DALI stands for Digital Addressable Lighting Interface. It is a 2-way communications protocol that is used to provide control over, and communication between, the components in a lighting system.
DALI originated in the late 1990s and was defined in IEC60929. Since then it has been substantially modified. The current (2020) version of DALI is called DALI-2 and this is defined in IEC62386.
The original DALI (version 1) logo and the newer DALI-2 logo.
Both logos are the property of DiiA. This is the Digital Illumination Interface Alliance, an open, global consortium of lighting companies that aims to grow the market for lighting-control solutions based on digital addressable lighting interface technology.
There is a very wide range of DALI enabled lighting control products available from all the leading manufacturers and it is now widely recognised to be the global standard for lighting control.
Key features of DALI:
It is an open protocol – any manufacturer can use it.
With DALI-2 interoperability between manufacturers is guaranteed by mandatory certification procedures.
Installation is simple. Power and control lines can be laid together and no shielding is required.
The wiring topology can be in the form of a star (hub & spoke), a tree or a line, or any combination of these.
Communication is digital, not analogue, so the exact same dimming values can be received by multiple devices resulting in very stable and precise dimming performance.
All devices have their own unique address in the system opening a very wide range of possibilities for flexible control.
HOW DOES DALI COMPARE WITH 1-10V?
DALI, like 1-10V, was designed for and by the lighting industry. Lighting control components, such as LED drivers and sensors, are available from a range of manufacturers that have DALI and 1-10V interfaces. However, that’s where the similarity ends.
The main differences between DALI and 1-10V are:
DALI is addressable. This opens the way for many valuable features such as grouping, scene-setting and dynamic control, such as changing which sensors and switches control which light fittings in response to office layout changes.
DALI is digital, not analogue. This means that DALI can offer much more precise light level control and more consistent dimming.
DALI is a standard, so, for example, the dimming curve is standardised meaning that equipment is interoperable between manufacturers. The 1-10V dimming curve has never been standardised, so using different brands of drivers on the same dimming channel could produce some very inconsistent results.
1-10V can only control switching on/off and simple dimming. DALI can manage colour control, colour changing, emergency lighting testing and feedback, complex scene-setting and many other lighting-specific functions.
ARE ALL DALI PRODUCTS COMPATIBLE WITH EACH OTHER?
With the original version of DALI there were some compatibility problems because the specification was quite limited in scope. Each DALI data frame was just 16-bits (8-bits for the address and 8-bits for the command), so the number of commands available was very limited and there was no collision detection. In consequence, several manufacturers tried to expand its capabilities by making their own additions, resulting in some incompatibilities.
With the advent of DALI-2 this has been overcome.
DALI-2 is much more ambitious in its scope and contains many features that were not in the original version. The result of this is that the additions that individual manufacturers made to DALI are no longer relevant. For a more detailed description of the DALI-2 architecture, please go to “How does DALI work”, below.
The DALI-2 logo is owned by DiiA (the Digital Illumination Interface Alliance) and they have attached strict conditions to its use. Chief amongst these is that no product can carry the DALI-2 logo unless it has undergone an independent certification process to check for full compliance with IEC62386.
DALI-2 allows for 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 a DALI-2 installation.
HOW DOES DALI COMPARE WITH KNX, LON and BACnet?
KNX, LON and BACnet are building control protocols, designed for integrating and controlling multiple devices and systems throughout a building. There are virtually no LED drivers available in the market that can support a direct connection to these protocols (though a very small number of LED drivers is available with a KNX interface) so they cannot be implemented as lighting control protocols.
In contrast, DALI and DALI-2 were designed specifically for lighting control and the DALI-2 command set contains many lighting-specific commands. These include commands and features for dimming, colour changing, scene-setting, emergency test and feedback and circadian lighting. There is a very wide range of lighting control components, especially LED drivers, that support a direct DALI connection.
In many implementations KNX, LON, BACnet and similar protocols would be used by a building management system (BMS) for overall building control (integrating HVAC, security, access control, lifts etc), while DALI would be used to control just the lighting. Where necessary, a gateway would provide intercommunication between the BMS and the lighting system so that, for example, all the corridor lighting could be switched on via DALI if an intruder was detected by the security system.