I am interested in the lightgate idea created by samuraijack. The way i am hoping to design my vertical is as so (very crude representation of course).

I am hoping to avoid active cooling of the lcd. Instead of having glass close to the bulb i would like to use lexan pressed right up against the rear fresnel. So basically a "light gate" with an opening on top to control the light. I am using an unslipt design so there will be air space between the fresnels as well as between the lcd and front fresnel. My fan is 110v loud and powerful.


Does this look like a feasible way to cool the box on the lamp side of things?

Miklopolis - Sorry I missed samuraijack's lightgate work, but IMHO it seems that this design might create a buildup of radiant heat near the bulb, and near the LCD - if I'm understanding it correctly. The lightpath itself carries a lot of heat unless sufficiently absorbed right? Without really efficient passive or active cooling after your heatshield, I'd bet the temp would rise a little too high for comfort.

Maybe a small, quiet fan could be used to draw air across the LCD panel and fresnels?
Or how's about absorbing as much IR prior to lexan? ie. heat absorbing glass or similar?

DT

Thanks for the thoughts DT. I agree with the small quiet fan to help with the lcd. I figured my cooling would would be sufficient to pull the hot air buildup (since it is vertical) from in front of the lexan and fresnels. I was under the impression that our bulbs are rated for enclosed designs and didn't need active cooling, so the lcd would be the only concern. Once again thanks for your help.

The lamp itself does not need any extra cooling as long as the heat can radiate away the lamp will be fine. Rember the stock LL plan moves the air over the LCD fairly fast and even. Without the lexan to chamber the air the heat will build up on the LCD. Might be a problem?

Hi!
I looked at the design and I think it will have a few problems. The most concening is the heat build up at the top. I found that even with 60cfm moving in the chamber it still built up heat by convection. The best thing you can do with a vertical gate is to build a wash chamber between LCD/Fresnel and the gates apeture. You will need to seal it so it rejects the heat. Cooling the bulb itself is almost needless since it can operate in temps of excess of 250C at the base. Defintely consider IR blocking glass as your first layer above the bulb. It will save you a lot of hassle. I drew out some rough gate designs for a verticle a while back. Want me to try and find them?

Please do SJ. I am starting my vertical also and I have been tinkering with idea of a lightgate.

Yes. I would love to see what you were thinking of. After reading about the hot mirrors that brain hopes to stock my plans will change I am sure. The fan i would be using is the 110v artic, i believe it pulls + 100 cfm.

You might not need anything near that big. I found that it wasnt the CFM but the way the air was routed that helped the most. Try to take advantage of natural tendencies of heat as well. It rises and it likes to spread to the area of lowest resistance. I hope I can find those plans, but if not, I can help you design one pretty easily.

I appreciate you're looking for them. This is a slightly better representation of what i was thinking. What i really want is no active cooling of the lcd and no lexan/tempered glass. It was mentioned before that the combination of the new reflector with a hot mirror could eliminate the need for a heat shield (lexan/glass). So getting rid of the heat in the chamber where the fresnels are located will hopefully be my only concern. If you cannot find the plans i would really appreciate your help as would anyone else interested in your idea, i'm sure.

I've begun my prebuild cogitation, just came across this thread, and felt like chiming in. I see it's been inactive for awhile.

BTW Miklopolis - I hail from central PA.

First, this lovely sketch:



I'm going to build a somewhat large enclosure that will house a tower-style DIY HTPC within but separated from the 17" vertical pro projector. I greatly admire samuraijack's modular lightgate/lightbox work and am going to go with one. The sketch does not show what's above the sled and beside the lightgate area and obviously omits many other details.

NOTES: The diagonal lines forming a "cone" above the lightgate are meant to represent the light path and not any physical obstruction. Also, the sketch is FAR from being to scale!

Points:

• All enclosure guts readily accessible due to entire side being a tightly sealed door.
• Lightgate on rails and indexed for ready removal and insertion.
• Standard, replaceable HVAC filter covers entire bottom of enclosure for clean, unrestricted cool airflow into box.
• Dual PCAC's for redundancy.
• Baffles strategically placed for balanced airflow and adequate light blockage.

