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Demystifying the internal structure and working principle of the computer shaking head lamp


Computer shake head lamp is a set of electronic, mechanical, optical as one of the high-tech products. Qualified computer shake head lamp must be stable and reliable, excellent light efficiency, accurate positioning, good heat dissipation, lamp body and material structure meet the requirements of ergonomics. Computer moving head lamp 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 paper focuses on the analysis of the construction principle of 1200W moving head lamp. In a nutshell, the head shaking computer lamp is composed of three 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 light 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 lamp. Its characteristics are compactness, high brightness, high color temperature, good color rendering and light source in the process of dimming, can maintain a relatively stable color temperature. The disadvantage is that the delamination problem of the filler in the lamp tube, that is, the color band of the filler appears in the arc imaging or condenses in the arc tube, forming a shadow effect, which 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 divergent or narrow beams, a reflector with scale processing or surface texture should be selected. A reflector system made using a specular reflective material is better than a refractive system. When it is desired to obtain several light beams from one light source, a refractive system with a combination of prisms or lenses can be used. At present, in the optical design of 1200W moving head computer lamp at home and abroad, the lens combination is adopted, which is composed of aspheric (I. e. parabolic) quartz lens.

The most important feature of the parabolic lens is to place a point light source at the focal point, and a parallel beam will be obtained. In the light path design, it is also necessary to consider the correlation 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 range of mechanical systems is wide, including materials, structures, mechanical properties, housing requirements, heat dissipation requirements, and so on. The main considerations of lamp material selection are: to meet the functional requirements of the lamp, the degree of difficulty and economy of manufacturing. At present, the international and domestic 1200W moving head lamp materials are mainly steel, plastic, aluminum alloy. Considering the overall function of the lamp, the structural model of the lamp is designed, which is divided into different parts and different materials. For Aceda-spot1200III1200W moving head lamps, the lamp body shell is made of plastic parts, and the lamp body support frame, base, side plates 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. International and domestic 1200W shaking head lamps all adopt double-arm support structure. The lamp body rotates horizontally up to 540 degrees and vertically up to 255 degrees. The base part must be strengthened to meet the suspension and inversion requirements of shaking head lamps.

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, earthquake-resistant, and pressure-resistant during continuous and effective work time; the lamp housing must be strictly 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 the 1200W high-power computer lamp requires heat dissipation. If the heat dissipation system is defective, it will usually cause electrical parameter drift, color film and film rupture, plaque, crash, out of step, uncontrolled and other serious consequences.

 

3. electrical and program control

 

1. Electrical characteristics and circuit design of computer shaking head lamp

 

The vast majority of professional 1200W shaking head computer lamps worldwide use rare gas discharge bulb light source. The starting and stable operation of the gas discharge bubble depends on the design of the circuit type, the choice of electrical components such as power supply and ballast. After the rare gas discharge bulb is started, generally no stabilization time is required. In order to ensure stabilization, the difference between the maintaining voltage of the circuit and the instantaneous voltage of the bulb 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 bubble is very high, which requires the use of transformers, starter 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 current runaway and to operate the light 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 advantage of inductive rectifier is good stability, the disadvantage is heavy, the strength of the lamp body, handling, loading and unloading have higher requirements; electronic rectifier is essentially a power conversion circuit, the input power current frequency, waveform and amplitude changes. 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 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. It is difficult to trigger the light source immediately, and the restart can only be triggered after the gas pressure in the lamp is reduced to the cold state value. At present, international and domestic production enterprises basically adopt conventional circuit design.

 

2. Program control part

 

At present, the international and domestic computer lights generally use DMX data format to write program files. Principle of DMX512: The speed of DMX data stream is 250K, that is, each BIT is 4 microseconds of standard. 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 beginning of DMX data packet is a forecast {header} of 88 microseconds low level output; 3)MARK AFTER BREAK(MAB):MAB is after BREAK, is an 8 microsecond high level or 2 pulses; 4)STARTCODE(SC) start code: SC is the channel data at the beginning of the data stream, which 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 second, and MTBF can be high level before each channel start bit, which is; 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 valid data is sent.

The computer light effect is produced through different modeling scenes, different color changes, different viewing angles, horizontal and vertical light angle changes, speed, strobe speed, aperture size changes, focal length changes and other comprehensive performance. The work of all these attribute indexes is realized by the drive of the stepper motor, and the electrical operation parameters of the stepper motor are defined and programmed to complete the control of the computer lamp.