What You Need To Know About D4i

December 18, 2023 Paula Santa Cruz

What Is The D4i Standard, Relevant Applications, Considerations For Specifiers & Applicable eldoLED D4i-Enabled LED Drivers

Fig 1: Roadway Application that can leverage the D4i protocol

Several years ago, excitement started to grow in the lighting industry regarding an entirely new market—the Internet of Things (IoT). The hope was that the luminaire could widen its scope of operations. Extending its capabilities into a hub for all the sensors and other devices that monitor and control the illuminated space.

According to this vision, a smart luminaire responds to the presence or absence of people, modulates its output depending on the intensity of ambient light and uploads local data to the cloud. From there, the software performs analytics for new smart city or smart building functions.

It was in this context that the Digital Illumination Interface Alliance (DiiA)—an industry consortium—developed the D4i™ interface. An extension of the DALI-2™ control and data-gathering protocol for IOT-ready luminaires.

What Is The D4i Standard?

Fig 2: Intelligent driver communication that occurs between a D4i-certified LED driver and its components 

A D4i-certified LED driver or other device must implement DALI standards governing the following fields of operation:

  • DALI Part 250 – integrated bus power supply
  • DALI Part 251 – luminaire information used for lighting asset management
  • DALI Part 252 – energy reporting
  • DALI Part 253 – diagnostic data used in the servicing of lighting equipment and for predictive maintenance
  • DALI Part 150 – an additional and optional standard for the provision of a 24V auxiliary power supply

To enable these functions, the D4i specification also sets a standard protocol for data exchange between the luminaire components—and from the luminaire to an external controller. Every D4i-certified component is guaranteed to interoperate with every other D4i-certified component since the D4i technology is an industry standard.

D4i Application Example: Roadway Lighting 

Fig 3: OPTOTRONIC by eldoLED 60W DEXAL D4i-enabled LED driver used in roadway applications 

Let’s use a highway light mounted on a high mast as an example. D4i devices within the luminaire—such as a temperature sensor, ambient light sensor and energy meter—will upload data to an intelligent D4i LED driver such as our 60W OPTOTRONIC® DEXAL D4i-enabled UL Class 2 driver.

The driver operates as the hub for multiple sensors and a smart wireless IoT controller that transmits the operating data to an analytics application running in the cloud. The analytics software uses the data to regulate the luminaire’s operation, optimize energy efficiency and schedule planned maintenance and replacement cycles.

The D4i protocol ensures that sensors, the driver and wireless controllers from different vendors interoperate seamlessly. This protocol also covers data formatting and transmission. Ultimately, providing a uniform interface to software and easing the task of developing analytics and other lighting software programs.

What Are The Best Applications For D4i?

Adoption of the D4i interface is strong in two types of applications. Both applications have differing reasons for using D4i technology and take advantage of various features of the specification:

  1. Outdoor Infrastructure: Streetlights and roadway lighting
  2. Large Commercial Buildings

Roadway Lighting: DALI Part 253

DALI Part 253 diagnostic data for servicing and predictive maintenance provides the essential functions for this application. Roadway lighting and streetlights incur high financial penalties for every hour that a light is out of operation. Part 253 is necessary for utility obligations and infrastructure operators to maintain high lighting quality of service. Enabling the operator to quickly replace a failed lamp versus taking on the financial burden of an unplanned replacement with road closures.

As a result, road lighting operators prefer replacing large groups of lamps simultaneously to ensure that none of the lamps age and reach imminent failure. The diagnostic data from a D4i streetlight equips the operator to optimize the timing of scheduled replacement—balancing factors such as historic operating temperature, drive current, and duration of operation. Combined, the diagnostic data avoids the expense of premature replacement and minimizes the risk of a costly lamp failure before replacement.

