Replace a LCD projector lamp with LEDs?

Do you think it is possible to replace an old LCD projectors broken bulb with say 4 Cree XRE's @700ma?

4 x Average Cree XRE @ 700ma ~500 lumens Vs Original bulb 150W Metal Halide 700 lumens.

The original lamp is probably much brighter than 700 lumens if that is the projectors rating. Im sure all the optics in the projector lose alot of light.....

chadwide said:

The original lamp is probably much brighter than 700 lumens if that is the projectors rating. Im sure all the optics in the projector lose alot of light.....

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700 lumens is the projectors rating... so maybe 6 Cree XRE's? Still cheaper than the $400 replacement bulb

What about the color temperature? Seems like that could cause some weirdness in the display.

That's a really interesting proposal! Hmm though i believe the others are correct, the 700 lumens is usually out the front door; LCD/DLP projectors tend to lose a lot of lumens inside. If you figure a 12 watt HID makes around 600 lumens, a 150 watt metal halide bulb might make quite a lot. Do you have the lumens rating for the bulb itself?

This would be cool if it worked... a lot of LCD projectors suffer short panel life due to the heat and other emissions from their bulbs damaging the organic compounds in the panels. Also, the bulbs are super pricey, and the long warmup sucks. Also, the cooling fan could be turned down considerably. I think the color temp would probably be close since metal halide bulbs aren't exactly warm (in color temp).

Another problem you'll likely face is the fact that 6 LED's is not a point source of light like 1 metal-halide bulb. this will result in errors with the optics.

LEDoutlet said:

Another problem you'll likely face is the fact that 6 LED's is not a point source of light like 1 metal-halide bulb. this will result in errors with the optics.

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True but the size of the original bulb + its reflector and carrier is really preatty big, I think it could be possible to fit the LEDs and still have the room for some type of lense/reflector system to focus it.

BTW, Mitsubishi make an LED based projector with an option battery pack. It puts out a whopping 25 Lumens and is intended for small screen sizes. Heres a link. Were going to see some cool really tiny projectors based on LEDs shortly.

http://www.mitsubishipresentations.com/products/projectors/PK20.html

The 700 lumens rating is just what light escapes through the optics. At the bulb level, a typical 150W HID projector lamp puts out upwards of 10,000 lumens.

LEDs aren't yet in the same league.

And yes, the light source in a projector should be as close to a point source as possible. 80 XR-Es in a 10K lumen panel won't work as a projector source.

Hahah very cool, an LED+DLP projector. Man, just 25 lumens though? Most home theater projectors are upwards of 500 lumens, and that's considered dim compared to business projectors. I could only imagine that being useful in a totally dark room.

I picked up the samsung LED DLP projector a few months ago, just to see what they are like and im must say not bad for its purpose. Yes 25 Lumen out the front is not a lot but in a nice dark room it is just as good if not better than the average priced HID-LCD combo and soo small.
The color temp is very important in a projector any LED based unit actually uses one LED each R_G_B where the hid powered units have to break the light down into this RGB spectrum using a spinnning color wheel.(might only apply to DLP and not LCD)
This is of course only how i understand it and i might be off somewhat. So what a i trying to say here i would just try it with one white cree LED and see what happens you can always pop in more cree`s or bite the proverbial bullet on the HID replacement.

just my thoughts feel free to correct my techno perception here.

Too much variation in color I'd imagine.

Arcoholic said:

r any LED based unit actually uses one LED each R_G_B where the hid powered units have to break the light down into this RGB spectrum using a spinnning color wheel.(might only apply to DLP and not LCD)

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Single chip DLP systems need a color wheel. LCD and three chip DLP systems do not.

Very true at 150 watts that metal halid is producing tons of light (anyone in for a mac custom using the bulb??? :naughty it would take quite a lot of cree's to produce enough light. Im not going to say it cande be done but it would take serious design and very precise placement and the LA would be huge to house enough mirrors lenses and optics to get a convuling beam that was straight. Plus the color. I woudl bite the bullet and go for another HID light. they should havea long life though HID has one of the more durable light producing areas out of any leds win though.

