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Old 20th January 2008, 10:21 AM   #281
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Location: Vista, CA
There are a variety of reasons. The most compelling economic reason is that you can build a pretty good high resolution projector for less than the purchase price of a new one with similar resolution, as long as your design falls in "the sweet spot": 15" LCD, two fresnels, a 400 W MH lamp & ballast, a fan or two, and an opaque projector lens. That combo will give you a 1024 by 768 projector that yields a very nice 95" picture, that can be driven by any source that provides a VGA-compatible output. For around $50 more you can add a converter box that will connect to S-video, composite, and component video.

The other very compelling economic reason is the cost of operation. The UHI-S400DD MH lamp I use runs for 20000 hours and then cost $44.52 to replace. That is many many times as long as a normal projector lamp, and 1/5th to 1/10th the price. When you go to buy a replacement lamp for your commercial off-the-shelf projector, you will discover that the lamp costs almost as much as your projector! And then you get to buy another lamp a few thousand hours later, and then another one a few thousand hours after that...

But of course, the main reason is the same for everybody on DIY Audio.com: fun!
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Old 21st January 2008, 12:05 AM   #282
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Quote:
But of course, the main reason is the same for everybody on DIY Audio.com:

Exactly what I was getting at.
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Old 12th February 2008, 06:33 PM   #283
elewton is offline elewton  Ireland
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Good day! This is fairly impromptu, but I'm amazed by the knowledge floating around here. If someone could comment, I'd really appreciate it.

I'm working on a project with a strong A/V component. My dad's office recently upgraded and let me have an EMP-600 minus bulb and ballast (missing).

I was wondering whether it would be smarter to buy a new bulb and ballast (around E220 from random websites) or whether a much cooler LED array was practical.

I read through the old posts, and it seems to have gone from proof-of-concept to debatably-worthy of use.

Prettiness isn't a factor, as all but the exit lens will be hidden.

Any info would be helpful,
Thanks,
Eric
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Old 13th February 2008, 06:52 PM   #284
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Hi,

I think it might be better for you to find a new bulb and ballast because I don't think we'll see decent LED lighting for some time yet (hence the fact I haven't been on this thread for a while.)

I did buy a ballast from ywh a while back which works great. It's not amazingly compact, but smaller than some ballasts! He could also recommend the correct bulb to go with it. The main problem you'll have is if you don't have a reflector to put the new bulb into.

Then again, I found a genuine new lamp for my Dell projector on eBay for around 80, which isn't a bad price for a "proper" lamp. If you can get a ballast to match your projector's original bulb spec, it's worth trying to get hold of a genuine lamp really.

I've stalled on the LED project because in it's current state, it wouldn't be bright enough for anything much larger than a 20" image in complete darkness (in which case, you might as well watch a big TV!).

Many months ago, I did actually send off for the correct filters for combining the light from these K2 LEDs, but the company never replied (they probably have a Hotmail filter on!). So, I still haven't seen a full colour image from the current setup. Again though; although it might be impressive for an LED source, I don't think it would be practical for every day use. (The issue of combining multiple light sources into a narrow beam is THE major hurdle faced by all optical engineers with things like projectors - not that I'm an engineer by any means).

EDIT: Just read your bit about an LED array - I suppose if you wanted to put the work in, it's apparently quite possible to use a large LED array with a TFT panel and produce good results.....

http://www.hack247.co.uk/2006/08/14/...lcd-projector/

(I think you'll need an account to view the photos on Lumenlab.)

OzOnE.
P.S. Ywh is the guy on the "I got my new lamp" thread who sells the replacement bulbs and ballasts.
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Old 14th February 2008, 12:35 PM   #285
elewton is offline elewton  Ireland
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Thank you!

Pity, but I'll definitely keep the LED/TFT projector as a fun long-term project.

And thanks for pointing me toward Ywh. Now to scrape some cash together...
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Old 15th February 2008, 11:24 AM   #286
irome is offline irome  Spain
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Default help i need bulb canon lv-7350

type lamp top c4
200w uhp 1.3
thanks
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Old 20th February 2008, 07:12 AM   #287
kl8ce is offline kl8ce  Malaysia
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Here is an interesting diy LED mod for DLP projector.

http://www.elektor.com/magazines/200...r.372582.lynkx
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Old 20th February 2008, 07:40 PM   #288
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Hi,

An interesting article, thanks for that, kl8ce!

Although quite informative, it's a bit disheartening for me to see that they're just using a fixed frequency for the colour wheel "emulator" pulse!

You see, in most DLP proectors, the colour wheel will actually change speed depending on the refresh rate of the input video signal. I spent many months of work on doing "proper" colour wheel emulation by actually decoding the colour wheel motor control chip data using an FPGA design. This allows for different input refresh rates (video sync rates.)

It's nice to see that it will work with a fixed frequency on some projectors though (plus, an AVR or PIC chip is quite a bit cheaper than an FPGA and easier to program IMHO.)

If you know the frequency of the input signal that you will likely always use (say 60Hz VGA), then it might work OK with some projectors to just use the same fixed frequency to send to the colour wheel opto.

Note: many projectors might use a 60Hz colour wheel rate for all input refresh rates between 60Hz and 120Hz (they just drop frames or repeat frames to match the differences.) In other words, the colour wheel speed won't neccessarily match the refresh rate on all projectors, especially on data / business projectors.

Most projectors use the Allegro A8902 motor control chip (or similar), and many projector chipsets out there will try to keep the colour wheel "in sync" with the pre-determined frequency from the control board. I found out that on my test projector, if the frequency of the colour wheel "simulator" wasn't exactly in phase with the expected pulses, it would cause flickering or corrupted images.

