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Designers of smart homes, offices and factories are constantly seeking new ways to improve the efficiency of the systems used to deliver and manage building facilities. Historically, data networks and power networks have been installed separately, each with the purpose of performing distinctly different functions, but this has required the installation of two completely different cable types in the building structure.
The development of Power over Ethernet (PoE) now offers a way to reduce the need for AC power cables by allowing some devices (such as cameras, phones, wireless routers) to draw power from their data lines. One area that has received more attention as a potential application for PoE is lighting.
In this article, we examine the role that connected lighting systems can play in the deployment and management of smart building systems and consider the potential relationship between lighting and building automation (Figure 1). We also review standard approaches to their design and explain how new applications for connected lighting systems can be enabled while greatly simplifying their design. 1. Smart lighting plays a key role in building automation Connected Lighting and Building Automation
Once inside a building, lighting is ubiquitous, whether it is for domestic, commercial or industrial use. Inefficient incandescent and halogen bulbs have been largely replaced by lower wattage and more efficient LEDs in recent times. However, the method of powering the lights has not changed significantly, and cables are still laid wherever the light fixtures will be installed.
Since LEDs require DC power, the luminaire must include an AC-DC transformer and possibly a DC-DC converter to provide the required voltage levels to the LEDs and ultimately the control current. This approach considers the luminaire to be responsible for only one function – lighting – and while providing efficient lighting, it completely ignores the fact that the luminaire is ideal for hosting a range of other smart building functions.
The first step to leveraging ubiquitous luminaires is to provide them with digital connectivity. By digitizing individual luminaires and interconnecting them into a unified system, they can serve as a backbone, ideal for hosting IoT applications throughout a building.
In a connected lighting system, each luminaire has a unique IP address that enables two-way data communication over the building’s data network. Connected lighting is an obvious candidate for transmitting IoT data in homes, offices, and factories because the electrical and data communication networks are already in place. This approach could allow connected luminaires to have additional sensor capabilities and countless applications.
By integrating different types of smart sensors (temperature, humidity, proximity, air quality, etc.), connected lighting systems can simultaneously capture data on occupancy and other environmental indicators in rooms throughout the building as actionable inputs to smart building automation systems. This information helps optimize spaces, improve operational efficiency, and help maximize comfort within the building. The information collected about occupant behavior can also be used for energy management.
Implementing connected lighting systems
One way to add digital connectivity to light fixtures is to include Wi-Fi radios. However, because wireless RF signals are subject to varying degrees of attenuation, depending on their location and the building materials between them and the nearest access point, it can reduce the speed and reliability of data communications.
A better approach would be to provide an Ethernet interface to each fixture. But this would require running Cat5/6 twisted pair cabling to each fixture, doubling the amount of wiring (assuming power wiring has been planned) and increasing installation cost and effort.
Ideally, connected lighting should require only one cable to power LEDs, cameras, and smart sensors, and transmit their bidirectional data to a remote control. This would eliminate the need to run separate power cables to each fixture—a significant advantage. PoE can transmit DC voltage to power devices and network data at the speed of implemented Ethernet standards, making it ideally suited for this task.
Fully integrated solution
PoE-connected luminaires use separate LED driver ICs and PoE interface ICs to deliver power over Ethernet. Taking a different approach, Onsemi developed the NCL31010, which combines these two components in a single package that can serve as the basis for a fully connected and managed lighting system (Figure 2). 2. Onsemi's NCL31010 PoE interface LED driver is targeted at networked lighting systems The device is PoE compliant (capable of delivering over 90 W of system power) and IEEE802.3bt/at/af certified. Its buck LED driver is 97% efficient and supports high bandwidth, high linearity analog and PWM dimming (down to zero current). Spread spectrum technology helps reduce the amount of conducted and radiated EMI.
Two auxiliary DC-DC converters in the device can power microcontrollers and other peripherals such as sensors. High-precision metering and diagnostic functions are also included for measuring input and output current and voltage, LED or system temperature, DC-DC voltage and current. One application of the device is low data rate visible light communication (VLC). In this application, digital data is modulated onto the LED light emitted from the luminaire, which becomes a location beacon in indoor positioning systems such as YellowDot. The modulated data of VLC is imperceptible to the human eye.
Lighting for the future
PoE-based connected lighting provides the most flexible and efficient lighting for all types of future smart buildings, with LED luminaires controlled via data networks and powered via data cabling. By combining the use of sensors, smart luminaires and smart control systems, smart buildings will provide levels of comfort and efficiency that cannot be achieved with traditional lighting. Those who manage smart building systems will also enjoy lower costs during construction and once the building is fully occupied and operational. |
