Buttsplice's escape from ittybittyTVland

Testing of the light and ballast after finishing the box and wiring. It takes 4-5 minutes for the bulb to completely warm-up, but the crazy-bright white light is worth the wait!



This is a view of the box in its functional state. The threaded rod squeezes the focus box after the focus is set for the desired screen distance. It's crude but works beautifully. Now that I have a rough estimate for the projection triplet placement I can eliminate the focus box and mount the lens on a threaded PVC pipe cap and twist it for a more precision focus, but the focus box ain't half shabby. The black paint up front is to limit spurious light from washing out the main projected image. Air enters the top of the box between the LCD and rear lens/glass, cools the entire LCD and rear lens, travels under the rear lens/glass, then exits the box via the fan, pulling bulb and ballast heat with it.

The basic function is as follows: the rear fresnel lens collects light from its focal point (the bulb) and distributes it evenly on the back side of the LCD panel. This light then picks up the image from the LCD and travels into the forward fresnel lens, which takes this light and focuses it into a beam that converges to a point, which is where the projection triplet lens is at the front of the box. The image flips as it leaves the triplet so the LCD is actually mounted upside down to account for this. The fresnel lenses are acrylic and flexible so they are mounted to 1/8" glass with simple binder clips from the wally world stationary dept. The glass also keeps the rear lens from melting and a piece of UV filter sheet is placed between the glass and rear lens to protect the LCD and viewer from UV radiation. This may or may not be a real concern but it's cheap insurance.



Here are the circuit boards for the LCD. Placing them would've been much easier had I made the box a little wider. The red wire is to provide a ground between the 3 boards since the original metal chassis ground is gone. I soldered to two of the boards and sandwiched the wire under the third since I had no ring terminals on hand. I would recommend ring terminals since they allow for easy removal. The small green board contains the front panel controls for contrast, brightness, etc. This is one area where the Benq monitor shines since it uses a modular control panel that can be easily mounted to outside of the projector box. The Samsung is pretty crappy but you really don't need access to these controls except for the first setup, and I believe you can install the included software and control them remotely if you need to change them on a regular basis.



These pics show the layout of the light box. The ballast and capacitor are mounted to the floor right under the fan for cooling and all the wiring and 12V power adapter for the fan are under the piece of flashing below the light bulb. There really is no specific placement of the flashing, just be sure that no wiring or wood is exposed to direct light. I found out the hard way that my initial method of placing the flashing using duct tape was a bad idea when it started emitting a foul odor as the adhesive on the tape melted and turned yellow. The flashing is now all screwed into place.



One important thing to note here is that I have the fan wired separately from the lighting. This is because the fan must run after the light is turned off in order for the remaining heat to be sucked out rather than transferred to the LCD panel. For now I am doing this manually but I plan to add a switch and a circuit that will run the fan for a few minutes after shutdown. The fan is 12Vdc 0.45 amp and pushes a ton of air, which also is fairly noisy. Adding a thermostat will allow the fan to run slower and still keep the panel cool, which is also in the works. Most LCD's are rated to function up to 100 degrees F and mine has yet to breach 79, thanks to the fan.



Here's what the beast looks like after its first test run. After adjusting the focus box and verifying that the LCD temp was fine, a 10-ft diagonal screening of Return of the King was enjoyed with an ear-to-ear grin. The heavily taped area is where the LCD power and signal cables enter the box. They could be routed inside the box to the rear panel if desired. Most people simply cut a slot in the lid of the box for an air intake but I found it easier to cut the lid into two pieces after I placed the LCD and lenses so that I knew where to cut. This has proved convenient for tweaking the focus box and LCD controls while not having to wear a welding mask to shield my eyes from the bulb. I'm going to get a couple more hinges and leave this lid as two pieces.



Parts list (shipping and tax included):
Item Source Price
Samsung 512N 15" LCD monitor eBay (new in box) $197
EYE (Iwasaki) BT28/U 400W metal halide bulb 1000bulbs.com $115
Sola 400W metal halide ballast
Mogul base for bulb
2 fresnel lenses, projection triplet lens, UV filter sheet Lumenlab.com $79
4x8' sheet of 3/4" MDF and 6 cuts on their big saw Lowes $25
Two pieces of 13.5x10" glass (custom cut free by Lowes) $10
Wire nuts, power cord, strip foam, etc. $10
Galvanized steel flashing, duct tape, 12V fan and power supply already had on hand ----
TOTAL --- $436

I have not included a projection screen of any kind but it looks like the best solution is going to be the 110"x80" blackout cloth that Lumenlab sells for $40. Even with this included, the price is still less than half of what a decent XGA (1024x768 native resolution) projector costs. This does not account for the fact that commercial projectors use a special bulb that lasts only 2000 hours and costs over $400! The bulb I used in this project costs $35 and will last 20,000 hours. Bulbs can be found as cheap as $15 but they are huge so the box would have to be a little bigger and the bulb mounted diagonally.

I cut the wood for the box before I received the components and it was actually a little small for everything to work right so I extended the height by 3/4" using a frame I cut out of a piece of MDF. I also extended the box lengthwise by building the focus box that faces the wall such that it extends out of the box by ~3". I could've saved myself some work if I had sketched out the requirements for each component rather than relying on rough external dimensions from other folks' guides. Measure twice, cut once. An internal size of 15"Wx13"Hx29"L would leave plenty of working room.

The monitor I used is one of the easiest (if not the easiest) monitor to strip due its circuit board layout and FFC (flat flexible cable) placement. The only board that's attached to the glass ends up at the bottom of the projector so it's out of the projection area and can simply rest on the floor. Other brands require soldering an extension FFC and mounting boards in odd places so the 512N is a real time-saver in that regard. The power board and IO board can be mounted nearby with a fair amount of slack in the factory connectors. The other reason I chose this monitor is that it has a 450:1 contrast ratio and 16 ms response time, both of which are about as nice as you'll find for a 15" LCD monitor. Thanks to eBay, it didn't cost me any more than the monitors that have less to offer and are harder to utilize. I hear Benq has a few models that are worthy of a projector as well, so check the two forums listed in the links section for the latest monitor list.