Tags : First PLOG, crappy design, bad results, but lots of fun !

[µC] Hi, I am Guillaume and I have a PJ Addiction problem.
[LL ] Welcome Guillaume, congratulation on your first step ! *clap clap* When did it start ?
[µC] I started to browse LL forums a month ago, and then... then it got crazy... I started ordering parts everywhere in the world, USA, Austria, France, UK... And then the long wait...Then, yesterday, I got the last package from LL. The fresnels, triplet and pro reflector from the S15 kit and that's when it began.

-- Parts lists --

• LL : optic part of the S15 kit (triplet, reflector, fresnels) + 12V fan
• Ebay : LCD 15" NEC 1527, french model
• Izzotek : 250W MH kit
• DIY-Beamer : FFC extension, 20pin 0.5mm for NEC 1527
• Brico-dépot : Everything else, from screwdriver to saw, from paint to duct tape

Price tag : ~350€ (starting from scratch, no tools at all)

-- Design --

At first it was supposed to be the simplest design ever : straight, beautiful of mechanical precision, with pixel so sharps that you could actually use them as chessboards. But then it dawned on me : I have no tools whatsoever, not even a table where to cut wood, hell, I don't even have a PEN ! So I bought a few cheap tools to stay on budget, but you get what you pay for. So the design turned to "Almost straight", "Almost fitting together" and "Close to be nice".

Underlying Theory
It works based on a simple mathematical hypothesis : the sum of a set of sufficiently random non-biased numbers in the range [-a,a] will be 0. Every piece of this projector is off by about [-3 mm, 3 mm] so I think that with the very large sample of errors made, my design will be very close to perfection. I'll add a few more errors if it doesn't work.


-- Results so far --

General view:
Click to view attachment

Lightbox:
Click to view attachment

The focus and LCD panel:
Click to view attachment

-- Questions to the communauty --

- As you may see from the pics, it's not painted and not ventilated. Those are the next step. I have a question for the fans : I have a glass heat shield very close to the lightbox with enough space between the two to put the 120mm fan from LL. Is that enough ventilation to protect the LCD, considering it's only a 250W bulb ?

- I haven't added any eletrical protections yet, even the switch is inside the box for now. Am I right in thinking that because I use a higher voltage (230 instead of 120), the currents drawn should be less (twice less for the same power) and as such, it's less fragile ? I am basing that on P=U*I, that little thing I learned way back then ;p What is the most important part of the eletric protection ? Heat switch ? 5-10amp fusible ?

Special thanks to the LL staff, QuasiMojo and D for helping me a lot when I was lost in the woods and keep tuned for more picture!

Wait, where are you thinking of putting the fans? The red or the blue, or some other place?

Your blue fans sound like a good idea, and I have two 80 mm to do just that !

As for the 120mm, I planned to put it as on the attached picture, sucking air. Would that be effective ?

Click to view attachment

I think we are gonna need a bit more info. Are you going ot have a slot in the top of the box between the LCD and rear Fresnel? And will the air be able to get from that slot to the rear of the box? Do you have more pics of the PJ all put together?

Yes to both first question : the rear fresnel is mounted in such a way that air (and light ) can come from the sides of it as I tried to draw using Paint (gf went away for the W.E with her camera -.-) and I plan to have a slot at the top of the box to allow air to come in this LCD part of the box (between the LCD and the "heat shield" from the lightbox part).

No more pictures yet, but if it gets really critical, I'll unleash the power of my cellphone's camera. Tho, trust me, you'll prefer to see a Paint drawing than this ;p

Is you LCD upside down in the projector?
The usual mounting of the LCD in the projector would have the LCD's PCB at the bottom as the triplet inverts and flips the image.

Yes, it is ! I was also surprised and at first I didn't pay much attention to this, so I build the LCD case with the PCB at the bottom like in every other PLOG I saw, but then I realised it just happened that my PCB wasn't at the usual place so I flipped it upside down and built a bigger case around it to hide my mistake.

-- Friday's evening update :

Paint is almost finished. Corrected many of the line-up problems and built a new rear fresnel that doesn't like it'll break down when the fan starts blowing. I couldn't have bet on that with the previous one. Hey, it's starting to actually look nice !

