DIY Video Projector

[Evaas]

You guys are great! I just returned from vacation and I'm astonished by the progress you're making. I know that there are still hurdles, but I'm impressed by the LED idea. The reliability, and especially the lack of heat and LOUD FANS are huge improvements, and I hope it works. Plus, with these charachteristics, it wouldn't be too hard to add more and more LEDs until you get the brightness you want. Youd have to get a new condenser, but that would be easy. Ultimately, I think the maximum brightness would be more a factor of the LCD screen than anything else, since contrast will eventually suffer.

Thanks for the updates! I'm jealous and I want to start making one too but I need to finish my amp first. still looking for those pesky heatsinks...


Evan

[vdi_nenna]

Evan, thanks for the encouragement! You wouldn't believe how many people are always posting for DIY LCD video projectors,but there's more persons asking for a DIY projector, then persons giving answers on the subject.

This is what I have found so far:

After taking apart the 5.6" LCD, I found that 2 small circuit boards on the back were joined by a .5mm flex cable at a right angle. In order to get a clear path for the light source, I had to order a six inch flex cable and connector. The 2 boards are connected to the screen w/ flex cable, so the boards do bend out of way, but they need to be joined again. That's where the 6 inch flex cable comes in. But...I need to do some surface mount device soldering. It's a trick job. I'll probably need to use a magnifying loop or something to see the small leads. The flex cable is available from Digi-Key. Use a fine, clean soldering tip.

Creating an LED cluster is more difficult than I originally imagined. First, you need to decide how many LEDs you'll have in series, then is what shape and pattern, e.i., square, rectangle, circles, star, ect. I read that it's not a good idea to parallel several LEDs. I used 3 in series w/ a 33 ohm resistor, giving .024mA for the 10.8 forward voltage (3.6v each). You can also use 2 sets of 3 in series w/ a 15 ohm resistor. But mind the wattage, use ohms law.

The geometric pattern is also a problem if you try to bunch them up too close. You need to have tight spacing, but give yourself room to line up the LEDs straight.
I'm using a rectangle shape more or less since that's what the screen is.

I'm going to construct the enclosure out of wood. I bought a RotoZip from Home Depot for $59. I should wip up a box in no time.

I was doing some reading yesterday about pixelation issues. I'm probably going to try to keep the screen six to 6.5 feet wide. That's about 80" screen, and at a short throw distance. When I initially projected the images, I used the MI:2 DVD. Tom Cruise's nose was about as big as my window. The pixels were evident, but the image was about 12ft wide! Shortinging the distance should help, but that I'll leave to my experiments tomorrow!

Later

Vince

[vdi_nenna]

I couldn't make the .5mm flex cable. It's just too tiny. I have to read up on how they are made. The solder beads are just too big and they join lead next to it. I'm going to try to find one already made up w/ a connector attached.

After the light source, it's best to add a condenser lens. Light gathering seems to be very important...obviously.

I started to build an enclosure. I got partically done. Too hot to continue working!

Vince

[Roger]

Vince this project is simply outstanding.

I am very interested in youre progress. I would love
to build one myself.

I am new to DIY, and know nothing about projection.

Youre pioneering footsteps are a wealth of information.

Roger.

[tim0]

Hi,

wouldn't it be an idea to put a white-LED cluster into a defective projector (projector lamps don't last long)?
That would have the benefit of a standard product, maybe almost the same quality as the new product and additionally the silent, cool LED light.

But;
How "white" is the white LED?
in any way comparable to the gas emission lamps used in projectors?
I think the brightness of today's projector generation is not needed for home use. But if the light isn't white, the colors will be wrong.

Vince, what's the resolution of your LCD screen? How bright does it get?

I think this is a VERY interesting project, i will definitely stay tuned. Until now i didn't buy a (used) projector because of the high cost for replacement light bulbs. If this LED cluster is really an alternative, count me in.
I would probably not do total DIY because of all the issues with screen control and optics (i hate mechanics).

Best Regards and KUTGW!
Timo

[vdi_nenna]

I'll try to answer some of your questions, if I can...

First, you could replace the conventional light source of a projector w/ LEDs, but the voltages would be wrong. LEDs use DC and I'm not sure if the high powered lights projectors use are AC or DC...probably AC. Also, your cluster would be larger than conventional lamps. This could create problems for you.

Large LED clusters in a DIY project that are built from the ground up are much easier to deal w/ than an pre-config'ed enclosure, but worth a look, if you're careful of power considerations. And...don't go defaulting warranties on new projectors just yet. Let me successed or fail first.

