A standardised digital protocol for dimming
DALI (Digital Addressable Lighting Interface) is a standardised digital protocol for dimming. DALI is supported by the major manufacturers of HF-ballasts in Europe (Helvar, Osram, Philips and Tridonic). Other companies within the lighting industry have also joined the group of DALI-manufacturers.
DALI uses a single multi-core cable through which a duplex digital signal is transferred between all units in the system. Connected HF-ballasts, control panels, sensors and the programming units communicate with each other. The “intelligence” is distributed, (read stored) in the system’s different component parts. This creates greater safety and reliability as the system is not dependent on any central unit.
The DALI-system is also very flexible and future-proof as any change to the design of the premises or usage, results only in the need to reprogram the settings. Generally the cabling does not need to be changed.
In the DALI-system information is transferred between components via an addressed digital signal. As the signal is digital all included luminaires are controlled in exactly the same way, irrespective of the distance between the control unit and luminaire. The HF-ballasts used in DALI are adapted to the sensitivity of the eye for light level adjustments, a.k.a. logarithmic compensation.
Apart from the phase, neutral and earth conductors, two other wires for the digital signal are connected to the luminaire. These cables are polarity free which simplifies installation.
The digital control signal is also insensitive to external disturbances. The lighting is switched on and off by means of a digital command via the DALI-conductors. It is therefore beneficial to connect the mains voltage directly from the fuse panel to the luminaire.
Combining DALI with other control systems
DALI can easily be combined with other control systems such as analogue 1–10 V. When there is no need to control or monitor an individual luminaire, or when existing rows of luminaires are to be incorporated into the new control system, it may be possible to use, for example, a DALI to 1–10 V interface (converter). The existing luminaires, equipped with HF-ballasts for analogue 1–10 V dimming, are connected to a DALI to 1–10 V interface.
Using this solution the luminaires can be controlled centrally via DALI-panels for example. The solution is more economical and it also significantly increases the number of luminaires that can be controlled in a DALI-installation. This is because a single DALI address now controls several luminaires. The same solution can be used with luminaires equipped with HF-ballasts for DSI dimming, with the help of a DALI to DSI interface.
- Addressability. Possibility to individually control different luminaires/HF-ballasts in the same system. Max 64 addresses/system.
- Light scenes and groupings. Possible to pre-program different light scenes. Up to 16 groups of luminaires and 16 different light scenes can be created in each system.
- Ignition and extinguishing of luminaires takes place via digital commands.
- Control conductors for the digital signals have no polarity (positive/negative), which reduces the risk of incorrect connection.
- The digital control signal is not sensitive to disturbances transferred from other conductors. The control conductor can be routed together with the main voltage conductors without the risk of disturbances (note however that the control conductors should also be of a heavy current type).
- Duplex communications via the control conductors is possible. Status and any error indications from components in the system can be gathered by any connected software.
- The control signal is transferred in the same way to all luminaires independent of the control conductors’ length.
- Digital technology also allows the system to be controlled via computers.
- DALI can also be integrated with a BMS system (for example KNX).
- Multiple DALI systems can be controlled over routers connected to an Ethernet network.
- Programming is carried out using wall panels, remote control units or with the help of computers and software. The use of software is recommended for all large installations.
- DALI requires the control circuit to be fed with a current. This current may be max 250 mA, which is obtained by means of an external DALI power source. A high current in the circuit results in a communications breakdown or damaged components. Consequently, it is important that a DALI-system is planned and dimensioned correctly.
- Maximum cable length for the control circuit is 300 m.
- The characteristics of the units from different manufacturers deviate slightly.