The success of theater lighting design is marked by the proper handling of stage lighting. Stage lighting should not only illuminate the actors, so that the audience can see 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, so that the audience has a sense of being on the scene. The installation position, function and lamp configuration of stage lighting Stage lighting is mainly divided into two types according to its use function: dimming circuit with dimmable light; direct circuit with non-dimmable light.
The way of stage lighting
a. General lighting: Refers to the ceiling light and the pendant light ring of the protruding stage as part of the top light, as well as the lighting on the grape trellis and the overpass.
b. Accent lighting: refer to surface light, ear light, column light, side light, foot light, flow light and low-angle surface light of the protruding stage, internal (external) side light, flow light of turntable and music score light set in the orchestra pit low-voltage socket.
c. Decorative lighting: refers to sky lighting, ground lighting, and laser effectors, chasing lights, flowing music fountains and various computer lights used on the stage.
Structural module of stage lighting control system
1. Man-machine interface module
The function of the human-machine interface module is mainly to receive control instructions from the controller, which can generally be realized with a simple industrial control panel. After the module receives the command, it does not translate the command, and directly transmits the button information to the main control module through the RS485 bus.
2. Main control module
The main control unit is the core part of the entire lighting control system, responsible for the connection between the upper control interface and the underlying hardware control module.
After receiving the key information sent by the control module, the main control computer translates to form a binary control command; then the main control computer composes a complete frame of data according to the received command and the relevant control module address, and transmits it through the RS485 bus On the downlink bus, each bottom control module obtains its own data according to address matching.
3. Bottom control module
The underlying control module is a hardware device that directly controls the action of stage lighting. Since the number of stage lights is generally large, the number of control modules is generally between 10 and 20. All control modules are connected to the same bus and programmed independently of each other.
When the master 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 three modules use the RS485 bus to communicate with each other, and transmit data at a fixed baud rate. The main functions of the stage lighting control system control module are two aspects: one is to communicate with the main control unit and receive instructions from the upper layer.
The second is to control the hardware circuit according to the instruction to realize the control of the light action. The two modules are described below.
Stage lighting receiving communication module
1. Communication method selection
Since the control signal is relatively simple, the serial communication method is adopted here.
This method is more convenient to use, and the requirements for peripheral devices are not high, and the half/full duplex method can be freely selected. The most important thing in the asynchronous method is the setting of the baud rate. If it is too high, it will increase the burden of the single chip microcomputer, and even cannot be realized; if it is too low, it will affect the response speed of the entire operation.
2. Transmission standard selection
There are currently many transmission standards, each with its own advantages and disadvantages. Since the lighting system is used in the studio, there will be a lot of interference from various audio and electrical appliances. Therefore, the selected transmission method should be relatively strong in anti-interference. Considering this, when the communication distance is tens of meters to thousands of meters, it is ideal to use RS485 bus for transmission.
The 485 bus uses two transmission lines, adopts balanced transmission and differential reception, so it has the ability to suppress common mode interference, and the receiver has high sensitivity and can detect voltages as low as 200mV, so it can greatly enhance the anti-interference ability during transmission , the transmission signal can be recovered at kilometers away.
The RS485 bus is easy to use, and a pair of twisted-pair wires can realize multi-station networking to form a distributed system. It is simple in equipment, low in price, and capable of long-distance communication, so it has been widely used in engineering projects.
3. Transceiver selection and use
The 485 level is transmitted on the 485 bus, but the single-chip microcomputer and the main control microcomputer can only recognize the TTL level. In this way, there must be a dedicated chip design conversion circuit between the two, which is the transceiver. There are many types of transceivers, and different levels can be converted according to needs. In applications, in order to reduce the interference between communication circuits and other circuits, isolation levels must be provided.
Although you can directly use a higher-grade 485 transceiver with an isolation stage, considering the price, it is better to design an isolation circuit by yourself.
Here, optocoupler devices, separate power supply and other means are used to achieve isolation. Pay attention to the control of the enable terminal when using Max483.
The transceiver is in receiving state only when /RE = 0, and portability avoids unnecessary duplication of work. The module function management layer, the hardware driver and the basic function interface layer belong to the Opentv middleware. The module function management layer is a function related to audio, video and channel operation management and control written in accordance with certain middleware function interface standards for the convenience of writing user applications.
The driver and basic function interface layer is the bottom layer of OpenTV middleware. The software writing at this level should be modified according to the specific hardware driver, and the purpose is to provide a unified driver interface function for the module function management layer.
4. Operating system and hardware driver layer.