DALI-2, Zhaga, and D4i — How a Smart Street Luminaire Communicates

Three Standards — Three Different Things

It is common to see “DALI”, “Zhaga”, and “D4i” used almost synonymously in marketing text. They are, however, fundamentally distinct:

A luminaire can have a Zhaga Book 18 connector without having a DALI-2-certified driver. A DALI-2-certified driver can support some DALI Data Parts without meeting all D4i requirements. Full D4i certification for an LED driver requires Part 207 and Parts 250–253, together with a current entry in the DALI Alliance product database.

DALI-2 — The Protocol That Controls

DALI (Digital Addressable Lighting Interface) is a two-wire, half-duplex protocol for dimming, on/off commands and status. A DALI-2 subnet can address up to 64 control gear and an additional 64 control devices; these are separate address spaces. DALI Alliance

DALI 1 was the original version. DALI-2 differs in one principally important way: certification requirements. A member manufacturer can perform the tests using approved test equipment and the DALI Alliance’s official test sequences, or use an accredited DALI test house. The DALI Alliance then verifies the test results and lists the certified product in its product database. A product that is not listed is not DALI-2 certified, even if it is described as “DALI-compatible”.

What DALI-2 Handles — and Does Not Handle

DALI-2 is a local bus communication system. It handles:

• Dimming from the driver’s minimum level to 100 %, plus a separate off command
• On/off commands and scene recall
• Group addressing (up to 16 groups per segment)
• Status queries: lamp failure, power supply failure, temperature warning
• Time schedules via DALI controller (not built into the protocol itself, but into the controller)

The core DALI-2 functions do not automatically include:

• Standardised energy reporting via Part 252 or operating time and diagnostics via Part 253 — support must be verified for the selected driver configuration
• Wireless communication — DALI is a cable protocol
• Direct IP communication — a gateway is required to bridge DALI to the network

Zhaga Book 18 — The Connector That Enables Replacement

Zhaga is a consortium that standardises mechanical and electrical interfaces for LED lighting components. Book 18 specifically defines the interface between an outdoor luminaire and an OLC node (Outdoor Luminaire Controller) — that is, the external control unit mounted on the luminaire.

The Book 18 connector standardises:

• Connector mechanics and pin layout
• DC supply and reference potential as specified by the interface; the reference is not the mains neutral conductor
• DALI communication between node and luminaire
• Power budget for the selected node

Replacement without opening the luminaire depends on a compatible interface. Zhaga specifies interoperability for a Zhaga-D4i-certified luminaire combined with a certified node; a matching connector alone is insufficient. Check the node’s CMS connection separately. Zhaga Book 18

D4i — Data for Predictive Maintenance

Parts 251–253 are the three DALI Data Parts for luminaire/asset data, energy reporting, and diagnostics and maintenance. D4i certification for LED drivers also includes Part 250 for integrated DALI bus power and requires Part 207: DALI Alliance — D4i

Data from Part 253 can support a shift from reactive maintenance (“replace when broken”) towards predictive maintenance (“act when operating time and fault flags indicate increasing risk”). This is directly linked to the field failure mode hierarchy — see MTBF is not Lifespan. CLO is a separate driver or luminaire function and must be verified for the selected configuration; Part 253 does not provide CLO. CLO is included as standard in every VALDUR luminaire.

Wireless Alternatives

When cable infrastructure is absent or too costly, wireless communication is an option. Common protocols in street lighting:

• Zigbee (IEEE 802.15.4) — a mesh network with a gateway for internet/CMS access. Assess range for the actual site.
• LoRaWAN — a network protocol using LoRa radio technology for small data volumes over long distances. Requires a compatible node, gateway coverage and network server.
• NB-IoT — mobile-based (4G/5G network). No local gateway, but subscription-dependent.
• Proprietary protocols — common from system vendors. Lock-in risk if not documented and open.

An SMC housing can allow internal radio integration. Range also depends on antenna, frequency, placement and surroundings and must be verified in the assembled product. Metal housings may need an external antenna, external node or suitable RF window. Casambi

Five Questions to Ask About Controls in Procurement

1. DALI-2 certification: Is the selected driver variant listed in the DALI Alliance product database, and which Parts does the entry cover? Tests may be performed by the member manufacturer or an accredited test house; certification relies on the DALI Alliance’s verification of the results.
2. D4i implementation: If full D4i certification is claimed, does the product-database entry cover Part 207 and Parts 250–253? If only data support is stated, which of Parts 251–253 are included in the selected configuration?
3. Zhaga Book 18: Is the connector standardised? If the node is replaced — must the luminaire be opened? Replacement without opening the luminaire depends on a compatible interface. Zhaga specifies interoperability for a Zhaga-D4i-certified luminaire combined with a certified node; a matching connector alone is insufficient. Check the node’s CMS connection separately.
4. Platform dependency: If a wireless node is included — which CMS platform is it tied to? What happens to the data if the supplier ceases?
5. Data rights: Who owns the collected operational data — the municipality or the system supplier?

Sources

1. DALI Alliance — Introducing DALI and the DALI Alliance
2. DALI Alliance — D4i overview
3. DALI Alliance — Product database
4. Zhaga — Smart interface between outdoor luminaires and sensing / communication modules (Book 18)
5. Casambi — The science behind wireless control