Things Newbies Should Know

[Guy Grotke]

There are LED-based projectors: They project very small and not very bright images. Contrary to popular thought, LEDs are not the most efficient light sources! Compact fluorescent lamps are better, and Metal Halide are even more efficient than CFL. The only standard available lamp that is more efficient that a MH lamp is a low pressure sodium lamp (which is useless for projection because of its poor spectrum).

So if you put together enough LEDs to make a competitive projector, you will generate a lot of unwanted heat and spend many many times more than you would for a MH lamp-based projector. Your LED projector will also use more power to generate the same size and brightness of image.

Then there's the problem of Conservation of Etendue: Your array of LEDs will "look" like a very large light source, since the rays emitted by each LED will have different origins. There is no reasonable way to reflect or refract such a "beam" into a set of parallel rays. The net result is that each pixel on the screen will be illuminated by rays passing through all areas of the projection lens. (And quite a few of those rays will not even reach the projection lens.) All the possible distortions and aberrations in the lens will smear each LCD pixel over a wider area of the screen. The resulting image will be blurry.

When you use a point-source lamp, (or at least as small as possible) then each screen pixel will be illuminated by rays that only pass through a very small area of the lens. A less-than- perfect lens can still give you a very sharp image because the distortions and aberrations are much smaller if the rays only use a small area. This is similar to using a small aperature on a camera to get a deeper field in focus.

LEDs will become competitive when you can get one that emits 10000 lumens from a very small point, in a cone that matches the focal length of an available fresnel. But before that happens, you might be able to just buy an active-matrix color LED display that would not need any other lamp for projection.

[verbose mustafa]

Originally posted by nzshy
Great info, thanks tones. After reading everything till my eyes bulged out of my head...he he he. I put together a projection system; here it is,

overhead= DA-Lite 5000 also used an Elmo HP4K by Dukane 4000
LCD Panel= Nview Z115
screen= home made 72" x 112"
Sanyo Home theater DVD 5.1 player


WOW! WOW! WOW! my family thinks it's great, and my kids now play the PS2 games on it. Thanks to all here for educating me to the point
where I could do this. Please keep up the great work.

The z115 is a great panel. How much did you pay for it? Back in the day when they where popular around here I used to buy untested panels for $20 and resell them for much more! I got to test almost all of them including the infamous sharp qa-2500. My fav panel was the z115/z215 series. Glad everything worked out great.

Originally posted by Guy Grotke

So if you put together enough LEDs to make a competitive projector, you will generate a lot of unwanted heat and spend many many times more than you would for a MH lamp-based projector. Your LED projector will also use more power to generate the same size and brightness of image.

Well put, I think this is the best way it has ever been explained. I remember researching the super bright leds and my mouth hit the floor when I saw how much heat they put out. I have projected in image with nothing more then an lcd back light. To get a 500 ansi lumen image though, probably not any time soon. Thanks for the great post.

[don2kk7]

Thanks for the information.

[ranaidu]

Hi All

I am unable to get MH with Ballast at my place, the dealer has offered few alternatives.

1. Philips Aluline Pro 37/56 mm
Product Description
• Low-voltage halogen burner in a lightweight, high-gloss anodised aluminium reflector giving a white halogen light

Product Feature
• Integrated protective front glass
• Choice of clear or frosted glass
• High-intensity beam with an extremely clearly defined beam shape (clear glass versions only)
• Excellent color rendering

Product Benefit
• Excellent accent lighting effects due to reduced spill light (clear
versions only) Application
• Excellent light source for accent and general lighting in shops,
home, restaurants, galleries, exhibitions and museums

Rated Lamp Wattage: 35W
Beam Angle : 6D
Lumens Intensity: 18000
Rated Voltage : 6V


Another Choice
Philips MASTERColour CDM-R 35W/942 E27 PAR20L 10D
Watt : 39W
Voltage : 85
Color Tempeature : 4200
Chromaticity Coordinated : x - 371, y - 366
Luminous Intensity : 21500
Beam Angle - 7.5D, Spot

Option3
Philips MASTERColour CDM-R 70W/942 E27 PAR20L 30D
Watt : 73W
Voltage : 88
Color Tempeature : 4200
Chromaticity Coordinated : x - 371, y - 366
Luminous Intensity : 13000
Beam Angle - 26D, Narrow Flood


Please help me in taking a decision

Regards
Naidu

[Guy Grotke]

These lamps will not give you a bright image. They might work for a small screen image in a dark room. Can you buy online? Here is a good place to buy MH with ballast, and also anything else you need:

www.exclusiv-online.com

[ranaidu]

Metal Halide - Double ended with 150Watt power and 4200K color output, 12500lm lumens, 12000 hrs life

how about this options

GE Ceramic Metal Halide – PAR 64
watts: 150Watts
Color : 4200K
Lumens : 154000lm
Life: 8000hrs
CRI RA - 90+ (Colour rendering index)

I thisk this bulb should be a better choice

[ranaidu]

Sorry I forgot to post the link

http://genet.gelighting.com/LightPro...FieldCode=null

[liuduidui]

Osram UV Stop 250w Double

Metal Halide Colour Temp Info

CRI Ratings

[viki_v2]

guys, i have got a pretty big problem,

I purchase super brand lcd tv 9.2" res-800x256. With built in tuner, I purchase it for 4200/-Rs.(100$)
Vga & video connectivity

while stripping the lcd i destroyed it , The lcd is not working now.
i am in a fix now.

I was Making the projector for a friend, Now he wont be able to buy new set.

i have the controllers . i looked throughly and found that the controller is
based on techwell inc chip TW 8816.

I downloade the data sheet it specifies that the chip supports wxga . but the
lcd which came as package was only 800x256.

So is it possibe that i buy some other wxga lcd and connect to this controller,
will it work.

Kindly suggest if there is any compatible lcd, Will laptop lcd work .
laptop lcd's have great resolution in small size.

all the gurus present here please help.

[jesuslove]

What does grounding the wires mean, how do you do this.