DALI-2 and D4i: Certification, Multi-Master and Luminaire Data
“DALI” printed on a product never guaranteed it would work with your system. DALI-2 was created to close that gap; D4i then turned the luminaire itself into a data source. Knowing the difference is half of choosing the right product.
In short
- Original DALI defined only drivers; sensors and controllers sat outside the standard.
- DALI-2 brought control devices into the standard, added multi-master and mandatory certification.
- Compatibility is now documented — look for the DALI-2 logo.
- D4i is about in-luminaire bus power and reading data from the luminaire.
- D4i exposes asset data, energy consumption and diagnostics.
- Sensor-ready luminaires accept a sensor with no extra power supply, thanks to D4i.
The original problem: interoperability
The original DALI standard only described control gear — ballasts and LED drivers — in detail. Control devices such as sensors, push buttons and controllers were left outside the standard, and every manufacturer went its own way.
The result was predictable: brand A’s sensor would not talk to brand B’s controller. There was no official test programme either, so “DALI compatible” was simply the manufacturer’s own claim.
What DALI-2 changed
DALI-2 is the second edition of IEC 62386 and brings three fundamental changes:
- Control devices entered the standard. Part 103 defines sensors, push buttons and application controllers, so different brands can now work together.
- Multi-master support. Several control devices can share one line — an occupancy sensor, a daylight sensor and a wall panel can all coexist.
- Mandatory certification. No product may carry the DALI-2 logo without passing the official test programme run by DiiA (Digital Illumination Interface Alliance). Compatibility is now documented rather than claimed.
Look for the logo
When specifying, ignore the words “DALI compatible” and look for the official DALI-2 logo on the box. The list of certified products is public in DiiA’s online database. On a mixed-brand project it is the cheapest insurance you can buy.
D4i: the luminaire becomes a data source
D4i is a DiiA specification built on top of DALI-2 with an entirely different focus: the DALI bus inside the luminaire, and data about the luminaire itself.
A D4i certified driver provides:
| Part | Content | What it gives you |
|---|---|---|
| Part 250 | Integrated bus power supply | The driver powers the DALI bus inside the luminaire; no separate PSU needed |
| Part 251 | Luminaire asset data | Brand, model, serial number, luminous flux and manufacture date, read from the luminaire |
| Part 252 | Energy reporting | Instantaneous power and cumulative energy consumption |
| Part 253 | Diagnostics and maintenance | Operating hours, temperature history, overload and fault logs |
This turns lighting into a data source for a building management system. Which luminaire consumes what, which one is shortening its life through heat, which model is installed where — all readable without anyone climbing a ladder.
Sensor-ready luminaires
This is D4i’s most visible practical outcome: the luminaire contains a DALI connection powered by the driver. You can plug an occupancy or daylight sensor straight into it — no extra power supply, cabling or mounting. Moving to smart lighting becomes as simple as fitting the sensor.
Backward compatibility
The good news: DALI-2 and D4i devices are designed to work with first-generation DALI systems for core functions. You can fit a new D4i driver on an old line and dimming and scenes will work. To use the extra features — energy reporting, asset data — the controller must support them too.
Which should you specify?
- On a new architectural project: insist on DALI-2 certified products. The premium is small and it removes interoperability risk.
- If you need energy monitoring or BMS integration: D4i.
- If you may add sensors later: choose D4i certified, sensor-ready luminaires; retrofitting costs far more.
- If you are adding a few luminaires to an existing system: staying within the same generation is the lowest-risk route.
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