Demystifying the internal structure and working principle of the computer moving head light

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 excellent light efficiency, accurate positioning, good heat dissipation, and the lamp body and material structure meet the requirements of ergonomics. 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 paper focuses on the analysis of the construction principle of the 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 elements.
1. Optical system
The optical system design mainly considers the utilization rate of the luminous flux 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 ability to maintain a relatively stable color temperature during dimming of the light source. The disadvantage is that the delamination of the filler in the lamp tube, that is, the filler appears color bands in the arc imaging or condenses in the arc tube to form 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 reflector can be used. To collect divergent or narrow beams, a reflector with scale processing or surface texture should be selected. Reflector systems using specularly reflective materials are preferred over refractive systems. When it is necessary to obtain several light beams from one light source, a refraction system composed of prisms or lenses can be used. At present, in the optical design of 1200W moving head computer lights at home and abroad, the way of lens combination is adopted, which is composed of aspherical (ie parabolic) quartz lens and so on.
The most important feature of a parabolic lens is to place a point light source at the focal point, and a parallel beam will be obtained. When designing 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 aperture size of the reflective lens, and the shape of the light source.
2. Mechanical system
The scope of mechanical systems is very wide, including materials, structures, mechanical properties, housing 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 materials of international and domestic 1200W moving head lights mainly include 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 divided into different materials. For example, the Aceda-spot1200III1200W moving head light, the lamp body shell is made of plastic parts, and the lamp body support frame, base, side panels, and end plates 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 a double-arm support structure. The horizontal rotation of the lamp body can reach 540°, and the vertical rotation can reach 255°. The base part must be strengthened to meet the suspension requirements of 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 will not be deformed, wear-resistant, corrosion-resistant, shock-resistant, and compressive during continuous and effective working time; the lamp shell must have strict Waterproof, dustproof, antistatic, moistureproof requirements. According to the degree of dustproof and waterproof, the protection level requirements of different shells are divided: for example, the protection requirement level of indoor computer lights is usually IP20, and the protection requirement level of outdoor computer lights is usually IP44.
The mechanical structure of the 1200W high-power computer light requires very important 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 crash, out of step, and out of control. .
3. Electrical and program control part
1. Electrical characteristics and circuit design of computer moving head lights
Most of the professional 1200W moving head computer lights in the world currently use rare gas discharge bulbs as light sources. The start-up and stable operation of gas discharge bulbs depend on the design of the circuit type, the selection of electrical components such as power supply and ballast. After the rare gas discharge bulb is started, it generally does not need a stable time. In order to ensure stabilization, the difference between the maintenance voltage of the circuit and the instantaneous voltage of the bulb should be sufficiently large during the entire AC cycle.
The circuit should be designed according to the characteristic requirements of the light source for the start, stability, extinguishment and restart of the light source. The start-up voltage of the rare gas discharge bulb is very high, and it is required to use transformers, start-up devices, semi-resonant circuits, etc. to increase the instantaneous start-up 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 runaway and make the light source work under its normal electrical characteristics. At present, manufacturers usually use two kinds of ballasts, one is an inductive rectifier and the other is an electronic rectifier. The advantage of the inductance rectifier is good stability, the disadvantage is that it is heavy, and has high requirements for the strength, handling, loading and unloading of the lamp body; the electronic rectifier is essentially a power conversion circuit, which converts the input power current in terms of frequency, waveform and amplitude. Change. Its advantages are light weight, convenient loading and unloading, and handling; the disadvantages are high structural design requirements and high maintenance costs.
The restart of the light source, in conventional circuit design, due to the high temperature generated when the gas discharge bulb is working, the saturated gas in the bubble forms a vapor pressure resistance, and it is difficult to realize the immediate retriggering of the light source, and the gas pressure in the lamp must be reduced to the cold state value Only then can a restart be triggered. At present, international and domestic manufacturers basically adopt conventional circuit design.
2. Program control part
Currently international and domestic moving lights generally use DMX data format to write program files. The principle of DMX512: The speed of DMX data flow 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 A forecast of 88 microseconds low-level output {head}; 3) MARK AFTER BREAK (MAB): MAB is BREAK, followed by 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 second, less than 1 Seconds, there can be MTBF before the start bit of each channel, which is high level; 6) CHANNEL DATA (CD): the logical format of the channel data frame is 1-512 or less than 512 after SC; 7) MARK TIME BETWEEN PACKETS (MTBP): Send a high level after sending valid data.
The effect of moving lights is produced through different modeling scenes, different color changes, different viewing angles, changes in horizontal and vertical light output angles, speed speed, strobe speed, aperture size changes, and focal length changes. The work of all these attribute indicators is realized through the transmission of the stepping motor, and the control of the scanner is completed by defining and programming the electrical operation parameters of the stepping motor.