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Homebrewed LCD Projectors
pseudofrog writes: "Seems the new thing to do may be to build your own LCD projector. For a couple hundred bucks, some guys are making projectors similar to the professional ones that cost thousands. And it looks pretty simple, too."
See this page cached@google :)
http://meshier.com/mirrors/www.audiovisualizers.co m/madlab/lcd_proj.htm
- Book sided pc with a Celeron 566/128mb, integrated sound (mostly left over parts+$75 for the case)
- Generic BT848 tv tuner ($50 CompUsa)
- Dukane 4000 lumen projector (ebay $100)
- Active matrix Nview projector panel capable of 1024x786 native resolution ($200)
Total $425I also got a 72" wide screen for $75 retail, but a flat white wall will do almost as well.
The quality on the system with DScaler is very impressive at 1024x768. The only difference in parts between what I have an the author of the linked site is that I've not tried putting it all in a box. Currently it all sites on an end table next to my couch and projects onto a screen which hangs down from rafters. I see no reason why putting in a box would make a difference in the quality. It would probably make it better by blocking out extraneous light that escapes from the overhead projector.
Now while the quality is excellent (you have to play with the brightness/contrast to get a good picture), there are quite a few drawbacks that don't have to do with image quality:
My setup could use a little more CPU power. A better graphic card would be good too 'cause I had to settle on a Geforce 2 MX 200 because it was the best half height video card I could find. Also a sound card with a dolby decoder would make it even better.
It does work, 'though, and looks great, but as you can see it's not perfect.
-dameron
Sounds like these guys are not aftercooling the bulbs. Most projectors I am familiar with allow one to shut it off, and if it remains plugged in, will keep its fan on until whatever internal thermal parameters for prevention of heatsoaking are satisfied.
Allowing the bulb to heat soak is just as bad as running it without cooling.
David
You can get 800X600 lcd projectors on ebay for less than $500.00
and these dont need a computer, just plug in composite video.. (I can hear it now the videophiles that have their 2048p projectors that use fiberoptic digital video and HDTV ready HD-DVD players will whine that it's grainey,low light because it's lower than 95,000 lumens and doesnt have glass lenses made by Plossol in germany... Go to hell videophiles..)
The dayton hamfest is coming up very soon, you can get a (GASP) old technology video-tube projection tv for probably less than $300.00 that works fine. (granted, it's a coffee table, but hey...)
the golden rule is that you scroung for a used one first, then look for cheap new, and THEN create it by hand.
Do not look at laser with remaining good eye.
diyaudio has a 100+ page discussion of this. Most people are using an overhead projector with their standard lightsources, or mercury vapor or metal halide bulbs. The OHP's fresnel lenses get around the problem of having an LCD panel and lens with different sizes and not wasting a lot of the light(but they're kinda big). Pretty good results have been obtained. However, there are some caveats, the contrast ratio of lcd panels from desktop monitors are pretty poor(under 300:1), decent commercial projectors have contrast ratios > 1000:1. Although I haven't built one yet, I think this can lead to washed out images. Also, nobody has found a supplier for the nice 1-2 inch LCD's used in commercial projectors
Please note that the monitor suggested for the experiment (at this link), claims to have a resolution of "960(H) X RGB x 240 (V)=230400" which can be a bit misleading if you're not too tech-savy on these numbers.
Note that the horizontal resolution is NOT 960 pixels, but rather 320, since they're counting each RGB pixel as THREE pixels (very sneaky indeed).
So just be warned in case you thought this was the deal of the century.
Sure, you can use a fairly normal lamp and a fairly normal LCD panel to produce large images on a wall. Heck, you can do it even cheaper with a bunch of colored markers, some saran wrap, and a light bulb.
If you absolutely do not care about video quality, it's easy to get/build a projector on the cheap.
However, today's typical $3500 projector includes:
- A truly full-spectrum lamp. Retail price: $425. Wholesale price: $300. Manufacturing price: $250.
- Built-in line doubler. Most LCDs have 768 vertical pixels; some have 600, some have 1024. DVD's have 525 vertical lines. VHS has something like 240 lines. How do you get from 525 or 240 to 768 or 1024? Anyone who knows anything about computer grahpics will realize that the answer is not "double every 1/X line". Line doublers interpolate lines on the fly.
- Progressive scan support. Again, not a huge big deal, but the way I read the article, not supported.
- Component video in support. Like progressive scan, increasingly critical for decent video.
- Distortion correction, especially trapezoid. It's very rare to be able to project from the geometric center of the screen. Most of us have to live with projecting from the ceiling or floor, and use optical or digital means to correct the image for that.
Sure, you can build a "projector" for $400. Heck, you can probably build one for $100 (see earlier lightbulb, saran wrap, and markers note). But if it were really that easy to produce a home theater quality projector for $1000, don't you think any of the mass producers would have done it? For less than the cost of a one-off? (Anyone who responds that all 8 major projector manufacturers are colluding in price fixing should be laughed at).
Cheers
-b
There is some reasons for the high bulb cost. As noted in other comments, heat is a killer to LCD's. ;-)
The high lumen projectors have 3 things special about the bulbs. 1 is point light source. Light from a point can be focused with the mirror to get most of the light to the LCD's instead of scattering. (A mag light can be focuesd to a bright narrow beam. a flourescent tube can not focus tightly and is not useful for projectors). Porjector lamps are usualy manufactured as a prefocused assembly so it is user installable without a difficult alignment procedure.
2 is a cold mirror. The light from the bulb has to hit a cold mirror reflector to get to the LCD's removing the IR component. This allows a higher power bulb to be used without killing the LCD's. The light from the arc does not directly go to the LCD. The end of the bulb with a terminal faces the LCD's shielding them from the IR output of the bulb. Cold mirrors are not inexpensive. Try buying one.
3 is it is a discharge lamp. This produces more visable light over an incandecent lamp of the same power. Discharge lamps are usualy rated for 2000 hours instead of the typical 8-24 hours for a 3400 degree incandecent. They also have better daylight color tempeture (5600 degree typical) for better color so the pictures can provide a true rendition of the blue screen of death.
The truth shall set you free!
I'll try to list them.
You need a metal halide light bulb and ballast. Metal halide light bulbs are many many times more efficient at turning electricity into light, and thus produce far less heat. They also provide a 'whiter' light than a standard bulb. These are about $200 from hydroponics shops, and range in power from about 200-1000watts.
You need a 'cold filter' to block out the UV rays the light produces. Without this, the ultraviolet rays will actually start killing pixels. This happened to my projector. These little peices of glass alone cost around $200. But without one, you will cook an LCD very quickly, especially with higher powered lights.
By the time you get a decent lense, so you can actually get a decently sized and focussed image, you are starting to get into the sort of money that a decent 2nd hand projector goes for, without all the pitfalls.