Computer moving head light is a high-tech product integrating electronics, machinery and optics. Qualified computer moving head lights must be stable and reliable, good light efficiency, accurate positioning, good heat dissipation, and the lamp body and material structure must 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 for professional performance venues. This article focuses on the analysis of the construction principle of the 1200W moving head light. In a nutshell, moving head computer lights are composed of three major systems: optics, mechanics, 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 most important consideration in the design of the optical system is the utilization of light source luminous flux. 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 optical system structure and material selection. At present, domestic and foreign manufacturers and users basically recommend OSRAM or PHILIPS 1200W short arc double-ended metal gas discharge lamps. Its characteristics are compactness, high brightness, high color temperature, good color rendering, and the lamp source can maintain a relatively stable color temperature during the dimming process. The disadvantage is that the layering of the filler in the lamp tube, that is, the color band of the filler in the arc imaging or condensation in the arc tube, forming a shadow effect, needs to be controlled to a minimum range during the design of the optical structure. In the optical structure, in order to obtain a uniform mixed beam, a parabolic mirror can be used. To collect a divergent or narrow beam, a mirror with scale processing or surface texture should be selected. A reflector system made of specular reflective material is better than a refractive system. When several beams need to be obtained from one light source, a refraction system combined with prism or lens can be used. At present, in the optical design of 1200W moving head computer lights at home and abroad, the lens combination method is adopted, which is composed of aspherical (that is, parabolic) quartz lenses.

    The most important feature of the parabolic lens is to place a point light source at the focal point and get a parallel beam. When designing the light path, it is also necessary to consider the relationship 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.

    2. Mechanical system

    The mechanical system has a wide range, including materials, structure, mechanical properties, housing requirements, heat dissipation requirements, etc. The main considerations for the selection of lamp materials are: meeting the functional requirements of the lamp, the difficulty of manufacturing and the economy. At present, the main materials of international and domestic 1200W moving head lights are steel, plastic, and aluminum alloy. Under the premise of satisfying the overall function of the lamp, the structural model of the lamp is designed, divided into different parts, and different materials are used. For example, Aceda-spot1200III1200W moving head light, the lamp body shell is made of plastic parts, and the lamp body support frame, base, side plate, and end plate 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. Both international and domestic 1200W moving head lights adopt double-arm support structure, the lamp body rotates up to 540° horizontally and up to 255° vertically. The base part must be strengthened to meet the suspension and flip requirements of the moving head lights.

    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 pressure-resistant during the continuous and effective working time; the lamp housing 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 enclosures are divided: for example, the protection level of computer lights used indoors is usually IP20, and the protection level of outdoor computer lights is usually IP44.

    The mechanical structure of 1200W high-power computer lights requires heat dissipation. If the heat dissipation system is defective, it will usually cause electrical parameter drift, color chips, film cracks, plaques, and serious consequences such as crashes, loss of synchronization, and uncontrolled .

    Three, electrical and program control part

    1. Electrical characteristics and circuit design of computer moving head lights

    The vast majority of professional 1200W moving head computer lights around the world use rare gas discharge bulb light sources. The starting and stable operation of the gas discharge bulb depends on the circuit type design, power supply, ballast and other electrical components. After the rare gas discharge bulb is started, it generally does not need a stable time. In order to ensure stability, the difference between the circuit's maintenance voltage and the bulb's instantaneous voltage should be sufficiently large during the entire AC cycle.

    The starting, 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 bulb is very high, requiring the use of transformers, starting devices, and semi-resonant circuits to increase the instant starting voltage. The stability of the light source after starting depends on the matching of the ballast and circuit parameters. The basic function of the ballast is to prevent current runaway and 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 the inductive rectifier is its good stability, but the disadvantage is its heavy weight. It has high requirements on the intensity, handling, and loading and unloading of the lamp body; the electronic rectifier is essentially a power conversion circuit, which performs frequency, waveform and amplitude of the input power current. change. Its advantages are light weight, convenient loading and unloading, and transportation; 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 during the operation of the gas discharge bulb, the saturated gas in the bulb forms vapor pressure resistance. It is difficult to realize the light source to be triggered immediately, and the gas pressure in the lamp must be reduced to the cold ＆#118alue. After that, the restart can be triggered. At present, international and domestic production companies basically adopt conventional circuit design.

    2. Program control part

    At present, DMX data format is generally used to write program files in international and domestic computer lights. The principle of DMX512: The speed of DMX data stream is 250K, that is, each BIT is the standard 4 microseconds. The DMX data format is divided into the following parts: 1) IDLE (idle) or NO DMX situation (situation): when there is no DMX data packet output, it will be a high level signal; 2) BREAK: the beginning of the DMX data packet is An 88 microsecond low-level output forecast {head}; 3) MARK AFTER BREAK (MAB): after MAB is BREAK, it is an 8 microsecond high level or 2 pulses; 4) STARTCODE (SC) starts Code: 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, there can be MTBF before the start bit of each channel, which is high; 6) CHANNEL DATA (CD): The logical format of the channel data frame after SC is 1-512 or less than 512; 7) MARK TIME BETWEEN PACKETS (MTBP): Send a high level after the effective data is sent.

    The computer light effect is produced through different modeling scenes, different color changes, different viewing angles, changes in horizontal and vertical light angles, speed, stroboscopic speed, aperture size changes, focal length changes, etc. The work of all these attribute indexes is realized by the transmission of the stepping motor, and the electrical operation parameters of the stepping motor are defined and programmed to complete the control of the scanner.