DALI is an acronym for Digital Addressable Lighting Interface. The protocol was developed in 1999, and the standard was adopted in 2002. While DALI was initially created to control fluorescent light fixtures with electronic ballasts, it has proven to be the optimal solution for LED fixtures. The international DALI Alliance supports and improves the protocol.
Protocol Features
Digital signals are transmitted at 1200 bits per second over a bus consisting of a pair of wires. These same wires also supply 16–18 V DC to power control panels, sensors, and controllers.
In the DALI protocol, the concept of a "control gear" is linked to a specific function. For instance, each dimmer channel is a separate control gear. Therefore, a single physical light fixture can be treated as several control gears, each with its own unique address. Control gears can be grouped, and scenes can be programmed for them. Commands can be individual (sent to a specific address), group (sent to a group of control gears), or broadcast (sent to all devices on the bus at once).
A single bus can support up to 64 control gears. Up to 200 buses can be combined, allowing control of up to 12,800 devices. The maximum communication range (using AWG 15 wire) is 1000 feet.
The protocol supports two-way data transmission, so in addition to controlling a fixture, it's possible to monitor its status.
Advantages
The main advantages of the DALI protocol that have led to its widespread adoption are:
- Cabling is simple: Information cables have no special requirements and can be run alongside power cables without interference concerns
- Flexible network layout: The network topology can be anything except a ring, and no terminators are needed at the line ends
- Direct sensor connection: To implement basic control from a light or motion sensor, these devices can often be connected directly to a DALI fixture without an extra controller (under specific conditions).
Disadvantages
The downside of having no special cable requirements is a significant command transmission delay, which prevents the creation of dynamic lighting effects with DALI. A wireless DALI implementation is theoretically possible but faces major technical hurdles, so it's rarely used in practice. DALI is designed specifically for lighting control; integrating it into a smart home system requires a special gateway.
Current Status
The DALI protocol continues to evolve. Since 2018, several new variants have been created:
- DALI-2: A further development of the DALI standard. Its main advantage is improved support for Human Centric Lighting (HCL)
- DALI+: This standard describes how to transmit DALI control commands over IP networks
- D4i: An interface, based on the DALI protocol, between a luminaire and an add-on module that provides smart functions. It has become widely used in street lighting
Thanks to its advantages, DALI has become the most popular protocol worldwide. Leading global manufacturers continue to create new products supporting DALI-2 and DALI+, despite competition from other control protocols.