To all beginners with no experience in DIY : News Flash : you can make your own PJ even if you have two left hands ! I may have all my fingers burnt (thanks Hot Glue Gun), I have a few cuts (I don't like you, eletric saw), but at the end of the day, I lit up the thing, and it actually displays a picture on the wall. Sure, it's not as pretty, as contrasted, as even as what the more experienced can do, but IT IS still great and all in all, a great experience.

I think I'll go with the fans as proposed earlier for the two 80mm and the 120mm as I proposed... Does that look right to you, PJ gurus ? heh.

From your drawing I think you may have a problem with cooling. It looks like you are going to have your cooling slots on the side of the rear fresnel. I have a feeling that if this is in fact how you are planning it, then you will not get enough air moving across your LCD to cool it down.

Tomorrow I'll first add the 120 mm fan in the ligthbox, that probably can't hurt !

As for the cooling the LCD, you are probably right, the best that'll happen if I put the two 80 fan facing each other between the heat shield glass and the rear fresnel is that it'll create some kind of cool wind barrier. I don't really believe in that ;p It may be more interesting to put one of the 80 mm fan behind the LCD and the other one in front of it. I'll make some test and see which configuration is best. Really, my LCD case is terrible but I can't seem to find a better design right now, so I'll make do.

Thanks !

-- Friday's night update :

Now the power switch is outside. That's right, you don't have to put your fingers in the wire mess to lit up the little sun ;p Kids, this PJ will soon be safe enough to get hmm.. a bit less than 5m away. Re-duct-taped the LCD in the LCD case because I noticed it was at a slight angle which might explain the slightly blurry bottom part of the picture. Can't wait tomorrow to start cutting and drilling again (You have to respect the neighbor, they say...)

I just did a quick model in Sketchup to try to clarify your cooling setup. HERE it is.

Are you going by the LL guide at all?

Hello

Thanks Windcalmer, I really appreciate you going into so much trouble to help me with my foreseen cooling issues! I am trying to learn my way with sketch up, which isn't that intuitive compared to Inventor or Catia, but it does seem like an interesting tool, especially as you could make such a nice drawing in a short time !

So until I manage to put holes where I want to, I have taken a picture with my cellphone of the 120mm fan because there is just one place where it can go, in the lightbox (it can't hurt to have one here!) :

Click to view attachment

As for the 80 mm ones, I thought I could put one here :

Click to view attachment

The Fresnel holder is shorter than the heat shield, so it can let air go through there, to the LCD. I also plan to put another 80mm in front of the LCD, and the air would go through a hole at the top of the box...

If that's not clear, then I'll draw it in sketch up using your base model ^^

As for the LL guide, obviously I read it and I tried to follow it as much as possible, but clearly, the air path is going to be different, there are gaps, but not at the same places than in the guide. The first culprit is my very small tempered glass, the second one is my craftman ship ;p Guess which one is the most responsible and distribute blame !

I have to get a thermometer and do some tests with the 120mm fan in place to see how hot it gets...

The reason why it's best to have a cooling slot between the LCD and rear fresnel is that when the light hits the LCD, 90+% of it is converted into heat. Having the 80mm between the heat shield and the LCD might work, as long as you have an air intake on the opposite side - so that air flows across the LCD.

Honestly though, you only need one fan when using a 250W lamp - as long as you follow a method of cooling that's similar to the cooling described in the LL Guide. An air intake slot that allows air to enter and move between the LCD and rear fresnel, exiting towards the rear of the projector around the rear fresnel (top, bottom or side - as long as it's opposite the air intake slot), under, over or to the side of the heat shield and then exiting through the exhaust fan.

That single piece of information (90% of light turns to heat) is priceless ! I wish I had known it before, I'd have understood the cooling system more, I thought the point was to cool the bulb as much as possible, so my whole "design" (randomly put together as I went) was based on making the lightbox cool, and I thought the rest would follow.

Right now, the lightbox is indeed cool and the area between the lightbox and the rear fresnel is also cool. But there is no air flow across the LCD as such. I'll have to add a third fan to deal directly with that problem, even tho it seems cool, I don't want to put the LCD under more stress than it already went through throughout the build ;p

This afternoon I watched some parts of Matrix on a 2m+ wide screen. It somehow made everything okay ;p One more day ending on a soon "completed" first PJ !

Thanks everyone, it's a quite fun week end

Post up some pics of the screen. We like screens!