DALI-2 explained

01 · The standard

An open standard, tested to work together

DALI stands for Digital Addressable Lighting Interface. It's defined in IEC 62386, an international standard split into parts, one for each kind of device.

DALI-2 is the current generation. It added standard control devices (buttons, sensors and controllers) and a certification scheme run by the DiiA, the Digital Illumination Interface Alliance. A product carrying the DALI-2 logo has passed the standard's test sequences, so a driver from one manufacturer works with a sensor or controller from another.

101

System components, including the DALI power supply

102

Control gear: the drivers inside the lights

103

Control devices: application controllers and inputs

207

LED drivers (device type 6)

209

Colour control (device type 8)

202

Self-contained emergency lighting (device type 1)

301

Push buttons

303

Occupancy sensors

304

Light sensors

In the diagram, each device is tagged with the part it's certified against.

02 · The old way

Zones set by copper

In a conventionally wired room, each switch controls a circuit and every light on that circuit does the same thing. The zones are decided the day the electrician pulls the cable.

Dimming adds a second system. Analogue 1–10 V dimming needs its own control pair for every zone. It's polarity-sensitive, it still needs a relay to switch the light fully off, and it can't report anything back.

Want the lights by the window to dim separately from the ones by the door? That means new cable, a new switch drop and time up in the ceiling.

03 · Wiring

One DALI line twin pair for everything

A DALI line is a twin pair, and polarity doesn't matter. Either wire can go to either DALI terminal on a driver, button or sensor, so a swapped pair still works. Every device on the line connects to the same twin pair.

The DALI line usually runs in the same 5-core cable as the mains: live, neutral and earth, plus the DALI line twin pair. Each light gets one cable. Mains supplies the power, and switching and dimming arrive as messages on the DALI line. DALI wiring has to be rated for mains voltage, which is what allows it to share the cable.

A DALI power supply provides a nominal 16 V. The one in this diagram is rated at 235 mA, inside the standard's 250 mA limit for a line. The rules are short:

• Line, tree and star layouts all work, and so does any mix of them. Only closed loops don't.
• No terminating resistors.
• Up to 300 m of cable per line, sized so the voltage drop stays under 2 V.

04 · The signal

Short digital messages

A controller talks to lights in forward frames of 16 bits, sent at 1200 bits per second. The bits use Manchester encoding: each one has a transition in the middle, rising for 1 and falling for 0, which makes the signal robust and self-timing. A frame takes about 16 ms. The diagram slows it down.

The first byte is the address and the second is the data. Address byte 0AAAAAA0 means "short address AAAAAA, and a light level follows". Here the data is 1110 0101, arc power level 229. On each pass the demo sends a different level: 229, then 254 (full), then 0 (off).

Arc levels run from 1 to 254 on a logarithmic curve, from 0.1% to 100%, which matches how the eye sees brightness. Level 229 is about 50%.

Lights answer back. A query gets an 8-bit backward frame, so the controller can read the level, check status or spot a failed lamp.

05 · Commissioning

Addressing

One DALI line holds up to 64 control gear, each with a short address from 0 to 63. DALI-2 adds up to 64 control devices, such as buttons and sensors, on the same line with their own address space.

Nobody sets addresses with DIP switches. During commissioning the controller tells every light to pick a random 24-bit number, then runs a binary search that keeps asking one question: "Is anyone's number at or below this?" The lowest light found gets short address 0 and drops out, and the search repeats.

You end up with a number for every light, in no particular order on the ceiling. The commissioning engineer then flashes each address to find it and gives it a name, such as "A3 · meeting table".

06 · Groups

Zones become groups

Each light can belong to any of 16 groups, in any combination. Group membership is stored inside the light, so a single frame addressed to a group reaches every member at the same moment.

• Group 0 · Window row80 xx
• Group 1 · Desks82 xx
• Group 2 · Corridor side84 xx
• Group 3 · Presentation wall86 xx

The presentation wall overlaps the three rows, because a light can be in several groups at once. Click a group to jump to it.

Rezoning takes two configuration commands, REMOVE FROM GROUP and ADD TO GROUP, each sent twice as the standard requires for configuration. Watch the bottom-left light move from the corridor group to the desks group: its pink Group 2 dot is removed, then an orange Group 1 dot is added, without anyone touching a cable.

07 · Scenes

Sixteen presets inside every light

Each light stores up to 16 scenes of its own. With tunable-white lights a scene stores a colour temperature as well as a level, so one press can take the room from bright, cool focus light to a low, warm evening. The labels in the diagram show each light's level as it fades. Click a scene to jump to it. Recalling a scene is one broadcast frame, GO TO SCENE, and every light fades to its own stored level and colour over the same fade time.

In the diagram, the scenes are recalled from the push-button panel by the door. It's wired from the nearest light, not back to the controller. A press sends an event along the twin pair, and the controller answers with GO TO SCENE.

• Scene 0 · Full
  every light 100%, 4000 KFF 10
• Scene 1 · Presentation
  screen wall 8%, everything else 45%, 3000 KFF 11
• Scene 2 · Focus on desks
  desk row 100% at 6000 K, everything else 35%FF 12
• Scene 3 · Evening
  window row 6%, everything else 16%, 2700 KFF 13

Standard fade times run from 0.7 s to 90.5 s, and DALI-2 adds extended fades of up to 16 minutes.

