Hello, let me introduce myself.

I am black bart, or betheviper on www.totallyamaha.com . I am usually building weird sleds or selling wrecked sleds and or parts. I happend on this site as alot probably have through the article in popular science. I never really thought about using it in the house, I wanted one for the back yard for the kids sleepovers.

Well here I am, I have aquired a free screen, free bulb and balast. I own a glass shop so lexan for the screen is free as well. I ordered the fresnels and lens the other night as well as two 120 fans with speed switches. I have read most of the forums and understand most everything so ill go easy on the questions.

I plan on making a standard 15in pj and thanks to this sight and all of you who have continued to perfect it I have every confidence it will be a snap. This fact has made me confident enough to spend more time on making it look like something on the outside. I plan on going with a theme, like a submarine, blimp, jet etc. most of it will probly be welded wire fram and glass over canvas cover, kina like an old plane airframe. I am very surprised i never found any like this on the forum especially seeing as they usually end up in the ceiling. what better shape than a large model air ship.

My first question is where and what thermostat switch are you using in the pj to make sure the fans run after the light is shut off so i can make this wife proof?

Second, what size screen can I hope to get decent quality out of outside at night with a 15in 400w pj so i can get to making the screen?

Third, I dont see anyone lining the light side of the pj with simple flat mirror to help gain light lost to the non reflective surfaces, Is there a reason for this. I would think you would want the light side to be completely all reflective material, polished stainless, crome, mirror, even tinfoil. Maybe im missing something, please straighten me out before I assemble.

I guess for now that will be all. Any help you can give would be great. I'll take pictures as I build so if anyone wants to see and also so some with expierience may save me some issues I might miss.

thanks in advance

scott

P.S. if you ride sleds, go to totallyamaha, its a great bunch of guys, pics, tech, rides, chat

Houdy!

About reflections: the only light you want to go through the first fresnel is light coming from that fresnel's focal point. Light reflected off the sides etc. is not likely to be reflected back through the focal point. Light that doesn't come from the focal point is not collimated properly, and therefor doesn't go through the second fresnel properly, and therefor doesn't go through the LCD and triplet properly.

Hi Black Bart,

It sounds like you have all of the needed materials to get started. Congratulations, you are going to have a lot of fun.

You are right about no-one taking many chances on the enclosure design. Everyone has been extremely fixed on getting the best possible projection quality, so an attractive enclosure has been largely ignored. Recently there have been a few creative ones, but most are the dog-coffin type. It'll be great to see what you come up with.

A popular thermostat is this Attic thermostat switch as seen in this thread COOLING THE BOX, Don't melt that plastic! . I haven't heard anything bad about it. If anybody else has had problems with it , please speak up.

The quality of your projection will depend on the quality of your optics and your light engine. Bottom line, the brighter you can get it, the bigger you can make it.

As far as a reflective lining in the light side of the enclosure to make the most use of the light ...... I think it's a great idea. It seems like most others think it is a bad idea. There is a popular notion that the the light coming from the bulb has to be collimated by a fresnel before going through the LCD. When I look at how the backlights on LCD monitors work, and see how sharp the screen is anyway, it doesn't seem as important. In a DIY projector a fresnel before the LCD does help in making the illumination more even, since the light is coming from a single point. If you want to try mirrors in the light side, go for it. Just keep in mind that more light hitting the lcd will make it heat up more and faster, so double the ventilation. You will more than double the brightness.

I agree that collimating the light before it goes through the LCD does help with the sharpness of the projection if you have damn good projection optics. But, I don't care if I can see razor sharp edges on the pixels when I'm six inches away from the projection screen. That's not how I'm going to be watching it. You'll be getting a lot of opinions on this.

Enjoy your project. You're gonna go "Wow" when it is finished.