Questions:

1. Must the fresnels have a gap between them?
2. How confident can we be that lexan (or other) will not be necessary? AND, wouldn't it be preferable to provide some barrier between the relatively dirty/dusty, actively cooled area and the rear fresnel to keep it clean?
3. Might sagging be a problem with the fresnels?
4. Will the hot mirror require cooling attention?

That seems enough for some discussion . . .

I plan on building something like you are describing (tower style vertical). Here are some other ideas i have. If the heat reducing glass works well enough, and the heat doesnt seep through the aluminum lightgate (building up on the first fresnel) then i plan on to extend the hood all the way down on all 4 sides, isolating the bulb from the air chamber between the fresnels and gate. Click to view attachmentClick to view attachment

The bulb is passively cooled with vents that allow the air to rise from the lightgate and out of the box via the hood (heat rises, hopefully). The fresnel is cooled by a fan that pulls what hot air might escape through the lightgate across the first fresnel. Both fresnels are seperated by 8mm of air (sealed) and the lcd will be another inch or so from them (sealed). Hopefully this way i do not need to cool the lcd since there are a few layers of "air" insulating it, as well as ir and uv protection.

My only concern is that the fan pulling the air across the fresnel will be forecful enough to not allow the heat from the lightgate to rise out of the box, if this is the case, i will permanently mount the bulb and bring the hood to the lightgate sealing it off.

That was a mouthful.

Edit: Double post.

Durachko, where in central PA?

I live in Centre County. I work (when they can pry me from these forums ) at the University Park campus of Penn State University.

Based on samuraijack's results I'd expect the temperature profile around the bulb in your design to be quite toasty. I'll be interested in seeing how this works out for you.

Did you ever get further info (perhaps via PM) from samuraijack regarding his design for a "vertical" lightgate? I haven't checked his plog for awhile - I'll have to do that.

Have you sourced hot mirrors or are you waiting for word from Brainchild?

I think it's wise for me to provide for some active cooling between the LCD and unsplit fresnels JIC so I'll likely incorporate that into my final design.

I have a friend who lives out there at University Park. I agree the area around the bulb is gonna be HOT but the bulb is designed to take the heat. I can always add a small fan to pull some of the air away from it. I agree about the cooling between the unsplit & LCD, i plan on using a little fan to do so. Since I am not cutting the fresnels and i am using a 17 widescreen, i have room on either side of the LCD for an different method of cooling. Something like this:

The fan is internal so that should help with noise.

BTW I haven't found any hot mirrors (but will, or will wait on brain) and I haven't followed up with Samuraijack.

Dang! Your "secondary" cooling is basically what I was thinking of doing!! Great minds think alike.

Your friend up here isn't working on a DIY projector - is he/she???

Finding a hot mirror ain't my hangup. Finding one that's fits my budget is!

I've waited a long time for this and plan on giving Brainchild a few weeks to source some hot mirrors. I'd just as soon give LumenLab my money as someone else.

What bits and pieces have you thus far anyway? Or are you - like me - almost entirely in the planning stage?

Nah, my friend up there wouldn't even know where to start. I am in the planning stage and have been for some time. I have the LL PS kit, reflector and pro lenses coming, hopefully they will be here before the weekend or early next week. Once I get them I have everything I need and will start building, yay! I expect this one to go much more smoothly than my last.

Hi Mik, the 'no active cooling' of the LCD just isn't going to work in an enclosed box, the hot mirror will cut down the IR, but it won't stop it completely. A combination of the IR pass Pro reflector and a 'hot-mirror' at the front of the luminaire will cut down the IR a fair bit so only a small airflow is needed.

I have a 5" square hot mirror from Rosco. I originally had a polycarb shield and without the hot-mirror it was getting up to 100°C, with the hot-mirror it cut down to about 60°

Mine's a horizontal design with the fans below the box forcing cooling air directly onto the LCD/Fres sled. Exhaust air goes out the box at the rear top, the luminaire cools via convection. More pics/details in my plog soon.

I recently removed the barrier polycarbonate, the lux at screen centre jumped from 95 to 105. A bit more adjusting and i've been able to get 110 from it.

oztang, thanks for the comments. I figured i would need some active cooling, and have planned for it so it's not a huge deal. I defintely would like to eliminate the polycarb. Can't wait to see your pics.