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Searching for a Cheap Overhead Projector?
stinkjones asks: "I recently found a project on
Hackaday, which I found very interesting. It was linked to
Tom's Hardware, and involved a massive, and cheap, projector. I have an LCD projector, but this seems like a great project with a pretty cool result. I already have an LCD that's perfect for the job but overhead projectors are hard to find. Retail they are around $500 new or a lot more, and if you can find them used they have a huge range of prices. Does anyone know where to find a cheap one?"
Most universities will get rid of old stuff the school doesn't need. Old computer equipment, everything from Pentium 133 PCs to beige G3s to old IBM mainframes, big plotters, copy machines, desks from renovated dorm rooms, and all manner of odd scientific equipment that nobody knows what it does. Sometimes a university will have a big warehouse that they sell this stuff continuously from, and sometimes it is just a big auction sometime during the school year.
You could probably find an overhead projector there.
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If you resign yourself to spending $150-$200 in addition to the LCD, you can get some amazing results. To be honest, any cheap overhead projector will have a halogen lamp that has too low of a color temperature, too dim of an output, and will need to be replaced every 25-50 hours. The cost adds up. Also, virtually no overhead projector is big enough to light the entire area of a 15" LCD. You will lose up to 60 pixels on both sides of the screen.
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If you instead build your own enclosure, you can do some neat stuff. First, you can show the full 1024x768. Also, you can use a metal halide bulb, which typically have a clean white color and put out less heat for the amount of light produced. And metal halide bulbs last anywhere from 8000 to 20,000 hours. You will also be able to get a high-quality lens for good focus across the whole display, something a cheap overhead might not be able to do.
Go to http://www.diyaudio.com/ and visit the Moving Image forum. There are thousands of posts containing ideas, plans, calculations, optics sources, and photos. I'm in the process of building my own projector with a 400W 6500K metal halide bulb, here's a photo of the image projected by a test mockup: http://lserve.homelinux.net:7780/diyaudio/lightso