The original DALI (version 1) logo and the newer DALI-2 logo.

Both logos are the property of the DiiA. This is the Digital Lighting Interface Alliance, an open global consortium of lighting companies that aims to develop a market for lighting control solutions based on digital addressable lighting interface technology.

All leading manufacturers offer a very wide range of lighting control products that support DALI, which is now widely regarded as the global standard for lighting control.

 120-130lm/w 30w/35w DALI Track Lighting

Key features of DALI

• It is an open protocol - any manufacturer can use it.

• A mandatory certification process guarantees DALI-2 interoperability between manufacturers.

• Easy to install. Power and control cables can be laid together and do not require shielding.

• The cabling topology can be in the form of a star (hub and spoke), a tree or a wire, or any combination of these forms.

• Communication is digital, not analog so multiple devices can receive exactly the same dimming values, resulting in very stable and accurate dimming performance.

• All devices have their own unique address in the system, thus offering a very wide range of possibilities for flexible control.

How does DALI compare with 1-10V?

DALI lighting is designed for the lighting industry in the same way as 1-10V. Lighting control components, such as LED drivers and sensors, are available from a range of manufacturers with DALI and 1-10V interfaces. However, this is where the similarities end.

  120-130lm/w 30w/35w DALI Track Lighting

The main differences between DALI and 1-10V are

DALI is addressable. This opens the way for many valuable functions such as grouping, scene setting, and dynamic control, for example changing which sensors and switches control which luminaires in response to changes in the office layout.

DALI is digital, rather than analog. This means that DALI can provide more precise luminance control and more consistent dimming.

DALI is a standard so that, for example, dimming curves are standardized, meaning that devices are interoperable between manufacturers. 1-10V dimming curves have never been standardized, so using different brands of drivers on the same dimming channel can produce some very inconsistent results.

1-10V can only control switches and simple dimming. DALI can manage color control, color changes, emergency lighting tests and feedback, complex scene settings, and many other lighting-specific functions.

Are all DALI products compatible with each other?

There were some compatibility issues with the original version of DALI, as the scope of the specification was very limited. Each DALI data frame is only 16 bits (8 bits for addresses and 8 bits for commands), so the number of commands available is very limited and there is no conflict detection. As a result, some manufacturers tried to extend its functionality by adding their own, which led to some incompatibilities.

With the advent of DALI-2, this problem has been overcome.

DALI-2 is more ambitious in its scope and includes many features that were not present in the original version. The result is that the additions made to DALI by individual manufacturers are no longer relevant. For a more detailed description of the DALI-2 architecture, see "How DALI works" below.

The DALI-2 logo is owned by the DiiA (Digital Illumination Interface Alliance) and they have imposed strict conditions on its use. The main one is that no product can carry the DALI-2 mark unless it has undergone an independent certification process to check full compliance with IEC62386.

DALI-2 allows the use of both DALI-2 and DALI components in a single installation, subject to some restrictions. In practice, this means that DALI LED drivers (as the main example) can be used in DALI-2 installations.

How does DALI compare with KNX, LON, and BACnet?

KNX, LON, and BACnet are building control protocols that are designed to integrate and control multiple devices and systems throughout a building. Few LED drivers on the market can support a direct connection to these protocols (although very few LED drivers have a KNX interface) and therefore they cannot be implemented as lighting control protocols.

In contrast, DALI and DALI-2 are designed for lighting control and the DALI-2 command set contains many lighting-specific commands. These include commands and functions for dimming, color change, scene setting, emergency testing, and feedback as well as circadian lighting. A wide range of lighting control components, especially LED drivers, support direct DALI connections.

In many implementations, the building management system (BMS) will use KNX, LON, BACnet, and similar protocols for overall building control (integrated HVAC, security, access control, lifts, etc.), while DALI will be used only for controlling lighting. If necessary, the gateway will provide intercommunication between the BMS and the lighting system, e.g. if the security system detects an intruder, all corridor lighting can be switched on via DALI.

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