DALI‑2. The language of intelligent lighting.

DALI stands for Digital Addressable Lighting Interface: a digital protocol for controlling lighting, defined in the international standard IEC 62386. Instead of an analogue control signal (such as 1‑10V) or simple switching, every luminaire receives its own digital address. Each light point can therefore be dimmed, switched, grouped and queried individually — without changing the wiring.

DALI‑2 is the second generation of the standard. The biggest step compared with the first version is organisational rather than technical: since DALI‑2, products are independently tested and certified by the DALI Alliance (formerly DiiA). The standard has also been extended: where DALI version 1 only described control gear (drivers, ballasts), DALI‑2 also covers controllers, sensors and user interfaces. The result: components from different manufacturers demonstrably work together in one system.

DALI‑2 has become the common language of modern lighting installations — from a single office space to entire buildings where lighting is part of the building management system.

The heart of every DALI system is the DALI bus: two wires carrying both the communication and the supply for the bus participants. The bus runs at around 16 volts and is polarity-free — the wires cannot be connected the wrong way round. No special bus cable is required: two cores of standard installation cable are sufficient, and they may even share a sheath with the 230V mains supply.

The topology is free: line, star, tree or a combination. Only a closed ring is not permitted. One line can host 64 control gear devices (luminaires) with their own short address, plus addresses for sensors and user interfaces. Each device can also belong to up to 16 groups and respond to 16 lighting scenes — all configured in software, so layouts can change without moving a single wire.

Commands are sent digitally (1200 bps, Manchester-encoded), making them immune to the interference that plagues analogue control signals. A crucial difference from one-way protocols: DALI is bidirectional. A luminaire reports back whether a command arrived, what its current dimming level is and whether a fault has occurred — from lamp failure to driver errors.

D4i (“DALI for IoT”) is a certification within DALI‑2 that turns a luminaire into a true data source. A D4i driver does three things an ordinary driver does not: it powers a sensor or communication module directly from the driver (no separate supply needed), it stores standardised data in so-called memory banks, and it makes that data available over DALI to any system that asks for it.

The memory banks include energy consumption, operating hours, diagnostics (temperature, voltages, fault reports) and asset information such as the luminaire's manufacturer, type and power rating. Combined with a Zhaga connector (Zhaga Book 18/20), a sensor or wireless module can be added or replaced per luminaire — even years after installation.

That makes D4i the bridge between lighting and IoT: predictive maintenance, per-light-point energy monitoring and occupancy data come within reach without extra cabling or meters.

Offices are classic DALI territory: presence and daylight control per workspace, scenes for meeting rooms and integration with the building management system. Education and healthcare add human centric lighting — light colour that supports the daily rhythm. Car parks and logistics benefit from robust presence-based control: light where there is movement, a low base level where there is not. In industry, reliability and diagnostics matter most; in retail and hospitality, scenes and colour control take centre stage.

Outdoor lighting is also shifting to DALI: street lighting with Zhaga-D4i nodes combines dimming profiles with tele-management per pole. And because emergency lighting (DT1) runs on the same bus, a separate test regime disappears: function tests and reporting run automatically.

Wiring

The DALI bus requires two cores of standard installation cable (typically 1.5 mm²). Many installations simply use a 5-core cable: three cores for 230V (L, N, PE) and two for DALI. The bus is low voltage but, as a basic-insulated circuit, may share a sheath with mains voltage. Keep the total line length under ~300 metres (max. 2 V voltage drop) and avoid closed rings; line, star and tree topologies are all permitted.

Sizing

Calculate the bus load: every device draws a number of milliamps from the bus (a typical driver 2 mA, sensors often more). The total must stay below the 250 mA of the bus power supply — in practice this is the second limit of a line, alongside the 64 addresses. Larger buildings are split into multiple lines, linked via routers or application controllers on an IP backbone.

Commissioning

After installation comes addressing: the configuration tool assigns each device a short address, after which groups, scenes and control behaviour are configured. Worth arranging in advance: an address plan per room, consistent naming and an export of the configuration as documentation. That makes later extensions and fault analysis considerably easier.

Common mistakes

• Two bus power supplies active on one line (e.g. a controller with built-in supply plus a separate supply).
• Bus load not calculated, making communication unreliable.
• DALI wires interconnected between two different lines.
• No documentation of addresses and groups, making later maintenance costly.

The DALI Alliance (formerly DiiA) maintains the standard, the test procedures and the trademark. Only products that pass the independent test procedure may carry the DALI‑2, D4i or DALI+ logo and are listed in the public product database. For specifiers and buyers, that is the practical check: if the product is in the register, interoperability is assured. The old DALI logo (version 1) relied on manufacturer self-declaration — precisely the difference that makes DALI‑2 a dependable multi-vendor standard.

With DALI+, the familiar DALI protocol runs over wireless and IP-based networks, starting with Thread. The same commands, device types and certification — but without a bus cable where cabling is impractical, such as in renovations and heritage buildings. Together with D4i and Zhaga, lighting evolves from a controlled installation into a fine-grained sensor network throughout the building. Specifying DALI‑2 today is therefore not a dead end but a route: wired where possible, wireless where necessary, with one protocol as the constant.