Computer moving head light is a high-tech product integrating electronics, machinery and optics. A qualified computer moving head lamp must be stable and reliable, with excellent light efficiency, accurate positioning, and good heat dissipation. The lamp body and material structure meet the ergonomic requirements. Computer moving head lights can be divided into 250W, 575W, 1200W and other varieties according to the power used. Among them, 1200W is the main lamp type for professional performance venues. This article focuses on the analysis of the construction principle of 1200W moving head light. In a nutshell, the moving head computer light 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 factors.
1. Optical system
The most important consideration in optical system design is 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 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 light source can maintain a relatively stable color temperature during the dimming process. The disadvantage is that the layering problem of the filler in the lamp tube, that is, the filler appears in the arc imaging ribbon or condensation in the arc tube, forming 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, a parabolic reflector can be used. To collect a divergent or narrow beam, a reflector with scale processing or surface texture should be selected. A reflector system made of specular reflective materials is better than a refraction system. When you need to get several beams from a light source, you can use a prism or lens combination refraction system. At present, in the optical design of 1200W moving head computer lights at home and abroad, the lens combination is used, 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 on the focal point, which will get a parallel beam. In the design of the optical path, it is also necessary to consider the correlation between the light intensity distribution curve, shape and the size of the light source, the size of the aperture of the reflective lens, and the shape of the light source.
2. Mechanical system
The range of mechanical systems is very wide, including materials, structure, mechanical properties, housing requirements, heat dissipation requirements and so on. The main considerations for the selection of lamp materials are: meeting the functional requirements of the lamp, the degree of difficulty in manufacturing, and the economy. At present, the materials of international and domestic 1200W moving head lights 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, divided into different parts and using different materials. Such as Aceda-spot1200III1200W moving head lamp, 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 the international and domestic 1200W moving head lights use a dual-arm support structure. The lamp body rotates horizontally up to 540 ° and vertically rotates up to 255 °. The base part must be strengthened to meet the requirements of hanging head flip.
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 continuous and effective working; the lamp housing must have strict Waterproof, dustproof, antistatic and moistureproof 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 level of outdoor computer lights is usually IP44.
For the mechanical structure of 1200W high-power computer lights, the heat dissipation requirements are very important. If the heat dissipation system is defective, it will usually cause electrical parameter drift, color film and film rupture, plaques appear, resulting in serious consequences such as crash, out of step, uncontrolled .
3. Electrical and process control
1. Electrical characteristics and circuit design of computer moving head light
The vast majority of professional 1200W moving head computer lights worldwide used rare gas discharge light sources. The start and stable operation of the gas discharge bubble depends on the design of the circuit type, the selection of electrical components such as power supply, ballast, etc. After the rare gas discharge bulb is started, generally no stabilization time is required. To ensure stability, the difference between the circuit's maintenance voltage and the instantaneous voltage of the bulb should be sufficiently large during the entire AC cycle.
For starting, stability, extinction, 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, which requires the use of transformers, starting devices, semi-resonant circuits, etc. to increase the instantaneous starting voltage. The stability of the light source after starting 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 make the light source work under its normal electrical characteristics. At present, production enterprises usually use two types of ballasts, one is an inductive rectifier and the other is an electronic rectifier. The advantages of inductive rectifiers are good stability, and the disadvantages are heavy. They have high requirements on the strength, handling, and loading and unloading of the lamp body; electronic rectifiers are essentially power conversion circuits, which carry out the input power current in frequency, waveform, and amplitude. change. Its advantage is light weight, convenient for loading and unloading, handling; the disadvantage is high structural design requirements and high maintenance costs.
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 saturated gas in the bubble forms a vapor pressure resistance. It is difficult to realize the light source to be triggered again immediately. The pressure of the gas in the lamp must be reduced to the cold ＆#118alue Only then can a restart be triggered. At present, international and domestic production enterprises 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 data packet output, it will be a high level signal; 2) BREAK: the start of the DMX data packet is Forecast of a low level output of 88 microseconds {head}; 3) MARK AFTER BREAK (MAB): After MAB is BREAK, it is a high level of 8 microseconds 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 seconds, less than 1 Seconds, MTBF can be high before the start bit of each channel; 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 high level after sending valid data.
The effect of computer lights is generated by different scenes, different color changes, different viewing angles, horizontal and vertical light angle changes and speed, speed, stroboscopic speed, aperture size change, focal length change and other comprehensive performance. The work of all these attribute indexes is realized by the transmission of the stepper motor. The electrical operating parameters of the stepper motor are defined and programmed, and the control of the computer light is completed.
