What Is D4i?
D4i is a set of specifications, managed by the DiiA (Digital Illumination Interface Alliance), that extends DALI-2 inside the luminaire. Where a classic DALI system needs an external power supply and separately commissioned control devices, D4i puts a small, standardised 24 V bus and a memory store inside the fitting itself.
What D4i actually adds
- Bus power inside the luminaire. A D4i bus power supply (covered by DALI Part 250) feeds sensors and communication nodes directly, so a node can be added without rewiring the control cabinet.
- Self-certification. Every D4i device carries a DiiA-issued certificate and a unique ID, so a luminaire controller can report exactly what it is.
- Memory and data. D4i nodes store operating data — energy use, thermal history, diagnostics — that a building management system can read back over the bus.
Why it matters for outdoor and street lighting
Because the node is powered and described within the fitting, a street light can arrive from the factory as a Zhaga-D4i luminaire: clip in a standard sensor node, commission it once, and let it report faults and energy automatically. That is the core promise of D4i — luminaires that are smart out of the box.
D4i and the DALI Parts
D4i reuses DALI-2 device types and adds luminaire-focused parts: Part 251 (luminaire), Part 252 (in-line module), Part 253 (independent module) and Part 250 (bus power supply). A D4i device is, first, a certified DALI-2 device. See D4i vs DALI-2 for the boundary.