The DALI “Digital Addressable Lighting Interface” protocol and its most recent evolution DALI2 constitute the state of the art of wired digital management of luminaires. Thanks to this technology, the luminaire drivers can communicate bi-directionally with the control system, which can send on, off and regulation commands as well as configure the operating parameters and obtain diagnostic information.
Originally this technology was developed in the headquarters of the ZVEI where the DALI-AG Working Group was established and then, in 2017, it was moved to the DiiA – Digital Illumination Interface Alliance (www.dali-alliance.org), which today includes the main manufacturers of lighting components. Like other technologies, DALI has also been implemented as a regulatory standard. The first edition of IEC 62386 standard – Digital Addressable Lighting Interface was published in 2009 and had as its key characteristic that of being an open regulatory standard, ensuring interoperability between devices from different manufacturers.
In 2014, the publication of the second edition started, generally called DALI 2, which introduces a significant technological evolution of the DALI standard. In addition to ensuring full compatibility with existing devices, manufactured in compliance with the first edition of the regulation, functional standards are defined for control devices (buttons, sensors, etc.), which had been developed up to that moment by the various control system producers based on customized and often closed DALI protocols. In addition, the Multimaster architecture is introduced which allows the insertion in a DALI system of multiple Master devices able to send messages simultaneously. Furthermore, the functions implemented by the luminaires are further expanded, with the definition of new and innovative Device Types.
IEC 62386 Standard is divided into several parts:
Part 101 – Basic System: contains the general specifications common to all devices, the definition of the physical layer with the voltage values, the coding of information, etc.
Part 102 – Control Gear: contains the general requirements for the luminaires control devices (eg LED drivers) and defines the set of commands and instructions that can be sent to a lighting fixture.
Part 103 – Control Devices: introduced with version 2 of the standard, this part contains the requirements and specifications common to all command and control devices, therefore buttons and sensors, defining the functionalities of the Application Controller and a new type of messages which is used by this category of devices.
Parte 104 – Wireless Devices: contains the specification relating to the use of means of communication different from the simple twisted pair (eg wireless or IP networks).
Parte 105 – Firmware Update: introduces the possibility to update the firmware of a DALI device.
Product certification
The devices produced in accordance with the first edition of the DALI Standard were subject to a sort of self-certification by the manufacturer itself. The test and checking procedures were contained in the standard but there were no reviews by third parties. This has led over time to some compatibility problems when maybe the device did not properly support the entire set of commands. With the publication of the second edition of the Standard, and in particular with the management attribution to the DiiA association, the DALI 2 items are subject to a product conformity certification which requires a verification of the test results by DiiA, also relying on accredited external laboratories. This procedure ensures full and total compliance of the devices but, on the other hand, involves a longer and more complex certification process. Devices that pass the certification process can be branded with the new DALI 2 logo and are included in a database of certified products accessible on the Association’s website (www.dali-alliance.org).
Technical specifications DALI vs DALI 2
A DALI system is made through a Master/Slave communication architecture. A single device, the Master, can start communication on the bus while the Slave devices receive and execute the commands sent and, if applicable, can answer to a request with a message that generally indicates a status or condition of the device itself. Under no circumstances a Slave device can initiate a communication autonomously. The system has to be equipped also with a DALI power supply able to supply power to the connected devices and generate the direct voltage (typically 16 Vdc) used for signal coding. The power supply can consist of a specific device or be incorporated within a luminaire, for example the Master controller.
Up to 64 Slave devices can be connected to a DALI system, each of them has a unique address called short address. To send a simultaneous command to multiple Slave devices, a group command is used, using the group address. It is possible to divide the 64 Slaves into a maximum of 16 groups; a Slave device can belong to one or more groups or to none of them. Instead, a broadcast type command is used to send a command to all the modules connected on the DALI bus.
As anticipated, in the first version of the standard there was no support for control devices such as sensors or buttons which, if present, communicated directly with the Master device without being connected to the DALI Bus, or they were but used proprietary solutions developed by some manufacturers to manage communication.
The second version of the IEC 62386 (DALI 2) Standard standardizes the use of command devices (Control Devices), introducing some important changes to DALI protocol. Thanks to MultiMaster functionality is now possible to send commands on DALI bus avoiding collisions, thus allowing multiple devices (for example sensors) to communicate events independently and in a prompt manner. The management of all this information, typically coming from the input devices, is entrusted to the Application Controller which processes them and generates the appropriate commands sent to the Slave devices.
The second version of the standard also avoids compatibility problems between the new DALI 2 devices and those built in compliance with the first DALI version (which we will easily indicate as DALI 1). In practice, we can create systems composed as follows:
- DALI 1 control systems (master, sensors, button interfaces from the same manufacturer) with luminaires equipped with DALI 1 and/or DALI 2 drivers
- DALI 2 control sytems (master, sensors, button interfaces also from different manufacturers) with luminaires equipped with DALI 1 and/or DALI 2 drivers
In this category we also find the driver status query commands and therefore specific information on the presence of faults or operating anomalies.
Types of DALI command
As mentioned in the previous paragraph each lighitng fixture can be part of one or more groups and also can be configured to have a specific light level associated to a one or more scenes (maximum 16). This allows the implementation of punctual static scenes, so when the Master calls up a given scene, each luminaire moves to the light level associated with that scene (also called preset) using a transition – from the starting point to the arrival point – timed according to the fade time and fade rate parameters. These transitions are managed by the DALI driver of the luminaire itself and not by the Master, which is therefore limited to sending only the scene recall command.
In summary, the control of a lighting fixture can therefore be carried out by:
- Single command, sent to the Short Address of a luminaire;
- Group command, sent to the Group Address;
- Command to all devices connected to DALI bus sen as Broadcast;
- Preset recall (Scene).
The organization of control groups and presets can be modified at any time allowing the system operation to be adapted to architectural or layout changes that inevitalby occur during the use of a building. These changes don’t require any intervention on cabling or luminaires but are managed via software.
In addition to the commands for controlling the light flux (On, Off, Dimming) there are also those for configuring the drivers that allow to set the parameters of the lighting fixture. Among these are:
- Minimum Level e Maximum Level: set the maximum and minimum levels of light flux emission of the luminaire;
- System failure level : set the luminaire level in case of failure on DALI bus (default is 100%).
- Power On level: set the luminaire level upon the arrival of power supply (before receiving commands from DALI bus).
Finally we find driver status query commands which allow to get specific information about the presence of faults or operating anomalies (for example short circuit/open circuit of LED output, driver failure etc.)
Device Types
DALI technology was initially developed to define the luminous flux control of luminires. Later and gradually the Stadanrd also covers other devices and different types of lighting fixtures, which inevitably have inherent functional differences, making it necessary to define specific commands. These functional or application extensions are defined Device Types and, for each of them, a specific part of the IEC 62386 Standard is published. For example, as regards LED luminaires (DT6), part 207 of the Standard has been published.
In addition to covering the particularities of different types of luminaires, the DALI standard has extended the DALI standard has also extended the specification to functional aspects of lighting, such as colour control (DT8) or emergency lighting control (DT1).
The most interesting DALI Device Types are listed below:
- DT0 – Ballasts for fluorescent lamps
- DT1 – Emergency lighting
- DT6 – LED Driver
- DT8 – Colour control
- DT50 – Extended product information
- DT51 – Energy report
- DT52 – Diagnostics and maintenance.
The combination of functionalities introduced with the Device Types DT50, DT51, DT52 and additional installation options have been grouped by DiiA into a product category named D4i (DALI standard for intelligent, IoT-ready luminaires). Further information is available at the following link www.dali-alliance.org/d4i.