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Cool post. Good to know something like this can be a DIY project. Wouldn't try it myself for entertainment value, but definitely a worthwhile science project.
 

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Cool. It shows it can be done.


You can not even get a used CRT at that price. Maybe if you are lucky and the seller do not know nothing and I mean nothing.
 

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Discussion Starter · #4 ·
I'm glad you liked it. :)


I thought this would become a very active thread when I posted it. I guess I was wrong.


Tor Arne
 

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Can you imagine what the overall brightness would be? I'm thinking somewhere around 80-100 lumens if one uses plain off the shelf lighting.
 

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Hi everybody. I finished "Phase 1" :cool: of my DIY LCD project a few days ago. I can get a 105" diagonal (4:3) with an acceptable picture quality, for me at least. I'm sure it doesn't even compare to the "big boys", but neither does the price---I have spent a little over $140 USD !!


There is a HUGE thread at www.diyaudio.com that deals with DIY projectors. There is some interesting content there.


What most people are doing isn't really DIY...they just buy an Overhead Projector (like the ones in classrooms that project transparencies) and an LCD panel designed to fit on top of the projector stage. Both of these can be found for cheap on Ebay. Resolutions range from 640x480 (what I have) to 1024x768 and higher. Some people are working on using LCD computer monitors with the backlight removed, giving much higher resolution and quality than the OHP LCD panels. I am dismantling my OHP and panel to create a more compact, integrated projector.


Bottom line: Cheap projection video can be had for $200 or less if you look for bargains. Add a DIY screen, and you are rollin'!


Here is a screenshot from a guy on the www.diyaudio.com board using an OHP and an OHP panel...

http://pws.ihpc.net/joejas/projector/NK1.JPG


I think there is a bad pixel in the LCD. Anyway, not too bad!


The only thing I have to address now is circumventing Macrovision. My Toshiba SD-3750 thinks my LCD is a VCR, so I get that Level 1 fade/bright pulsing. :( Any DIY ideas??


-f4
 

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Discussion Starter · #11 ·
Hey! What about using one of those portable DVD-players with widescreen LCD-displays? That would also work. But I like the idea of a 1024x768 laptop as an integrated HTPC/projector. :) A little expensive though at almost the same price as a "real" projector. :)


I have seen devices which remove macrovision from the video-signal. They're called macro-killer and similar names. :)



Tor Arne
 

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It would be neat to use a widescreen LCD monitor to make a projector but they are too expensive.


fender4,


Would love to see some screen shots. A project like this might be a good wait to allow me to save up for a full LCD pj setup. Do you need an HTPC do do this? If not, what happens to non-anamorphic DVD's?
 

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The widescreen issue has never really been addressed in the diyaudio forum, but I know that small, mobile video widescreen LCD's are out there for car installations. Originally, most people focused on using the smaller, mobile LCD types with composite inputs, but the OHP/panel route was pretty much fool-proof. Several are still working on more compact, mobile LCD based projectors, but the primary limitation is resolution (highest resolution for vertical is 234...yuk).


The LCD panel I am using is designed to be placed on an OHP (do an Ebay search for "projection panel"). Mine has S-video, composite, and VGA inputs. I'm not sure what non-anamorphic DVD means, but the S-video input is nice feature. Too bad the Macrovision is degrading the quality of my signal...and I don't even want to copy ANYTHING!!!


Some are using HTPC's, but I am just using a Toshiba SD-3750 as my source.


I don't have any screenshots...I don't even have a screen! ;) My digital camera is not up to any medium- or low-light tasks. There have been a few people post with screenshots, but most hardcore DIY'ers are still in the building phase (it's just never good enough!). I am planning on adapting a metal halide light/ballast commonly used in reef aquaria as a light source for my project....some of these bulbs last 20,000 hours! Drawbacks are large bulb size, relatively large arc, and difficult reflector design.


Here is another screenshot from the same guy:
http://pws.ihpc.net/joejas/projector/NK6.JPG


This next one is from a standard cable TV broadcast on a 640x480 panel:
http://www.diyaudio.com/forums/attac...=&postid=26576


There was a guy that posted a few weeks ago that said he got an old OHP from a university that was throwing it out and somehow got a 800x600 panel for $30 on ebay. That's all you need! Normally, though, a good panel could cost as much as $150 on ebay.


Hope this helps give you some ideas.


-f4
 

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That first picture doesn't look too bad. So what is the total cost of this contraption? Its cool :)


So you mean like an Over Head Projector? Wow. Thats not hard to find but you need a good one I guess. Oh well. Let us know how it goes.


So what is the panel exactly? Is it the LCD things that go on top of the OHP? What do they look like? They have S-video inputs? Could you connect the panel to VGA say, from an iscan? :cool:
 

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The system that produced the first pic is using an "nView Z-350" projection panel (simply an transmissive TFT LCD panel) and an over head projector (OHP). That panel only has VGA inputs, so you would be limited to HTPC use. This is fine for many, and you wouldn't need a video-out card. I'm not sure what implications that has, because I am fairly new to the world of HTPC/projection. It has 1024x768 native resolution, which is quite high, but it is from 1995, so the technology isn't quite current. One issue is lower contrast ratios that are common on these panels.


