Teaching projectors are also called transmissive projectors (national standard product name). At present, domestic LCD projectors have copied the optical structure of this machine, but only made some improvements. There are several advantages to using a teaching projector to make an LCD projector. One is to reduce the difficulty of production. The production process is reduced and the production time is shortened.
For friends who are interested in making but lack confidence in their hands-on skills or have tight time, the teaching projector is a mature product. It is safe and reliable to use, and its design is reasonable. Unfamiliar friends take many detours. Secondly, for friends who like to use hands-on, using the teaching projector to make the projector can easily replace the LCD screen, which is conducive to future experiments and upgrades. This article will introduce the whole process of making a projector with a teaching projector for the reference of friends who are interested in making.
First of all, you need to buy a teaching projector. The size of the tabletop of the projector can be 250 & TImes; 250mm, it is a little longer than the length of 10.4 inch LCD screen, and it is not affected when it is used. If you choose the 200 & TImes; 200mm platen model (this model is relatively rare), you cannot make a 10.4 inch screen full display. The left and right sides of the screen are blocked by about 1cm. However, this projector is small in size and low in price, and can also be considered. Here we choose a 250 & TImes; 250mm panel product produced by the original Nanjing Film Machinery Factory. The machine uses a 250W / 24V halogen lamp, the price of the bulb is 8 yuan, and the life is about 100 / hour. There are two bulbs in the machine, which are converted by a mechanical lever. If one bulb is damaged during use, it can be easily and quickly converted into another bulb without having to be replaced immediately, which is very practical. The lens of the projector has two types: single-chip and multi-chip. The first choice is of course multi-chip. However, if you can't buy it, you can also buy the single-chip, because the lens is convex and concave. The image quality is much better than that of the lenses with flat convex and biconvex structures that we usually see. The model I purchased is a monolithic, with a focal length of 290mm, which is shorter than the diagonal length of the panel, and is a wide-angle type. Regardless of the model and lens, you should turn on the power at the time of purchase and check the projection effect by aligning a white wall with a distance of 2 to 3 meters and adjusting the focus handwheel when the inside of the panel When the projection of the edge is the clearest, see whether the projected image has dispersion I. There is a rainbow-like color band at the light and dark junction) and deformation (concave toward the center or convex outward). If there is an inconsistency between the upper and lower broadband, the mirror is not at 45 degrees. ~ Generally there is no noticeable deformation, and the dispersion is within 2mm. Because this is the edge of the screen, even the best lens is inevitable, not to mention that the LCD screen we use will be smaller than the size of the platen, so this phenomenon will be reduced in actual use. The inspection time should be as short as possible. When you just touched the projector. It is often out of curiosity and long-term fiddling, and nothing is set on the panel, which is incorrect (the same warning content is also included in the manual of the projector, so be sure to read the manual carefully), especially in the mirror. When you open it, you only need to feel it with your hand to know why: turn on the power, put your palm on the table, there is only a little warm feeling, slowly move your palm closer to the lens, the temperature will become higher and higher, to Your hand will feel a burning sensation when under the lens. The temperature above the lens is higher. It is enough to ignite paper and matches, and if the mirror is placed horizontally at this time, it will be burned out, but as long as a small density slide is placed on the panel, this phenomenon will be greatly alleviated. Another thing is that under the strong light, the reflector will look very dirty. At this time, it must not be wiped with a cloth or liquid of any material, and can only be blown with a balloon.
After purchasing a projector, the next step is to choose the LCD screen. To get a larger size projection screen, and to get the highest brightness, 10.4 inch screen is of course the first choice.
With an LCD screen, you have to make a shell to protect the LCD screen from damage during use.
It is not difficult to make a shell for an LCD screen. Place the screen and decoder board, socket board, and control board on a flat surface as close as possible. At this time, pay attention to the screen anyway and up and down. Because in the official projection, the front of the screen (the correct direction of the subtitles when the screen is displayed) faces the lens, the back faces the projector panel, and the bottom of the screen points in the direction of the screen. Then measure the length and width dimensions they occupy, add 2crn to this size, and make an inner frame. The thickness of the frame should be thinner. The frame material must have a certain strength, and the material is not limited, preferably an insulating material. The material of the frame should not be too thick, so as not to make the shell collide with the lens support rod on the projector, and the screen cannot be placed in the center of the panel, generally within 2cm, there will be no problem. To make a panel with the outside dimensions of the frame, it is best to use plastic material or flat thin wood board. Glue the panel and the frame with "302" AB glue, install all the components, then dig a rectangular hole with the same size as the display part of the screen on the panel, and the shell is finished by painting. Align the screen with the holes on the case, and stick some small posts with hooks around the screen to fix it with the panel. Then use the same method to fix the decoder board and other components, and lead the power cord and AV cord out. Place the screen with the shell on the projector panel and center the screen. Check for light leaks around the shell and add leaks. Turn on the LCD screen power and signal source, turn on the projector power, and adjust the mirror to 45 degrees. Turn the focus handwheel and the image will be displayed on the screen.
After turning on the projector for a few minutes, the temperature of the LCD screen should be monitored. LCD screens with low light transmittance are often damaged by heat absorption. Therefore, an exhaust fan with a size of 10 & TImes; 10cm must be placed next to the screen. After adding the exhaust fan, the temperature of the LCD screen is very low. At this time, you can sit down and enjoy the happiness brought by the large screen projection! 0
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