LED Projector?

[jborts]

Thank you Inkog for your advice. While I agree with your assessment that a DIY projector may be overkill, this is what has been asked of me. I am to evaluate consumer projector models and am trying to present a cheaper (DIY) version. They would like a high enough resolution to show satelite television, as this will help with the sustanability of any project here. But I do agree, for the overall goal, this is too much.

[Squalish]

Definitely go with a metal halide setup.

A 20,000 hour 400 watt metal halide bulb, a 15" consumer LCD monitor stripped of its case, a custom made(out of plywood, MDF, or metal) box, along with split fresnel lenses, a polished steel bowl, a triplet lense, and a fan or two. This is the standard build that Lumenlabs uses. At this stage, their standard kit would probably be the most cost effective choice - expect around US$500. I highly recommend you explore their result gallery, and consider buying their guide + private forums: http://www.lumenlab.com/

Luxeon may be able to offer 20 or 30 lumens, but you need 1000 or so to get a decent image on an average sized projection screen. Metal halide is also actually much more efficient than a white LED is, in lumens per watt.

Using a 15" computer monitor panel gets you more than enough resolution for most things, but you need to add the price of a TV tuner that outputs DVI or VGA, $100-$200. Another benefit: The screendoor effect that can become distracting when your pixels are a quarter inch tall is next to nil.

The size is another thing to consider. A projector built this way is about 1/3 meter by 1/4 meter by 0.6 meter. An average consumer projector is a probably less than a tenth this volume. By virtue of this, the LCD panel can get very dirty before you ever notice it, and is relatively easy to clean. Most commercial projector users seem to take them in for service when they get a tiny dust blob in the tiny image element. Cleaning a comparatively huge LCD panel, even if it's somewhat delicate, requires maybe a sponge.

How big do you need the image to be?

What resolution is the satellite TV you mentioned?

[ancorp]

Well if its just sattelite tv, than I think its best to find a cheapers lower res panel. Maybe even a projection panel. Why? because even though screendoor (not if you get an XGA panel) will become more noticable, or the contrast wont be soo good, but you can save the money for the tv converter box, and may not even need one, seeing how some panels have svideo input.

Just my 2 cents

Cheers,
Alex

[jborts]

Image quality is not a great concern. While it would be nice to have the highest resolution, non-pixulated image, price is a more immediate priority. This certainly seems to favor low rez projector panels. I do not know the resolution of the satelite system off hand, I will try and find that information.

Would I still need a TV tuner card to change the station?

As for size, any projection greater than 30 inches would be wonderful. And the size of the projector itself does not matter, expect perhaps for bigger is better (easier for non-techies to replace parts when they break)

[Squalish]

Size of the projection seems to be anything from about 60" diagonal to about 144" diagonal, depending on how bright you want the image to be. They don't put out a huge amount of light, compared to business projectors, though I think they're competitive with home theater projectors.

Projectors are drastically different from how a TV works in their reaction to ambient light. A cathode ray tube is a different technology that is capable of using a dark grey screen, which absorbs ambient light. Projectors require a white screen, and the darkest black on the image is only going to be as dark as the screen is when the projector is turned off. This means that they're only practical in places with very, very little ambient light. You want all the lights to be off, all the shades to be drawn, etc. Or, you can project at night.

Also, regarding the lamps, using a 250 watt HQI bulb with comparable life specs is also possible, if you can tolerate a slightly darker/smaller screen (It sounds like you can).

15" monitors run $150-$200 new. I'd really need details of your source material to describe how you'd have to hook things up.
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I've been reading your website. Very interesting stuff, really makes you sit back and think about what you have. Regarding cooling the pentiums, I'd like to ask you a few questions:

What kind of availability is there for water in the areas that you're talking about? How many processors per site need to be cooled? How close together are they? Is cooling the processors to within, say, 5C of ambient tolerable?

Also, what is the cost of a kilowatt-hour of electricity in the area that you're working?

[dyne]

http://genmay.net/showthread.php?t=511662

$85 each, 20w draw, ~560 lumens

[fingernailX]

This is a site that explains a working led based microfiche projector which is hardened for the third world field use.

http://www.designthatmatters.org/k2/...nt_design.html

Over a 100 students from places like MIT and Cambridge have been working on this since 2002. As the guy who started this thread said they are looking for a multimedia projector design. There are some nice design disscussions there along with other good research. Most is over my head but might be worth checking out by some of the more experienced and knowledgeable diy pj types.