DALI

What is DALI?

DALI (Digital Addressable Lighting Interface) is an open, internationally standardised protocol defined in IEC 62386 for digitally switching, dimming and querying lighting in buildings over a two-wire bus that connects up to 64 addressable drivers and 64 control devices such as sensors and push-buttons. Every luminaire gets its own address, can be assigned to groups and scenes, and reports back whether its lamp is working or has failed. That makes DALI the lighting building block of building automation, connected through gateways to KNX, BACnet and the building management system.

🧠 Where does DALI come from and who manages it?

DALI was developed in the late 1990s by a group of lighting manufacturers as the successor to analogue 1-10 V dimming control, and as an open alternative to proprietary systems. The first specification appeared as an annex to IEC 60929, the standard for electronic ballasts for fluorescent lamps. DALI later got its own multi-part standard: IEC 62386. The standard was substantially revised at the end of 2014; since then it covers not only lamp drivers (control gear) but also control devices such as sensors, push-buttons and application controllers.

The trademark and certification are managed by the Digital Illumination Interface Alliance (DiiA), which now operates as the DALI Alliance. The former working group AG DALI was dissolved on 30 March 2017, and DiiA has certified products since June 2017. The DALI Alliance also writes new specifications, which are then passed to the IEC for inclusion in IEC 62386.

🔧 How does the DALI bus work technically?

DALI uses two wires that carry both the bus supply voltage and the data. A bus power supply typically delivers 16 V DC (permitted range 9.5–22.5 V) and is limited to a maximum of 250 mA. Devices communicate by briefly pulling that voltage down to zero, using Manchester encoding at a fixed rate of 1200 bit/s. That is slow compared with Ethernet, but more than enough for switching and dimming commands.

Key characteristics:

• Polarity-insensitive - most devices work regardless of how the two wires are connected, which prevents wiring mistakes.
• Free topology - line, star or tree, as long as the voltage drop across the cable does not exceed 2 V. In practice that means a maximum of 300 metres between the devices furthest apart with 1.5 mm² conductors.
• Not safety extra-low voltage - the DALI bus is not classed as SELV. The conductors need basic insulation from the mains, which is why they may run in the same five-core installation cable as live, neutral and earth. Local wiring rules apply; in the Netherlands that is NEN 1010.
• Addressing - each driver gets a short address (0–63), can belong to up to 16 groups and stores 16 scenes. Commands go to one address, a group or to all devices (broadcast).
• Logarithmic dimming curve - light levels run from 1 (0.1%) to 254 (100%) in steps that the eye perceives as even.
• Feedback - a driver answers queries with an 8-bit backward frame, for example about lamp failure, the current level or its operating status.

Alongside the 64 drivers, DALI-2 adds a separate address space for 64 control devices. These send events such as “motion detected” or “button pressed” in 24-bit frames. The common claim that DALI-2 supports more than 64 drivers per line is wrong: if you need to control more luminaires, you use several bus lines with a controller or gateway per line, or DALI+ over an IP network.

🏭 What is DALI used for in practice?

DALI is used in offices, hospitals, schools, shops, warehouses and industrial halls. Typical functions:

• Occupancy detection and daylight harvesting - a sensor dims the luminaires when there is enough daylight and switches them off in empty rooms. This is often the largest energy saving in a lighting installation.
• Time schedules - luminaires switch or dim to a fixed schedule, for example corridor lighting that drops to a low level outside office hours.
• Flexible layouts - after a refurbishment, groups and scenes are reprogrammed without rewiring.
• Colour temperature and colour - with device type 8 (IEC 62386-209) a luminaire can shift from warm to cool white, for example for human centric lighting in healthcare and education.
• Emergency lighting - emergency luminaires to IEC 62386-202 run their own function and duration tests and log the results, so periodic inspection no longer has to be done manually luminaire by luminaire.
• Energy and diagnostics data - D4i drivers record consumption, operating hours, temperature and faults. That data feeds asset management and predictive maintenance.

🔄 How do you connect DALI to building management and IT?

DALI is a local bus per room or floor. The link to higher layers always runs through a gateway or application controller that translates DALI into a building protocol or IP network:

• DALI-KNX gateways - a widely used combination in Europe: KNX controls the building, DALI the luminaires.
• BACnet/IP or Modbus gateways (usually Modbus TCP) - for integration with the BMS, which also handles HVAC and meters.
• Cloud and IoT platforms - via an edge device or the gateway itself, using MQTT or REST APIs for dashboards and energy reporting.

This is where lighting becomes an IoT topic. Energy and fault data from the drivers can feed an energy management system to ISO 50001 and support the Dutch GACS obligation: non-residential buildings with heating or air-conditioning capacity above 290 kW have had to operate a building automation and control system that monitors energy use since 1 January 2026, and from 1 January 2030 the threshold drops to 70 kW. The obligation is tied to climate installations, but a DALI installation with energy metering supplies the lighting data alongside it.

