DALI has been around for a couple years but has just recently started to gain significance. The reason is that the professional applications which are so far the main users of DALI are switching to LED. This gives them a properly dimmable light source contrary to the formerly dominant discharge and flourescent lamps. A rising demand for more control than just on and off is the result.


Know the differences

Planning a DALI system is significantly different from planning a classic lighting system. The classic method controls the light by modulating the power supply. In the simplest case switching power on and off. For dimming phase chopping is used. All luminaires connected to a cable branch do always receive the same control information. Complex functions like color control are not feasible with classic cabling.

DALI separates power and control. All DALI lights are constantly supplied with power. The operating status of the luminaire is controlled by commands being send via the DALI bus. This allows controlling individual luminaires and implementation of functions like color mixing or tuneable white.

The bus connects all DALI devices. Two additional wires for the bus slightly increase the installation and material cost. But this is compensated for with simpler wiring for power since no separate branches are required to switch different groups of luminaires.

Classic solution:

 0001

Any change of function requires rewiring

DALI solution:

0002

Changes of function can be done by reprogramming. Adding more luminaires or user control elements can be done at any point. Power supply for individual luminaires can be more flexible, e.g. using safe low voltage for wet areas.


Choosing the solution that fits the application

DALI can have a maximum bus length of 300 m and up to 64 luminaires. This is sufficent for large single rooms, a floor, or a small house. For larger installations multiple DALI buses are used. Since DALI is focused on lighting it is not a solution for a complete building automation. For the automation of whole buildings DALI is frequently used in combination with a higher level bus like KNX or Ethernet.


Master and Slave

DALI distinguishes 'Control Gear' and 'Control Devices'. Control Gear are the slave devices which control the lamp. They are either part of a luminaire or external "ballast" units. Control Devices send commands to the Control Gear.


Luminaires

Many DALI-enabled luminaires and ballasts are available on the market and the ones that violate the standard are fortunately relatively few. Several parameters of a DALI luminaire can be programmed, such as minimum and maximum brightness limits, default brightness levels for power on and bus failure can be set, and other parameters. Those settings are permanently stored in the luminaire.

Existing luminaires can sometimes be converted to DALI by replacing the ballast. For many luminaires that internally use low DC voltage it is possible to add DALI control with a LED-Warrior07 module.

LED-Warrior07-01MOD generates a PWM signal to control ballasts which have PWM inputs:

lw07 01

LED-Warrior07-02MOD directly drives constant voltage LEDs at up to 4 A and up to 40 V. This can easily convert LED strips or halogen replacement LED lamps to DALI. The LW07-02MOD is simply inserted between the power supply and the LED:

lw07 02

The LED-Warrior04 is a good option to build a completely custom made DALI-enabled LED luminaire. LW04 directly drives high power LEDs. The current can be programmed individually for each channel in a range of 80 mA to 1000 mA. Dimming is independent of the current setting with a spread spectrum PWM that avoids flicker and interference.

 lw04


Distributed or centralized

There are two basic approaches to build a DALI bus. Which one is actually chosen depends on the requirements of the application.

The bus can be build around a central control device that is the sole master, or there can be multiple control devices each one capable of sending commands into the bus.

With a central control device all user interface elements like switches, dimmers, and wireless access need to be connected to the central device which generates the DALI commands from the input. The advantage of this approach is that the central device has full control of the bus and always knows the complete status of it. But the cabling is more complicated since every switch and dimmer needs a separate connection to the central controller.

DALI with central control device:

0003

Switches, dimmers, and other user interface elements can be masters and directly send commands. In this case multiple control devices are present on one bus. The advantage is that cabling can be much simpler. Many of the control devices can draw their power off the DALI bus. So only the two lines for DALI are necessary to connect them. A small disadvantage is that not all the masters may know the comple status of the bus at all times. So it could happen that a switch sends an off command to a luminaire that already is off, which means the user will see no reaction to pressing the switch.

DALI multiple control devices:

0004

 

Our LED-Warrior09 and LED-Warrior13 can be used for a DALI bus with multiple control devices. LED-Warrior13 is available only as a chip, but there are ready to use products based on the LED-Warrior09.

