Smart street light standardization – NEMA vs Zhaga

Two major trends in LED street lighting

Because of the above outstanding advantages, LED street lights have been widely used in urban road lighting in recent years and have gradually become mainstream. In the early stages of the development of LED street lights, the main development of LED street lights focused on structural design, light efficiency improvement, light distribution design, life extension, etc. Of course, there are still many opportunities for improvement in these areas, so special attention is still needed in the later stage. If LED street lights want to continue to develop, there is still a lot of room for energy saving and high efficiency, real-time control, convenience and easy replacement, and smart cities. It is worth noting that this technological upgrade of LED street lights is not a simple “replacement” of traditional lighting equipment, but a systematic change. In the process of this change, two trends worthy of attention have emerged – intelligence and standardization.

Smart street light

One of the development trends of LED street lights is intelligence. As mentioned earlier, LED lights have strong controllability, which makes it possible to automate smart street lighting systems. In this street light system, a precise algorithm based on environmental information (for example, ambient light) realizes automatic adjustment of street light switches and brightness without manual intervention. With development, it can have the ability to learn (such as sensing the existence and activities of people or things, etc.) to realize intelligent control of lamps. In addition, as a covering urban infrastructure network, street lights themselves may become more intelligent edge nodes of the Internet of Things, which allows LED street lights to have more additional functions (such as weather, air quality monitoring, Wifi nodes, etc.), making them more popular in the Internet of Things, which plays a more important role in smart cities. D4i and Zhaga (NEMA) are two of the highlights when it comes to these.

Street light standardization

One of the development trends of LED street lights is standardization. We can imagine that the trend of LED street lights developing towards intelligence will inevitably pose new challenges to LED street light design – the LED street light system will be more complex. It will require street lights to include LED modules, drivers, sensing, control, communication and other functions and more extended functions when the appearance space is limited. If we hope that LED street lights can meet this challenge, standardization is the only way out, and it is also another important development trend of current LED street lighting. The advantage of standardization is that it can enable more technology suppliers’ functional modules to be seamlessly integrated with LED street lights, thus greatly improving the scalability of the system. Common ones include dimming function, NEMA, Zhaga, D4i (including data transmission).

Intelligence promotes standardization, and standardization promotes the deepening of intelligence. The interaction of the two trends promotes the continuous evolution of LED street lighting technology and applications.

The evolution of smart street light architecture

The evolution of LED street light architecture is largely influenced by industry standards, of which NEMA(National Electrical Manufacturers Association) and Zhaga are the two main standards organizations. These standards organizations promote the standardization and interoperability of LED street light architecture and promote the development of LED lighting products. The standardization of street lighting has been around for a long time. The most familiar one is the ANSI C136 standard, which is widely used in many parts of the world. Many street lights today are produced according to this standard. In recent years, the Zhaga standard has begun to gradually appear in the eyes of industry workers. Of course, in addition to the interface of the controller, Zhaga also standardizes the standards of other components (LED modules, lenses, power supplies, controllers, etc.). We will explain one by one below.

ANSI C136.10

The original street lights used traditional lighting fixtures, and the control logic was very simple – turn them off during the day and turn them on at night. This can be achieved with only a photocell (light controller). In order to achieve the interchangeability of control units such as light control, the ANSI C136.10 standard defines a common platform and standard interface for road lighting equipment, namely NEMA socket. It enables standardization of sockets for light controllers based on AC line voltage and 3-pole connection, i.e. NEMA sockets from different suppliers and different light controllers can be used interchangeably. The standard interface developed based on ANSI C136.10 gradually became the standard in the industry after 1988. The following is a specific diagram.

ANSI C136.41 NEMA socket in smart street light

You may find that the ANSI C136.10 standard can only meet the non-dimmable control architecture of 3-pole light controllers. And with the application of LED technology to street lights, people are increasingly demanding high energy efficiency. Therefore, street lights equipped with dimmable functions are increasingly appearing in the eyes of industry players. However, ANSI C136.10 does not put forward requirements for dimming lines. A new standard and architecture need to be proposed to fill this gap. This new standard is ANSI C136.41. The ANSI C136.41 architecture adds signal output contacts to the 3-pole line voltage connection. In addition to connecting the grid power supply to the ANSI C136.41 light control system, the architecture can also accept logic voltages from other devices. This voltage signal can be output to control the switching power supply in the system, thereby achieving control and adjustment the brightness of LED lamps. This standard is compatible with the original lighting system and uses wireless communication technology (that is, converting wireless communication models into voltage signals) to provide an economical and reliable solution for smart street lights. Specific diagram can be seen in above pictures, while the wire connection can be seen below.

