Hello everyone. Here's my first build. I've been reading the forums here for a couple years and am finally building. I think i've read enough on here to solve most of the problems but I'm sure there will be more. I have started with a DIY that someone was building and finished but with marginal results. Picked up his stuff for $150 and came with the following:
-15" 1024x768 LCD monitor stripped (DVI input only)
-an unsplit fresnel lens (2 of them) i expect from an OHP, also a bit narrower than the screen.
-a dublet lens (made with PVC and 2 OHP lenses)
-a solid state ballast
-400W lamp and holder (its big, almost 4" diameter of outer glass)
-2 - 120 mm led fans
-and a very rectangular box, 2 sides made of clear plexiglass.

since then i have purchased a few more parts:
LL 330/220 fresnels and standard triplet
couple lightswitches
1/2 plywood to make a new case
2 light switches
a 12v fan controller
xl10 plexiglass for heat shield
a couple reflectors....the one with most promise is from IKEA. I think it is for a double boiler but it is as close to perfectly hemispherical with some handles attached. made of stainless steel.

This is a cad drawing of the general idea. I am trying to keep to separate areas. one with the bulb and ballast with air coming in from the top and sucked along the bottom and out the front. The other chamber will house the fresnels, LCD and triplet. Air will come in be forced past the LCD and out the front as well. A piece of XL10 lexan framed in wood will separate the 2 areas.

As for focusing light i am hoping to employ a combination of lens shifting and keystone correction to get about 15 degree projection up from horizontal. It will be sitting on the floor about 7 feet from the screen. I will project onto a 56x72 piece of blackout cloth making about a 90" screen.

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As the picture shows i have my reflector wrapping around the bulb. if i use 2 reflectors and cut a hole out of one just big enough to let out the light i need i am hoping to increase my light output. sorta like a light box i guess. Anyone have ideas on how i should position them? meaning spacing between them? Should there be any gap? or just get them as close to perfectly spherical as i can?

Here's an electrical question for those with some experience.
I am planning on running 2 switches. 1 will turn on the fans the 2nd will only turn on after the 1st and will switch on the bulb.
I have it wired up right now and it works properly. However i want to make it look better and get matching switches. I am planning on using the standard light switches....well black low profile ones but that will work with standard 110v homes. It works for the fans (to the 12v DC adapter then to fans) the question I have is if i can replace the current switch (shown below) with one of these lightswitches. From what I see there is 1 hot wire coming in and 2 wires coming out that promptly join together. So can i just bring the hot wire in and 1 wire out? I just don't want to blow anything up. Thanks for any answers you can give.

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I hope that I gave enough info to get some answers.

I'm not an electrician, but I do know you should be switching both Live AND Neutral for safety. You can't just switch Live.

Hope this helps.

Ahhh, no you switch the line side only never the neutral.

You should have no neutral when using AC going through your switch. In the case of DC currant there's no need of running the negative through the switch either.
You would be well off using a terminal board for many of your connections, makes for a cleaner install. And makes tracing and testing connections a little easier. One word of caution on using a terminal strip though. The exposed screw heads where the 110v wires are attached will be live!

I am a bit confused. In an AC circuit I thought as long as you broke the circuit in any place it would shut off. I guess that's not critical for my question above. From that picture i have a hot wire coming in, getting switdhed but the switch has 2 outputs (both are still hot correct?) They promptly join together. I assume it is just a case of going from 1<2=2>1. This seems odd to me. Can I just use a switch that goes form 1-1-1? There isn't some sort of voltage increase by splitting and recombining the wires.

So can I swap it out? Any other thoughts?

Oh those terminal strips that were mentioned....where can those be purchased? I looked when I was at Home Depot with not luck. There is a radio shack which would be my next guess. Oh and for a fuse....Radio shack as well? What do i need? Thanks

Radio Shack should have them.

Well i made some significant progress with the holidays.
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I got most of the box built. You picture is of the box upside down. the final cover I but on will be the bottom.
As you can see i got the bulb and ballast mounted. The wires have been cleaned up quite a bit since this picture and I have to 2 new switches in place. In the picture the 3 holes back by the lamp are 2 incoming air vents surrounding the box where switches will be mounted. In the front the two holes will have 2-120mm fans pulling air out of the 2 separate chambers. I have not cut the hole for the triplet as i want to make sure after lens shifting and keystone correcting i have it in the right place. the front and back walls have a 15 degree slope to them giving it the trapezoidal shape. I want the image to be shooting up from the box onto the wall. I think 15 degrees should be enough as well as about the max you can get with the components that i have.

