Issue link: https://www.e-digitaleditions.com/i/1414667
October/November/December 2021 I 39 WHY PoE-CONNECTED LIGHTING IS A SMART CHOICE PoE-connected lighting leverages Ethernet cabling to provide power and data transmission control capa- bilities that integrate into a building's smart system. This ability to migrate lighting controls to an IP-based infrastructure makes lighting a key IoT building asset, one that can be controlled synergistically along with other building functions. Digital integration means more meaningful data can be collected by a distributed sensor system as part of the lighting network infrastructure. According to ledsmagazine.com, "Ethernet provides data and low-voltage DC power for everything from phone systems to cameras. PoE brings the potential for low-voltage devices to be installed away from AC power sources, such as in a ceiling. A PoE lighting system eliminates the AC-to-DC power conversion within each lighting fixture, improving overall building efficiency." 1 And according to securitymagazine.com, "Many smart building devices employ PoE to provide electrical power to the device using the same structured cabling that enables data connections, eliminating the need for separate AC outlets. Devices that are not yet PoE-enabled likely will be in the future. In 2018, IEEE ratified the 802.3bt standard, which allows up to 90 W of power to be transmitted over Ethernet cabling. These higher levels of PoE enable a new class of building devices—lighting, wireless access points, PTZ cameras and more—to be powered via the IP network." 2 PoE FOR DIGITAL BUILDINGS The main limiting factor affecting PoE use in new applications was the amount of available power. The 15.4 W at the power source is sufficient for most IP phones and 802.11a/b/g wireless access points (WAPs). Although some IP-based pan-tilt-zoom (PTZ) cameras are supported by 15.4 W, it may not satisfy the power require- ments of today's advanced surveillance cameras, such as ultra-high-definition 360-degree cameras, outdoor thermal cameras with heaters, or PTZ cameras designed for low light, night vision, or thermal imaging functionality. Today, there is demand for even higher power to support additional devices connected to the Ethernet network, such as connected lighting, motorized shades, dispensers, thin client, 802.11ac WAPs and small cells, all of which can benefit from PoE. The latest IEEE 802.3bt standard, published in January of 2019, increases the maximum PoE power available mainly by utilizing all four pairs of the struc- tured cabling. Furthermore, IEEE 802.3bt extends the power classification information exchanged during initial negotiation to allow meaningful power manage- ment capability, enabling support of multiple PoE classes while also being backward compatible. These enhancements solve the challenge of higher power and more efficient PoE delivery systems. FIGURE 1: (Top) shows two balanced twisted-pair used for power and data, (bottom) shows four balanced twisted-pair for power and data. The IEEE802.3bt standard also introduces Type 3 and Type 4 power sourcing equipment (PSE) and powered devices (PD), working over four pairs as shown in Figure 1. The standard also improves the mutual identification process between the PSE and the PD. Additional fea- tures include automatic class functionality, extended power capability if channel length is known, and low standby power support. Powered Device Switch/Midspan Data Pair Spare Pair Spare Pair Data Pair Data Pair Spare Pair Spare Pair Data Pair Powered Device Switch/Midspan Data Pair Spare Pair Spare Pair Data Pair Data Pair Spare Pair Spare Pair Data Pair PD PSE PD PSE POE and POE+ (IEEE802.3af/t) Powered Device Switch/Midspan Data Pair Spare Pair Spare Pair Data Pair Data Pair Spare Pair Spare Pair Data Pair Powered Device Switch/Midspan Data Pair Spare Pair Spare Pair Data Pair Data Pair Spare Pair Spare Pair Data Pair PD PSE PD PSE IEEE802.3bt