With the rapid development of digital technology in all walks of life, professional stage lighting field also gradually into a comprehensive digital era.
Of the current domestic large outdoor performances, such as square party, solo concert of large and medium-sized and large and medium-sized indoor stage (including studio) used in professional lighting equipment, all the tone light platform, the amount of control, computer, digital silicon box in the light, color changer light, follow spot color changer, laser, etc., the vast majority are adopted digital control. And connected between the devices to achieve accurate control, realize the whole stage lighting, and is for the general lighting control headaches.
The modern stage lighting designers put forward a new management concept of stage lights, unified management, centralized control. Is more than one function effect of different digital lighting equipment connected by a digital dimming control. Such as we put the digital dimming silicon box, digital color changer, light, color changer light effect of computer, digital machine, bubble machine, etc. All connections on a computer console, to be controlled by a lighting engineers. Proved to be feasible. Here is involved in the industry are known as the DMX512 signal transmission system.
The abbreviation of DMX is Digital Multipiex. Translation for the digital multiplexing protocol, defined by the American society for theater technology (USITT), has received the world's recognition and observe the production stage equipment manufacturers, as a widely used digital light data agreement; That is in the link of each controlled unit to conform to the requirements of this agreement, to achieve the centralized control.
DMX is based on RS422 / RS485 serial transmission, data transfer rate of 250 kbit/s largest loop control for 512 (of course, there are 1024\2048 loop, but that was in 512 based on the complex). Because the DMX signal transmission rate is high and the special needs of application environment, DMX signal, signal transfer interface and signal transmission between each unit has a strict requirements, to ensure the accuracy of signal transmission.
DMX allows effective transmission distance is 250 m. Condition is to use high quality signal lines, and should put it in when construction independent shielding groove; If mobile performance or external interference, want to reduce the length of the signal corresponding to shorten transmission distance. If the engineering requirement of signal transmission distance is greater than 250 m, should be equipped with in line with the 512 agreement signal amplifier. Most often a DMX512 interface can drive 32 digital equipment; If all of the receiver DMX487 integrated block is used to receive signals, then a DMX output interface can drive 128 digital devices.
If a DMX512 system equipment more than 32, is equipped with signal distributor, it is the function of signal isolation, signal distribution, signal amplification. A signal distributor from two to six outlet (imports have 4 ~ 8 outlet), a signal input port, a loop interface, it can satisfy the small and medium stage or studio lighting system, signal distribution; If in larger square (such as the stadium), is equipped with many sets of signal distributor to meet the needs of the system.
In our practice, the stage like this in multi-cell centralized control link with a conform to the DMX512 protocol signal distributor, in addition to signal amplification, prolong the manipulation of the distance the disintegrated, there's another advantage is: if a lighting equipment failure (such as leakage, short circuit, etc.), the distributor has a photoelectric isolating device, can effectively protect the lights in the link.
DMX link in a multiple devices unit, finally a lighting device interface signal should be equipped with "terminal", in an impedance matching, eliminate clutter reflection in the signal transmission and purify the signal component. Then ensure the normal order of the DMX512 signal transmission system is an important link. "Terminal" specific connection is as follows: in a context of five core plug welding between 2 ~ 3 feet a Ω 1/4 90 ~ 120 W small metal film resistor, the size of its impedance should refer to the instruction manual dimming units. Well, after plug it into the signal output end of the last device. There are some digital lighting device itself has a terminal switch, if the equipment placed at the end of the link, should set the switch to allow, otherwise should be moved to the location of the invalid. Use five core plug-in DMX agreement calls for the link. Only three core in the construction, namely: 1, 2, 3, 4, 5, the core is empty. The lighting system most of the imported equipment are the five core interface.
To sum up, do a good job in large lighting system of centralized control, need clear concept construction personnel, standard installation to ensure system reliable operation. To ensure a large gala, major conference scene lighting effects such as well.