Computer moving head light is a high-tech product which integrates electronics, machinery and optics. Qualified computer head shaking lamp 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. Computer headlamp can be divided into 250W, 575W, 1200W and so on. Among them, 1200W is the main lamp type for professional performance venues. This paper focuses on the analysis of the construction principle of 1200W headlamp. Generally speaking, shaking head computer lamp is composed of optical, mechanical, electrical and program control systems. The three systems are interrelated and organically combined to meet the needs of light, color, speed, direction, effect, heat dissipation, noise, location and other elements.

一、Optical Systems

Optical system design mainly considers the light flux utilization of light source. Specific performance indicators include light intensity, uniformity, saturation, spot size. There are two factors affecting the above indicators, one is the light source, the other is the structure of the optical system, material selection. At present, domestic and foreign manufacturers and users basically recommend OSRAM or PHILIPS 1200W short arc metal gas discharge lamps. Its characteristics are compactness, high brightness, high color temperature, good color rendering and the relative stable color temperature can be maintained during the darkening process of the lamp source. The disadvantage is that the stratification of filler in the lamp tube, that is, the filler appears in the arc imaging ribbon or condenses in the arc tube to form a shadow effect, which needs to be controlled in the minimum range when designing the optical structure. In optical structure, in order to obtain uniform mixed beams, a parabolic reflector can be used. To collect divergent or narrow beams, a reflector with scale processing or surface texture should be selected. Reflector systems made of mirror reflective materials are better than refractive systems. When it is necessary to obtain several beams from a light source, a refraction system composed of prisms or lenses can be used. At present, in the optical design of 1200W shaking head computer lamps at home and abroad, lens combination is adopted, which consists of aspheric (parabolic) quartz lens and so on.

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.

二、Mechanical System

The mechanical system has a wide range, including material, structure, mechanical properties, shell requirements, heat dissipation requirements and so on. The main considerations in the selection of lamp materials are: meeting the functional requirements of the lamp, manufacturing difficulty and economy. At present, the main materials of 1200W headlamp at home and abroad are steel, plastic and aluminium alloy. Considering the overall function of the lamp, the structure model of the lamp is designed, and different materials are used in different parts. For example, Aceda-spot 1200III 1200W headlamp, the shell of the lamp is made of plastic parts, the lamp body support frame, base, side plate and end plate are made of aluminium alloy casting, stamping parts and car parts of 1200W headlamp at home and abroad are steel, plastic and aluminium alloy. Considering the overall function of the lamp, the structure model of the lamp is designed, and different materials are used in different parts. For example, Aceda-spot 1200III 1200W headlamp, the shell of the lamp is made of plastic parts, the lamp body support frame, base, side plate and end plate are made of aluminium alloy casting, stamping parts and car parts.

The structure of the lamp determines its mechanical performance, heat dissipation, intensity, noise, weight and other factors. Both international and domestic 1200W shaker lamps adopt double arm support structure. The horizontal rotation of the lamp body reaches 540 degrees and the vertical rotation reaches 255 degrees. The base part should be strengthened to meet the requirements of hanging and flipping of the shaker 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 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. 

三、Electrical and Program Control Section

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

   
   

Most of the professional 1200W head-shaking computer lamps in the world used rare gas discharge bulb light source. The starting and stabilization of gas discharge bubbles depend on the design of circuit type, the selection of power supply, ballast and other electrical components. In order to ensure stability, the difference between the maintained voltage of the circuit and the instantaneous voltage of the lamp should be large enough during the whole 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. 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 logic 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.