Over the last few months, the prices these panels are commanding on Ebay.com has been increasing...I am assuming this is because of people realizing their potential. For example, there is an "nView Z-350" on ebay with 2 days left in the auction that is at $180 already. If you only want 640x480 and VGA inputs, your selection would be much larger on ebay. Composite and S-video inputs on these is not as common as the the VGA-only input. For some pretty basic reviews of different panels, click here.


Any OHP should work, although higher lumen projectors are more popular, of course. Unfortunately, the bulbs used in most OHP's are inefficient halogens that have a life of 100 hours or so. That is why many have focused their DIY efforts towards retrofitting OHP's with common metal halide bulbs (better color temp, efficiency, lumens, price, much longer bulb life, etc.). You could find a suitable OHP on ebay for $60 or less, but nicer ones would cost considerably more.


I don't think anyone working on these projectors expects "commercial projector quality". Most are just looking for a way to have a large, mid-fi quality image for the same price as a 19" or 25" CRT TV. I am drawn to it for that reason, and I love DIY projects. One poster on diyaudio has compared his OHP/panel projector to a single panel "commercial projector" from several years ago, and he said his DIY projector was on par with commercial unit.


I hope that clears some things up!


-f4
 

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Cool. Keep us updated on your adventure :)
 

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I was reading a lot at www.diyaudio.com about this project. However, no one seemed to have any solid progress and screen shots until now.


I have the following questions/comments for brain-storming:


(1) For the LCD panel, how about using a 15" laptop or LCD monitor, with the backlight assembly removed? These things provide better contrast ratio especially the new ones. I know this is pretty expensive and risky, but I just want to know if it's do-able. I learned that a lot of the TFT LCD screen are backlit with some sort of diffuser from the back and florescent light source from the sides/bottom/top of the screen. Does anyone know if the diffuser is attached permanently to the LCD panel? If not, then removing it seem possible.


(2) For the light source, how about using a couple 5000K florescent bulbs? These bulbs should provide the whitest and most efficient light (20-30w), and we don't need to worry about heat. What are the issues then? Light source convergence?


Please provide your comments/questions.


Thanks,

Kelvin
 

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kelvink,


You bring up some valid points. The LCD monitor idea is a good one, and currently, there are a few people trying this approach. Laptop LCD's are troublesome because they would most likely need to remain attached to the computer for proper operation (not very practical).


The major obstacle with LCD monitors is removal of the driver boards that are often behind the backlight. The backlights, I think, I pretty easy to remove. If several short ribbon cables attach the driver board to the LCD, it can be next to impossible to move the board. The VG150 (Viewsonic?) has been successfully "projector-ized". Here is a website put together by SuperDave from diyaudio.com that gives an overview of the process: http://www.csun.edu/~hbpsy028/projector/index.htm


Resolution, contrast ratio, and refresh rates should be MUCH better with a new LCD monitor like the VG150 when compared to many of the OHP panels, but:

-Most quality LCD monitors are 15" or larger. This makes it tough to fit on an OHP (special lens solutions will be needed...just makes it more expensive)

-They are more expensive

-It is riskier, because you could damage the LCD or circuits while disassembling it.


At some point, you begin to wonder if you could buy cheap, used "commerical" LCD projector. But, one of the main goals of the DIY project is to avoid high-cost and frequent bulb changes. This lowers operating costs significantly. For example, a 400 watt metal halide bulb can cost as little as $20 USD, and it lasts for 20,000 hours.


I have personally tried the fluorescent light approach, and it has several shortcomings. LCD's need parallel light to project efficiently because of polarizers integrated into the panel. These help contrast and minimize washout, I think :eek: . Fluorescent lights are difficult to direct in parallel rays consistently, or at least that was my experience.


The big issue is this. To use a "normal size" projection lens (less than 4" or so in diameter), you need to either use a small LCD (like commercial projectors) or use a system of fresnel lenses with a larger LCD (like an OHP). To use fresnels, you need a light source that radiates consistenly like a point-source light. Fluorescent lights are diffuse sources that will not work properly with fresnels. That is why we have been focusing on metal halides and such.


There has been success with small LCD's and fluorescents, although the screenshots were taken with a video camera and only show in black-and-white :( . Here is the link.


-f4
 

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What about a mirror that deflects light in parallel? Not a parabola, cause that focuses the light at one point, but something analogous to a parabola but for parallel light. A mirror? Something else? Looks like fun nonetheless. LED's are a cool option too. I prefer the less power hungry methods :)
 

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A parabolic reflector would work with a point source light at the focal point...most people making reflectors for metal halide bulbs are using some variation on parabolic reflectors.


LED's might be a practical option in the future. But currently, LED's are no more efficient than a metal halide bulb. To produce as much light as a metal halide would require hundreds of LED's, which would difficult to implement.


Good ideas!


-f4
 
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