🛠️ How do you approach a DALI project?

A practical approach for new builds and refurbishments:

1. Choose certified products - check the DALI Alliance product database to confirm that drivers, sensors and controllers are DALI-2 or D4i certified. Version 1 products were only registered and do not always interoperate.
2. Calculate the bus load - add up the current drawn by all devices and stay below the 250 mA maximum that bus power supplies may deliver. Watch out with D4i: every D4i driver has an integrated bus power supply, of at most 60 mA in a single-driver luminaire. Four such luminaires together supply 240 mA; if you connect more, one or more of those integrated supplies must be disabled. Control devices with higher power needs, such as wireless modules, get a separate 24 V auxiliary supply.
3. Design the addressing - no more than 64 drivers per line, with spare capacity for expansion, and a logical group and scene scheme per room.
4. Document everything - record addresses, groups, gateway settings and firmware versions in the asset inventory, so a replaced driver can be re-addressed quickly.
5. Secure the connections - treat every gateway as a network device (see below).
6. Test and commission - verify feedback, emergency lighting tests and energy data before handover.

Refurbishments are also driven by the EU phase-out of most fluorescent tubes since 2023: many installations with DALI ballasts for fluorescent lamps are now being replaced by LED luminaires with DALI-2 or D4i drivers.

🔐 How do you secure DALI lighting?

From a security perspective, the wired DALI bus has no authentication and no encryption. Anyone with physical access to the bus, for example through a luminaire in a ceiling or an unlocked distribution board, can send commands and switch off lighting or tamper with emergency lighting. The biggest risk, however, lies not in the bus but in the gateways: they have web interfaces, default passwords and sometimes direct internet access for remote management.

Recommended measures:

• Network segmentation - place lighting gateways in their own VLAN or zone for building services, separated from the office network and from process networks running SCADA.
• Firewalls - allow only the traffic between gateway and BMS that is actually needed.
• Hardening - change default passwords, disable unused services and keep firmware up to date.
• Physical protection - lock distribution boards and plant rooms.
• Defense in Depth - combine these layers with monitoring of the building network.

DALI+ with Thread relies on the security of the underlying network layer, supplemented by application-layer security features. For organisations covered by the Dutch Cybersecurity Act, such as hospitals and data centres, building services that support the service belong in the risk assessment; IEC 62443 provides the framework for zones and conduits.

❓ Frequently asked questions

How many devices can be connected to one DALI line?

One DALI line supports up to 64 drivers (control gear), each with its own short address. DALI-2 adds a separate address space for up to 64 control devices, such as sensors and push-buttons. For larger installations you use several DALI lines or DALI+ over an IP network.

What is the difference between DALI and DALI-2?

DALI-2 is the current generation of the DALI protocol, based on the IEC 62386 revision of 2014. DALI-2 standardises sensors, push-buttons and application controllers as well as drivers, and products are independently tested and certified by the DALI Alliance. Older DALI version 1 products were only registered, so interoperability between brands was less certain.

What is D4i?

D4i is a DALI Alliance certification programme that extends DALI-2 inside the luminaire. A D4i driver has an integrated bus power supply and stores luminaire data, energy consumption and diagnostics data according to IEC 62386-250 to 253. D4i is widely used in street lighting and in combination with Zhaga sockets for sensors.

Can a DALI cable run in the same cable as 230 V mains?

Yes, the DALI conductors may run in the same installation cable as the mains supply, because the DALI interface has basic insulation from the mains. It also follows that the DALI bus is not safety extra-low voltage (SELV) and must not be accessible to touch. The installation must comply with local wiring rules such as NEN 1010 in the Netherlands.

Is DALI secure against cyberattacks?

The wired DALI bus has no authentication or encryption, but it can only be reached by someone with physical access to the cabling. The main cyber risk of DALI lies in the gateways to the IP network and the cloud. Segmentation, firewalls, strong passwords and up-to-date firmware on those gateways are therefore the most important DALI security measures.

What is DALI+?

DALI+ is the variant of DALI that carries DALI commands over IP networks, starting with the wireless mesh protocol Thread. The DALI Alliance published the DALI+ test and certification specifications in 2024. Through bridges, DALI+ networks work together with existing wired DALI-2 and D4i devices.

📌 In summary

DALI is the open standard (IEC 62386) for digital lighting control: a simple two-wire bus at 16 V and 1200 bit/s with up to 64 addressable drivers, groups, scenes and feedback. With DALI-2, D4i and DALI+ the protocol has grown into a source of energy and diagnostics data that reaches the BMS, KNX or the cloud through gateways. Those gateways are exactly what turn lighting into a full part of a building’s OT, with the same need for segmentation and hardening.

DALI makes every luminaire individually controllable and readable; if you choose certified DALI-2 products and secure the gateways as carefully as any other OT, you get flexible, energy-efficient lighting without a new attack surface.