I like to host LAN parties. We mostly play console games, because they are easily accessible. All my friends have consoles, but it's nearly impossible to get people to bring high-definition displays. Usually, they are just too big to move, or are mounted on the wall, or are otherwise inaccessible. I didn't have the room or the money for another HDTV, so I decided to look into projectors.
- Projector needs to be cheap
- Displays at least 480p
- Supports component input (optional)
- Is small enough to transport (other LAN parties!)
I did some research on projectors, but I could never find a solution that was cheap enough. The only truly inexpensive solutions were terrible 480i units. The only option left was to build my own. See how I did it after the break!
I didn't want a LumenLab projector, because they require a lot of work, are pretty big, and a little cost-prohibitive. I finally decided to begin on a project that I'd wanted to start for a long time: converting an old overhead projector to an LCD video projector. It's not a new or unique hack, but it's one of those hacks that very few people have actually done.
The first order of business was to obtain a screen and an overhead projector. The projector was procured for $25 from a local electronics surplus shop that specializes in awesome. The screen was a bit of a wild ride.
- Can't be a laptop panel, those use proprietary controller boards, so getting one of those to work is beyond my scope of knowledge
- Can't be bigger than 15" diagonally; those won't fit most overhead projectors
- Can't block the light path (critical electronics must be able to swing out from behind the panel)
- A contained power supply/controller board assembly would be preferable
- Component inputs preferred
- I posted an ad on Craigslist, asking for broken screens with a reward of $5. I had tons of offers for 17" screens - one of which I did accept - but no offers for 15s. The 17" had a broken backlight, and even though it was far too big, I used it to prove my concept.
Proof of Concept Problems
- The 17" monitor was just too big
- The panel got very hot, so I rigged up a household can blowing across it to keep it cool
- The panel needed to be suspended above the projector for cooling, but barely, because the image size tapers off the more the panel is suspended
- Panel, electronics, fan, and all of the extremely fragile connections in between made for very delicate and involved setup and teardown: the final product needed a protective enclosure and built-in cooling system
- The image quality was clear, but contrast was poor
I broke two 15" monitors just getting them apart. The first suffered a cracked screen from too much force prying it apart, the second died from ESD along the way; the panel showed no image after I got it apart. Moral of the story, go insanely slow, figure out exactly how the next piece comes apart before you try, and expect to ruin a few monitors. The third LCD panel had circuitry blocking the light path, and I broke one of the backlight CCFL's putting it back together. Luckily, only one of the monitors I broke was good. The rest were all old or broken.
Finally, a local TV/monitor repair guy saw my ad and called me up. He offered to give me a 15" 720p HDTV in exchange for some computer repair. Score! Now for that enclosure and cooling system.
The LCD frame needed to accomplish several goals
- Contain the LCD panel
- Protect the LCD panel
- Secure all wiring
- Provide a mounting point for the LCD panel electronics
- Allow the overhead projector to be converted back to it's original state
Cooling System Considerations
- The frame would need to suspend the panel .2" about the surface of the overhead projector
- The frame would have to provide mounting points for fans
- 3 1" 12v computer fans would be used for cooling (2 1" fans would have been enough)
- The fans would be powered by a 12v 1A power adapter (modifying the power supply sounded too risky, and this working panel was hard to find)
LCD Panel Considerations
- A 4:3 15" panel would fit, but a 16:9 panel is too wide
- The panel must support running at 4:3, so the edges wouldn't be chopped
- The tradeoff would be worth it for component inputs for this application
- I forgot to consider that consoles only output at 480p when run in 4:3, but VGA runs closer to native (tradeoff is still worth it)
I drew up a design for an enclosure with built in cooling fans, and took it to my brother (www.crane-designs.com). He measured up the panel and various parts with a micrometer and drew up a model in SolidWorks. We grabbed a 1/2" slab of cuttingboard material from Interstate Plastics for $25, and milled everything out on his CNC router.
The frame around the LCD performs several functions. First, it holds the panel .2" off the surface of the overhead projector, allowing 3 1" fans to force air under the panel. The air exhausts out an opening on the far side of the frame. 2 1" fans would have been completely sufficient, but I left the 3rd in so there wouldn't be an empty spot. If you only have 1 3" fan, that should also do the trick. My 1" fans have a gap on the top as well, which keeps the fans from bogging down, and blows a bit of air across the top of the panel. If I wasn't worried about damaging the fans, the gap wouldn't be necessary.
The fans are powered with a separate 12v 1A power supply. It may have been possible to run them off the HDTV power supply, but I didn't want to risk hurting it, as it took a long time to obtain a usable monitor.
The metal enclosure on the back contains most of the guts from the TV. I liked how everything was pretty self-contained, so I didn't have to do much for this part of the enclosure. The bottom has a plug that attaches the headphone jack, controls, and power light/IR receiver, so I routed them back under the case and out the sides. The speakers are terrible, so I didn't put much effort into mounting them nicely. Everything is attached with double-sided tape. Version 2.0 will include a prettier enclosure for the electronics and speakers.
The cutting board material proved to be very easy to work with. It's also pretty rigid. I found it easy to drill holes and countersink screws. The bridge on the exhaust end of the LCD panel was an accident; the CNC mill didn't like how narrow that section was when we tried to add exhaust slots. When I tried cutting it out completely, it introduced too much flex, so the bridge was added. It's totally solid now.
The LCD panel frame is totally removable from the projector. Only a couple of pieces of velcro mar the overhead projector itself. In theory, I could throw the frame on a different projector, but I designed it to fit this one perfectly.
The finished product performs well. The 3 fans keep the LCD panel completely cool to the touch. As stated earlier, 2 1" fans would have been completely sufficient. The overhead projector doesn't project a completely square image; there is a minor keystone effect, but it's hardly noticeable.
The pictures make the color look much more washed out than it is. Brightness is ok, if you are doing serious gaming or movie-watching, you'll want to turn the lights off and block the windows. Text is completely readable with the lights on, as long as the room isn't overly bright.
The only real downfall is the contrast. Brighter colors look great, but shadowy corners and dark scenes suffer a little bit. Again, it's not perfect but considering the price and simplicity of the projector, I really can't say I care.
It's a bummer that I have to run my 720p TV at 480p on component to keep the edges from getting chopped off. With 12 foot diagonal screen, the video still looks pretty good. VGA input will probably be much better, as I should be able to run higher resolutions at 4:3. I haven't had a chance to mess with this yet.
- Overhead Projector: $25
- LCD HDTV/Monitor: Free
- 22x18x1/2" + 10x13x1/2" cutting board material: $25
- Fans and power supply: $15 (most builders probably have these laying around)
- 12v 1A Power Adapter: $5
- Power connectors: $3 (Again, you could scavenge these from some PC parts)
In the end, this build cost me $73. You could cut the cost significantly but grabbing cutting boards from Wal-Mart or using fans that you already have on hand. I can't give you an exact design to work with, because every single LCD panel is different, but the pictures should help you get started.
Many thanks to Dave at The Reuseum for the supplies and parts. You must check out their website. My brother over at Crane Designs put a lot of work into drawing up and CNC routing all of the parts for me, without his skills this project wouldn't have been nearly as cool. Also, everyone at Open Lab Idaho, our brand new Hackerspace, where quite a bit of assembly took place. Of course, Badger32d, for telling me to send this in to Hackaday.
Thanks for reading, and good luck with your own DIY overhead LCD projector conversion! - Joel / Fuelcell250