The computer moving head light is a high-tech product integrating electronics, machinery and optics. Qualified computer moving head lights must be stable and reliable, with good light efficiency, accurate positioning and good heat dissipation. The lamp body and material structure meet the requirements of ergonomics. The computer moving head light can be divided into 250W, 575W, 1200W and other varieties from the power consumption. Among them, 1200W is the main type of lamp for professional performance venues. This paper focuses on the analysis of the construction principle of the 1200W moving head light. In a nutshell, the head light is composed of three major systems: optical, mechanical, electrical and program control. The three systems are interconnected and organically combined to meet the needs of light, color, speed, direction, effect, heat dissipation, noise, and positioning.

    First, the optical system

    The optical system design mainly 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 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 a relatively stable color temperature during lamp dimming. The disadvantage is that the delamination of the filler in the lamp, that is, the presence of the ribbon in the arc imaging or the condensation in the arc tube, forms a shadow effect, which needs to be controlled to a minimum in the optical structure design. 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 a scaled or surface texture should be selected. A reflector system made of a specularly reflective material is better than a refractive system. When it is desired to obtain several beams from a single source, a refractive system combining prisms or lenses can be employed. At present, the optical design of the 1200W moving head computer lamp at home and abroad adopts a lens combination method, and is composed of an aspherical (ie, parabolic) quartz lens.

    The most important characteristic of a parabolic lens is to place a point source at the focus, which will result in a parallel beam. In the design of the optical 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 size of the aperture of the reflective lens, and the shape of the light source.

    Second, the mechanical system

    Mechanical systems are available in a wide range of materials, structures, mechanical properties, housing requirements, heat dissipation requirements, and more. The main considerations for the selection of luminaire materials are: meeting the functional requirements of the lamp, ease of manufacture and economy. At present, the materials of international and domestic 1200W moving head lamps are mainly steel, plastic and aluminum alloy. Under the premise of satisfying the overall function of the lamp, the structural model of the lamp is designed, and different parts are used, and different materials are used. Such as Aceda-spot1200III1200W moving head light, the lamp body shell is made of plastic parts, 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. The international and domestic 1200W moving head lights adopt double-arm support structure. The lamp body rotates horizontally by 540° and the vertical rotation reaches 255°. The base part must be strengthened to meet the requirements of hanging and flipping of the moving head light.

   The mechanical properties of the lamp body are mainly reflected in the mechanical strength of the lamp body components, so that the lamp body does not deform, wear, corrosion, shock and pressure under the continuous effective working time; the lamp housing must have strict Waterproof, dustproof, anti-static, moisture-proof requirements. According to the degree of dustproof and waterproof, the protection level of different enclosures is required: for example, the protection level of computer lights used in indoors is usually IP20, and the protection level of outdoor computer lights is usually IP44.

    The mechanical structure of the 1200W high-power computer lamp is very important. If the heat dissipation system is defective, it will cause the electrical parameters to drift, the color film, the film break, the plaque, the crash, the out of step, the uncontrollable and other serious consequences.

    Third, the electrical and program control part

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

    Most of the world's professional 1200W moving head computer lights use rare gas discharge bulb sources. The start-up and stabilization of the gas discharge bubble depends on the choice of circuit type design, power supply, ballast and other electrical components. After the start of the rare gas discharge bubble, a stable time is generally not required. To ensure stability, the difference between the sustain voltage of the circuit and the instantaneous voltage of the bulb should be sufficiently large throughout the AC cycle.

    The start, stability, extinction, and restart of the light source shall 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 a transformer, a starting device, a semi-resonant circuit, 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 the ballast is to prevent current runaway and to operate the source under its normal electrical characteristics. At present, manufacturers usually use two types of ballasts, one is an inductive rectifier and the other is an electronic rectifier. The advantages of the inductive rectifier are good stability, and the disadvantage is heavy. It has high requirements on the strength, handling and loading and unloading of the lamp body. The electronic rectifier is essentially a power conversion circuit that converts the input power supply current in terms of frequency, waveform and amplitude. change. The utility model has the advantages of light weight, convenient loading and unloading and handling; the disadvantage is high structural design requirement and high maintenance cost.

    The restart of the light source, in the conventional circuit design, due to the high temperature generated during the operation of the gas discharge bubble, the vapor pressure resistance of the saturated gas in the bubble is formed, and it is difficult to realize the immediate re-triggering of the light source, and the gas pressure in the lamp must be reduced to the cold state value. After that, a restart can be triggered. At present, international and domestic production companies basically adopt conventional circuit design.

    2, the program control part

    At present, international and domestic computer lights generally use DMX data format to write program files. The principle of DMX512: The speed of DMX data stream is 250K, that is, each BIT is standard 4 microseconds. The data format of DMX is divided into the following parts: 1) IDLE (idle) or NO DMX situation (case): 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): MAB is BREAK, is a high level of 8 microseconds or 2 pulses; 4) STARTCODE (SC) begins Code: SC is the channel data starting from 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 seconds, less than 1 Seconds, can be MTBF before each start bit of the channel, high level; 6) CHANNEL DATA (CD): channel data 邏輯 after SC, the logical format is 1-512 or less than 512; 7) MARK TIME BETWEEN PACKETS (MTBP): Sends a high level after the valid data has been transmitted.

    The effect of the computer light is generated by different modeling scenes, different color changes, different viewing angles, horizontal and vertical light angle changes and speed, stroboscopic speed, aperture size change, focal length change and other comprehensive performance. The operation of all these attribute indicators is realized by the transmission of the stepping motor. The electrical operation parameters of the stepping motor are defined and programmed, and the control of the computer lamp is completed.