This paper introduces the development and composition of stage lighting, the structure of stage lighting control system, the position and function of equipment installation, and expounds the relevant technical knowledge in power distribution, control and engineering design of stage lighting.
Keywords: stage lighting, control system, communication module
Since the appearance of the stage, stage lighting has become a part of the stage. Stage lighting pays attention to four elements: vision, realism, aesthetics and expression. Has evolved for many years. Gradually developed into a more perfect and advanced lighting system today. The first prosperous period of drama appeared in ancient Greece more than two thousand years ago. The theaters at that time were all open-air or semi-open-air. The lighting of the stage depends on the huge "lamp" in the sky-the sun, so it can only be performed during the day. However, the need for rest and entertainment at night, the vulnerability of outdoor performances to the weather and the development of drama have made stage lighting a problem that people must solve.
Proper treatment of stage lighting is a sign of successful design of theater lighting. Stage lighting should not only illuminate the actors, let the audience see the facial expressions, demeanor and movements clearly, but more importantly, make full use of lighting technology, mobilize lighting operations and other means to enhance the artistic effect and let the audience feel immersive. The installation position, function and lamp configuration of stage lights are mainly divided into two types according to their use functions: dimmable dimming circuits; Non-adjustable optical direct amplifier circuit. Stage lighting methods are generally divided into three types:
A. General lighting. Refers to the ceiling lamp and the hanging lamp ring that extends the stage as part of the ceiling lamp, as well as the lighting on the grape trellis and overpass.
B. accent lighting. Refers to the surface lights, palm lights, column lights, side lights, foot lights, streamers, low-angle surface lights, inside (outside) side lights, turntable streamers, and low-voltage sockets for connecting music lights set in the orchestra pit.
C. decorative lighting. It refers to sky lighting, ground lighting, laser effector, spotlight, mobile music fountain and various computer lights used on the stage.
Stage lighting is so important that the above description is relatively simple. Let's analyze it from a technical point of view:
The structure of stage lighting control system can be roughly divided into three modules; Man-machine interface module, main control module and bottom control module. These three modules communicate with each other through RS485 bus and transmit data at a fixed baud rate.
The function of the man-machine interface module is mainly to receive the control instructions of the controller, which can generally be realized through a simple industrial control panel. After receiving the instruction, the module does not translate the instruction, but directly transmits the key information to the main controller module through RS485 bus.
The main controller is the core part of the whole lighting control system, which is responsible for connecting the upper control interface and the lower hardware control module. After receiving the key information sent by the control module, the master computer translates it into a binary control instruction; Then the upper computer composes a complete frame of data according to the received instructions and the addresses of related control modules, and transmits it to the downlink bus through RS485 bus, and each bottom control module obtains its own data according to address matching.
The bottom control module is a hardware device that directly controls the action of stage lighting. Because the number of stage lights is generally large, the number of control modules is generally between 10 ~ 20, and all control modules are linked on the same bus and programmed independently of each other. When the host computer sends data to the bus, all control modules receive the data information, and analyze their own instructions according to the address information contained in the frame structure and execute them.
The control module of the stage lighting control system mainly has two functions: one is to communicate with the main controller and receive instructions from the upper level. The second is to control the hardware circuit according to the instruction to control the lighting action. The following two modules are introduced respectively.
The following is the receiving communication module:
① communication mode selection
Because the control signal is relatively simple, serial communication is adopted here. This method is easy to use, with low requirements for peripheral equipment, and the semi/full dual-function mode can be freely selected. The most important thing in asynchronous mode is the setting of baud rate. Too high, it will increase the burden of single chip microcomputer, or even impossible; Too low will affect the response speed of the whole operation.
