I managed to strip my 7" Redant screen over the weekend, it came apart kinda easy what i was happy about

I know the res is going to be very poor but for my first attempts im only going to aim for a 40" screen

Im very crap with maths etc and wondered if any kinda soul will help me out with measurements etc ?

I have MSN and im online in the day

When i stripped my screen there was a thin lens inbetween the screen and the back light.

Could i use this to help the keystoning ?

Many thanks all.

Sorry if im asking stupid questions

-Tom

Thin lens?
Is it clear?
Do you have any pics

Ill try to take a pic ........ im 90% sure its a fresnel lens.

No takers on the helping me with the maths then ....... hehehehe

What math? (Be specific...)

The measurements are all clearly laid out in the guide. The only difference is if you are using a 7" panel:

you'll want to change the dimensions of the box

you'll need to cut down your fresnels

you'll need to use a smaller bulb (I believe brain's recommending a 250W MH)

there's not much math there, you've got a ruler or a tape measure, right? There ya go...

That thin lens is just a diffuser. You can't use it.

Thanks brainchild


Okflyboy> Im disputing the fact that the guide is a great guide ...... im just saying i dont know how to do the math so that i can sort out my box side etc.


I would like a 40-60" screen ........... thinking about it 60" would be better for the future so i can just swap out the LCD for a higher res version.

I understand that i will have to cut down the len's.

I would like to go for the 2 lens version so i can adjust for keystoning.

(I Just need the 1005 kit right?)


Thanks

-Tom

Tom
Lets see if I can answer some of your questions. The same distances that the guide has for lens placement will still apply with your small lcd. The 1005 kits in lumenlab store will give you all the len's you need for the projector, but you will need to cut the fresnels down to a size to match your lcd (cut them a little bigger then the usable screen). When you cut the fresnel len's make sure you cut equal amounts from each side so the center is still the center. As far as your 40" screen size, you will have your projector about 87" from the wall to get that size screen. To get a 60" screen you will be around 124" away from the wall. Other then that you will have to decide what kind of projector design you want. One of the things about using the smaller lcd was that you would use mirror(s) to bend the light path or the picture to make a smaller enclosure. Once you make that choice then we may be able to help you along further in your construction. If we can help you along the way let us know. The lumenlab focal calculator will help you to determine the distance to place your projector for a given screen size.
http://www.lumenlab.com/focal_calc.php

Thats awsome mark many thanks

In that case i think ill hold fire for the time being and maybe adaopt joe2000's build with a frame and a floor based projector.

I suppose i could start my frame and go from there.

Many many thanks Mark

Ah, I see. I'm sorry if I wasn't clear, what I was trying to say was that all the Focal lengths for the various lenses would be the same whether you were using a 7" or 15" panel. (I thought you thought there was math involved there somehow). I see now that you were looking for screen-size calculations. It looks like mark's got you all taken care of.

Welcome aboard, Tom, sorry I couldn't help you. I'm glad mark was able to step up to the plate and take care of you...

Would you have to cut down the fresnel for a smaller screen? or could you use a mat like in a picture frame to mask off the part you don't need?

That seems like it would work, build an enclosure for a 15" lcd and use a 7"-8" panel for testing and still be able to upgrade in the future by swaping the lcd and removing the mats.

Randy Ferrill
Projector builder in the near future!

Yep you could do that.

Ive got a pic of my LCD stripped down if anybody is intrested ....................................... prolly not though

Looks very DIY friendly, like to see more pics, shine a light through it with an image on

tomlewis007,
yes i am interested, can you please post some more pictures of the lcd. i have built my 15" projector and really love it. but now i have nothing to build and too much info to just not build another sooo, lets see where this goes.