| mikekniner |
| Hey, ya you can more or less cut your fresnels with a router, when done properly the fresnels wouldn't be damaged, o ya alan you gotta advertise that site of yours in every post lol? |
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| diylabs |
| quote: | Originally posted by mikekniner
o ya alan you gotta advertise that site of yours in every post lol? |
Yeah *scratches head* sorry about that. In this case I really was trying to help. I've been mentioning my URL a lot recently because I've disappeared from google all of the sudden. I used to be ranked #4 when you did a search for "DIY Projector", but then one day I ceased to exist under that search criteria. When I contacted google, they suggested that I pay extra to have my listing shown at top on the side, which I tried for a while, but it's just too expensive for me. I'll try not advertise in here unnecessarily ;) |
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| mikekniner |
| Ya don't worry about it, just a small thing I noticed that I wanted to bring up lol |
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| copasetic |
| Hi, I just joined, and before reading I will keep this small...I didn't see much on the super cheap flourescent bulb idea that Kevin Wyatt did, but he is here somewhere, since I got this link from his website. I have a Barco that is working fine, but since it will cost more than a new computer (and a car) to replace, I decided I had better get with finding a replacement... :) |
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| The Alchemist |
Hehehe, my light is not that parallel as i thought :D. I accedently projected the bulb on my roof (10 feet away). So not completely parallel, but a focal at ~9 feet away is parallel enough.
But i made some pics so we can look at the beautifull arc without the change of getting burned :P. I thought they are quite nice :D.
zoom:
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| dj_crisis |
Hi everyone!
I've been reading up on the DIY LCD projectors, and think I could build one. I'm pretty handy with a circular saw and soldering iron! The setup i'm going for will be quite compact, which is always important...
I do have a question though. I was thinking about setting it up using and LED light source with a slight diffusing lense (lightly-frosted plastic) above them, then reflecting off a 45deg mirror into the LCD panel. You might have covered this, but I was just wondering what you all think?
Anyway, apologies if i sound like an idiot, and I hope you can help me with my new project.
Aaron |
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| diylabs |
| I love the idea of using LEDs, but I just don't think that it will work. Recently I tried using an LED cluster to test whether they were feasible and found that they had neither the output or the CRI to work well. I was using 16,000mcd LEDs. If you want to read more, I have a thread about it at www.diylabs.org/projector/forums.htm if you want more reading or if anyone else wants to post their experience as well. |
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| mathias |
| The LEDs idea is great, there are some new super bright white (5500K) LEDs that puts out 80 lm eath. So you only need about 125 of them to get 10000 lm and they last least 100000 hours. Unfortunaly this story has a bad end, the price. One LED cost about $18 + Vat, 125 * $18 = $2250 + Vat. |
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| ace3000_1 |
| quote: | | The LEDs idea is great, there are some new super bright white (5500K) LEDs that puts out 80 lm eath. So you only need about 125 of them to get 10000 lm and they last least 100000 hours. Unfortunaly this story has a bad end, the price. One LED cost about $18 + Vat, 125 * $18 = $2250 + Vat. |
Its also not a point source so maybe you could use just the 1 frensel, those leds mathias are big, about 1/2inch round each lol.
Trev |
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| mathias |
| quote: | Its also not a point source so maybe you could use just the 1 frensel, those leds mathias are big, about 1/2inch round each lol.
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Who have said anything about a pointsource ? We are talking about LED clusters, you can get those LEDs with a lens that have a spreading angle of 10 degrees, with that lens they give 576cd, compare that with those 16cd LEDs diylabs tested. Yes they are big 1" with the lens, but you don´t need so many of them. If you want a pointsource just use a fresnellens over the LED clusters.
I haven´t tested this and I don´t plan to do it either, I don´t have $2000 to spend on this, but if you have, please tell me if it works. In the future when the price have decreased, I think this will be an incredible lightsource, 100000 hours lifetime, you don´t live forever but they do. |
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| ace3000_1 |
| quote: | | I haven´t tested this and I don´t plan to do it either, I don´t have $2000 to spend on this, but if you have, please tell me if it works. In the future when the price have decreased, I think this will be an incredible lightsource, 100000 hours lifetime, you don´t live forever but they do. |
Yeah i agree with no frensel its fine, but the only problem that may acur is the hotspoting from each led through the lcd, if the angle is wide enough on each led we may not get this effect.
Just to add to the thoughts though, i can get a frensels lens here that is actually manny frensels in the one sheet, from memory they are 1 inch across so maybe they would work to create a large evenly lit backlight.
If i had the money sure id be in the testing too, but when i can buy a metal halide setup for way less , why bother lol, yeah yeah ok heat and life ect but still i wouldnt pay 2k for a light source.
I got my light today btw and thanx, it got here in 1 peice.
