: My winter project



Elvis
08-20-04, 09:22 PM
A Home-brew projection TV!!!

I accidentally ran across this idea this afternoon at work while I was killing time and trying to come up with an excuse to leave early. It's actually very inexpensive. Kind of like a 4th-grader's science fair project.

http://www.bigscreentv.20m.com/photo.html

I think I can start small with a small, cheap unit like that one, and then work up to something a little more complicated like this one, which uses a backlighted LCD:

http://www.diyprojectorcompany.net/designs/MkIII_step_1.htm

The key is the Fresnel lens. Augustin Jean Fresnel invented the concept in the 1800's and it was used primarily in lighthouses.

http://www.howstuffworks.com/question244.htm

It's scary what this thing can do.

http://www-personal.umich.edu/~bclee/lens.html

Anybody ever do anything like this? Any advice?

Stoneage_Caddy
08-21-04, 12:04 AM
very interesting , after awhile of playing with it you could make something really professional looking (ie less tape )

tru504187211
08-21-04, 04:28 AM
I started it...but ended up just buying an overhead projector and an lcd panel to place on top of it to input the video signal...looks good, but im still working out the bugs...bugs being 1 = not as bright as it could be! I will eventuallly, maybe next week set up a webpage for this setup...


I am drunk. I like Hennessy.

Elvis
08-21-04, 11:05 PM
Problem #1 with the first link is that the image is reversed (I think). In order to do it right I think you have to reflect it against a mirror.

The LCD projectors bounce it off of a mirror, then run it through another lens. Bulb life and heat seem to be major issues, which is why you don't just use one of those 500W Halogen tubes in a $15 portable fixture. They're big on ventilation. That's okay because I have several dead PC's in a barn. Stripping fans out of those cases would be pretty easy.

I dunno if I'm going to have the patience to endlessly experiment with this, but it would be really cool to have a big party and project something that big and bright up against the side of the house. Nobody I know knows anything about this kind of stuff, so it would be cool to blow their minds with a homemade box that can be built for under $500.

Too bad I don't have any kids. This would be a great science fair project.

T_Dogg8
08-23-04, 08:53 AM
you're right. check this site www.maxtheater.com/

a friend tried it and said it sucked. it worked but was a little blurry and not very bright.

tru504187211
08-23-04, 04:38 PM
You will be impressed, once you get it tweaked to your liking. The only downfall for the OHP and LCD panel on top for me is sometimes it is not as bright in very dark scenes as a TV would be. Also, there is a good amount of heat output...heats up the entire room! (like my computers already don't). Here is a forum that may be able to give you specific answers (I've you've got questions) for your project....

http://www.diyaudio.com/forums/forumdisplay.php?forumid=20