DIY Video Projector Part II

[Smoke Eater]

Have you tried it both ways? (Using a plano-convex lense instead of the fresnel for projection?) I was wondering which would give the best clarity. Are you getting a pretty good image with just the fresnels?

[Billett]

Originally posted by Smoke Eater
Have you tried it both ways? (Using a plano-convex lense instead of the fresnel for projection?) I was wondering which would give the best clarity. Are you getting a pretty good image with just the fresnels?

Yes...

I've tried the pc as a final lens but I found it impossible to focus more than 35% of the image. It also magnified to strongly. With the regular frensel my projector is about 8 feet from the wall giving me an 80 inch image. The PC lens would have done it 3 feet from the wall.

I am very happy with the quality of the cheep fresnel. I am able to focus 95% of the image perfectly. So much so that the "screen door" lines in the LCD are visible. The other 5% of imperfect image may be do to the beat up or slightly bent nature of my fresnel. I'm going to get a new one that hasn't lived through a few hundred experiments and try it.

Paul

[Smoke Eater]

Thanks Paul, I've been messing around with mine pieces and parts since I saw you diagram and I can see what you're saying. You mentioned that you're working on a reflector for your MH, I've been working on this myself. My problem is what type? Should I go for a spherical (and make the rays parallel right into the lcd screen) or ellipsical (focus the rays to one spot and then spread them out again with a lense), or some other design? I'm leaning (mainly because of the huge size of those MH bulbs) to a spherical or rectangular-spherical shape and sending parallel rays directly into the lcd screen. Is there any advantage to eliptical and converging them into a lense to re-spread them? Randy

[Bobo]

Thanks man!

[multiplexor]

Originally posted by Billett


Any Questions?

very cool, looks like a nice simple setup.

did i miss the pics? If you haven't posted any yet, please do post pics of your setup

[thecrumbum]

I'm a lazy DIY'er. I simply want to buy and LCD pad and slap it onto an overhead for cheap video. My question is: There are thousands of cheap projectors on ebay, but I'd like one that utilizes metal halide lighting. Could anyone provide any additional make/models that use MH lighting? thanks

So far:
Elmo HP 305A
Osram HMI

[Mystircal333]

Please Billett post a pic of you setup and the projected image possible. I would really like to know more about what kind of result you are getting. I really want to know if the 400w MH really imporve the image quality then my 250wMH.

Or you could just describe the quality of projected image. Like if you are able to see all the detail in a dark scene from a movie. Was it able to project all the color shade property (especially a dark grey color in a dark scene). Mine was really horrible (it could just be my setup or the bulb).

[rbraithwaite]

Does anyone know if it's safe to put a dimmer switch between the mains cable and the ballast of a 400w MH lamp. Just wondered if I did this that I might affect the volts, amps, etc. going to the lamp?

Thanks in advance, Richard

[slize]

after several failures i decided to spend MORE than 200$ for my diy projector, because until now, with all the failures, I already have spent about 300$ and nothing but experience came out.

So I decided to built a projector for the half of the price of a new one (the cheapest on the market is 1800$ with a replacement bulb for 250$). So my limit is 900$

I bought:

500W halogen bulb (4.99$) (10000 lumens)

15" Belinea (Max Data) 101515 TFT Monitor 1024x768 dots TCO99(230$ on ebay)

a PC only for the projector: CPU 700MhZ (AMD Duron)+256 SDRAM+tv capture card(typhoon)+5.1Soundcard(with spdif out; typhoon)+Seagate 40GB(very silent HDD)+Creative CD-R(with Remote Control)...all in all 330$

a lamp for the 500W bulb with dimmer (8.99$ on ebay)

an overhead projector; bulb didn't work but i just needed the lens and the fresnel lens (30$ on ebay)

two fans (20$)

all costs 623,98$+projection wall (25$) ===> 650$

Call me crazy but I think it is worth it. My projector costs less than the half of a new projector and has a resolution of 800x600 and a replacement bulb for 4.99$ and a picture of 2.5m in a darkened room. If you buy a used projector on ebay for that money you never know how long it will work or the bulb will work. And a new bulb costs half of the projector. If something is damaged i can replace it by myself and i do not need expensive services.

I put some of my experiences in this "BIG" projector:
(the projector is not big at all, its measurements are like a 17" CRT Monitor; and the PC stands on the floor)

- first of all: a PC TFT works very well, you cannot use the whole image because of the controllers in the back of the panel but i use 2/3 in my tests so i guess i have a resolution of about 800x600... (you have to put everything away behind the panel)

- important: no wood, plastic or anything else than metal to sourround the bulb, to build the case for the bulb. I used aluminium...

- to avoid the heat comming to the panel I use two glasses (1cm thick) then the fresnel lens from the ohp and then another glass (0.5cm thick). I use the fans to put out the heat of the case, because the lamp would bake itself in it. one fan (near the bottom) brings new cold air in, the other brings hot air out (hot air goes up so the 2nd is higher than the first fan)

____________________________________
bulb/glass/glass/fresnel lens /glass /tft panel
___/____/____/_________ /_____/_______

The rest is set up like a normal panel-on-ohp construction(there are many in this forum), but smaller and more quite and with a better picture.

- I use Dscaler for the inputs through the capture card (DVD, VHS, TV, PC...) which is outputted on the panel. i use power-dvd for div-x movies, vcd, svcd etc...

The tests worked very well; i had a good picture, a good picture size in a darkened room, now I just have to put everything together and hopefully it will be finished in about 3 to 4 weeks. then i will post some pics.

Andy

P.S.: I know my English is very bad , so if there are any questions I'll try to answer them as good as possible

[prjctr_builder]

the previous post sounded to me like it was written about 2 years ago, when we knew nothing about projection....

my point is... though we did have some progress with learning a thing or two about projection, and some people even had pretty good results, most of us never applied new concepts to their projects. Many people told us which way not to go, but still everyone keeps trying their luck. to me, this forum seems like a closed circle that has no beginning, and seemingly no end as well.