What the FPGA design does is to emulate a real colour wheel by taking the motor speed control data from the PJs control board and emulating the rotation / timing of the colour wheel. This allows the projector to keep the simulator pulses "in sync" (just as it would expect from the real colour wheel.) Plus, it also keeps up with refresh rate / wheel speed changes and can be programmed for very accurate timings for the LED colour changes etc.

Also, my current FPGA design allows you to fine tune the overall LED colour temperature to match the ideal colour calibration and colour efficiency. This can be controlled from a PC, or eventually using an on-screen menu generated by the FPGA itself. (it already has a VGA test pattern output!)

One thing about the Elektor design is that by using many LEDs and the "tin" light tunnel, it will be very inefficient in collecting the available light. Having said that, I don't think most people would care as long as the image was watchable and the LEDs didn't cost too much. The truth is, you won't get a particularly bright image unless you DO use multiple LEDs per colour (like Elektor have), but it will be terribly inefficient. Single LEDs are starting to produce more than 200 lumens per colour (fairly efficiently), so I'm sure LED projectors will be the next big thing in a few years.

The only other problem with this (apart from the efficiency) is that you may notice multiple images of each LED on the projected image. The extent of this will depend on the light tunnel, LED optics and projector design. The effect is usually more noticable when the projector is slightly out of focus....

When the projector is out-of-focus, the images usually look much worse than with the original lamp because there are now multilple point sources (LEDs). This reduces the "margin for error" slightly when focusing the image. In other words, most of your multiple LEDs will be outside of the usable collection area for the projector's optics and their light will be mostly wasted.

For example, I did try a very nice BL-3000 RGB "light engine" from Lamina Ceramics on a DLP projector, but the multiple images of the LED dies (dice?) appeared on the projected image and very few of the LEDs actually "fit" into the light path. These might work much better with LCD projectors, but I haven't bought LCD in years. I believe the BL-3000 series is now discontinued. They sell the Atlas RGB LEDs.....

http://www.laminaceramics.com/docs/AtlasDatasheet.pdf

But, a much cheaper option is a Prolight....

http://cgi.ebay.co.uk/1-PC-3W-PROLIG...sid=p1638.m122

I used a Prolight for testing - there's no colour combining needed and they're easier to setup. Not amazingly bright though, you could just about watch Shrek on a 20" image in a completely dark room.

The Elektor article is definitely helpful in the fact that the projector they're using doesn't seem to care much about colour wheel sync. It probably uses a 100Hz colour wheel speed for most video refresh rates too.

It's a shame they don't give a more accurate idea of how bright it really is compared to the original lamp. (It might not be amazingly bright even with tons of Luxeon Rebel LEDs.)

Good to see a decent effort though. It has definitely spurred me on to get these dichroic filters ordered for my LED project. I've been meaning to order the correct filters for some time now, but I keep putting it off. (the filters aren't even that expensive.)

I still have the FPGA design, LED drivers, heatsinks and lenses in place, but I've yet to see the full potential of the three Luxeon K2 LEDs. (I can get partial results, but I ordered the wrong filters before, so I can't efficiently combine the available light into one beam.)

I like the idea of the Luxeon Rebel LEDs because they are almost as powerful as the K2s, but can be arranged much closer together.

If I get time (one day), I'll try to get some photos on here of my current LED setup.

OzOnE.
P.S. Jeez, I still type way too much!
This just in: http://catalog.osram-os.com/catalogu...t=showBookmark
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Old 25th February 2008, 03:18 AM   #289
JZatopa is offline JZatopa  United States
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I have just found a infocus x2 for sale by me for $50 but it has a blown lamp. Being a college student I currently cannot afford to buy a buy the $270 lamp if I wanted to pick it up and fix it. I am looking into finding a way to make it work using some sort of other light source.

LED is the way to go for a projector if you are to ask me. It's not about heat, it's bulb life. If I can get a LED setup to give me 80-90% of the brightness of a bulb but at 50,000 hours instead of 4,000 then I would be ecstatic. The question is if this is possible yet though. I have been looking at these 250 lumen leds as a possible option. The x2 puts out 2000 lumens. This means that I would need 8-9 LEDs to get the same light output (these are guesstimates, I know little about light. Could I just hook up 8-9 of these as close as possible together and place them in the stock bulb reflector and put a small Fresnel somewhere in front of them to help reduce the problem of multiple points of light?

My other option is to try something like this.
http://www.instructables.com/id/Head...ctor-Mod-V1.2/

Do you guys think it is worth trying to get LED's to work now that they are available with higher levels of output?
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Old 25th February 2008, 03:47 PM   #290
zzonbi is offline zzonbi  Abu Dhabi
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Default Led projector update

"It's not about heat, it's bulb life."

Actually with the latest arc lamp prices it's all about heat/noise rather than price/lamp life. You need to hunt bargains on ebay or try a deal from China/ywh though.

"This means that I would need 8-9 LEDs to get the same light output"

If only things were that simple!

Right now I get about 8 lumens from the 150lm I drive the led to. And that is with fine optics, because light collection is the challenge. The image is good in the dark, and if I keep it less than 1m I can even follow it with some light on. The upside is the damn thing is pretty much heat/noiseless.

Reallistically I could probably approach 20lm with some effort, but it would still be a far cry from emission displays, light and convenience wise. And they announced 150lm led projectors, so it's just a matter of time. Meanwhile Guy is right: the arc rules the projection world. Non laser leds can't touch its luminance.

Nice to see you still around ozone. Have you measured your light output?
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