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Intelligently controlled light. A look at the potential of DALI 2.

The clear advance of the LED into all areas of lighting technology has led to major changes in the control of luminaires. What was controlled via dimmers or analogue 1....10 V interface a few years ago is now linked digitally to the central nervous system of the building. The standard for the control of luminaires is DALI (Digital Addressable Lighting Interface). Originally created to dim fluorescent lamps, this system has developed into an all-round tool for lighting. The triumph of the LED has also meant a real boom for DALI since LED luminaires provide the best technological conditions for digital control.

What can DALI do? And how does DALI function?

DALI is the most widely used luminaire interface in the control of architectural lighting. Anyone who deals professionally with light and lighting control cannot escape DALI. The standards were laid down in 2000 in the IEC 62386. There are now products developed by many different manufacturers available for a wide range of applications. The functions offered by these devices have increased significantly over the years. Multifunction luminaires with several colour channels enable the direct control of any chromaticity coordinate. Depending on which primary colours the luminaire generates, colour temperature and/ or saturated colours can be controlled absolutely or relatively. Multi-channel luminaires - with up to six output channels - can be operated without any complicated channel allocation. DALI emergency lighting systems can be monitored and tested easily. 

All these devices are standardized and classified in the DALI standard IEC 62386.102 (see illustr. 01) The different types of devices  (device types 0-8) are defined in standards 201 to 209. For example type 6 focuses especially on LED, or type 1 on the properties of DALI emergency lighting devices. Data communication, sets of parameters and topology are also defined in IEC62386.

Since November a new version of this DALI standard has been available - Edition 2. DALI is expected to close the gaps in the existing standard and to enable better interoperability. While in the first edition only Control gear’s and general communication were described, DALI 2 opens up the world of sensor technology to manufacturers and users. Part 103 "Control devices" was added to IEC 62386. New types of devices in the sensors sector, such as push-buttons, light sensors, motion sensors or remote control interfaces, are now defined in the standard.

DALI Edition 1 functions according to the pure master-slave principle. That means that no control gear (slave) may ever communicate independently on the bus since this does not have any collision detection. The Master Control Device has to inquire about the status of a luminaire so that this may then reply with an 8-bit telegram. So it becomes very clear that comprehensive sensor functions are restricted since a master must continually inquire about the status of all the sensors. Until now this has only been possible with proprietary manufacturer solutions.

For BMS (Building Management Systems) access to the sensor functions is barred completely since there are also no standards for this. The extension of the standard, or rather its completion, in Edition 2 now makes it possible in future  to transmit control commands, operating data for the luminaire ballast and also sensor functions from and to devices of any manufacturer.


DALI 2: Which is the most important innovation?

For the first time DALI 2 now allows sensors to access the bus independently and communicate either with the master control device, luminaire ballast or other sensor control devices. The sensors therefore have the option of bus access control. The sensor telegram is defined as 24-bit and contains an address byte, instance byte and command code byte. Control devices can be addressed and grouped in 32 instances. However, there is a difference to other operating devices in that control devices can transmit group and address information. So, for the very first time, event-driven actions and logical links are possible and intended in the DALI standard . Control devices now have their own address area. That means that with DALI 2 64 ballasts and 64 sensor control devices can be operated on one line.


What does this mean for future applications?

Imagine a multi-storey office building which is fitted throughout with DALI-capable luminaires. On the different floors DALI multi-function sensors have also been fitted throughout. These sensors can, in the same way as luminaries, be allocated to zones within the room. This can be done very flexibly  so that the use of the building can be changed or adapted. When room zones are redefined, then the sensors move accordingly. Complex (re-)programming is no longer necessary and the lighting can be controlled efficiently , "out of the box", depending on the incidence of daylight and human presence in the room.

Superordinated building automation systems such as BACnet  (Building Automation and Control Networks) are also able to process the sensor information and optimize it with the data from other building technologies such as heating, ventilation, temperature. Central maintenance functions can monitor the status of lamps, energy consumption and display the status of these functions visually. The total automation of buildings thus becomes much simpler and more controllable. Let us take a small digression into the future of product design. It is possible to imagine the integration of sensors into luminaires, into control gears or even into an LED module.


How is compatibility ensured?

How can the intercommunication of DALI devices be ensured? How can we be sure that they are interoperable? With the DALI 2 standard the foundations are laid for future interoperability. For the very first time a standardized control gear is not controlled according to the classic master-slave principle. DALI 2 enables event-driven communication between the application controller and the control device. And of course this is downwardly compatible and parallel to the existing DALI 1 installation. 

To guarantee full compatibility, tests must be carried out to compare products with the standard. Until now control gears have been tested with the DALI test device "ProbitLab". The corresponding test sequences are part of the standard and must all be completed successfully. For testing control devices and the bus Interface power supply a new testing device is required. This testing device is expected towards the end of 2015 together with the publication of the standard.

Manufacturers of DALI components can of course test these themselves and compare the results with the IEC62386 or employ the services of a specialized testing laboratory such as DIAL. With the DALI 2 logo the manufacturer declares the conformity of his product with the standard. To enable validation the test results must in future be passed on to the AG DALI. For this purpose an online service is available which publishes all devices with DALI conformity in a product data bank. Designers and users can thus very quickly obtain an overview of the available devices of a particular type.  


A lot is going to happen 

The changes in Edition 2 which have been described here form for the basis for interesting products and applications. The roughly sketched example of an application highlights how much DALI can achieve in the future and what kind of product development we may expect. And this development will have proportions of which designers, manufacturers and users are only just becoming aware.