45 replies to this topic

[boltsniper]

You really don`t need a lot of electonics knowledge or experience. You could get by with minimal soldering or probably known if you just used wire nuts and clips. Basically all you need to do is supply power to the light ballast and the 12V supply for the LCD. I added some electronics just for fun but you definitely don`t need to.

DIYprojectorcompany has step by step plans available along with kits available. All the available plans are for large bulky units and I wanted something portable, so I came up with my own design. The layout is pretty simple: light source into a collimnating fresnel through the LCD through a field frsenel and through the projection lens. You have to mind the focal lengths of the lens and place them accordingly but the rest is up to you.

[cxwq]

I saw the fresnels in your pics and wondered if they don't introduce noise with the size of your throw? I had always thought that they generally avoided fresnels except in the old school RPTVs as the front element and that glass optics were preferred.

In any event, it's a cool project and I may have to try my hand at it some day. Thanks for the post.

[merlinski]

Regarding the need for a dark room:

Most high end rear-projection home theater setups are set up by home theater buffs who want a huge diagonal screen and powerful surround sound with it. For that reason, many of the people who do projectors put them in rooms with no windows or very small windows - I've seen tons of setups where the room was designed originally to be a projector screening room, with no windows and sensitive to acoustics. There really isn't a way around this, and its the biggest reason projectors haven't replaced big screen tv's.

The best chance to get around this is a technology recently developed by Sony (though not on the market yet) for projector screens. It's a black screen that only reflects pure red, green, and blue light, and absorbs white or wide-spectrum light coming from flourescent or ambient lighting. This means that projectors can have pure blacks and sharp contrast even in bright environments. However, I'm pretty sure this only works for DLP projectors because they use only those three pure colors - I doubt this would be successful with an LCD projector.

[boltsniper]

I saw the fresnels in your pics and wondered if they don't introduce noise with the size of your throw? I had always thought that they generally avoided fresnels except in the old school RPTVs as the front element and that glass optics were preferred.

In any event, it's a cool project and I may have to try my hand at it some day. Thanks for the post.

You will run into artifacting with the fresnels if you place them too close to the LCD. As long as there is a reasonable gap between the two nothing will show up. Some people will argue that you should put both fresnels behind the LCD and have a straight shot to the projection lens. I messed around a little and didn`t see any noticable difference. I don`t know if commercial projectors use fresnels or not. Witt the size of the LCD's used, (about 2-3 inches) they may use true convex lenses.

[taita cakes]

Thanks for clearing that up bolt and merl, but I understood about all that, my Dad raves about light and contrast and everything as an artist, and loves his Audio Visual. I meant more so if it was feasible to use like a tv in terms of warm up time, bulb replacement, but most of that has already been answered. A guy at school was saying that you can use cheap old 15" LCD monitors with dead pixels, I'm going to have a looksee at the link to see how exactly these projectors work, but is that true?

[boltsniper]

Don`t worry about bulb replacement too much. The lamp I am using is rated for 15-20000 hours, depending on who you are looking at. Compare that to the lifespan of a typical CRT of about 25000 hours to half brightness. Not much difference and you don`t consider lifespan when you are buying a TV. Besides, even if the bulb does fail its a 1 minutes job to replace it and the cost is only $30-50.

There is a warmup period before the light reaches full brightness. During the breakin period of the bulb, supposedly the first 100 hours, the lamp can take between 10 seconds and 2 minutes to ignite. Once ignited it usually takes about 30 seconds to reach full brightness.

Most of the DIY projector sites give plans for projectors with 15" LCD's. And that is what most people build. Because of the market 15" LCD monitors are the highest resolution you can get for the least money. The resulting projector is massive though and that is why I went with the 7" screen.

"dead pixels" is such a vague term. If it jsut had a couple dead singular pixels and they were "dead off", it proably wouldn`t make a difference and you wouldn`t notice. If the pixels are "dead on", meaning they are stuck shining full red, full blue, or full green....then that might get annoying. I had a pocket TV with a bunch of dead pixels stuck on red. Drove me crazy. Also "dead pixels" could also mean that an entire row or column is out which would obviously be noticable. Any monitor that is branded with dead pixels I would try to check out before I bought it. I`d be cautious about buying a used LCD with dead pixels off of ebay or an online store.

