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/diy/ - Do-It-Yourself - DIY Projector

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DIY Projector Slave to Aramok 05/15/14(Thu)07:49 UTC+1 No.638576 Report

Hi /diy/. I am going to be building a simple LCD projector from an overhead projector, but with a little twist, an upgraded lamp.

However I can't decide if I need a lens in front of the non-pinpoint LED light source. What does /diy/ think, and what do you think about these diy projectors in general, any tips?
Slave to Aramok 05/15/14(Thu)07:55 UTC+1 No.638578 Report


this is the 100W LED, it will need a large heat sink. It puts out a 5k-7k color temperature, an equal light source of Red Green and Blue is about 6550k. over head projectors typically have a lamp that produces 1500 lumens, the LED puts out 10,000 (note: Chinese eBay distributors lie a lot about specs)
Anonymous 05/15/14(Thu)08:02 UTC+1 No.638579 Report

overhead projects have a lens between the light source and the surface, so I'd assume you would too, but maybe it depends on just how big your LED is.
Anonymous 05/15/14(Thu)09:06 UTC+1 No.638590 Report

This thread is relevant to my interest.

I tried replacing the bulb in an old projector with LEDs a few months ago. I could never get it to work right and I should probably get back to it. The focal point of the big flat Fresnel lense was always a few feet above the smaller set of lenses, making 80% of the light just shine up to the ceiling. I tried removing the lense that went directly over the bulb, and moving the bulb to various heights inside the case. It didn't have much effect.
Anonymous 05/15/14(Thu)09:12 UTC+1 No.638592 Report

I'd use a lens. It isn't essential for this kind of thing, meaning you can get it to focuse properly without it, but it certainly raises efficiency for the whole thing. Then again, lenses cost money, so if you're tight, just leave it out. Source: Physics student with focus on optics and photonics. I had to put up so many lens-systems that i'd kill myself if I have to do another one.
Anonymous 05/15/14(Thu)09:13 UTC+1 No.638593 Report

Pic of the LED source inside the case meant for the prjector's incandescent bulb. I think my problem is that the incandescent bulb was close to a point source but my LED board is a four inch wide disk.
Anonymous 05/15/14(Thu)15:42 UTC+1 No.638666 Report

Use it without the extra lens. That lens will actually reduce the overall brightness by x% and become a hot spot for heat. Every extra lens the light passes through will diminish the effectiveness of the projector.

As for the light source. Always use a single light source. They produce the best picture. LEDs with a viewing angle about the same as the width of your Fresnel lens will be what you need to match up as best you can. Then all the light will fall on the lens than much anything else.
Anonymous 05/15/14(Thu)15:51 UTC+1 No.638668 Report

Too many points of light for it to work effectively. A high power LED with as few lights in it as possible is best. Like those with the small center and big heat sink on the back.
Slave to Aramok 05/15/14(Thu)16:46 UTC+1 No.638674 Report

wow yeah this is what I suspected would happen. because the leds are to the left and right of the center, the light leaves the Fresnel lens at a different angle than towards the top lenses.

my led >>638578
its about an inch and a half wide square
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