Trev |
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| diylabs |
| quote: | Originally posted by ace3000_1
but still i wouldnt pay 2k for a light source. |
Indeed - $2k would be much better speant on a xenon system like movie theater light booths use, though it's been a while since I priced them (maybe there not as expensive anymore?) |
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| ace3000_1 |
| quote: | | Indeed - $2k would be much better speant on a xenon system like movie theater light booths use, though it's been a while since I priced them (maybe there not as expensive anymore?) |
Duno about going down in price, all the things i see these days go up in price lol.
Xenon would be nice but then we have the issue of heat, more so then metal halide unfortunatley, but yeah xenons are nice.
Trev |
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| XanderSnyder |
i was thinking of using a xenon for a while till i talked to my roomate. he is a theater projectionist so he took me up to the booth and we looked at the projectors. There is absolutly no way we could use even a smaller xenon bulb, 1) the heat is much much to high (and the fact that if you get hand oils on them they will explode:devilr: ) and 2) the power required to run a xenon bulb would cause your power bill to skyrocket. Ive currently been looking at using the 400w HQI bulb from alan (so far with the psyudo ace/t800 and my design it should work quite well, i cant wait till ace releases his design so i can use some of his design ideas (i dont care how much his plans cost I WANT THEM!!!! lol)
X |
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| DEDan |
| I use the xenon bulbs in surgical illuminators at the hospital that I work at. Heat is a major problem. On the higher wattage ones, there is more heatsink in the bulb area than bulb. And one finger print on the quartz, and KABOOM!! |
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| Altec |
| quote: | Originally posted by mathias
A 75W Halogen PAR30 30 degrees give 2400 cd. I if you change that 75W bulb inside the reflector with a 150W-250W HQI, it will give much much more. Lumens is not used with reflectorbulbs. |
Not true really. ENH is ansi spec for a 250watt TUNSTEN Halogen bulb with integrated IR UV filter 25o mr-16 refletcor. They give lumen ratings though nto easy to find I had to search. TWO as a matter of fact. One for filiment. One for focused beam of reflector. ENH, is 15,000 lumens (at filiment) 65% relative brightness (beam light) 9,750 lumen beam. Not candles. All pj bulbs use IR/UV dichrotic refelctors to remove heat. Not sueing one forces us to use hyper cooling and have hot panels. I totally agree with ya on that. I too after about 3 years (was "tinker" at first here) have done NOTHING but play with light engines. Sad as that is. I foudn out lots of stuff. Very interesting and major payoffs. My brightness is nothing even compairable to the original images I got. LOL. I can get a tiny 50watt EXT bulb to work with a 5" panel, have two windows without blinds on them shinning light in, 4 40watt bulbs on and still see a Image! With lights off its pretty good-wouldnt WATCH it though. Was a test of some ideas I had and I need a low watt non blinding mr-16 reflector bulb to do it. I wouldnt think about actually desinging around it. LOL. The 250 tungsten halo is for that. I also found mr-16 to be a key reflector. I have also used 2 bulbs at once with good output useing them. A 2" diameter reflector is really controlable. One is still best as no glare that way. If two-must use glare filter.
Also if anyone interested. I found a chart of what o beam is what size at said feet. Nice to know how big beam of light is. I scaled it down to inches even. Mine is 5.6" FD for ENH. So beam smallest there. Then goes back up. Good spot for removing heat with my little setup.
;) |
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| mathias |
I really don´t understand what you mean ? I hope you or someone else can explain this.
Here is some exemple what the lumens output of some bulbs are:
50W 12V Halogen 4000h 930 lm
100W 12V Halogen 4000h 2400lm
250W 24V xenon-halogen 50h 10000lm
400W 36V xenon-halogen 50h 14500lm
150W HQI 12000h 12000lm
250W HQI 12000h 20000lm
Sure you get a brighter beam with a reflector, but not more lumens. When you use a reflector the light beams concentrates in one direction and light what goes in one direction is measured in candels not lumen.
If you put a 1000lm bulb in a reflector and then change it to a 20000lm bulb, which is brightest ? |
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| ace3000_1 |
Who said we cant retrofit out a pro projector with a cdm-t bulb, i have and it works fine.
Trev |
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| ace3000_1 |
Here is the old bulb, im going to drop it off of my balcony just to see how much of a bang they actually will make lol, the arc size on this old fellow is 6mm, and is metal halide.
