The Value of Two-Node Architecture in Street Lighting

Two Node Architecture in Street Lighting: The Smart City Platform?

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Smart cities have been discussed for many years and yet they have still not been realized. Municipalities have previously focused on replacing incandescent light sources with LED lighting. And as the industries’ accepted number for the amount of energy spent powering streetlights is 30 percent of a municipality’s energy budget. This change has created significant savings in energy and therefore cost savings with a city’s lighting department budget often being in the black.

TE believes the future of street lighting is controls. With controls having the promise of further energy savings and the continued discussions of their use in smart cities, we are now seeing cities and governments creating departments and allocating budgets. But even this isn’t driving the smart city forward.

In recent years, two-node architecture has been the most exciting development in the industry. The two-node architecture has the potential to be the backbone of a smart city, enabling an eco-system that will allow innovative communication and sensor nodes to be created that will all work together.

Interoperability has been the promise of Zhaga. It started in 2017 when Zhaga released the first edition of Book 18 (Figure 1). TE Connectivity released the Endurance S streetlight interconnect and Signify released its Xitanium SR Driver. This was the first time a solution had been created specifically for LED street lights. But it wasn’t until 2019 and the release of Book 18’s second edition that the fully formed two-node architecture was realized.

The key to the eco-system is the intra-luminaire communication protocol. DALI has been a very popular lighting protocol for many years. Although DALI-2 is a multi-master solution, it has no hierarchy built into it. When more than one control device is on the bus, whichever one speaks last the driver will respond to. This is a situation that could not be allowed to exist in street lighting.

The D4i digital communication protocol was created through a liaison between Zhaga and the DALI Alliance. This protocol has baked in arbitration, creating a hierarchy between two control devices on the same bus. As the image shows in the Zhaga architecture, the driver is now permanently powered (Figure 1). Typically, an AUX 24VDC PSU is built into the driver, although a separate PSU is allowed. This means that a 24V rail is always available, creating opportunities for communication and sensor-nodes designs that can be used not just during the dark period. Wiring is greatly simplified with the two control devices and the driver connected to the same communication bus.

Figure 1: The image shows the driver is permanently powered in the Zhaga architecture. (Source: TE Connectivity)

This edition also defined the power budget that the driver is required to deliver from both the AUX power supply and from the powered DALI bus power supply—as well as the power that different types of control devices are allowed to pull from the system. This is all controlled through a certification program. Drivers are certified D4i by the DALI Alliance, while luminaires and control devices are certified Zhaga-D4i by the Zhaga Consortia.

Powered upward-facing interfaces have been available for several decades through the ANSI C136.10 interface. This standard was updated eight years ago to allow for signal contacts and dimming controls, and C136.41 was created. But this two-node architecture now allows for sensor devices that need a downward field of view. We are now starting to see motion sensors being released, although other innovations are happening. For example, the Lake Macquarie City Council in Australia organized a hackathon to create sensors for smart-city applications for the two interface luminaires they have installed throughout the city.

In many regions the ANSI C136.41 is dominant, and therefore the Zhaga Book 18’s third edition detailed a hybrid two-node architecture. With an ANSI interface facing upward and a Zhaga interface facing downward in this edition, the wiring of a luminaire is defined and the requirements of a control device.

Zhaga is now talking about the next phase of the book and looking at how it adopts this architecture for other form factors, other than cobra heads. Heritage lighting is recognized as an important subset of street lighting and is increasing in popularity but will provide its challenges for the two-node architecture.

TE Connectivity supports the Zhaga and ANSI streetlight interconnect platforms. For the Zhaga interface, TE Connectivity offers the LUMAWISE Endurance S product range. It is made up of the receptacle, which mounts to the street light, shown on the left of the image below (Figure 2).

Figure 2: Features of the LUMAWISE Endurance S (Source: TE Connectivity)

TE released the second-generation version of that product. Featuring dual-wire poke-in, an updated seal for certain mounting configurations and a unique locking washer for a featureless plain mounting hole. The dual wire poke-in is designed specifically for the two-node architecture, allowing daisy chaining to crate the D4i bus and 24V_DC rail. This receptacle is for Zhaga applications that use the D4i protocol. For where people have a different application or a proprietary communication protocol, TE Connectivity has a keyed version. This is to keep the Zhaga architecture clean and ensure the promise of interoperability. TE Connectivity also supplies a sealing cap, bases, and domes in different sizes.

For the ANSI interface, consider LUMAWISE Endurance N or dimming receptacles (Figure 3).

Figure 3: LUMAWISE Endurance N Features (Source: TE Connectivity)

TE Connectivity has the standard five- or seven-pole dimming receptacles as well as rotatable versions for north-facing photocells. Even having a toolless version, used extensively in the North America market. TE Connectivity has also recently released the original 3 pole C136.10 interface to complete the product line. Again, TE Connectivity has bases and covers in different sizes and colors, and a range of shorting caps, with and without surge protection, and open circuit caps.

We are now starting an exciting journey for street lighting with technology advancing more in the last decade than the previous six. Maybe this is the platform and kick start the smart city needs.

About the Author

Jonathan Catchpole is a System Architect at TE Connectivity, within the Industrial group. In this customer-facing role, he spends his time understanding their applications, products, and technology. Combined with insight into market trends, Jonathan aligns industrial’s roadmaps to better support customers. For the last 5 years, this has been focused on lighting and mainly streetlighting. During his 23 years at TE Connectivity, Jonathan has in the most part been in engineering leadership roles. Leading teams to develop products for industries which include rail, renewable energy, drives & controls, pumps and lighting. Jonathan is a black belt in lean design and holds an honours degree in Mechanical and Manufacturing Engineering from the University of Brighton, in the UK.

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