Tgreenwood


Well, Hirudin beat me to the punch....see what I mean? Different opinions.

heres an experiment you can try to see why lining the box with mirrors to reflect wasted light probably won't help and what happens when light doesn't come from near the focal point of the rear fresnel, take a laser pointer(I used a laser level,a cheap laser pointer at a gas station is like 4$) and just start randomly pointing it thru the rear fresnel, I think you will be surprised how narrow of a range will actually make it thru the triplet,
I took my lcd out of the pj to do this(makes the laser easier to see) its pretty instructive how many places the light can start at end up going nowhere near the triplet(and thus the screen), you might start at the point where the arc of the bulb will go and moving it from there... I always find an actual demonstration much easier to understand than a lot of theory..
its generally thought that light has to enter the lcd at no more than 7 degrees from vertical to the panel to make it thru the triplet, but don't let that stop you fomr experimenting, ya never know
this also makes me wonder why gas stations have laser pointers

That was fast, thanks for the info, the focal point makes sense on the reflector. I wonder if my bulb will be too long if the above is the case?
my light looks a little longer than the ones i see on here. it is a GE R400 multivapor mvr400/u, it is 9 1/2" long but the filiment that acually burns is about 1 1/2" long. so if I under stand correctly I need a reflector that is as small as posible, and is bowl shaped, positioned equally from the Real center of this bulb? If I understand this correctly, if you use a curved plain reflector you would only get a gain from the center, all light reflected from the sides of a curved plain reflector will just end up bouncing around in side the box, little adding to the light going through the focal point of the fresnel? So a bowl style reflector should give more even lighting of the lcd as it is reflecting at infinate angles all aimed at the focal point?

thanks again.

so the arc length is about35-37mm? that should be fine, and yes a spherical reflector is best, make sure it doesn't have a flat bottom ...you might look at the pro reflector in the store, its pretty cheap and they don't come any more reflective than it...

what happens if no rear fresnel is used and the complete inside is covered in mirror?

I checked on a attic fan switch today and they are non adjustable. I found a 12v adjustable(with knob) that should work, it has a probe that is about 1foot long and is used for aftermarket electric car fans. cost $20 new but i had one i took off my jeep so once again, freebees. Also picked up some hope chest friction slides that are used to hold the lid open on a chest to use for keystoning as this pj will be in the back yard, gararge in the winter, might take it camping with the inlaws, etc. I think making this part easily adjustable will help set up easier as its not going to be in the same place all the time.

another couple question

keystoning: what is the range of movement that should be built into the front fresnel?

UV: I see some talking about UV shields to protect the screen, is this nessasary? If so, what is it, where does it go, and where do you get it.

Triplet lens: How much adjustability needs to be built into it for focusing?

thanks again guys, great site

you need a rear fresnel to collimate (make parallel) the light before it enters the LCD.. without your brightness will suffer severely because much less light will reach the triplet.

for keystoning, around 20° adjustability.

for triplet, 20mm in either direction should be more than enough.

For UV/heat sheild, get a pane of X10 Lexan (home depot). This has inherent UV protection and is inexpensive. it goes between the bulb and the rear fresnel.

Question number 4,822, Is it nessasary to use a uv filter and is it used to stop uv damage to the monitor or the people who might be curious.

im still waiting for my stuff,

i watched "The Island" last night and couldn't help thinking that it would have been way better on a projector.
what a great movie

i have the parts to make the keystone adjustment electric adjust.

UV filtering seems to be a hot topic right now. The general consensus (as it seems to me) is that UV light will supposidly damage LCD screens, but nobody has any actual evidence of UV caused damage. In fact a lot of people (jonjandran sp? comes to mind) have been projecting for months/years without a UV filter without any perceived problems. It also seems to be the consensus that the UV light will not make it out of the projector because the light has to pass through so many things (2 fresnels, the LCD, the triplet (3 lenses by itself), some kind of heat sheild, and the bulb envelope itself, then bounce off the screen and into your eyes.

Personally, I'm putting one in, but I found one that is pretty much invisable (it's a photography lens) so I'm not worried about making my image dimmer by using it.

jonjandran, sorry if I butchered your name or completely made up the part about you not using a UV filter.