I hung my projector from the ceiling yesterday. It shines on the wall adjacent to the TV. I`ll snap a picture of the setup tonight and post it

Edited by boltsniper, 16 August 2005 - 11:56 AM.

[ompa]

What do you think of using an old laptop screen for a projector? I realize it's going to be bulky, but for me, it'd be the cheapest alternative.

Of course, the one me and my friend will hopefully be building will use the 7-inch screen you showed me.

~ompa

[boltsniper]

I`m not sure how you would input video easily for display on a laptop screen. You would have to include the entire motherboard since everything including the video is on one board. It would be kind of cool to have a computer that you could take around and projector on a wall.

[ompa]

True, but with the size of such massive beast, I'd easily be able to stick it on the top or bottom of the projector. Keep in mind the projector has to be at least the dimensions of the LCD, and the motherboard should be near the same size. I'm just worried about the resolution.

For conversion of computer monitors

~ompa

Edited by ompa, 16 August 2005 - 12:54 PM.

[boltsniper]

True, but most laptops don`t have VGA input, just VGA out. At least the ones I`ve owned and used.

You`re right, you`ll have plenty of room for al the electronics. I was just saying there is going to be a whole of unneccesary crap because of the integrated nature of a laptop

[Gamefreak]

Very nice Bolt.

If you don't care about bulk...

[boltsniper]

A lot of people do use overhead projectors as a platform to make a dedicated video projector. The halogen bulb doesn`t provide a good color temperature and isn`t that bright and a lot of people replace the halogen light with a metal halide bulb. The projection lense of an OHP is also usually a singlet or a duplet les which isn`t the best for accurate projection.

I took some photos of the projector after I hung it. Today I painted the border around the screen which frames the image very nicely.


Projector hung and unframed screen


Projector on during the daytime with the blinds closed. For comparison the TV is a 27"


On at nightime. The image is very bright anc sharp with all the lights off.


On with lights in other room on. Even with a significant amount of ambient light the projected image is still very watchable. You can see the matte black border on the screen in this shot.

Projected image is 92" diagonal

Please excuse the quality of the photos, my camera does not perform well in poor light

Edited by boltsniper, 16 August 2005 - 09:20 PM.

[Crankymonky]

I just skimmed the thread, but it seemed like there was no walkthrough!

Tomshardware has one, don't have a link on me, but shouldn't be hard to find.

Nice mounting and end result. What LCD monitor (assuming you took the panel from one) did you use?

EDIT: Mentioned mounting since I mounted like 12 on generic mounts, took like an hour to align each one.

Edited by crankymonky, 16 August 2005 - 11:05 PM.

[LordoftheRing434]

According to my wife

I can`t...
clean up after myself
wash clothes
load the dishwasher
unload the dishwasher
make the bed
etc
etc
....you get the idea

Hahaha, that sounds exactly like me. And yet you've come up with the FAR, a projector, and several other guns. It sounds like you have a lot of free time.

I have seen a projector almost along those lines. I was out in Montana and the people we stayed with had a homemade projector. It wasn't LCD and it was pretty ghetto. My buddies and I watched Star Wars on it, and that was topped off with surround sound. It's not even close to your's though. boltsniper, you've got to be the most innovative guy out there. Nice work!

~Rings

[taita cakes]

Thanks again bolt.

A couple of questions:
1) Sorry, I know you roughly mentioned this, without an LCD [say I had one somewhere] and using low grade casing etc, how much would I expect this to cost?

2) What exactly is a 7" LCD, because I know PC's and Laptops range from 12-19" but what is the common use of a 7" if I was looking to source one?

3) I had a deeper look at the internals and one of the websites [when I finally found some pictures], and I wanted to know how the light passes through the LCD? I saw all the glass and fresnel stuff, but does it mean you have to dismantle your monitor to make the LCD transperant or something?

[boltsniper]

Thanks again bolt.

A couple of questions:
<below>

1) Sorry, I know you roughly mentioned this, without an LCD [say I had one somewhere] and using low grade casing etc, how much would I expect this to cost?

