Theater lighting design is successful, the stage lighting is handled properly as a symbol. Stage lighting should not only illuminate the actors, let the audience see the facial expressions, demeanor and movement, but more importantly, make full use of lighting technology and mobilize the lighting operation and other means to enhance the artistic effect so that the audience has the immersive feeling. Stage lighting installation site, function and lighting configuration Stage lighting according to their use of the function is mainly divided into two types: dimmable dimming circuit; not dimming direct amplifier circuit.

Stage lighting

A. General lighting: refers to the top light and extended stage as part of the ceiling light hanging light ring, and the grapevine rack, the bridge lighting.

b. Accent lighting: refers to low-profile surface light, inner (outer) sidelight, turntable flow of light and music for the instrument set up in the pool for light, slap, pillar, sidelight, Low voltage socket.

C. Decorative lighting: Refers to the days of light, to the light and laser lights used on the stage, chasing light, mobile music fountain and all kinds of computer lights.

Stage lighting control system structure module

Man-machine interface module

The function of the man-machine interface module is mainly to receive the control instructions of the control personnel, generally it can be realized with a simple industrial control panel. After receiving the instruction, the module does not translate the instruction, and directly transmits the key information to the host computer module through the RS485 bus.

2. Master control module

The main control unit is the core part of the entire lighting control system, responsible for the upper control interface and the underlying hardware control module. After receiving the key information sent by the control module, the host computer translates the data to form a binary control instruction. The host computer then forms a complete frame of data according to the received instruction and the related control module address and transmits the data through the RS485 bus To the downlink bus, the bottom control module and then press the address to obtain their own data matching.

3. The underlying control module

The bottom control module is a hardware device that directly controls the stage lighting action. As the number of stage lighting is generally more, so the number of control modules are generally between 10 to 20, all the control modules are anchored on the same bus, independently programmed with each other. When the host computer to send data to the bus, all control modules receive the data information, and according to the frame structure contains the address information to resolve their own instructions and execute it.

The three modules communicate with each other using RS485 bus to transmit data at a fixed baud rate. Stage lighting control system control module its main function has 2 aspects: First, and the master communication, receiving instructions from the upper. Second, according to the instructions to control the hardware circuit to achieve the control of the light action. The following two modules are introduced.

Stage lighting receive communication module

1. Communication options

As the control signal is relatively simple, here is the serial communication. This method is more convenient to use, less demanding on the peripheral devices, half / full duplex method is free to choose. The most important thing in asynchronous methods is the setting of the baud rate. Too high, will increase the burden on the microcontroller, or even unrealizable; too low, will affect the response speed of the entire operation.

2. Transmission standard selection

At present a variety of transmission standards, but each has its own advantages and disadvantages. Due to the lighting system in the studio, a variety of audio, electrical interference will be a lot, therefore, the transmission method chosen should be relatively strong anti-interference. From this consideration, the communication distance of tens of meters to thousands of meters, the use of RS485 bus transmission is ideal. 485 bus uses two transmission lines to balance the transmission and differential reception, which has the ability to suppress common-mode interference, coupled with the receiver with high sensitivity, can detect as low as 200mV voltage, it can greatly enhance the anti-interference ability of transmission , The transmission signal can be restored beyond km.

RS485 bus easy to use, with a pair of twisted pair to achieve multi-site network consisting of distributed systems. It is simple equipment, low prices, can communicate long distances, it is widely used in engineering projects.

3. Transceiver selection and use

The 485 bus is transmitted on the 485 level, while the microcontroller and the host computer can only identify the TTL level. In this way, between the two must have a dedicated chip design conversion circuit, which is the transceiver. Many different types of transceivers can be converted according to the needs of different levels, in applications, in order to reduce the interference between the communication circuit and other circuits, you must have isolation level. Although you can directly use the more upscale 485 transceiver with isolation level, but from the price considerations, or design their own isolation circuit is better.

Here the use of optocoupler devices, separate power supply and other means to achieve isolation. In the use of M ax483 is to pay attention to enable the end of the control. The transceiver is in receive state only with / RE = 0, and portability, avoiding unnecessary duplication of effort. The module functions in the management and hardware drivers and basic function interface layer belong to Opentv middleware. Module Functionality Management is a function for the management and control of audio, video and channel operations written for the convenience of user applications in accordance with certain middleware function interface standards.

The underlying interface for driving and basic functions is the OpenTV middleware. This level of software programming to be based on the specific hardware driver to make the appropriate changes in order to provide a unified management function module driver interface functions.

4. Operating system and hardware driver layer

The system used by the operating system is pSOS; hardware-driven layer for the main hardware modules, provide the appropriate driver. The main drivers include: Kernel module, is mainly responsible for providing the operation of the process, such as the process of creating and deleting, etc .; interface module, including the operation of the IC interface control, RS-232 serial communication, smart card control, etc .; audio module; OSD module; demultiplexing module; decoding module; Flash driver module; TUNER driver module.

The final step is set-top box system debugging: The system software is compiled on the basis of the pSOS compiler. The entire test block diagram shown in Figure 3. The system uses a TS code stream generator as a set-top box debugging TS source.

The TS stream is modulated into the channel by the QAM modulator, 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. TS stream can also be sent directly through the interface in the system board to debug the source code separately. System PC test is carried out on the PC + WINDOWS2000 platform. The system running software is in pSOS real-time operating system environment.

The compiled executable file is downloaded from the serial port to the RAM on the hardware platform through the emulation RoM, and then the system reads out and executes the program from a fixed address in the RAM. As the hardware platform does not provide network port, pSOS comes with online debugging capabilities can not be achieved, debug information can only be obtained through the output of the program during the implementation of information.