White LEDs are the closest light source to natural light that there is- by color temperture. You can see this at some of the links for LEDs I have posted. You won't get that yellow light like the typical lamps. They won't turn yellow for about 10 years.

I agree, if you use a theater setup for viewing, you could get a desent image, if it's a dark room.

The screen I'm using is *Resolution (dots): 960 (Hor.) x 234 (Vert.) = 224,640 *Overall screen dimensions (mm): 140 W x 105 H x 32 D *Active area (mm): 115.2 W x 84.2 H *Controls for brightness, color, tint and reverse image. This ia analog video, not digital. You won't find 640x400 or 800x600. All the screens availiable for video are nx234.
If anyone knows where I can get a 1.8 800x600 color LCD w/ a driver board, let me know right away!

Mine is from Parts Express #205-016. The driver board is already attached. I don't have to build a driver board.

What you should be aware of is you should use a screen w/ the most pixels and w/ the smallest sized pixels as possible.

The screen doesn't have brightness itself, but it does have a contrast of about 150:1 to 200:1. That's typical. If you want blacker blacks, you have to go w/ either DLP or CRTs, both of these I have NO idea how to get my hands on.

On the topic of brightness, I was thinking if this one cluster isn't bright enough, I could build another 48 and use 2 optical mirrors at 45 degrees to point the light source into the condenser lenses, then into the LCD screen. That should double what I had originally. I used 18 the other night, but it wasn't there yet. Still, you should see how bright 18 of these things are!

I have much to consider. This will take time.

Hope this gives you an idea.

Vince

[Evaas]

you had to go and mention dlp's didn't you! I'd love to find one of those.

Anyhow, I haven't seen the size of your flex cable, but I successfully soldered at least one tiny set before. It just took a lot of tries and good clamps and a steady hand. The other thing I've had success with is attaching i with a thin coat of solder and then cutting the bridges to adjacent terminals with a razor blade or file. Have you tried that?

Also, are you still having trouble building a larger LED array? are you wiring lead to lead or using a board?

I'm very curious about the LED's brightness as well. From your initial trials, to you get the impression that 50 or so will be bright enough? I'd like something that can work in a little brighter than pitch black. well heck, daytime viewing would be ideal but I'm realistic too

Evan

[tim0]

Hi,

thanks for your reply Vince.
That the white LED is actually white is very good news indeed.

If a LED light is to be retrofitted, the LED assembly with its mirrors, lenses and power supply could be built outboard and radiate into the projector with a suitably installed mirror.

It would be too nice if the LEDs fitted into the box of a projector but i think there's no chance.
I think the metal halide lamps used in HT projectors are operated straight off the mains voltage. No? Doesn't matter much anyway. Except if there is a HV DC supply in the projector, because that could be used to operate the LED cluster if all LEDs are in series connection.

Here's a page for a MH projector lamp:
http://www.peclamp.com/pecmh.htm

overall i don't think the MH power supply can be used for LEDs.

Well, your total DIY approach is definitely cheaper than retroffiting. Used projectors are typically still 1000-2000$. Also, i desire 800x600 and SVGA input because my DVD player is a PC.

KUTGW
Timo

[vdi_nenna]

DLP would be nice. But then you have the whole color wheel attached to a motor. I'm not totally sure how that works, but I'm hearing theaters are looking into using this technology. Studios already use digital cameras for production.

I bought a clamp w/ 2 hands and a magnifying glass, and still it was too small to work with...for me that is. I was thinking last night and I thought that maybe I could just over lay the 2 ends of the .5mm flex cable and then adhere and clamp both cables to make contact. It not an unsurrmountable problem, I'll get around it.

I haven't had trouble w/ the LED array. I just been lazy the last few days and have just thought about what directions to take. It's just time consuming.

With every three LEDs I add, it gets a bit brighter. The light is very focused coming from the LED, 'bout a 20 degree angle. I need to get those condensers to grab the individual beams of light and sort of magnify those smaller sources.

Better than pitch black would be nice and possible.

Worst case, I'll build another 48 and use mirrors to bank the light source into the LCD screen. $150 for a light source that lasts 10 years is much better than one that cost $500 every 2 years and turns yellow at 1-1/2 years.

The next few weekends look bad, but I might bring my tools in w/ me when I work my 2-12 hour shifts.

[Edited by vdi_nenna on 07-03-2001 at 08:16 AM]

[vdi_nenna]

Tim,

**I just remembered something about metal halides. They need large amounts of voltage to jump-start, like 400v to 600v. Best advise would be not to try anything w/ a pre-manufactured projector.**

I believe most LCD screens have the ablility to take a RGB input. But are set up w/ only composite for simplicity.