Computer moving head light is a high-tech product integrating electronics, mechanics and optics. Qualified computer moving head lamp must be stable and reliable, excellent light efficiency, accurate positioning, good heat dissipation, and the lamp body and material structure meet the ergonomic requirements. Computer moving head lights can be divided into 250W, 575W, 1200W and other varieties from the use of power. Among them, 1200W is the main lamp type of professional performance venues. This article focuses on the analysis of the construction principle of 1200W moving head light. Generally speaking, the moving head computer lamp is composed of three major systems: optical, mechanical, electrical and program control. The three systems are interrelated and organically combined to meet the needs of light, color, speed, direction, effect, heat dissipation, noise, positioning and other elements.
1. Optical system
The optical system design is the most important consideration for the luminous flux utilization of the light source. Specific performance indicators include light intensity, uniformity, saturation, and spot size. There are two factors that affect the above indicators, one is the light source, and the other is the structure and material selection of the optical system. At present, domestic and foreign manufacturers and users basically recommend OSRAM or PHILIPS 1200W short-arc double-ended metal gas discharge lamps. It is characterized by compactness, high brightness, high color temperature, good color rendering and the light source can maintain a relatively stable color temperature in the process of dimming. The disadvantage is that the delamination of the filler in the lamp, that is, the color banding of the filler in the arc imaging or condensation in the arc tube, forming a shadow effect, needs to be controlled in the optical structure design to a minimum. In the optical structure, in order to obtain a uniform mixed beam, a parabolic reflector can be used, and to collect divergent or narrow beams, a reflector with scale processing or surface texture should be selected. A reflector system made using specular reflective materials is better than a refractive system. When several beams need to be obtained from a single light source, a refractive system combining prisms or lenses can be used. At present, the optical design of 1200W moving head computer lamps at home and abroad adopts the method of lens combination, which is composed of aspheric (i.e., parabolic) quartz lenses.
The most important feature of a parabolic lens is that placing a point light source at the focal point will result in a parallel beam. In the design of the optical path, it is also necessary to consider the correlation between the light intensity distribution curve, the shape and the size of the light source, the aperture size of the reflective lens and the shape of the light source.
Second, the mechanical system
There is a wide range of mechanical systems, including materials, structure, mechanical properties, housing requirements, heat dissipation requirements, and more. The main considerations for the selection of lamp materials are: meeting the functional requirements of the lamp, the ease of manufacture and the economy. At present, the materials of international and domestic 1200W moving head lamps mainly include steel, plastic and aluminum alloy. On the premise of satisfying the overall function of the lamp, the structural model of the lamp is designed, which is divided into different parts and different materials. For example, Aceda-spot1200III1200W moving head lamp, the shell of the lamp body is made of plastic parts, and the support frame, base, side plate and end plate of the lamp body are made of aluminum alloy castings, stamping parts and car parts.
The structure of the lamp determines its mechanical properties, heat dissipation, strength, noise, weight and other factors. International and domestic 1200W moving head lamps are all using double-arm support structure, the horizontal rotation of the lamp body is up to 540°, the vertical rotation is up to 255°, and the base part must be strengthened to meet the hanging inverted requirements of the moving head lamp.
The mechanical properties of the lamp body are mainly reflected in the mechanical strength of the lamp body parts, so that the lamp body is not deformed, wear-resistant, corrosion-resistant, shock-resistant, and compression-resistant in the continuous and effective working time; The shell of the lamp must have strict waterproof, dustproof, anti-static, and moisture-proof requirements. According to the degree of dustproof and waterproof, the protection level requirements of different shells are divided: for example, the protection level of computer lights used indoors is usually IP20, and the protection requirements of outdoor computer lights are usually IP44.
The mechanical structure of the 1200W high-power computer lamp, the heat dissipation requirements are very important, if the heat dissipation system is defective, it will usually cause the electrical parameters to drift, the color film, the film cracks, the appearance of plaques, crashes, out of step and other serious consequences.
3. Electrical and program control part
1. The electrical characteristics and circuit design of the computer moving head lamp
Before the world's professional 1200W moving head computer lights, most of them use noble gas discharge bubble light sources. The start-up and stable operation of the gas discharge bubble depends on the design of the circuit type, the choice of electrical components such as power supply, ballast, etc. After the noble gas discharge bubble is activated, it generally does not need to stabilize for a long time, and in order to ensure stability, the difference between the maintenance voltage of the circuit and the instantaneous voltage of the bulb should be large enough throughout the AC cycle.
The start, stability, extinguishing and restarting of the light source should be designed according to the characteristics of the light source. The starting voltage of the rare gas discharge bubble is very high, and it is required to use transformers, starting devices, semi-resonance circuits, etc., to increase the instantaneous starting voltage. The stability of the light source after starting depends on the matching of the ballast and circuit parameters. The basic function of a ballast is to prevent runaway current and to make the light source work under its normal electrical characteristics. At present, manufacturers usually use two kinds of ballasts, one is inductive rectifier and the other is electronic rectifier. The advantage of inductance rectifier is good stability, and the disadvantage is that it is heavy, and it has high requirements for the strength, handling, loading and unloading of the lamp body; An electronic rectifier is essentially a power conversion circuit that changes the frequency, waveform, and amplitude of the input supply current. Its advantages are light weight, easy to load, unload and handle; The disadvantage is that the structural design requirements are high and the maintenance cost is high.
In the conventional circuit design, due to the high temperature generated during the operation of the gas discharge bubble, the saturated gas in the bubble forms vapor pressure resistance, and it is difficult to realize the re-trigger of the light source immediately, and the gas pressure in the lamp must be reduced to the cold state ＆#118alue before the restart can be triggered. At present, international and domestic production enterprises basically adopt conventional circuit design.
2. Program control part
At present, international and domestic computer lamps generally use DMX data format to write program files. The principle of DMX512: The speed of the DMX data stream is 250K, which is the standard 4 microseconds per bit. The data format of the DMX is divided into the following parts: 1) IDLE or NO DMX situation: when there is no DMX packet output, it will be a high signal; 2) BREAK: The start of the DMX packet is an 88 microsecond low output prediction {header}; 3) MARK AFTER BREAK (MAB): THE MAB IS A HIGH LEVEL OF 8 MICROSECONDS OR 2 PULSES AFTER BREAK; 4) STARTCODE: SC is the channel data at the beginning of the data stream, it has the same format as the channel data, generally 11 pulses or 44 microseconds; 5) MARK TIME BETWEEN FRAMES (MTBF): MTBF CAN BE 0-1 SECOND, LESS THAN 1 SECOND, AND THERE CAN BE MMBF BEFORE THE START OF EACH CHANNEL, WHICH IS HIGH; 6) CHANNEL DATA (CD): THE LOGICAL FORMAT OF THE CHANNEL DATA FRAME IS 1-512 OR LESS THAN 512 AFTER SC; 7) MARK TIME BETWEEN PACKETS (MTBP): SEND HIGH AFTER THE VALID DATA IS SENT.
The effect of computer lights is produced through different modeling scenes, different color changes, different viewing angles, horizontal and vertical light angles, and comprehensive performance such as speed, strobe speed, strobe speed, aperture size change, focal length change, etc. The work of all these attribute indicators is realized by the transmission of the stepper motor, and the electrical operation parameters of the stepper motor are defined and programmed, and the control of the computer lamp is completed.
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