Indoor LED lighting technology based on vision and information inversion
As an emerging light source, LED has received extensive attention. At present, the research focus of the industry is on the improvement of its optical and thermal properties. This paper attempts to explore the superiority of LEDs for indoor lighting from the perspective of visual ergonomics and intelligent lighting.
As a light source that has developed rapidly in recent years, LED has significant advantages over traditional light sources, such as long life, high light efficiency, fast response, artistry, safety, flexibility and reliability. However, the main application of LED is still in the field of backlights and outdoor lighting such as street lamps and landscape lights. In the field of indoor lighting, there are still some shortcomings, such as high cost, poor color rendering, high brightness and consistency. In terms of the advantages and disadvantages of LED integration, from the application point of view, in indoor lighting, we should make full use of the advantages of LED and avoid its shortcomings. In the future, LED will be widely used in indoor lighting, and its technology combined with lighting control can achieve better results.
The key to combining LED with lighting control
Lighting control is a distributed lighting measurement and control system composed of computer, wireless communication data transmission or power carrier communication technology and electrical control technology to achieve the adjustment of brightness and timing of lighting, timing control, regionalization and personalization of lighting scenes. Control [1]. Generally, the bus control mode is adopted, which requires that the controlled luminaire can be digitally dimmed and has a good fast response characteristic.
At present, the lighting control is generally in the form of a bus, digitally dimming a halogen lamp, a fluorescent lamp with a digital dimming rectifier, etc., realizing dimming of the combination of lamps in the area, adjusting the ambient illuminance, or adjusting the color temperature by fluorescent lamps of different color temperatures, and lighting performance. The technique is still relatively simple. The advent of RGB mixed-light LED technology makes it possible to adjust the ambient light color and is very convenient. LED adjustment generally adopts PWM duty cycle adjustment mode, which can be conveniently implemented in digital form. As long as the digital interface is reserved on the drive, communication with other digital systems is easy, making system construction very simple. As shown in Figure 1.
The key to combining LED with lighting control is to use the flexibility and artistry to choose the right system topology. The LED lighting system generally has a large number of nodes, a large number of communication channels, a large system scale, and a high requirement for system response speed.
At present, many lighting control systems use RS485 bus control, which is a control mode based on master-slave structure. The controller sends control commands or queries sensor detection values ​​through master-slave response mode and timing inspection. RS485 only specifies the physical layer, which is convenient for customizing communication with the system. The practice in the field of lighting control is that each LED luminaire has a built-in MCU control and is connected to the bus via an RS485 interface chip. This method is simple and reliable, but the application layer standards are not uniform, and the engineering application configuration is inconvenient.
Another widely used control method based on DALI bus, which addresses the nodes in the system, the data signals are composed of instructions and addresses, and different lighting units can be flexibly grouped to realize multiple combinations. Set up 16 lighting scenarios, the system's reliability, stability, and compatibility are very good. However, there are no more than 64 DALI network nodes, which is not convenient for large-scale lighting applications. In addition, the refresh rate in the DALI system is slow, which limits the artistic performance of the LED.
In the field of LED control, the DMX512 protocol is widely used. The protocol is based on frames. Each frame of data consists of a sync header and 512 bytes. The data is transmitted and received in a serial manner conforming to the EIA 485 standard. It is 250KBit/s. This mode has a fast transmission speed and a large system scale, and is widely used in stage lighting and outdoor LED landscape lighting. However, the protocol is a one-way transmission mode, and the system cannot receive the luminaire information or the external sensor signal, and cannot meet the closed and intelligent requirements of the indoor lighting.
After research, we believe that a distributed topology based on Zigbee wireless communication can be used in indoor lighting. Operating frequency is 2.4GHz wireless frequency band, can accommodate more than 60,000 nodes at the same time, control range up to 10,000 meters, can be used in home, hotel, commercial lighting and other indoor lighting places [2], Zigbee network has low power consumption The advantages of self-organization and convenient positioning are quite advantageous for building wireless sensing and lighting control networks.
The system uses a star network structure controlled by a central controller. The main controller performs the setting of the lighting scene and the processing of the feedback information, receives the data of each sensor through the wireless network, performs related algorithm calculation on the collected data, obtains the adjustment instruction of each node, and sends the instruction parameter to the network through the network. Corresponding node. In addition to the luminaire nodes and sensor nodes, there is also a hand-held remote control for simple control operations.