Power Over Ethernet (PoE) in Smart Interface Lighting Applications

Introduction

Lighting plays a crucial role in human civilization. Modern indoor and outdoor lights in the industrial and commercial sectors come with enhanced competencies. For example, sensor attached street lights recognize pedestrian and live traffic information, which is then fed to monitoring centers engaged in safety and resource utilization.  Differentiated LED lighting systems advance energy efficiency, facilitate data gathering, and simplify installations. The global adoption of LED lighting makes the LED system a shoo-in for the Internet of Things (IoT). Sensors are affixed to LEDs for intelligence collation.

Power over Ethernet (PoE) is an integral part of communication infrastructure. Since Ethernet cables have simultaneous smart lighting applications, many companies have designed Ethernet-based lighting application solutions that support PoE, which is Cat5E performance capable. We will summarize PoE and its operation, benefits, and its use cases in smart interface lighting application.

Basic Concepts

PoE is a widely adopted technology where electric power and data are transferred over an RJ45 cable and can be used to power up networked devices. A single cable offers both electric power and data connection to Wireless Access Points (WAPs), Voice over Internet Protocol (VoIP) phones, Internet Protocol (IP) cameras and other compatible devices.  This lighting technology eliminates AC power processing complexity and associated safety threats. The process is elaborated in the IEEE 802.3 standard and enhancements include IEEE 802.3bt, IEEE 802.3at, and IEEE 802.3af. The IEEE 802.3at standard is the latest PoE update and known as PoE+.  The PoE+ devices supply a maximum of 30 watts per port, compared to PoE devices' 15.4 watts per port.

The PoE is implemented through two primary elements. Power is sourced through the Power Sourcing Equipment (PSE) device, and the Powered Device (PD) constitutes the end device that accepts power from the Ethernet cable and funnels it for operational use. A PSE device pipes power to PD devices through the standard Ethernet cable together with the data line. The PSE supplies the PD with a maximum of 15.4W and 350mA at 44V minimum voltage. A standard 100m Cat5 cable comes with ca. 20Ω resistance, corresponding to ca. 2.45W transmission loss.

The IEEE 802.3af standard subdivides the supplied PSE side power and the PSE side PD current consumption into five different classes, as shown in the following table

Table 1: PoE PSE-PD power classes

PoE Operation

A CAT5e standard Ethernet cable consists of four twisted cable pairs, and PoE transmits power through these pairs to PoE-enabled devices. The first two twisted pairs transmit data, and the remaining two for power transmission. The new PoE standards enable data and power to be sent over all four twisted pairs.

Although the same pairs are used for power and data, the two transmissions don't mutually interfere as electricity and data are ferried at the opposite ends of the frequency spectrum. Electricity has a low frequency of 60 Hz or even less, and data transmissions consist of frequencies ranging from 10 million Hz to 100 million Hz.

The endpoint PSE delivers power using two different delivery techniques either active data pairs or spare pairs. Active data pairs follows a simplex or 'phantom feeding' power delivery technique to the end device. Power and data are carried through the same conductors. CAT-5 cabling for standard 10BaseT and 100Base-TX Ethernet employs two data/signal pairs connected to pins 1 and 2 and pins 3 and 6 on RJ-45 connectors. Power sourcing equipment uses the center tap of internal signal coupling transformers to superimpose power on these pins. The reverse technique is used to energize the powered device (PD) from these lines.

The spare pair’s technique transports power over the cable's spare wire pairs. The power source applies positive voltage to pins 4 and 5 and negative voltage to pins 7 and 8. For both techniques, this method can be used only on networks with eight-wire cabling and are depicted in the following figure.

Figure 1: Active data pairs and Spare pairs cabling technique

Benefits/ Advantages of PoE

With PoE, Ethernet connected devices can be installed in inaccessible locations. A separate cable is not required to power up the devices. PoE thus negates installation costs. Other benefits include:

• Time and cost savings - Network cables can be fixed anywhere and do not require the services of a qualified electrician.
• Flexibility - Devices like wireless access points and IP cameras can be positioned wherever they are most required and repositioned quickly since there is no need for being tethered to any electrical outlet.
• Safety – The intelligent PoE delivery is designed to protect the network equipment from wrong installation, underpowering, or overload.
• Reliability – PoE power is sourced from a central and universally compatible unit, rather than a collection of distributed wall adapters. An uninterruptible power supply (UPS) can back up this source. Devices can be easily reset or controlled.
• Scalability – Since power is always available, network connections' installation and distribution are simple and effective.