Zhaga socket(Zhaga book 18) in smart street light

The ANSI C136.41 standard, commonly used for roadway and area lighting, specifies 7 contacts (each connected with 305mm leads), 14 AWG wire for use on three-wire voltage AC circuits, and four signal dimming wires (on DC circuits) is with 18 AWG wire. Socket assemblies are also available with 2 or 4 dimmer control pad contacts. In the case of 2 contacts, then it’s a 5pin NEMA socket. However, the ANSI C136.41 standard is not perfect. For example, it does not support the input of sensor information, which limits the implementation of more automated street lighting systems. To put it simply, although the 7pin NEMA socket has 4 dimming contacts, it only stipulates that the other two contacts can be connected to the LED driver to achieve dimming, but there is no explanation for the other two contacts. It can be used with microwave and other sensors, but it does not explain how to use it.

To this end, Zhaga, the global lighting industry alliance, has launched the Zhaga Book 18 standard specially developed for outdoor lighting. This standard introduces the D4i protocol of DALI-2 to solve the design of communication bus in lighting systems and solves the wiring problems that plague developers. An obvious difference between the Zhaga Book 18 standard and ANSI C136.41 is that the PSU is no longer integrated into the light controller assembly, but is integrated into the lamp as part of the LED driver or as a separate component. This architecture simplifies the wiring of lighting equipment control nodes and supports a new “dual-node architecture”, that is, in the street light system, one node device connected upwards serves as a photocell control or communication node, and the other node device connected downwards Nodes can be used for downward motion or other types of sensors. In this way, a complete intelligent street light system is basically formed, and the expansion of its control, communication, sensing and other functions can be easily realized by accessing standardized modules.

Zhaga socket combined with NEMA socket in smart street light

Some LED street lights use a combination of NEMA and Zhaga standards to achieve greater interoperability and scalability. For example, a streetlight might use a NEMA-standard luminaire housing and mounting interface, while using Zhaga-compliant replaceable LED modules. This combination can provide users with greater flexibility and choice while ensuring the safety and performance of LED street lights.

It is worth noting that this dual-node architecture of Zhaga Book 18 is not the end of the evolution of LED street lighting architecture. In recent years, a “hybrid dual-node” architecture has been developed that combines the advantages of ANSI C136.41 with the convenience of Zhaga-D4i and an open architecture. “Node architecture” is on the rise again. Simply put, the node devices on the hybrid dual-node architecture upwards are light control or communication nodes connected by a 7pin ANSI C136.41 interface(Some says it’s 4pin NEMA socket-ANSI C136.58, no conversion of grid power to the LED driver), either from the auxiliary PSU, the driver internal/external or DALI The bus powers the ANSI C136.41 nodes; the downward facing nodes still act as sensor input devices and are connected via the Zhaga Book 18 interface. The street light system based on this structure further simplifies wiring and can make full use of standard ecological resources such as ANSI and Zhaga.

Obviously, with the evolution of LED street light architecture, the technical options before developers have become more abundant. People can choose the most appropriate architecture based on actual design needs to upgrade the street lighting system. Moreover, thanks to the advancement of standardization, there are now more and more LED lighting components and functional components on the market that comply with ANSI or Zhaga standards, which will make the intelligent journey of LED street lighting systems smoother.

Difference between NEMA and Zhaga in smart street light

What is the difference between NEMA and Zhaga? Generally speaking, the lighting fixture with Zhaga may be more expensive because it requires a D4i LED driver which has enhanced capabilities of smart street light. In order to achieve more functions, street lights with NEMA controller often require more components, which will inevitably lead to a larger physical size of the lamps. In addition, Zhaga controllers are usually much smaller than traditional NEMA controllers. Zhaga sockets and controllers are usually only half to one-third the physical size of NEMA sockets and controllers, and the cost is relatively low, but their power supplies are more expensive. Furthermore, Zhaga’s interoperability and the compatibility is higher. Below is a comparison between the two of them.