Moving head light is a high-tech product integrating electronics, machinery and optics. Qualified computer moving headlights must be stable and reliable, with excellent light efficiency, accurate positioning, and good heat dissipation. The lamp body and material structure conform to ergonomic requirements. Moving head lights from the use of power can be divided into 250W, 575W, 1200W and other varieties. Among them, 1200W is the main lamp type for professional performance venues. This article focuses on the structural principle of 1200W moving head lamp. In a nutshell, moving head light consists of three major systems: optical, mechanical, electrical and program control. The three systems are interrelated and organically combined to meet the needs of elements such as light, color, speed, direction, effect, heat dissipation, noise, and positioning.
First, the optical system
The optical system design considers the luminous flux utilization of the light source. Specific performance indicators include light intensity, uniformity, saturation, and spot size. There are two aspects that affect the above indicators: one is the light source, and the other is the optical system structure and material selection. At present, domestic and foreign manufacturers, users basically recommend OSRAM or PHILIPS 1200W short-arc double-ended metal gas discharge lamp. Its characteristics are compactness, high brightness, high color temperature, good color rendering, and a relatively stable color temperature during lamp dimming. The disadvantage is that the delamination of the filler in the lamp tube, that is, the filler appears in the arc imaging or condenses in the arc tube to form a shadow effect, needs to be controlled in the minimum range during the design of the optical structure. In the optical structure, in order to obtain a uniform mixed beam, parabolic mirrors may be used. To collect divergent or narrow beams, scaled mirrors or surface texture mirrors should be selected. Reflector systems made of specular reflective materials are better than refractive systems. When it is necessary to obtain several beams from a single light source, a prism or lens combination refraction system can be used. At present, in the optical design of 1200W moving head light at home and abroad, a lens combination method is adopted, which is composed of an aspherical (ie, parabolic) quartz lens.
The most important feature of a parabolic lens is to place a point light source at the focal point and a parallel light beam will be obtained. In the design of the optical path, the relationship between the light intensity distribution curve, the shape and the size of the light source, the size of the aperture of the reflective lens, and the shape of the light source must also be taken into consideration.
Second, the mechanical system
The wide range of mechanical systems includes materials, structures, mechanical properties, housing requirements, heat dissipation requirements, and more. The main considerations for lighting material selection are: meeting the lamp's functional requirements, ease of manufacture, and economy. At present, the materials for international and domestic 1200W moving headlights mainly include steel, plastics, and aluminum alloys. In consideration of meeting the overall function of the lamp, the lamp's structural model is designed to be divided into different parts and different materials are used. Such as Aceda-spot1200III1200W moving head lamp, lamp body shell adopts plastic parts, lamp body support frame, base plate, side plate and end plate adopt 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 lights adopt dual-arm support structure. The lamp body rotates horizontally up to 540° and vertical rotation up to 255°. The base part must be reinforced to meet the requirements for hanging and flipping of the moving head lamp.
The mechanical properties of the lamp body are mainly reflected in the mechanical strength of the lamp body components, so that the lamp body is not deformed, wear-resistant, corrosion-resistant, shock-resistant, and pressure-resistant during the period of continuous effective work; the lamp housing must have strict Waterproof, dustproof, anti-static, moisture-proof requirements. According to the degree of protection against dust and water, different protection grades for different enclosures are required: For example, the protection level of a computer lamp used indoors is usually IP20, and the protection level of an outdoor computer lamp is usually IP44.
The mechanical structure of the 1200W high-powered computer lamp is very important for heat dissipation. If there is any defect in the heat-dissipating system, it usually causes drift of electrical parameters. The color film and video will be broken and there will be plaque, resulting in serious consequences such as crash, out of step, and uncontrolled. .
Third, electrical and procedural control
1. Electrical characteristics and circuit design of moving head light of computer
Most of the world’s professional 1200W moving heads use rare gas discharge bulbs. The start-up and stabilization of gas discharge bulbs depends on the design of the circuit type, the power supply, ballast and other electrical components. After the start of the rare gas discharge bubble, a stable time is generally not required. In order to ensure stabilization, the difference between the maintenance voltage of the circuit and the instantaneous voltage of the lamp should be sufficiently large during the entire AC cycle.
For the start, stability, extinguishment, and restart of the light source, the circuit should be designed according to the characteristics of the light source. The starting voltage of the rare gas discharge bubble is very high, requiring the use of a transformer, a startup device, a semi-resonant circuit, etc., to increase the instantaneous startup voltage. The stability of the light source after startup depends on the matching of ballast and circuit parameters. The basic function of the ballast is to prevent the current from running out of control and to operate the light source under its normal electrical characteristics. At present, production companies usually use two ballasts, one is an inductor rectifier and the other is an electronic rectifier. The advantages of the inductor rectifier are its good stability and disadvantages. It has high requirements for the strength, handling and handling of the lamp body. The electronic rectifier is essentially a power conversion circuit, and the input power supply current is used in frequency, waveform and amplitude. change. Its advantages are light weight, convenient loading and unloading, and transportation; the disadvantages are high structural design requirements and high maintenance costs.
The restart of the light source, in the conventional circuit design, due to the high temperature generated when the gas discharge bubble works, the saturated gas in the bubble forms a vapor pressure resistance, and it is difficult to realize the light source to immediately trigger again, and the gas pressure in the lamp must be reduced to a cold ＆#118alue. After you can trigger a restart. At present, international and domestic production companies basically adopt conventional circuit design.
2, program control part
At present, international and domestic computer lights generally use DMX data format to write program files. Principle of DMX512: The speed of the DMX data stream is 250K, which is 4 microseconds per BIT. The data format of 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 level signal; 2)BREAK: The beginning of the DMX packet is A forecast of low level output of 88 microseconds {head}; 3) MARK AFTER BREAK (MAB): after MAB isBREAK, it is a high level of 8 microseconds or 2 pulses; 4) Start of STARTCODE (SC) Code: SC is the channel data at the beginning of the data stream. It has the same format as the channel data, typically 11 pulses or 44 microseconds; 5) MARK TIME BETWEEN FRAMES (MTBF): MTBF can be 0-1 seconds, less than 1 Seconds, before each channel start bit can have MTBF, high; 6) CHANNEL DATA (CD): Channel data SC SC after the logical format of 1-512 or less than 512; 7) MARK TIME BETWEEN PACKETS (MTBP): Sends high level after valid data is sent.
The effects of computer lights are generated through different modeling scenes, different color changes, different angles of view, horizontal and vertical light angle changes and speed, strobe speed, aperture size changes, focal length changes and other comprehensive performance. The work of all these attribute indicators is achieved through the drive of a stepper motor, and the electrical operation parameters of the stepper motor are defined and programmed to complete the control of the computer light.
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