how many people are running unvented light boxes? The design I want to use is basically a light box with a completely open front, but no vents on the sides, back, etc for airflow through it. I am afraid this will cause it to get hotter thus increasing the overall temp inside the enclosure. Alternately I could break it down into individual pieces with overlapping gaps so air can flow through & heat can escape but light will not. Thoughts?

edit: this will be built completely from metal flashing which is why lack of airflow would cause it to get hotter

I was thinking of the same setup, with the addition of heatsinks on the outside of the flashing. Just an idear.

well people put big ass metal bowls inside.. closer to the arc than my flashing would be. I imagine it wouldn't make much of a difference

here's what I have so far.. just a big piece of flashing with two ~45* angles. this is basically it but with a top and bottom allowing for little airflow.

I think SamuraiJack kind of broke ground in this direction. Should be able to make it work.

well SJ uses heat sinks, vents, and fans.. I don't want to get involved with any of that

When all is said and done you'll use what you must use. I think it's workable though and you may very well be able to get away with a totally passive system. Best of luck and keep us all posted as to your progress and results.

Easily done. The reason for my control of the heat was the exposed surfaces and my kids..Its is entirely possible to make a vented passive system that has no active cooling. These bulbs are designed to be used in enclosed areas and they can take the heat. If your really only looking to cut stray light out of the equation, then use a gate. The one I used was based on a 4x3 ratio and cuts off nearly all of the spare light. My black bars are truly black...

That said, the box enclosure is easy enough to do, but the thing you want to gaurd against is your reflector getting too hot. The coating WILL degrade with too much heat.

The box itself will be fine, just make sure that you allow for the natural convection when you design your cooling the heat will concentrate at the top of the box and could get very intense so you would want to draw air from the top of your box and out after it passes the LCD fresnel array.

Keep us posted.
SJ

The purpose of this box isn't to block stray light from the projection, just to protect the wood directly behind/above the bulb, and the wiring, etc on either side of the bulb. Originally I was going to use seperate pieces but constructing a box seemed like a better idea to conceal all the light and protect everything in one swoop. My question about heat was not from fear of overheating the bulb as I know they are designed to handle very high temps Solely because I feared a super hot light box would raise the temp in the enclosure to a level above what I might concider acceptable. For example, say hypothetically without the light box my LCD hovers around 95*.. if the light box raises the temp 2-3*, it would be too close to 100 for my liking.

As you can see, I have 2x 120mm fan holes near the top of the PJ unobstructed by the light box. there will be an air slot on top, behind the LCD.. air will travel down the backside and under the fresnels into the bulb chamber. So, there will be semi-active cooling on the sides of the light box. I'm also thinking I will attach the top of the 'box' to the enclosure's lid instead which would put a gap of a little over 1cm between the sides/back and top where heat can escape. Thehe fans should subsequently pull a little air through the box and out the top. I suppose I could also cut a couple slats on the sides and back of the box. I was unaware of the effects of heat on the pro reflector so I guess a box sealed on 5 of 6 sides isn't a good idea.

If its just to protect the wood then have nothing to worry about. Its basically flashing, just closer to the bulb.

I decided to make a 2.5x2" vent on either side, slightly higher than the center of the arc/reflector, with a single louver pointing up right at the fans. This will allow the fan to pull some air through the light box and make sure the reflector doesn't get too hot.

Whoa....I was off topic there. Ignore this message !