LED-Warrior09-02MOD is a module that allows to use two momentary switches to generate DALI commands. The function of the switches is programmable via a USB adapter.

lw09 02

LED-Warrior09BT-UP comes in a case for a flush mount box. It connects two switches to DALI but at the same time works as a wireless to DALI bridge (compatible with Bluetooth 4.0 LE, Bluetooth is a regsitered trademark of Bluetooth SIG).

This allows to control a DALI bus via smartphone or tablet.

lw09bt up


Power for the Bus

A DALI bus must have one special power supply for the bus to work and to supply power to some control devices. There must be only one power supply on a bus, not multiple supplies.

Some control devices integrate a bus power supply. There are also separate bus power supplies for DALI. A special current limiting is required for DALI so a standard power supply cannot be used, it has to be a power supply especially designed for the DALI bus.

Care has to be taken with the selection of the parts for the bus. Some DALI switches, dimmers, or central controllers have a built in DALI power supply. A DALI bus needs about 230 to 250 mA. Some of the built in power supplies can provide only a fraction of that current. When using such products care has to be taken that the total of the connected power supplies does not exceed 250 mA. If the limit is exceeded the bus communication can fail and in extreme cases the connected devices can get damaged. It is usually better to avoid such products and use a single DALI power supply that has the full current rating.

Our LED-Warrior11 offers two easy options for the DALLI bus power. LED-Warrior11 requires 24 V DC input which is quite common in many systems. It provides typ. 230 mA to the DALI bus. It is possible to supply multiple LED-Warrior11 from the same 24 V power supply if multiple DALI buses are required.

LED-Warrior11-MOD is very low cost but somes without a case:

 lw11

LED-Warrior11-DR is designed for mounting on a DIN rail:

lw11dr


Commissioning

When all DALI devices are connected to the bus and have power, it is time to configure the bus. During this precess addresses are assigned and settings are selected.

There are two types of tools for the bus configuration. Building autmation systems often have a built in configuration function. Usually this is an option for basic configurations and not all options of DALI may be available through these integrated tools.

More comfortable is to use a USB to DALI adapter with a confguration tool running on a notebook computer. This also allows stored setups to be uploaded for configuring multiple identical buses.


Addressing

To talk to a specific luminaire it needs to have an address assigned. In the factory setting, luminaires do react only to broadcast addressing - which talks to all devices at the same time.

Addressing can be done fully automatic, but then the addresses are assigned randomly. This has to be sorted out afterwards to make sure to talk to the right device. To reduce that chaos it can make sense to connect one new luminaire to the bus, have it addressed before connecting the next one.

A second option is not available with all luminaires. DALI allows identifying the next luminaire to be addressed by manual manipulation. Originally the manipulation was to disconnect the lamp from the luminaire. With LED luminaires, there may be a button to press (LED-Warrior07 modules do have a button). This mode is called "Physical Select".


Programming switches

Assigning functions to switches and dimmers is handled in many different ways. If a central control device is used the functions are assigned there.

Distributed control devices have many different methods for configuration. Some switches and dimmers have fixed addresses they talk to. This kind of device has to be ordered for the intended function. Quite common are coding switches to select modes and addresses. More flexibility is possible with devices that have a service interface or can be programmed via DALI (though there is no standard for this).


Grouping

DALI has a low data rate. Addressing multiple luminaires without a visible offset is not possible by addessing them individually. This is solved by 16 group addresses. A luminaire can be programmed to be part of one or more of the 16 groups. So ceiling lights in a large room can be programmed to react all to one group and then to some other groups to control them in smaller zones.


Setting scenes

Another option for fast control of multiple luminaires are the scenes. Up to 16 scenes can be programmed for each luminaire. When a scene is called up, the luminaire will switch to a preprogrammed brightness value if it is part of that scene.


Select carefully

DALI is definitely more complex than the classic cabling method. This also opens more options for bad decisions. So a learning curve and some more planning are necessary.

But compared to a switched or phase chopped mains power supply for singalling, DALI has so many more features that it is definitely worth the investment in the learning time.

 


DALI is a registered trademark of DiiA
Bluetooth is a registered trademark of Bluetooth SIG