Commercial Buildings: DALI Part 252

DALI Part 252 specification for energy monitoring and performance is valuable for commercial buildings. This portion requires tight measurement accuracy of ±2%. Individual luminaire energy monitoring allows building operators to regulate power consumption in a granular fashion. Resulting in opportunities to reduce building-wide power consumption, limit operating expenses and qualify for valuable power usage rebates awarded by utilities.

D4i Considerations For Specifiers And Operators 

Many specifiers are considering what the benefits are in individual luminaire energy monitoring, predictive maintenance and diagnostics or integration with the IoT to merit implementation of D4i-enabled lighting. Specifiers that want to future-proof a new installation and upgrade a simple lighting network with IoT capabilities should keep several factors in mind.

Factor 1: Cost 

The first and perhaps most important is cost. The extra functionality that a D4i-certified luminaire provides requires additional and more capable hardware—and this costs money. Every D4i-enabled element of a luminaire—such as the D4i LED driver—is more expensive to its counterparts that only offer DALI-2 or 0-10V dimming control.

Factor 2: Capability 

The specifier must ask themselves whether the installation needs the capability for the D4i specification. An example is the case of energy monitoring. Is the availability of luminaire-by-luminaire energy monitoring data going to change the control of the luminaires? Or will universally applied policies—such as dimming or turning off a light when unoccupied—effectively reduce power consumption similar to more granular controls?

Factor 3: Diagnostic Data 

The same question arises for operators that implement predictive maintenance. Their intention with D4i technology could enable them to gain access to diagnostic data such as logs of the temperature, drive current and hours of operation.

Believe it or not, this data is also available under Part 253 of the DALI-2 specification and does not require full implementation of the D4i specification—which are Parts 250, 251 and 252. A DALI-2 luminaire that implements Part 253 is cheaper than a full D4i-certified luminaire.

Factor 4: Additional Protocols 

When evaluating the case for D4i, it’s also worth considering whether other methods for sharing intra-luminaire signals are possible. The LEDcode protocol is supported in many of our LED drivers and in lighting products from Acuity Brands companies. It provides a simpler and more cost-effective way to connect sensors, controls and other peripherals to a driver. The only thing to keep in mind is LEDcode doesn’t have a standard protocol.

Summary: Understanding The Use Case For D4i

The decision on whether to specify D4i-enabled lighting equipment—including an intelligent D4i LED driver—should consider the specific requirements of the application. The case is clear for roadway lighting. The cost of a failed lamp is very high, so predictive maintenance is essential. The same applies to other types of lighting that are difficult and expensive to replace. Installations that use granular energy data to reduce power consumption can also benefit from the implementation of D4i technology.

Applicable eldoLED D4i-Enabled LED Drivers 

In these types of applications, luminaire manufacturers have the choice of DALI-2 and D4i LED drivers. The North-American exclusive OPTOTRONIC® by eldoLED range of DEXAL LED drivers are all D4i-enabled and support the DALI-2 interface. Products are available to support both indoor and outdoor applications:

Indoor OPTOTRONIC by eldoLED LED Drivers 

Fig 4: Indoor OPTOTRONIC by eldoLED LED driver with DEXAL technology 

OPTOTRONIC intelligent D4i LED drivers are available with 30W, 50W and 85W power ratings. Features include Dim to Off, current setting to a resolution of 1mA and soft-start.

Outdoor OPTOTRONIC by eldoLED LED Drivers 

The 60W OPTOTRONIC DEXAL driver provides a primary output in the voltage range 15-55V and a Part 150 24V auxiliary power supply. Supporting DALI-2 dimming controls, this UL Class 2 driver is UL dry- and damp-rated and offers 6kV of surge voltage protection.

Fig 5: eldoLED DUALdrive family line-up leverages DALI-2 if the D4i functionality is not necessary.

When the data required by the application is possible without the need for full D4i functionality, a DALI-2 driver is a great replacement option. This greatly widens the choice of drivers available to include the ECOdrive, SOLOdrive, DUALdrive, POWERdrive and LINEARdrive families from eldoLED.

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