Hello DIY ppl :) help a n00blet?

I am planning to build a projector similar to lumenlab's guide but mine will be vertical to save some space.

I am in the process of looking for a suitable 15" LCD and was thinking about Envision EN-5400 15" LCD Monitor from staples as I can get it locally and it will cost about $175.

Would I have problem with its flat cable?

What are some known LCDs with fully compatible flat cable that is less than $180 ?

I already have a triplet lens from a slide projector and was thinking I can probably use that.

sorry, no cigar...

The fresnels are just used to capture as much light as possible, and direct it into the projection lens. The lens focal length has to be long enough for the LCD to receive light from the entire LCD surface. A lens from a 35 mm slide projector will have a very short focal length. It will "see" an entire 35 mm slide from just an inch or two away. If you try to use that projection lens with a 15" LCD, you will have to put it so close that it will only "see" an area the size of a 35 mm slide.

Try an experiment with two flashlight bulbs: Wire them up to a battery so the distance between them is adjustable. Put them on a table about 10 feet from a white wall, screen, or sheet. Adjust them so they are 1 inch apart, parallel to the screen, then focus an image of them on the wall with your lens. Then adjust the distance between the two bulbs until they appear right at the edges of your projected image. This demonstrates the LCD-to-lens distance and the maximum LCD size the lens can see at that distance. The distance would be a bit longer, and the corresponding field of view a bit wider, if you decrease the lens-to-screen distance. But not enough to be usable, for even a 5" LCD.