I am new here, so i am not sure if that works or is proper. But for homegrowers, there is a lamp called cool tube, which is basically the lamp in a tube with a fan on bottom and top. you can add on a flexpipe on the ends, to keep it movable as well. That way you only have the light source with pretty much no heat at all in the box (projector), except the electronics, which don't produce enough heat to be cooled anyway.

Do you think this is a good idea and would work? Do you also think a plexi-glass tube would work as well?

Would the back half of the tube (behind lamp) enough to cover with reflecting material (as a reflector) to beam the light properly onto the screen? it works on the cool tube, it actually spreads it evenly as well.

If plexiglas works (what i think it does, due to the hot air getting transported of right away in the tube), and by painting the backside with reflecting paint (outside is easy, inside you would have to tape the area off and just let the paint run through, let it dry and take off the taping), it would be a very cheap and effective way.

That way newbies like me might have it easier to build their first pj. When using same tubing size (when it works) it would be easy to reproduce the exact same thing.

The only questions now are how to calculate properly what diameter of tubing u need to fit the lamp and how much u gotta paint on the back (reflection paint, cheap) to achieve perfect reflection.


I hope this idea is realizeable. Please let me know what u think about it. if it is supposed to work i'll make myself a pj, and will post my progress with pictures and everything. Although i am doing a lot of professional carpentry, i'd like to keep the design simple, with little work included, so it will be possible to reproduce by almost anyone without hard work. Any ideas to that are apreciated. Like a precase or box you can use, switches, thermometer (still nedded?), circuit board etc. I would also appreciate it, where to buy it from and how much it will be. And if there are even prebuilt kits available. (lenses, box, etc.) I'd like to create an easy diy instruction with parts available in almost anyones area. prefered stores are located in the u.s.a like home depot, lowes, radioshack, etc..... when you help me out i will e-mail you the finished diy project and will post any process here as well. THANKS!



thomas

A couple people have some similar things

This should work well to control heat in the projector, however let me make a few suggestions. Definitely do not use plexiglass. plexy will melt if too close to the bulb.. if it melts and touches the bulb, it could cause the bulb to crack then youre out even more money.

Also I don't think the tube will work too well as a reflector. Sure it might spread the light from the bulb evenly, and this works great for growing, but this is not what you're looking for in your projector. The goal is to reproduce a point source as best we can. The optical reflector is meant to take light from the back of the bulb and redirect it back through the center of the bulb's arc. Any light that doesn't originate from the center of the arc, or close to it, will not be collimated by the rear fresnel, and will ultimately not make it into your projection as focused light. Some people have had some success with cylindrical reflectors, but I wonder how much better the results would be with a spherical reflector.

So the best would be a glasstube and in the back a spherical reflector. Do you think when i would even take a 12cm diameter plexiglass tube, with a 12c, fan on bottom and top, it would get to hot? there would be quite some space between the bulb and plexiglass. Do you really think, even when the hot air gets transported of right away, that the plexiglass might take some damage (on the cooltube you can even touch the glass after hours of running, just slightly warm)? a glasstube is about 40$ and a plexiglass about 10$. would save me about 30$. Would you also, when using a glasstube, to have to cool the freznels as well?

Cause that would make the tube useless then. i want to avoid spreading the heat from the light as much as possible.

anyone ever try car halogen lamps? they seem to be quite powerfull and last a lot of hours as well for a good price.

THomas

ok so the glass tube completely encloses the bulb gotcha. how far would the plexi be from the bulb?

yes I would stick a spherical in the back of the glass tube. cylinder and half parabolic reflectors (both used for growing) don't work well for projectors.

another thing you need to kep in mind is how hot the fans are going to get. plastic PC fans are not designed to take extreme heat. one member just said his metal light box (don't know if its directly vented by 2 fans) exceeds 800*F in some places. thats HOT! I wouldn't expect a cool tube to get that hot because it doesn't absorb nearly as much heat, but the fans can still get hot.

The other thing to keep in mind is (If I am correct) we want the bulb to be warm/hot. I beleive its been shown that for proper color rendering you dont want the bulb too cold. Plus it effects lamp life too. Correct me if I'm wrong.

yes thats true. the bulb will burn brightest and with correct color temp when its hot. most bulbs are designed to be used completely enclosed and they can stand the heat.

For a 400 watt lamp setup plexiglass is a bad idea I can not see how it would not melt. You could flash the back but the light will still have to come out the front and this will heat the plastic.

A non overdriven lamp need almost no cooling. A tube is still a good idea and easy too, just use a slow 120mm or even a 80mm fan.

so now I'm intrigued.... any idea where a tempered tube might be found (also UV block?)

One quick question. Since lenses themselves are molded glass ... will the tube have any detrimental effects to the characteristics of the arc as seen by the fres?

i've been wondering if you could get a tube made from optically pure tempered glass

the picture shows the prof. cool tube for growing, so you can imagine it better. As far as i know only the hot air gets transported of. should not affect the brightness and duration of the lamp. Otherwise growers would have never used that one then. they need maximum lumen (thats how u call it in the U.S i think) and i heard that it lasts even a bit longer as well and doesnt loose lumens so quick either. (lamps do get weaker like batteries). About a uv glass i was googling already (non-plexi), and has to be ordered from special glass producers who produce mostly chemical tubes etc. a glass blower told me it will run about 60$ when i want it in glass. Plexi should be way cheaper.

the cool tube is hard to get in the u.s.a, but aivailable though. the price is about 300$ - 350$, so therefire in my opinion too expensive to use the original and modify it for your needs. I think it will be a diy afterall.