② Selection of transmission standard
At present, there are many transmission standards, but each has its advantages and disadvantages. Because the studio uses a lighting system, there will be a lot of interference from various audio appliances, so the transmission mode chosen should be strong in anti-interference. Therefore, when the communication distance is tens of meters to thousands of meters, it is ideal to choose RS485 bus for transmission. 485 bus uses two transmission lines and adopts balanced transmission and differential reception, so it has the ability to suppress * * * mode interference. In addition, the receiver has high sensitivity and can detect the voltage as low as 200mV, so it can greatly enhance the anti-interference ability in the transmission process, and the transmitted signal can be recovered from thousands of meters away.
RS485 bus is easy to use, and a pair of twisted pairs can be used to realize multi-station networking and form a distributed system. Because of its simple equipment, low price and long communication distance, it has been widely used in engineering projects.
③ Selection and use of transceiver
The 485 level is transmitted on the 485 bus, while the single chip microcomputer and the main control microcomputer can only recognize the TTL level. Therefore, there must be a special chip to design the conversion circuit between them, which is the transceiver. There are many kinds of transceivers, and different levels can be switched as needed. Here, only 485-TTL level switching is needed. Use Compare-g. M ax48x series and Max 148x series with isolation. In application, in order to reduce the interference between communication circuit and other circuits, isolation stage is necessary. Although you can directly use the high-grade 485 transceiver with isolation stage, considering the price, it is better to design your own isolation circuit. Here, photoelectric coupling devices and independent power supply are used to realize isolation. When using M ax483, pay attention to the control of the enabling terminal. The transceiver is in the receiving state only when /re = 0, and it is portable, thus avoiding unnecessary repetitive work. The module function management layer, hardware driver and basic function interface layer in Figure 2 belong to Opentv middleware. The module function management layer is about the functions of audio, video and channel operation management and control. In order to facilitate the writing of user applications, it is written according to certain middleware function interface standards. Driver and basic function interface layer is the bottom part of OpenTV middleware. The software programming of this layer should be changed according to the specific hardware drivers, so as to provide a unified driver interface function for the module function management layer.
③ Operating system and hardware driver layer
The operating system used in this system is pSOS；; The hardware driver layer mainly provides corresponding drivers for each hardware module. The main drivers include: kernel module, which is mainly responsible for providing operations on processes, such as the creation and deletion of processes; Interface module, including I C interface operation control, RS-232 serial communication, smart card control, etc. Audio module; Video module; OSD module; Demultiplexing module; Decoding module; Flash memory drive module; Tuner driver module.
The last step is the debugging of the set-top box system: the software of this system is compiled on the basis of pSOS compiler. The whole test block diagram is shown in Figure 3. The system uses the TS code stream generator as the debugging TS source of the set-top box. The TS stream is modulated onto the channel by QAM modulator, and the QAM signal is sent to the front end of the set-top box for QAM demodulation, and then sent to the system board for source decoding. The TS stream can also be sent directly through the interface in the system board to debug the source decoding separately. The test of system PC is carried out on PC+WINDOWS2000 platform. The system running software runs in the real-time operating system environment of pSOS. The compiled executable file is loaded from the serial port to the RAM on the hardware platform through the emulation rom, and then the system will read and execute the program from the fixed address in the RAM. Because this hardware platform does not provide a network port, the online debugging function of pSOS cannot be realized, and debugging information can only be obtained through the output information in the process of program execution.
Therefore, the serial port on the hardware is connected with the serial port of the pc, and the debugging information when the program is running can be displayed on the screen of the pc, so that the programmer can get the needed debugging information.
[conclusion]
Nowadays, the control of lighting system has developed from manual operation to computer control. It also puts forward realistic requirements for dancers to improve their computer level. I believe that with the continuous improvement of lighting system and the improvement of dancers' quality, our stage will be more contemporary. More attractive and exciting.
References:
[1] Li Haidong Building Electrical Science and Technology Press, 2002.
[2], Dean Liu, Yao Han, Stage Lighting, Machinery Industry Press, 2004.
[3] Dou Weiping, Ma Yingjun, Color in Visual Design, Southeast University Press, 200 1
[4] Zhang Wenjie Television Lighting Science and Technology Press, 2005.