08 · Sensors

Buttons and sensors on the same wires

DALI-2 standardised input devices: push buttons (part 301), occupancy sensors (part 303) and light sensors (part 304). They sit on the same DALI line twin pair and send 24-bit event messages to an application controller (part 103), which decides what the lights do.

Here the floor is split into three rooms, each with its own occupancy sensor. As someone walks through, each sensor reports them and only that room's lights come on. Rooms they've left dim, then switch off after a hold time. When daylight arrives, the light sensor reports it and the controller dims the window office. That's daylight harvesting.

09 · Other control systems

No separate control network

In systems such as C-Bus, KNX and Dynalite, buttons and sensors sit on their own control network: a separate data cable run through the building back to the switchboard. The lights are wired back to dimmer and relay channels in that switchboard, so every zone is a load circuit run home to its channel.

• Separate control network (KNX example)
  second bus for inputs, gateway, extra power supplies and controllers
• DALI-2
  inputs on the DALI line, right next to the lights

Take a typical KNX lighting system. In the switchboard: a KNX power supply with its choke, an IP router or interface, a logic controller for timers and scenes, a KNX–DALI gateway to drive the lights, a DALI power supply for that gateway, and often switching actuators as well. In the ceiling: a green KNX bus cable to every button and presence detector, plus the DALI line to the lights. A press travels KNX bus → logic → gateway → DALI before anything happens.

That means two buses to install and test, and two commissioning jobs: KNX group addresses in the ETS software, then the DALI side in the gateway.

With DALI-2, buttons and sensors connect to the same DALI line twin pair as the lights, wherever is convenient in the ceiling. There's no second network to install and no load circuit per zone.

The input devices are standardised too. Push buttons (part 301), occupancy sensors (part 303) and light sensors (part 304) are tested for DALI-2 certification, so you can mix brands: one maker's sensor with another's drivers and controller. C-Bus and Dynalite are proprietary, single-manufacturer systems. KNX is an open standard, but it still needs its own bus cable, and the lights are typically driven from actuators in the switchboard.

10 · Schedules

Timers and schedules, kept in the controller

The lights don't know what time it is. Schedules live in the application controller, which has its own real-time clock. At each scheduled time it sends ordinary DALI commands: the same scene recalls and level changes you've already seen.

• 06:00 · Cleaning
  Scene 0, every light fullFF 10
• 07:30 · Workday
  Scene 2, focus on desksFF 12
• 12:00 · Lunch
  every light 40%FE DC
• 13:30 · Workday
  Scene 2 againFF 12
• 18:00 · Evening
  Scene 3FF 13
• 20:00 · After hours
  all lights offFF 00

Controllers typically offer weekday and weekend programs, holiday calendars, and astronomical times that follow sunrise and sunset through the year. Schedules work alongside buttons and sensors: after an after-hours OFF, a button press or the occupancy sensor can bring the lights back, and they time out again later.

The scheduling belongs to the controller, not the lights. IEC 62386 standardises the commands the controller sends, so every DALI-2 light follows the schedule.

11 · Emergency lighting

Emergency lighting on the same DALI line

Emergency fittings with DALI-2 emergency control gear (device type 1, IEC 62386-202) connect to the same DALI line twin pair as everything else. They get short addresses like any other light, and they keep their own battery and charger, so they still work if the mains or the controller fails.

• Function test
  every emergency fitting runs a quick diagnosticC1 01 · FF E3
• Read the results
  QUERY FAILURE STATUS to each fittingC1 01 · xx FC
• Duration test
  full 90-minute battery run, scheduled for quiet hoursC1 01 · FF E4
• Cloud report
  results uploaded from the controller4G / Ethernet

The controller runs the tests. Each fitting records its own results, and the controller reads them back: lamp failure, battery failure, battery charge, and whether each test passed.

With a cloud connection, the controller uploads every result. Facility managers get a live report of every fitting, an alert when one fails, and the records needed for the periodic testing that AS/NZS 2293 requires, without anyone walking the building with a test key.

12 · Level of control

How much control you actually get

1. Switched circuitsOn or off, one circuit at a time.
2. 1–10 V dimmingDimming per circuit. No addressing, no feedback.
3. BroadcastDALI One command reaches every light on the line.
4. Groups16 software zones that can overlap freely.
5. Individual lightsEach of up to 64 lights on its own, at 254 levels from 0.1% to 100%.
6. Scenes and fades16 stored presets per light, with timed fades.
7. ColourTunable white and full colour through device type 8.
8. Sensing and feedbackOccupancy, daylight, status and lamp-failure queries. D4i drivers also report energy use and diagnostics.

The diagram runs through three rungs of the ladder, highlighted as it goes: each light set on its own (5), a colour-temperature sweep from 2700 K to 6500 K (7), then a status poll that finds a failed lamp (8).

13 · Side by side

Why it's simpler

There are limits. At 1200 bits per second, DALI is built for building lighting, not fast show effects. One line carries 64 control gear, so larger buildings use several lines joined by controllers or gateways to the building management system.

14 · Try it

Send your own commands

Pick a target and send a level or a scene. Or click a light in the diagram to address it directly, or press one of the four wall buttons by the door to recall a scene. Click the occupancy sensor to empty or refill the room, and the light sensor to bring daylight in or out. The frame you sent appears under the diagram, byte by byte.