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Old 28th June 2002, 03:51 PM   #41
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Default We need a consise set of calcs

After seeing what Marklar did i think the thread would benefit by a very good rundown of the calcs that he did and how they were used.

I have a basic understanding of focal lengths, but like a lot of us dont really know enough.....i've read all 2K posts so don't say read them..

Specifically, can anyone tell me what calc Marklar used to find the dist between his light source (it has a focal length right and a lens right) and the fresnel/lcd......but more importantly how to do the distance between the lcd and lens and wall. What size aperature of this lens is necessary? I plan on using a lens that has a small aperature (35mm SLR).....if someone can give me a good set of calcs and what numbers are important it would be appreciated.

I already have an LCD/OHP, but would like the quality that Marklar's design has........i just dont know what calcs were done for bulb/light source placement.......what determined where in the reflector the bulb goes, where the lens in the reflector goes, and how far from the fresnel/lcd the light source goes.
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Old 28th June 2002, 05:53 PM   #42
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COOLING IDEA

allcorp has a thermoelectric cooling unit it's like miniture refrigirator it can produce cold temperture up to 68C in a small area this is great those metal halide bulbs it cost 26.00 at www.allcorp.com

I don't need this because i'm using a compact flouresent bulb from lights of america that puts out 3700 lumens. If you go to www.topbulbs.com they a compact flouresent light bulb that puts out 12000 lumens put it's 11 inches long.
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Old 28th June 2002, 06:01 PM   #43
cowanrg is offline cowanrg  United States
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TEC (thermoelectric cooling) is nice, but its HIGHLY unpractical, unless you are super cooling. you can really only cool point ot source with it. large surface area is really hard to do.

seconldy, they have MASSIVE condensation issues, so it has to be fully insulated, becuase you dont want moisture inside the projector.

lastly, they get cold, but they also get equally hot... i had a medium power heatsink/fan on one once, and it burned up in less than 30 seconds. you need to REALLY cool these things. and, that creates noise, but you have to get the heat OUT too. and powering them isn't the easiest task. they take a lot of power.

the thing is, we dont need something like that for this application. a fan will be FINE. just make sure its a GOOD one. i suggest a panaflo (panasonic). i have some that push around 60CFM each an operate silently. you can boost the power up a bit, and get 87cfm from them, and they are still barely audible. i used them to cool a radiator for watercooling.

quality, not quantity. a CPU in a computer gets in the hundreds of degrees C within seconds if not properly cooled. our projectors dont come close to that... and hell, we can cool the chips with just a heatsink and fan, as long as we dont expect amazing temps.

if a CPU can operate like that, i think our stuff can too.

Quote:
Originally posted by rmccoll
COOLING IDEA

allcorp has a thermoelectric cooling unit it's like miniture refrigirator it can produce cold temperture up to 68C in a small area this is great those metal halide bulbs it cost 26.00 at www.allcorp.com

I don't need this because i'm using a compact flouresent bulb from lights of america that puts out 3700 lumens. If you go to www.topbulbs.com they a compact flouresent light bulb that puts out 12000 lumens put it's 11 inches long.
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Old 28th June 2002, 06:05 PM   #44
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Yeah, TECs are nice, but not for this app....they draw a ton of power, and they have to dump the power somewhere.......they get awfully hot and require a huge heatsink wich requires something to cool it. Our MH bulbs have too much surface area to even think of placing these on them.....not to mention you couldnt evenly distribute the cooling properties resulting in hot and cold spots wich would most likely cause the glass to crack from the thermal stress
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Old 28th June 2002, 06:37 PM   #45
Marklar is offline Marklar  United States
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Default Answers!

Well let me say this dont build a projector based off of mine, it is nice but it needs tweaking. As for how I got my distances I didnt use any math I just layed everything out on a table and moved everything around untill it looked good. Math cant tell you if your gonna have a hot spot so you just have to play with it. I have also thought about using something to block the lcd when I want to watch wide screen but i have a nice da-lite pull down screen so i just pull it down to where it reaches the bottom of the image and Im gonna put a black cloth at the top to absorb that light. I tell you what Behind enemy lines was awsome in letter box the fighter jet part owned on the big screen :P. I can watch it during the day but I have to close the blinds. well thats all for now got any questions?
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Old 28th June 2002, 06:57 PM   #46
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Default Marklar question

Marklar, what type of lens did you use at the opening of the light source? Is that just sheet metal with a lens on it? Also can you explain how you decided where in the reflector to place the bulb? I dont quite understand what you said by putting your finger in and looking for flesh color.....I'm not copying your design...I plan on modifying it signifigantly, but need to understand yours better first
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Old 28th June 2002, 07:26 PM   #47
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what focal length was your projection lens.....i'm contemplating useing a crt projection lens to keep light output high. Just thought my 35mm lens might be too small an aperature for enough light to go through
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Old 28th June 2002, 08:06 PM   #48
woneill is offline woneill  United States
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Default LCD Monitor Panels...

Hi Guys,

Here's a whacky idea that might be of interest to those people with LCD monitors and Laptop Panels...

Would it be feasible to remove the CCFL Panel backlight and replace it with an "apparatus" that used an elliptical reflector surrounding either a 300 Watt double-ended halogen ("Torchiere" variety), or a high power fluorescent along the lines of the 11" LOA-style offerings mentioned above?

The halogen option would need an IR filter and excessive cooling in order not to melt the LCD, and all options would need some kind of long thin cylinder lens (possibly the cheap plastic type available for magnifying sections of pages).

The idea is that these panels already have a very efficient mechanism in place to give a uniform distribution of available light to all points on the LCD surface, and also to get that light to come out from the front of the panel.

Gunawan has already ratified that I am not criminally insane for suggesting the use of a fresnel in front of an LCD panel to collect all of the emerging light and focus it on the main objective.

If we could utilise the existing efficient mechanisms in a LCD monitor, but using a more powerful light source, we could produce a nice, compact hi-res projector...

Thoughts, anyone???

Bill.
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Old 28th June 2002, 09:53 PM   #49
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Default laptop panels

i think it nas been previously discussed that these(laptop) panels have the potential to be our ideal image source. the problem is getting controller boards for them at a reasonable price. check outearth lcd we're talkig $300-$400 for the setup. I'm hoping to find something a little less costly. if anyone can find a small( under 10") lcd monitor for less than $300 that would be perfect, as long as the controller, inverter, backlight can be easily removed from the light path.
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Old 28th June 2002, 11:05 PM   #50
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Default re: LCD monitor

we can use the lcd monitor, but i prefer to use a panel, because a panel is a lot smaller and is made for projection. and in any case you will HAVE to use some type of objectives to project the image. that will add whatever the focal length of the lens is to the length of a projector. BUt i am working on a new design that will cut projector size by a good 1/3. tell you later, gotta go.

aleksey
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