Application Information

Interior lighting in intelligent buildings performs as wireless devices and supports Ethernet, Zigbee, and Bluetooth connectivity.  Light modules present in convenience stores and smart homes can communicate with consumers' smartphones. The technology allows direct remote control and offers real-time information. Such smart lights are Power-over-Data-Line (PoDL) and Power-over-Ethernet (PoE) capable.

Standards for Lighting Industry

Zhaga Consortium, a global lighting-industry organization, wants to standardize components interfaces of LED luminaires, including LED light engines, electronic control gear (LED drivers), LED modules, LED arrays, sensing/communication modules, holders, and connectors.  Zhaga develops lighting solutions specifications termed "Books" to satisfy industry trends like smart lighting and creates interoperable components that can be serviced, upgraded, or replaced with technological improvements. Each Book describes the interface of one or multiple LED luminaire components. Book 20 mentions a smart interface sandwiched among a sensing/communication module and an indoor LED luminaire. The field installable sensory modules connect to a LED driver and control system.  Such an arrangement helps to establish communication between the network components.

Figure 2: Zhaga Book 20 specification

The new Zhaga-D4i certification program and logo, as shown in the following figure, indicates plug-and-play interoperability of luminaires, sensors, and communication nodes, and represent a vital collaboration between Zhaga and DiiA major, the two innovative lighting-industry organizations.

Figure 3: Zhaga-D4i luminaires

Marketplace needs drove the cooperation between Zhaga and DiiA for smart and interoperable LED luminaires having pluggable IoT connectivity. A plug-and-play, socket-centric connectivity system enables easy addition or up-grading sensors and communication nodes. Consequently, it allows luminaires to march in-step with advances in sensing technology and digital networking.

Dali-2 Interface

DALI-2 (Digital Addressable Lighting Interface) is an accepted bi-directional, digital communication smart interface protocol between lighting-control devices like indoor luminaires, sensors, and communication modules. DALI-2, the newest version of DALI protocol and DiiA driven, sets smart lighting control standards. The luminaires, through the use of intelligent DALI-2 drivers, collect, store, and report a broad swathe of data in a standardized form. The DALI protocol finds use in building automation. A smart luminaire communicates and interacts with a lighting control network, provides energy consumption data, fault detection, or many other parameters. The D4i driver standardizes data storage and retrieval in the DALI memory banks. The D4i specifications ensure that the luminaire's receptacle can access power. In addition to the integrated DALI bus power supply, each luminaire also includes a 24V auxiliary power supply.

In the Zhaga-D4i case, each receptacle on the luminaire connects to the internal DALI bus. When a node plugs into a receptacle, a bi-directional interaction between the node and the D4i driver(s) using the well-established and standardized DALI-2 protocol is established. With the smart lighting solutions and wireless communication offered by Zhaga Book 20, it finds multiple uses, from air quality testing to light level controlling and presence detection.

Zhaga Book 20 Connectors

Amphenol ICC offers a broad range of connectors to satisfy the lighting industry's expanding demands from Wire and PCB connectors to power distribution connectors. It also serves solutions designed with power and dimming/signal contacts to produce a connection between dimmable photocell and the luminaire for intelligent buildings, commercial and utility lighting, and sensor applications in IIoT-based street lighting. They are governed by two well-known lighting standards in the industry, ANSI/NEMA and Zhaga. These connectors are ideal for PoE capable interior lighting and support both Bluetooth and Zigbee connectivity.

Zhaga Book 20 specifies two-position connectors identified as Luminaire Extension Module Receptacles (LEX-MR) and Luminaire Plugs (LEX-LP), used for DALI-2 applications. Amphenol's FLM Series connectors are approved as the new Zhaga Book 20 standard, allowing modules to connect to the LED driver and control system. It also helps for modules to be easily field serviced and replaced as necessary.

Figure 4: FLM series configurationsFLM series configurations

FLM series connector enables DALI-2 protocol, and are available in Wire-to-Wire and Wire-to-Board configurations. The pin contact connectors (LEX-MR receptacles) are available as a right angle or vertical PCB mount with SMT tails, or as wire termination housings for crimp contacts. The socket contact connectors (LEX-LP plugs) are available for wire crimp contacts or with integrated contacts with poke-in wire termination. FLM series connector has versatile design options. It holds SMT connectors to board in secure orientation during soldering process, and ensures correct mating alignment with easy unmating. It has current rating options of 3A with 22 AWG wire, 5A with 20 AWG wire and 7A with 18 AWG wire.