DIY Video Projector

[Petter]

How about putting an array of three colour high-power LED's directly onto the wall in a cluster of say 16*9 feet ...

With the going rate of projectors, this would probably be cheaper and you don't even need to have any optics, no fans etc.

I am concerned with the time constant of LED's, though. I don't know how fast you can switch them on/off

Traffic lights are usually LED these days. I once read that HP sends most of their LED's to traffic light manufacturers!

Another alternative is laser LED's in the projector.

Petter

[vdi_nenna]

That's the spirit! Innovation, that's what I'm talkin' about!

But I wouldn't know a thing about controlling RGB LEDs to form images in a cluster. There is probably some computer controller that handles processing of a video signal.

I do know that LED Cluster screens need a minimum of 10ft from the viewer for the LEDs to be undiscernable.

Passing light through a LCD module is the route I'm taking.
With 48 ultra bright white LEDs I can get about 240 Candalas. (5000mcd each) 5cd x 48= 240. That's bright, but I'll have to see just how bright once it's passing through an LCD panel.

I'm hoping it will be bright enough to work in a theatre style darkened room. I'm not interesed in doing presentations with it, just entertainment!!

[tvi]

BG Micro has White LED-5,600 mcd typ. LED1044.......$2.49 ea
http://www.bgmicro.com/lmad.htm
as this is in their Lets Make A Deal section bulk prices might be pretty good.

They also have a len system at:
http://bgm.bgmicro.com/prodinfo.asp?...ri=LEN&stype=2
<i>"This "double throw down" lens assembly was apparently manufactured for a very large defense contractor. This assembly was one of the main parts of a "Buck Rogers" projection system, which was computer driven."</i>
at US$ 5.50 they might be worth investigating?

Hope this helps

Regards James

[vdi_nenna]

Thanks James, I'll look into that lense. Late last night, while I was working, I went to the All Electronics web site. I found 3 lenses. I was so surprised. I picked up 2 of the 3. One was $5.50 and the other was $6.00. The last one was $55.00. I'm going to check out the 2 cheaper lenses first and look at the $55 one later, as there was no description for it. The lesser priced ones had nice specs.

I picked up 50 White Light LEDs from

http://www.whitelightled.com/ for $1.50 each.

I also picked up a 47 watt power supply w/ +12v @ 2amps output for $8 from All Electronics. That enough to power the LCD screen and 48 LED. It has a built in power switch. All I have to do is mount it in an enclosure and turn it on.

I'd like to get my hands on a condenser lense that will work w/ a 5.6 diag. screen to concentrate the light through it. I'm hoping the LCD has a Polarized screen on the front, it should on the back. But, do to the light orientation during normal operation, the light passes through the back, so I might need to pick up some polarizig film from Edmund Optics. I have a link for them in another post above.

I'm starting my vacation on Thursday. I hope to have some or all the parts by then! Putting the lamp together will take some time, but I should have something together shortly.

So far this experiment has only cost about $250. It has a good chance of working w/out too much more monitary input.

Vince

[vdi_nenna]

Hi,

I don't know how much interest there is in this project, but I just wanted to let you know that my preliminary test have worked. I built the LED light source while on vaction...my girlfriend is the greatest! So far I have a cluster of 12 white light LEDs. I have 48 total, but only 12 going so far. I quickly set up the parts to a 12 volt power supply and it worked ok. I need to build a jig to hold everything steady, but there was a projected image on my (light green) wall I guesstimate it to be about 8 to 10 feet wide from 8 to 10 feet distance from the projector.

I found 2 projector lenses at All Electronics. One for $5.50 and another for $6.00. They were probably used for projection TVs or rear projection. You can see them on their web site.

I think I'm going to need to purchase a condenser or fernel lens to condense the light source to the LCD screen.

Anyway, I'm going to build a containment unit for this project tonight. I'll let you guys know tomorrow what happens.

later,

Vince

[Sawzall]

I for one am waiting to see how it goes. Would love to build one of these if it is at all reasonable..

[vdi_nenna]

Hey there,

Like I said, I only spent $250 so far. The light source
will last 10+ years if you leave it on day and night. Most other light sources will last about 2 to 3 years (2000 to 3000 hours), and start to go yellow before they burns out completely. The cost of replacing a metal halide lamp costs about $200 to $500 or more, and they are hot! I paid $75 for 50 of the brightest LEDs available. Best price anywhere. You can buy them as a kit from sites that I have posted in this thread for $200+.

But...I'm not going to get too ahead of myself here. There are caveats to this project, just like any other. Like light output and pixelation issues. This may only work in a darkened room, like a theatre environment- shaded room or 'night time viewing only' at worst case senerio. The pixelation problems can be helped w/ a corrective lense availible from Cygnus Imaging, but they are expensive, about 2 times the cost of this project. Or line doublers, like DVDO for around $500 to $600. But they need S-VIDEO or RGB inputs. I only have a composite input right now, but most LCDs have the ability to accept C and Y inputs (S-VIDEO). I haven't figured out how to do this yet, but I know a site where there is a forum where all they talk about is LCDs. This question has come up before.

I need to get my hands on a descent digital camera to document the process for my web site.

I'll keep you posted.





[Edited by vdi_nenna on 06-25-2001 at 12:21 PM]

[tvi]

I saw 2 cheap(?) condenser lenses at: http://www.goldmine-elec.com/
Catalogue Pages 69 & 70

Baush & Lomb Large Condenser len
This lens concentrates light into a projected beam for use in projectiors, spotlights, enlargers, IR systems, etc.
38mm made of Pyrex G8384 $5.95
or
Rectangular condenser 2.24" x 1.98" x 0.78" Focal Length approx 2.75"
G9576 $2.00 ea
they have a few other optical goodies you might like as well.


HowStuffWorks has a good section on Projection TV http://www.howstuffworks.com/projection-tv.htm
includes Microelectromechanical Systems, Grating Light Valve (GLV) and Liquid Crystal on Silicon (LCOS).

Regards
James

[vdi_nenna]

Very cool site. Great prices!

Remember to use cold mirrors for light source that produce heat.

http://www.edmundoptics.com/IOD/Disp...Productid=1900

[vdi_nenna]

I haven't made too much more progress over the last few days. I need to gather materials for an enclosure, then I have to figure out the focal point and distance for a given projections screen size. I should be working on it most of tomorrow.

Later,

Vince