Efficient and energy-saving connected lighting system

Globally, lighting is one of the largest energy-consuming applications. As costs and environmental concerns increase, it is becoming more and more important to find ways to apply technology and innovation to optimize the energy efficiency and functionality of lighting and reduce its power requirements.

With intelligent, network-connected lighting control, it can meet the demand for energy efficiency and more functions. The market capacity of smart lighting control in residential applications is four times that of industrial buildings. Together they constitute the fastest growing part of the Internet of Things (IoT). Generally, residential networked or networked lighting systems are much simpler than industrial lighting systems, with a smaller bill of materials (BoM) and lower cost.

The simplest networked lighting can only be controlled remotely, or the function of turning on and off the lights at a fixed time within a day. Furthermore, the networked lighting system can add additional functions, such as LED dimming and color control.

In addition, there are a variety of options to choose from, especially adding sensors to complex environments, such as controlling the lighting based on ambient light levels or detecting whether there are people in the room. For industrial applications, sensors such as temperature, humidity, and light levels are invaluable because their data can be used to control lighting and help system maintenance.

Today’s ubiquitous smartphones mean that lighting systems can provide sophisticated user interfaces on mobile devices, saving the cost of dedicated screens or complex buttons.

Connect everything together

Of course, the most important part of a smart lighting system is the way everything communicates and the connection technology used. The connection requirements include the connection between each device in use when the system is set, and the communication between the building management system and the controlled lighting.

First of all, we must determine whether we want to use a wired or wireless connection. For battery-powered lighting, the main benefit of wireless is that no wiring is required, which results in significant cost savings. Mainstream wireless protocols used in lighting control include Bluetooth Low Energy (BLE) and Zigbee Green Power, and Near Field Communication (NFC) can be used for setup and configuration.

For mains lighting, wireless is also a good choice because it avoids the need to deploy a second data line in addition to the power line. In addition, Power over Ethernet (PoE) also means that it is now possible to use one cable for both power supply and network connection.

Apply Ethernet power supply to lighting system

The PoE 2 standard (802.3bt) can provide up to 90W of power-this is sufficient for LED-based lighting, because the power consumption is lower than traditional incandescent bulbs.

A practical example is a 60W networked lighting solution, which uses an integrated controller compliant with IEEE 802.3bt to supply power through an Ethernet cable. The solution can support up to two LEDs in series, and has two LED channels, using ON Semiconductor's FL7760 high-side sensing, constant current step-down controller.

Through this configuration, the PWM signal can use 1.3MHz pulse width modulation (PWM) frequency to control 0-100% dimming. Brightness control is provided by Bluetooth low energy radios such as RSL10, which is suitable for RF-activated energy harvesting schemes. The power supply voltage of RSL10 is provided by a simple high-voltage LDO.

The solution can achieve more than 90% energy efficiency, ensuring that almost all the energy generated by the PoE controller is converted into lighting, so that the design can provide up to 6,000 lumens. Such performance can meet the current needs of lighting solutions that minimize power and provide networking.

Bluetooth low energy mesh network

Replacing simple point-to-point communication with wireless mesh network technology is very suitable for industrial lighting applications; because it supports interconnection between a large number of devices and external connections. Bluetooth Low Energy now has the ability to create a mesh network of up to 32,000 devices, with built-in standard security, which can greatly simplify the setup of an expanded range of lighting solutions.

In a mesh network, each node can be a light and has one or more other functions at the same time. Each node is indispensable to the functionality of the entire mesh network framework. The relay node can forward the received message, thereby expanding the network almost unlimitedly when necessary.

Proxy nodes can communicate with other nodes that do not support Bluetooth low energy and bring them into the mesh network, while "friend nodes" are those that operate in low power consumption mode. Other nodes store information. The low-power node will poll the friend node periodically to obtain information, and therefore it is more energy efficient.

Security is paramount in any networked system, and Bluetooth low energy mesh networks are no exception. All messages are encrypted/authenticated and obfuscation, making it difficult to track the messages, thereby preventing replay attacks. In the Bluetooth low energy protocol, there is a procedure for changing the security key and a security procedure for adding nodes to the mesh network; deleting nodes from the Bluetooth low energy network can also be done safely to prevent "trash can attacks "(Trashcan attack).

Another alternative to Bluetooth low energy mesh networking is Zigbee Green Power, which has a longer history. Based on IEEE 802.15.4 MAC and PHY, Zigbee has been applied to lighting products such as IKEA, Xiaomi and Philips. This environmentally friendly, low-power protocol conforms to new trends and is easy to implement, deploy and reconfigure in buildings.

Bluetooth Low Energy (current version) has a local mesh network model and uses a smart phone to connect to the cloud, while Zigbee relies on Dotdot or Zigbee Cluster Library (ZCL) and uses a dedicated gateway. Only a few mobile devices support Zigbee .

For example, ON Semiconductor’s NCS36510 component can help easily realize energy harvesting switch settings. This low-power integrated SoC provides advanced power management and IEEE 802.15.4 transceivers. Support the use of minimal external components to design a complete and secure wireless network.

Networked lighting platform

In order to make development easier and faster, ON Semiconductor has created a modular development kit for industrial LED lighting solutions. The networked lighting platform includes RSL10 system-in-package networked modules, which can realize on/off, dimming and programming controls. The RSL10 FOTA mobile application can be downloaded in Google Play and Apple's application store, and support for wireless firmware upgrades has been added. The RSL10 Sense and Control application enables developers to control and monitor environmental sensors and actuators from mobile devices. The application examples provided by the CMSIS package support the addition of new functions and further customization.

The networked lighting platform supports two LED light strings. The LED driver board has two FL7760 drivers, one for each LED string, and the power of each string is up to 70W. Overall, the system can provide up to 70W, 7,000 lumens of power, if you choose a more energy-efficient LED (such as 150 lumens/watt), you can provide more power. The choice of power module means that the platform can be powered by AC-DC power or PoE.

Flexibility and control

Even if the system is relatively simple, connected lighting can also bring the key advantage of reducing energy consumption, thereby saving costs. This makes it an ideal choice for many application cases in industrial and residential environments. With the development of connected lighting functions, we are seeing new applications continue to emerge, such as medical treatment and agriculture.

These applications require an optimized control system to keep the bill of materials cost low and to strike a balance between precision features and simplicity. Developers use design kits with EMS-friendly BoM, such as ON Semiconductor's connected lighting platform, no matter what the application, it can save the time and reduce the risk of building LED lighting systems.