Question for the masses of optic gurus:
With lens shifting you run into FOV issues. I don't know if anyone nailed down what the max shift you could get with a 15" LCD and standard 220/330 and standard triplet lenses. I hope to combine about 7-8 degree lens shift and 7-8 degree keystone correction to get a 15 degree total slope while not getting close to the debatable 15 degree keystone correction (using the front fresnel tilting) So after that long intro..does the lens tilt for keystone correction have any impact on the FOV? if so then my idea is flawed and i'd be better with sticking with 1 method or coming up with a new idea. Thanks to anyone who can shed light on this. I'm still waiting for my fresnels and triplet in the mail so I may play around a bit with my current unsplit and too small fresnels until they get here.

Firstly, you can't compare AC to DC - they are totally different.

All mains switches will generally be DPST with two "L" terminals (live/hot) and two "N" terminals. You can check the labelling on the back of most mains switches if you don't believe me.

When you throw the switch you make both the Live and the Neutral. Conversely, when you break the switch, you break both Live and Neutral.

I'm qute sure about this: you should always switch both Live and Neutral at the top of your circuit (i.e. where the mains comes in from outside).

You cannot ever be sure that the Neutral will always remain Neutral.

Make sure you switch both.

I haven't seen Neutral switched on/off on any of the wiring diagrams that I've seen on LL.

AC and DC are different, your kiddin right?

In the UK maybe you break the line and neutral but here in the US that practice was abandoned in the 40's.

Two reasons for this.

1. If you have no ground path and you get between the hot and the ground, you become the path to ground. And that's what give's you that funny copper taste in your mouth, if you survive.
2. In a switch if you include the neutral with the hot , AC,and there is any failure with the mechanics of the switch. The switch will explode, and that's a little too close to my pinkies for my taste.

But as I said in the UK it may be different.

Generally if you see a "N" on a switch it means it is a pilot switch, in the US, and has a small light bulb in the switch. But saying that most "lighted residential" switches now have a small neon lamp that is attached internally between the line and the load of the switch, no neutral needed.

As far a "mains switch" is concerned, the two top connections are for the line and the two bottom are for the load, in the US there is no place for a neutral connection. Unless it is a GFCI or Arc Fault protected breaker or receptical.

Anyone can do as they please.
If you want to put the neutral on your switch be my guest.

My apologizes to Ericman for the hijack.

Thanks for the info.

It must just be a UK thing then.

Well I got my first images projecting last night. Nothing too spectacular. Cool yet needs work. The image is upside down...which is good since the projector is currently upside down as i adjust things. I think i will put the bottom on and flip it right side up and take the top off for further adjustments. I still need to fine tune things and get fans hooked up, the heat shield,etc. I can't believe how hot this thing gets. I'm a bit worried right now to tell the truth. While i was getting my first image i put a piece of wood over the lamp area and in about 20 min the thing was warm/hot to the touch on the outside of the 1/2 in ply and didn't even want to touch the inside. I do not have my heat shield in place (though shouldn't effect this part) and fans are really set up right but will this be a problem? I have painted the surface with hi temp black paint but am still concerned. I plan on putting in a reflector so some of the heat from the lamp should not be hitting this surface but do i need some alum flashing or something else on these really hot surfaces? I was thinking about ceramic tile as ceramic is an excellent insulator. Any thoughts?

I found that all you need is a small 4x6 sheet of aluminum flashing (<$.50) attached to the lid of the PJ right above the lamp. Mount the flashing with 4 screws about 1/4" away from the lid using metal washers or spacers. This provides some air circulation and keeps the wood from scorching and getting too hot to touch. Ceramic tiles can withstand the heat, but will transfer the heat to the lid.

Thanks Bevo. I'll get that put in asap. was thinking of picking up a cookie sheet or cake pan from a garage sale or salvation army and using that for the heat shield.

I've been buying cookie sheets from dollar stores for my flashing - for $1 a piece.

Cookie sheets from a dollar store. What a great idea. You might also try a checking out a local swap meet.