Liquid Cooled Projector

[killernoodle]

So, do you want one of my bowls? I will have two of them.

[murray13]

Is this or this what you guys are looking for???

[killernoodle]

No, they cant be parabolic or ellipsoid, they have to be spherical. It must maintain a point light source.

[lolito_fr]

Have you guys checked out this forum:
http://www.diyaudio.com/forums/forum...php?forumid=20

From what I can tell, the LL guide looks a little outdated, but access to the protected parts of the forum makes up for it!
For example, I think Brainchild is recommending the smaller two-ended bulbs now, over the large mogul base bulbs. Maybe it's easier to source a decent mirror for these lamps?

Curse the internet for taking over my spare time...

Edit: ignore, smaller bulbs are for the 7" LCD's.

[killernoodle]

Yeah, plus they are really expensive for even something small like 250w.

The LL design is proven and has been replicated dozens of times with good results. I'm sticking to it.

[killernoodle]

Mmm, got a ballast today. This thing weighs a ton and a half!!!

[JWFokker]

Originally Posted by killernoodle

No, they cant be parabolic or ellipsoid, they have to be spherical. It must maintain a point light source.

WAIT! Those could work. Positioned correctly I think you could definitely do it. The ellipsoidal would be the way to go but they're too small (I didn't realize how huge the bulbs are). If you know of any other places to get similar reflectors murray, please post 'em.

[killernoodle]

You might be thinking that you can use the second focal point, but you cant. This would make 2 point light sources, the bulb and the second focal point. Not good at all.

[JWFokker]

Can you cook up a basic diagram because I don't understand what you're saying. I don't remember most of physics class so I'm having to relearn quite a bit of stuff.

[killernoodle]

Basically, a point light source is needed to generate the image, so this is why HID bulbs are used. You need a reflector to use as much of the wasted light as you can for maximum brightness, and to maintain this point light source you need it to be in the middle of a sphere. The focal point of a sphere is the very center, so if you put the bulb part in the very middle of the sphere the light will bounce off of the reflector and back into the bulb. It is hard to describe, so look at the pic:

[JWFokker]

I understand why the current system works with a point light source, but there's got to be a way to use a parabolic reflector to achieve a more even distribution of light. I had something along the lines of a spotlight, which is why I was looking at photographic reflectors.

[joesgarage11]

A very interesting project, I'd like to try one of those projectors someday.

Here's a link to the DIY Projector Company website. Lots of free information and theory. They've got some designs with mirrors to turn the light path in the projector to make the box smaller.

killernoodle writes:
The focal point of a sphere is the very center, so if you put the bulb part in the very middle of the sphere the light will bounce off of the reflector and back into the bulb.

It seems like a spherical reflector is recommended by most of the projector builders and parts vendors, but I have my doubts if it's the best, or even a good answer. You want to avoid having the light directed back to the arc tube to keep it from overheating. I've seen metal halide lamps after they've been operating in a poorly designed reflector that focused too much light and heat back at the lamp. In some the arc tube had bent, and in others the arc tube had bubbled before failing.

JWFokker adds:
I understand why the current system works with a point light source, but there's got to be a way to use a parabolic reflector to achieve a more even distribution of light. I had something along the lines of a spotlight, which is why I was looking at photographic reflectors.

I think you're on the right track.

killernoodle-I haven't seen a picture of your lamp. Was wondering what the diameter is. That lamp and ballast in a box are going to put out a lot of heat. If you've got a T-15 or ED-18 lamp, google for 'pyrex cooltube'. It's a pyrex bread baking tube about 4" in diameter x 12" long that these lamps will fit into. They're used by indoor gardeners with the same lamps and a similar heat problem.
Get some airflow through the tube, over the lamp, and out of the box and it might help keep some heat off your LCD panel.

[killernoodle]

I'm using an ED-28 lamp that has yet to come in the mail. It is a pulse start too, so it is better than a regular MH. So far, many projectors have been built and none of them have lamp overheating problems. If you look at the first page, you will see that i have already taken care of the cooling situation

[killernoodle]

New parts in today....

All hail the ungodly bright lamp!

The first pic was its first start, about 30 seconds in. The second pic is about 3 mins later. A little green at first, then blindingly bright white.

