DIY Video Projector

[icculus]

i've been a sponge on this thred for a couple weeks now and decided it's time to add my 2 cents. first off, I encourage anyone who hasnt't alredy done the OHP/projection panel setup to give it a try. i got my setup about 3 weeks ago for about $130 total and it works better than I ever expected.

I recommend trying to find the stuff locally, as the shipping charges on ebay tend to jack the price of larger(OHP) items beyond their real value. There are always companies selling off their old obsolete crap in the paper. I got my OHP for 50 bucks from a guy who bought out an A/V company. Keep in mind that to most people, these items are of little use, and don't let on that you're using it for something really cool. You could probably score a lot of them and sell them to readers of this thread.

So, you ask, where's the DIY? I fully intend to adapt/ modify/ improve my setup, but in the meantime iI have a working projector which I can disasseble quickly, use parts from, modify, etc... and if my ideas don't work, I just put it back together and I still have a pretty decent 80" image on the wall.
BTW.. MY first project used a headlamp from a car; good quality light, but couldn't get the light bulb out of the projected image

[multiplexor]

Originally posted by Bitch
Okay, I'm desperatly trying to think how to get the cooling in my box work better. Three 12x12cm (5 inch) fans should be enough!?

Here are two pics of my setup, one is the original "3d design" which looks quite much it, only lightsource is not in the bottom of the thing and there are not four of them. The other picture is the cooling setup right now. All the fans are located in the backwall of the thing.



Now, first of all, do you think the fan in the bottom is useless? Other thing is that should I also have a fan on top of the fresnel as well?

Any suggestions are welcome, even just your best shot, It'll be better than nothing.

in between the fresnel and the lens... if you placed a semi transparent glass so that the light doesn't go back down. And, if you made that small area all reflective material. Wouldn't that work? Make the middle area really bright and stuff.

just a thought...

[ZeCo]

way too big. Better if you work with mirrors. BTW, quantity doesnt mean quality. Better using one quality lamp instead of 4. Besides, your electric bill will be high hehe.

[ZeCo]

the lcd projector I got has more problems than just a need for a new bulb. In fact, the bulb even works (FXL). Powers up but the bulb wont come up.

Well, took a look at the parts and everything seems to be in fairly good condition but a fuse that is dark in the middle (hehe, burned?). Going to need to send it to someone to replace as the damn fuse is kind of glued or too tight and I cant even read the fuse type. Should be very cheap to fix.

Anyway, took a look at the parts and like I expected, nothing much on it. The projector has 2 boards. One for the inputs and the other for the power and stuff.

Optics is pretty simple and makes me really wonder why we cant really get awesome quality from our DIY projectors.

Ill try to draw later but here it goes.

1. lamp: there is a small part for the FXL lamps. Three are two on it and the projector figures it out itself when one is not working and automatically switches.

2. lens. Three is a small lens right on front of the bulb. it is a bit bigger than the bulb. So I guess we are making a mistake trying to make a reflector as big as the LCD panel. I think it should be as big as the condensor. Didnt measure but looks like it is about 3 to 4"

3. Mirror: About 6" ahead there is a mirror. The mirror is in on side of a orthogonal black box. This box looks like those from the 100" TV some people make.

4. LCD: There is a huge LCD in there right in the middle of the projector. It's about 8"

5. Mirror: another mirror in there. This one directs against the bulb but on the other side

6. Projector lens. three is an adjustable lens in there. Cant say for sure but it looks like a triplet or at least doublet lens.

xx: fans: three is one huge vertical fan right besides the bulb and one computer case type fan on the bottom right in front of the LCD. the huge one takes the heat out.

Thats about it.


so may plans now are:

1. find a small MH or mercury or xenon bulb
2. create a parabolic reflector for this bulb
3. buy two mirrors at about the size of the LCD width (8.4")
4. Find a quality condenser a bit bigger than the reflector diameter
5. buy a quality field lens.

To create the reflector and buy the mirrors should be very cheap. I already have a "testing" 640x480 LCD pnel (but will later upgrade for a 1024x768 one) and computer case fan. I only need to invest some money on the bulb, find a good fan for the bulb and condenser/field lens.

Ill NOT to use fresnel lens from the OHP as i have planned before.

k boys, time to start spending money!!!!

[prjctr_builder]

does the light go THROUGH the lcd?

[ZeCo]

well, cant edit anymore so here is the corrections.

there is a fresnel right before the LCD. Couldnt see that as it was "hided" into that orthogonal box.

So, I assume they used a pre-condenser and them a fresnel. So, here it comes me using the fresnel again hehe


so now my question is: althoug i knew some projectors use pre-condenser, what is its real function? to me it looks like it makes a lot easier for building the reflector as it would only have to be as big as the pre-condenser.

I might be wrong.


well, the fuse is burn and Ill have to find a way to fix it. (very bad position for the fuse and it is somehow "glued". Therefore I cant see the lights coming through,but im sure it goes now that i corrected my post

If the problem is only the fuse, Ill have this projector for the bedroom and the one ill build for the living room, if not i at least can use its optics. and since its LCD is as big as mine Id be set with the optics. Id just need to add better bulb. (MH)

[pod184]

Is there any advantage to using the vga input on the lcd panel instead of the composite? If there is, anyone have a good lead of where to get one? (A vga box, that is)

Pod

[Marklar]

In my OHP i have a F=327mm double convex lens I want to make the image smaller do I need to go for higher or lower focal length?

[xblocker]

Marklar,
short focal lenght = image larger
long focal lenght = image smaller

icculus,
i think it's a good point to start with a working setup like OHP+projection panel. You can go the way back if some adventures are not succesfull ! If someone builts a projector from the scratch and doesn't exactly know what he's doing, this can quickly end up in a waste of time and money, especially if he hasn't a clue, how optics work!

xblocker

[ZeCo]

Originally posted by pod184
Is there any advantage to using the vga input on the lcd panel instead of the composite? If there is, anyone have a good lead of where to get one? (A vga box, that is)

Pod

If you panel does not have line doubler on it (very likely not) then it make a lot of difference.