It sounds like you have a pretty inefficient projector. 700 lumen total output from a 150W Metal Halide source suggests that 95% of the light is being absorbed inside the device! I've seen some projectors with 150W bulbs rated for 2000 lumens, which would suggest an overall efficiency of 15%.

If they could get LED point sources to much higher power outputs (~25-30W each), in separate red, green, and blue chips, then we might be able to see the LEDs competitive due to the fact that they could be more easily focused than the HID bulbs using more compact optics. Lifespan would also be another benefit.

They'd still definitely need the fan cooling though, as the LEDs themselves will be very sensitive to heat, so for an LED of that much power output to be feasible, LED efficiency will need to improve to the point where the majority of their energy is output as light rather than waste heat (still a long way away).

As for using current generation LEDs though, not feasible in my opinion.

it is possible to use multiply light sources for a project.

just that you will need some amount of money for that optic that does the job of combining the sources light.

i was thinking of trying this using:

http://www.dealextreme.com/details.dx/sku.5848 20w @ 80lms 6500k color which i believe is dead on for the needed color temp.

an optic somthing like this: http://www.surplusshed.com/pages/item/pl1072.html saw it in the "got throw?" thread on this site. looks perfect as the resulting hot spot is squarish like a tv screen and beautifully brilliant.

and some type of peltier chip cooling (cascaded?) with a heatsink (prolly ducted out of the case)

so what do you guys think? if that led gets 800lm out of a single point are we approaching the technology needed to do this? i know the lms are a bit low for a projector but their are home ones with worse.

there's this other led: http://www.dealextreme.com/details.dx/sku.5766
but its too expensive and i don't like the form factor and the heat would be too high anyway i figure. maybe there is something in between the two possibly with better efficiency?

any suggestions or feedback?

thanks.

great forum site btw

Not going to happen. Projectors need a very small point source and smaller the source, the better. The OMNI-MAX theater use a special short-arc xenon, which isn't too efficacious, but provides extremely high intensity near spherical beam that works real well with the optics. The lamp power is something in the teen kilowatts and cost as much as a new Ford Fiesta.

thefish said:

Do you think it is possible to replace an old LCD projectors broken bulb with say 4 Cree XRE's @700ma?

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Now you are talking!

Handlobraesing said:

Not going to happen. Projectors need a very small point source and smaller the source, the better. The OMNI-MAX theater use a special short-arc xenon, which isn't too efficacious, but provides extremely high intensity near spherical beam that works real well with the optics. The lamp power is something in the teen kilowatts and cost as much as a new Ford Fiesta.

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Actually I think something like the rectangular LED array shown above might work reasonably well behind the LCD panel in an LCD projector, if the size matched up with the LCD panel and if it was used with a low F-Ratio main lens like they use with CRT projectors.

However this type of direct illumination would pose some problems with matching the emitters for output and color, so the LED array would most likely have to be used with a light mixer box and diffuser, to get uniform brightness and color.

I would go with Rebel 100's to get the highest luminous efficiency in the most compact array.

15 well matched Rebel 100's driven at 500mA in a 3 x 5 array on a thick solid copper heatsink, close behind an efficient light box diffuser with the LCD panel immediately in front of the diffuser, would make a reasonable home theater system with less than 30 Watts of drive giving more than 2000 lamp lumens and probably at least 500 lumens out the front, with efficient low F-Ratio optics.

The total lamp side light output of 15 Rebel 100's driven as described above would approach the light output of an efficient 150 Watt Halogen projector lamp, or 15 to 20 watt HID, but would have much longer lamp life.

15 rebels at about $7.00 each would cost 105 dollars, which is still less than even one bulb change of the typical HID bulb, and this would hopefully be a one time expense.

DLP's on the other hand need a very well collimated light source because they are a reflective device, and the easiest way to get that collimated light is from a very small high intensity source like an arc or HID light and an aspheric collimator lens, just as you say.