It makes me happy

[joesgarage11]

Gotta love the MH. It will bring you much joy. Lol

[joesgarage11]

killernoodle writes:I'm using an ED-28 lamp that has yet to come in the mail. It is a pulse start too, so it is better than a regular MH. So far, many projectors have been built and none of them have lamp overheating problems. If you look at the first page, you will see that i have already taken care of the cooling situation

So the cooltube is a nogo. Pulse start is good. Better color rendering and faster starting.

I can't tell from the picture-is it an open fixture lamp? How are you coming on the box to mount it in?

I'm looking forward to the rest of your build. I think the cooling will be a challenge if you're going for quiet operation. Youll be moving something like 450 watts of heat out of approximately a 27 liter box, about the size of a mid tower computer case.

The reflector is still bothering me, so it's time for an experiment. I gathered a 150W metal halide lamp and ballast, a parabolic reflector, a sheet of white plastic, and the only spherical reflector I have-a dog bowl. Just need to borrow a light meter from work tomorrow. I'd like to see which reflector generates the most light on a 15" x 15" square.

[killernoodle]

That dog bowl will be crappy because of the huge flat spot on the bottom.

And I just bought a CMV/Amptron 520D monitor for $179 shipped (digidal/analog, 16ms, 500:1, great specs for the PJ and no FFC issues). Should be here by monday. I should also have the box done this weekend when I go home. My dad has all the woodworking tools and knowlege.

Dont worry about cooling, people get by with 1 120mm fan. I have a 172mm fan running much slower, pushing more air, and with much higher pressure. Look on the first page for a pic of it. I have got a handle on the cooling issue for sure.

Should be a fun weekend project!

[JWFokker]

Let me know how the Amptron looks. I was looking at that model or a Samsung SyncMaster 515V. The only difference in specs is that the Samsung CR is 450:1.

But then again, the DIY Audio forums have some pretty cool projectors based on 8" XGA LCD's. I bet you could get more even lighting, easier, using a smaller LCD than with a 15". I do like small form factor approach quite a lot.

[joesgarage11]

That dog bowl will be crappy because of the huge flat spot on the bottom.

Hehe, I guess an experiment should use the proper equipment. Where did you get your cake pan reflector?

I've been thinking about something else. I'm wondering how you could adjust the lens to overcome the parallax error. Ideally, the projector lens would be at the same vertical and horizontal position as the center of the screen. Anything else and the image will be larger on one side than the other. In my room I'd like to mount a projector from the ceiling, but the center of the image would be about 24" below the lens. We have an LCD projector at work, I'll have to see how it's done.

For the adventurous, here's a link to a water cooled HPS lamp.

[lolito_fr]

I'm wondering how you could adjust the lens to overcome the parallax error

Keystone correction? The lens after the LCD has to be parrallel to the projection surface. Mount it on a pivot, etc
Gravity can make it adjust automatically if it pivots freely and has some weight at the bottom.

Alternatively, have a look at this guys PJ - it has a nice fine tuning keystone adjustment: http://www.lumenlab.com/forums/index...pic=2394&st=20

Regarding the spherical mirrors its interesting that the french diy trend is to use a fairly small reflector, such as this one http://www.izzotek.com/reflecteur.htm
Maybe this is just because they also use small bulbs (typically 250w MH)...dunno.

[superart]

joesgarage, watercooling a HID bulb takes away about 40% light intensity.

Also, you dont want to use a HPS light for this application. Stick with MH.

[superart]

Also, look on some of the R2D2 building sites. Theres a few people that are selling domes for an R2D2 "head" It might be a little big, but thts what you needed, right? Also, the guys that make these heads could probably spin a dome according to custom specs if you ask.

[killernoodle]

Parts Parts Parts!!!

Got my lenses and reflectors today. The reflectors are aluminum, not stainless as listed in the auction. I believe aluminum can be polished better though. Well, at least they are perfectly round, have no flat spots, will be easy to cut/polish, and cheap! They also dont weigh a lot.

JWFokker, if you want one let me know. I'll have the monitor in monday or tuesday, I'll see how it all turns out. I'll polish up one of these bulbs when I'm at home too. We can see how it all turns out.

[bigben2k]

Originally Posted by killernoodle

...The reflectors are aluminum, not stainless as listed in the auction.....

That really sucks; sorry!

Yes Alu can be polished, but it's hard to tell how long that polish will hold. Is chrome plating an option here?

[killernoodle]

Not really, that would cost far more than the actual reflectors. I'll just have to live with it. What is a good way to keep them polished and still heat resistant? If I polish it with that brasso for aluminum stuff, will it keep shiny for a while?