A basic projector
A TFT monitor and that’s it!
A prime consideration when buying a projector is the brightness, which mainly depends on the lamp used. I have used a simple data projector from Liesegang (OHP 2510), equipped with a 400 W halogen lamp, which, according to the datasheet, produces 3,500 ANSI lumens to demonstrate. The top-of-the-line models feature HQI lamps of 600 W and even more.
As most of the energy is given off as heat loss, operating a projector means the surroundings become heated. Most importantly, the LCD panel must be sufficiently cooled to prevent any damage!!!
My recommendation when all's said and done: for good illumination and adequate brightness, your projector should have at least a 350 W lamp. At low brightness, the room has to be effectively darkened to achieve a good picture on the screen's large dimensions.
TFT Display: Resolution, Color Intensity, Response Time
Comparison of various displays:
The table above lists the principal resolutions; note that resolutions higher than SXGA are seldom available in 15-inch format, with the exception of some notebook displays. This means the display no longer fits the overhead projector, as its dimensions exceed the light frame. The panel on our projector was taken from an older flatscreen from Iiyama, the 15.1" BX3814UT.
Several factors must be taken into account to avoid destroying any components.
I don't really need to mention color accuracy, as almost all older displays support 24-bit color depth, and hence 16.7 million colors for perfect DVD screenings. Response time poses no problems, even on relatively small displays up to 15 inches: less than 30 ms average is completely adequate for perfect picture reproduction.
Step by Step: Removing the TFT Panel
The difficulty of removing the LCD panel depends on the flatscreen you choose; it may prove easy or, in a few cases, nearly impossible. In our experience, the displays from Iiyama, such as our BX3814UT, make an excellent choice, because the LCD panel is adhered to the frame only lightly, and can be removed with just a little bit of care. Not all manufacturers follow this approach, and this raises the risk of breaking the panel during removal.
We must first take off the stand before disassembling the rest of the unit, ending with the entire casing. Start by removing the metal panels.
Rear view of the flat screen. The screws for the stand are removed first, then those for the casing.
Before the next step, we advise you to pull all the cables, so the inverter board and its panel can be removed. You might want to label all the connectors to make reconnecting easier later on. Removing the panel from the frame is a little trickier, as a hairline crack can quickly appear and destroy the conductor paths. LCD panels are glass with fine conductor paths vapor-deposited onto them, and the connections to the controller are made on the margins. All paths are very thin and extremely sensitive to tensile stress. A broken conductor path can lead to missing screen lines or to total destruction of the unit.
Be extremely careful: these miniature connections cannot be repaired!
The LCD panel is still on in this picture, but all cable connections from the controller and inverter have already been removed. The most sensitive work is in removing the panel from the plastic frame without breaking the display.
Done-the LCD panel removed from the frame.
Assembly: The Projector's LCD Panel
After carefully removing the LCD panel, you can now start putting the actual projector together.
Even during the initial test phases, the display must be firmly positioned where it can't slip. Furthermore, the panel may not be laid directly on the projector pane, as it will quickly get damaged by heat from the lamp. A thin strip of wood or plastic is good as a spacer; a height of 8 to 10 mm (about 3/8") is more than enough. I’ve used polystyrene of the sort frequently found in packaging; these strips can also be adjusted with adhesive tape. The following pictures illustrate what you have to do.
...and the first test installation of the LCD panel!!!
The necessary gap between the pane and the LCD panel can be clearly seen here.
Connecting the leads to the controller: mount with adhesive tape.
Once the panel and spacers have been successfully mounted, cables can be connected to the controller and inverter. This step requires the utmost care: the contacts on the flat cable are separated by tenths of millimeters, and the slightest tilt will cause a short circuit.
A view of the mounted LCD panel and flat cable.
Very Important: Permanent Cooling For the LCD Panel
Because of the incredibly high power consumption of the lamp (400 W), our homemade projector needs sufficient cooling -- the integrated fan in the Liesegang projector just doesn't cut the mustard. Heat build-up occurs especially between the projector's LCD panel and glass top, due to thermal conduction from the lamp that can only be prevented by permanent air circulation.
The initial sign of the display overheating is a brown ring that appears in the area that gets too hot, which shrinks again when the unit is cooled. If the heat level is not reduced relatively quickly, this is followed by failures in the corresponding areas. The display becomes permanently burnt out if repeatedly overheated, and will no longer display in the damaged area.
For the test construction, I fitted various fan types in a number of positions. The result: all you need is a single 8 cm fan that creates airflow under the LCD panel. An additional power supply for this can be created using a standard ATX power unit. An office fan set at the lowest speed is also an option.
Only for testing and adjustment: the 8 cm fan taped in place.
The Liesegang projector with installed LCD panel and leads. And we're off!
Made It: The Homemade Projector, Up And Running!
After about six hours' time assembling and tinkering, our homemade projector is ready to go. The following pictures should give you an impression of what the ambitious user can expect.
The LCD panel works - now the input source can be connected.
Fine-Tuning: Adjusting The Graphics Card And LCD Panel
Once all the components work together properly, all you have to do is adjust the LCD panel and graphics card to get the best picture. In practice, this means tweaking contrast and brightness. Only a few TFT monitors are set out of the box for maximum possible luminous efficiency, so subsequent fine-tuning can enhance both color and contrast enormously. In our case, adjusting brightness and contrast led to a much better display, enabling us to run the projector even in a sunlit room.
Conclusion: The Fun And Fascination Of Building Your Own Projector
The result was all the more pleasing: the projector we built convinced even the notorious skeptics at the THG lab in Munich
The homemade projector is great fun and provides great detail, as a result of its XGA resolution. But it's not just the money you can save that will motivate many users to action - it's the fascination of building, and the ability to select components for optimal picture quality. In our case, the overhead projector (Liesegang OHP 2510) and LCD panel from Iiyama cost just $250. And they don't have to be new devices. Used or cast-off 14" and 15" TFT monitors are widespread nowadays. A good one shouldn't cost more than $150, and the price for a model with non-functioning backlighting will be even lower. Projectors can be picked up at auctions for around $50.
Adding in the cost of small parts such as a fan and tape, you are still well under $300.
Considering the result, that's a great deal, especially when you compare the resulting picture quality to a cheapo projector costing at least $500 yet having only SVGA resolution. Another benefit of the homemade projector lies in its use of reasonably-priced halogen lamps (a 400W lamp costs about $30), compared to commercial models using $200 lamps.
What about the downside? Well, the appearance, characterized by a more-or-less chunky projector with a display on top, would certainly not win any design prizes. Also, the LCD panel must be adequately cooled if severe damage is to be avoided. In this context, an annoyingly loud noise may accompany operation. But this is also a well-known problem with low-end projectors.
Nothing to do over the holidays? Why waste time on facebook? How about spending a few free days building your own projector? It's certainly a worthy project!
THANKS TO “Tom's Hardware Guide PCs & How To: Supersize Your TV for $300: Build Your Own XGA Projector!”