Oh yeah, one more thing. Please don't hesitate to ask questions! But at the same time please also try to find the answers for yourself.

Quick tip for this (and any other) forum is that the built in search sucks, but we can use google instead. In the search query put the words or phrases you'd like to find, then add in:
site:www.lumenlab.com
What that will do is search for those words in this website only.
Here's a quick example.

@Hirudin..... you got it all right.

Yea I don't use any kind of UV filter and I haven't for around 6 months now I think. No problems yet.

It started out because I wanted to remove the Lexan which decreases lumens by 10%. But I don't know about the LL U.V. filter. It might not decrease lumens by that much ?

well, i have a piece of amiran on the way.

I have changed my mind about the box type though. I plan on using this in our family room as well as outdoor so I am just going to make it as trim and small as posible and mount it to the ceiling. You people have corrupted me, every movie I watch now I keep thinking how much better it would be on the pj so now this is going in the house. Ill make it removeable so we can use it out back in the yard.

I better finish this quick or you'll talk me into a larger screan as well

well my pj is working butttttttttttttt, i can not get my laptop to run the monitor correctly. the computer will show my background on the pj but nothing else, no icons, no windows, no curser, just the background.

has anyone else found this problem.

oh, now i have two monitors, one is a tv so i can use a reg dvd player, waiting for extensions to make this one work. would love to make this monitor work first though. im so close.

Right Click on the screen. Click Properties, then settings. Then click "Extend my windows desktop on this monitor". Should fix the problem.

this is what i have been doing. before i set the computer to this setting i get nothing on the screen. after setting it as an extended window i get just the background, nothing else. if i hit the identify screen button, it will say 1 on my puter, and 2 on the pj.

i am way confused.

thanks in advance for any help
scott

ps, any snowsledders out there building pjs

There may not be evidence of UV damaged LCDs here, but it is a documented fact Now, I don't know how individual LCDs would be effected, but I imagine all TFTs will be damaged over time to some extent.

For projecting video, as opposed to simply the desktop, you may want to make sure your video driver is set to allow overlays on all monitors. If not, or you can't because of the driver, you may need to set your projector as primary display. Then overlays would work.

If you are able to see the 1 and 2 pop up on both monitors, it is probably working okay. If you have extended your desktop across your projector, you may want to try bringing up a notepad window, then grabbing it and moving it around your two desktops.

Could it be that you have successfully extended your desktop to the projector, but nothing is on that part of your desktop, so you see nothing but black? The Start bar will only appear on the primary display.

Oh, also ... if you want the same image on both monitors, you can set your desktop to "clone" mode ... at least that is what NView calls it. Your options may vary.

all fixed, the problem was i needed to drag the screen over.

now i think i have the fresnels backward, not alot of light and am almost out to the end of focus.

which way is the fresnels supose to point when they are in? ridges pointing tward or away from the screen?

watched a movie toinight on it, it sucked, poor screen, poor optics, almost unwatchable without the condenser, that is why i am thinking the fresnels are reversed, and or in the wrong location.

will be measuring everything again tomorrow and checking in here to find out about the fresnels.

thanks for the info guys

Grooves face the Lcd in a split setup. Grooves face eachother in an unsplit setup.

Adjustability is a MUST. 1/2" can mean a world of difference. Tinker, tinker, then tinker some more.

im back.
i am replying to all my threads so others can see what i made so far. I never went any furthe with this prodject and it will be on ebay in the morning. ill post a link over in the classifieds.
I do appreciate all the help everyone give to me and i hope that i was able to help out a little as well with glass info, painting, and some other ideas.

I just didnt have time to put into this anymore and it has sat ever since.

scott

Well ,you gave it your best shot Black Bart.DIY projection is/can be a precise art .Getting everything right takes alot of time and in some cases,money.Gaining knowledge in any subject makes you a wiser person in the process in any case.