Development of the DALI interface
The Digital Addressable Lighting Interface (DALI) has become one of the dominant interfaces of the lighting industry. This article reflects on the latest developments regarding the DALI interface.
With the development of the first dimmable electronic ballasts for fluorescent lamps back in the 1980s came the need for control devices able to tell the ballast to dim up or down, as well as for a “language” for communication between the dimmable ballasts and the control devices.
With the technology in its infancy and in the absence of a standard, the main ballast suppliers looked into using their own interface. This, however, caused confusion and was seen as a road block for developing the dimming market, and it created the need for a standard interface. Back in the day, Philips Lighting decided to look into interfaces offered by other applications and decided to base its interface for dimmable electronic ballasts on a 0 – 10 V control used in theatre lighting, and to change it from a current source (the theatre dimming standard) to a current sink, the dimming ballast interface.
The choice for a current sink interface created the possibility to use passive control units like simple potentiometers to eliminate the need to create a current source outside the ballast. The fact that it was used by a major player and its simplicity made the current sink 1 – 10 V interface from Philips lighting the de facto standard in the market, and eventually became an IEC standard (IEC 60929 Annex E), as well as a standard in the USA (UL 935).
Fig. 1: Luminaire based components using the DALI interface.
Although sufficient in many applications the 1 – 10 V interface does have some drawbacks:
- It provides power setting only, switching must be done by a separate control circuit.
- Control circuits must be hard-wired because ballasts cannot be addresses.
- Ballast feedback is not possible.
- Signal degradation on long lines.
- Poor definition of minimum light levels (different ballasts can give different light levels at the same control voltage level).
Tridonic was the first company to address some of these drawbacks by introducing, in 1991, its proprietary Digital Serial Interface (DSI).
Building upon the DSI interface, a group of European lighting companies started working on a digital interface in a COMEX workgroup in 1996, with the objective of making each ballast addressable while connecting them in parallel on the two control lines.
Birth of the DALI interface
DALI was born because the digital interface was intended for the lighting industry only and should be able to address the ballast individually. When defining the standard, a firm decision was taken not to develop a complex building control system with maximised functional capabilities, but to create, instead, a simple system with clearly defined structures. DALI is not designed to be a complex bus system, but rather for intelligent, high-performance light management in a local zone (see Fig. 1). These functions can, of course, be integrated into a building management system by means of suitable interfaces.
Fig. 2: The parts of IEC 62386 standard that define DALI. Control devices on the right; control gear on the left.
DALI standardisation
Since its inception in the mid-nineties, the DALI interface has developed into a widely accepted standard for lighting applications, including specification in the IEC standard 60929 (DALI version 0) and IEC 62386 (DALI versions 1 and 2). Bringing the DALI standards to the market, managing the DALI trademark, logo licensing and promoting the right conditions for growth does, however, not fall within the remit of IEC, but was taken care of by the DALI AG working group. With a membership of about 140 lighting manufacturers, DALI AG was housed in the German ZVEI (German Electrical and Electronic Manufacturer’s Association) organisation.
The growing use of DALI, however, resulted in increased appearance of field issues and undesired system behaviour created by:
- Lack of knowledge of the standard by manufacturers developing DALI products.
- Ambiguities and different interpretations, resulting in commands implemented differently among different products, and in DALI timing aspects implemented differently.
- Interoperability of controls and ballasts was not covered in IEC 62386 (DALI V1).
- The lack of formal arrangement to address interoperability through DALI AG.In 2014, the relevant IEC standard
IEC 62386 was restructured (see Fig. 2), including:
- A major update on Part 101 (system components).
- A major update on Part 102(control gear).
- Addition of a new Part 103 (control devices).
Other parts are planned, such as dedicated input devices and additional functionality.
Along with the restructuring of the standard came a broadening of the scope with:
- Additional controls functionality.
- A system approach with application controllers, sensors and switches.
- Backward compatibility.
- Improved interoperability.
All-in-all, the 2014 restructuring of IEC 62386 resulted in a more robust, simplified, flexible and future proof DALI standard including additional functionality. What remained, however, was the lack of an independent certification process to address interoperability.
Fig. 3: The DALI v2 logo.
DALI product compliance used to be based on self declaration by the manufacturer which, however, brought the risk of interoperability issues. The arrival of the latest DALI standard with its additional functionality, complexity and global outreach made clear that an independent certification system was required to solve these growing interoperability issues in the market, instead of the mentioned manufacturers’ self-declaration system. This, however, proved impossible to realise under the statutes of the ZVEI and the DALI AG board was driven to the decision that a new, independent organisation was needed, with its own executive powers and control over strategy. This was the only way to speed up decision making and implementation of new activities such as the much-needed certification system. The DALI AG board has therefore requested its own dissolution and, as of 30 March 2017, DALI AG no longer exists.
DiiA and DALI 2.0
In the meantime, a new organisation, with the name, “Digital Illumination Interface Alliance” (DiiA) has been set up as the new, open, global, industry-led consortium. DiiA has stated that it aims to grow the market for DALI lighting controls solutions, to set up an independent certification scheme, and to work collaboratively with IEC in the future to accelerate the development of new functionality in the IEC 62386 series.
DiiA certification scheme
DiiA’s first task is to create an independently verified testing, certification and logo licensing programme that gives the assurance of interoperability for products using digital addressable lighting interface technology. Under DALI AG, the current practice of product compliance was based on self-declaration, which led to many inconsistencies and interoperability issues in the market. Part of the DiiA certification work will be to create and maintain test specifications according to the IEC 62386 series and to develop test sequences on approved test equipment, for manufacturer’s use. Product test results can then be submitted for verification and approval on the DiiA website and will be eligible for certification and licensing. Only certified products will be able to carry the certification mark, and only DiiA members will be able to certify their products. All certified devices will also be listed on the DiiA website to show which DALI products will be interoperable.
| Feb 2017 | Test sequences for Parts 101 & 102 available for download by developers |
| Mar 2017 | DALI AG dissolved |
| Apr 2017 | Certification process for DALI v2 established for parts 101, 102, 103, 207 |
| May 2017 | DALI trademark transferred to DiiA |
| Jun 2017 | First DALI v2 certified products on the market – ongoing process |
| Oct 2017 | Certification process extended with parts 209, other relevant 2xx, and 3xx |
| Dec 2017 | All relevant DALI AG members have become members of DiiA |
March 2017 and the future
In March 2017, DiiA counted 24 members and it is expected that this will increase rapidly due to the dissolution of DALI AG and the fact that only DiiA members can certify their products using the approved tester. Also, luminaire companies will join DiiA as community members and they may use the DALI v2 logo (see Fig. 3) if their luminaires contain DALi v2 certified components. Table 1 shows an indicative timeline for DiiA and DALI v2.
1 – 10 V interface
Given the advantages of DALI compared to the 1 – 10 V interface and all the recent developments, one would wonder whether there is still a place for the 1 – 10 V interface in the market. The South African market seemed to have converted to DALI already years ago. This is not the case for all other markets. In Europe, 1 – 10 V is still used in a limited number of outdoor applications, in combination with stand-alone controls, or in municipalities which chose to standardise on
1 – 10 V years ago.
A market where 1 – 10 V is still dominant and where, in fact, DALI never really took off, is the USA. Due to its lower price and the simple installation until now, 1 – 10 V is the leading interface in the American market.
Contact Henk Rotman, Philips Lighting South Africa, Tel 011 471-5000, henk.rotman@philips.com
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