The LCD and the light or going to be the most expensive components. Metal Halide lights usually run around $160 for a 250W and slightly more for a 400W. If you keep an eye out on ebay you could nab one for alsightly less. I got mine for $120.

The LCD I used was $200. You can get 7" panels for less but the resolution is usually much lower. Good 15" panels can be had for around $100 with good sales, rebates, and such. And you could always pick up a used one like you were saying earlier.

The lenses will probably run between $50 and $100 depending on what you choose to use. The fresnels are pretty cheap but the projection triplet can get costly. It is a video projection grade unit though.

The rest is just building materials and hardware. If you use wood for the enclosure it would be the cheapest. I already had a bunch of lexan and aluminum that I had bought for some other projects, so I used that.

You could probably build one for under $300 or better if you got some good deals on the LCD and light. If you already had and LCD you are probably looking at another $200.

2) What exactly is a 7" LCD, because I know PC's and Laptops range from 12-19" but what is the common use of a 7" if I was looking to source one?

Ever seen Pimp my Ride? I don`t know if they play it over there. Anyway, a huge market for smaller LCD's is automotive. In-dash or in-headrest screens. Most of them range from 7-9". And a nice thing about the ones designed for use like this is that they have both A/V and VGA input.

If you are looking for a 7-9" panel this site has a bunch.

3) I had a deeper look at the internals and one of the websites [when I finally found some pictures], and I wanted to know how the light passes through the LCD? I saw all the glass and fresnel stuff, but does it mean you have to dismantle your monitor to make the LCD transperant or something?

Bingo. The actual LCD is a thin sandwuch of glass and is quite translucent. The majorityof the bulk of an LCD panel is the backlight. You have to disassemble the panel and remove the backlight assembly. The back light is usually fastened to the LCD with a metal frame with tabs or screws. You will have to carefully remove everything involved with the backlight. The backlight is pretty cool in its own right. It's usually a cold cathode tube around the perimeter shining into a prismatic diffuser and through more unidirection diffuser lenses (I spent about a week walking around with these lenses up to my face running into walls). It's all layered up behind the LCD and should just lift off. What you need to end up with is the bare LCD and all its circuitry. They tend to use ribbon cables a lot so you need to be careful when removing and handling the LCD and boards.


Good luck if you decide to build one. It's really not that bad of a build. The hardest part is getting the lenses positioned at the right distances. If you ahve anymore questions feel free to ask.

[Oroku Saki]

That's a pretty cool project. One of my friends built a projector a while back, and he used it to play Halo 2 on a huge white wall in his backyard. Pretty kickass stuff....

[taita cakes]

Thanks once more bolt, but I spoke to a few people from school today and got roughly the same feedback. I can't believe I forgot what use a 7" LCD was
I plan to build one of these when I move out, so don't be rushing to help or anything, but maybe if I want to splash around some cash I might jump into it soon.

Just a thought, could you get a very small projection range by using a camera LCD As in by using the common 1.5" camera screen you could get a 15" or so projected size? I doubt it though, the LCD pixel quality and such would be pretty poor, and project quite badly I guess?

[cxwq]

Most small LCDs are actually reasonably high pixel density, but still not enough to give you a very sharp picture when enlarged significantly. My Treo 650 has a super high res 320x320 2" square display that would give *almost* standard TV resolution - kinda cool. The problem you run into here though is interfacing it to receive any kind of standard input.

[boltsniper]

I`ve seen some projectors made with a 2.5" LCD and the results were decent. I think it was on the lumenlab forums. He used a halogen bulb like you would find in an overhead projector. And because the LCD was about the size of the lamp there was no need for a condensing fresnel. The resulting projector was really small and didn`t project half bad. I think he got a few feet diagonal. It would be fun to mess with around with.

ETA: I ran across this 2.5" LCD. Resolution isn`t that bad at 480x234.

Edited by boltsniper, 18 August 2005 - 03:52 PM.

[taita cakes]

I hate to spam like this, but my brother has just set up an ebay store, and it sort of proves a lot of my previous beliefs wrong. He's importing some projectors and selling them in his store, and making a killing. The huge difference is that the bulbs last 6000 hours and only cost $200 according to him.

Check it out.

Tell him I recommended him if anyone purchases, okay? Remember prices are aussie so you'll make a killing.