Trev |
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| chasse |
| Is the beam wide enough to cover a LILLIPUT complety at a short distance.(8 or 9 inchs).The new comercial projector have a smaller hole for the lamp and you cant retrofit a cdm in it. |
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| ace3000_1 |
| quote: | | Is the beam wide enough to cover a LILLIPUT complety at a short distance.(8 or 9 inchs). |
heya chase, this isnt a parabolic reflector, its an eliptical so it will work with a condenser, i tried it out with a condenser and a frensel and it works fine, though i did get blind from it lol.
| quote: | | The new comercial projector have a smaller hole for the lamp and you cant retrofit a cdm in it. |
Ya very true, and this one had a hole too small too, u have to cut it out for the cdm-t to fit as i did in this one.
Trev |
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| Altec |
| quote: | Originally posted by mathias
I really don´t understand what you mean ? I hope you or someone else can explain this.
Here is some exemple what the lumens output of some bulbs are:
50W 12V Halogen 4000h 930 lm
100W 12V Halogen 4000h 2400lm
250W 24V xenon-halogen 50h 10000lm
400W 36V xenon-halogen 50h 14500lm
150W HQI 12000h 12000lm
250W HQI 12000h 20000lm
Sure you get a brighter beam with a reflector, but not more lumens. When you use a reflector the light beams concentrates in one direction and light what goes in one direction is measured in candels not lumen.
If you put a 1000lm bulb in a reflector and then change it to a 20000lm bulb, which is brightest ? |
here
http://donsbulbs.com/cgi-bin/r/b.pl/enh_ansi.html
"ENH ANSI bulb specifications:
--------------------------------------------------------------------------------
category: Projector
volts: 120
amp/watt: 2.08A / 250W
base: GY5.3 - Oval, 2-pin; flat .7mm x 2mm; 5.3mm centered
(found on high voltage MR bulbs)
glass: MR-16
filament: CC-8
m.o.l.: 1-3/4 inches
burn pos: burn lamp in Base DOWN to HORIZONTAL position
lumens: 15000 initial lumens
color temp: 3250 degrees Kelvin
notes:
Beam Angle: 25 degrees
Dichroic Reflector
Enlarger Lamp
fd:5.6
Multi-Facet Reflector
mod
Photoflood
Photoprinter Lamp
Rim mount
Reflector Multi-Facet
Tungsten Halogen "
:D |
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| mathias |
When it comes to the lumen output from a halogen bulb it´s true that you can get the same as a HID-lamp, but not with the same wattage. Halogen bulbs give max 37lm/W and HID 80-100lm/W. The halogen bulbs they use in slideprojectors and oh-projectors are not real halogen bulbs, they use a mix of xenon-gas instead of krypton, this give more lumens but less lifttime.
Here are some exemples of same wattage bulbs:
250W 24V xenon-halogen 50h 10000lm
250W 24V xenon-halogen 300h 8000lm
250W 24V halogen 2000h 5000lm
As I have said before the filament in a halogen bulb is smaller than the arc in a hid-bulb, this makes it much harder to control the light from a hid lamp, you need a bigger reflector with a hid-lamp than a halogen-lamp if you want use all light from the bulb. You can infact compare the halogen (12V-36V) filament size with a uhp-lamp arc size, they have about the same size and if you then compare the reflector size you find that they also are the same. This is why I recommend the PAR30 reflector it´s made to handel 10mm arc-sizes. |
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| mathias |
| quote: | | Who said we cant retrofit out a pro projector with a cdm-t bulb, i have and it works fine. |
Hm.....maybe because you change a MH-bulb to another MH-bulb, if I was you I had put back the lamp-modul in the projector and tried to start it. Are you sure the reflector is eliptical, it looks very parabolic to me, you can get the same collecting effect to a focuspoint with a parabolic-reflector.
When it comes to do the same on a UHP-lamp modul, I can only say one thing, forget it. The reflector in a UHP-lamp is really small mine is 37mm (1.45") wide and 37mm (1.45") high and the cdm-t lamp is 20mm (0.78"), not so very much left of the reflector after you have cut a 21mm hole in it. |
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| Altec |
| quote: | Originally posted by mathias
When it comes to the lumen output from a halogen bulb it´s true that you can get the same as a HID-lamp, but not with the same wattage. Halogen bulbs give max 37lm/W and HID 80-100lm/W. The halogen bulbs they use in slideprojectors and oh-projectors are not real halogen bulbs, they use a mix of xenon-gas instead of krypton, this give more lumens but less lifttime.
Here are some exemples of same wattage bulbs:
250W 24V xenon-halogen 50h 10000lm
250W 24V xenon-halogen 300h 8000lm
250W 24V halogen 2000h 5000lm
As I have said before the filament in a halogen bulb is smaller than the arc in a hid-bulb, this makes it much harder to control the light from a hid lamp, you need a bigger reflector with a hid-lamp than a halogen-lamp if you want use all light from the bulb. You can infact compare the halogen (12V-36V) filament size with a uhp-lamp arc size, they have about the same size and if you then compare the reflector size you find that they also are the same. This is why I recommend the PAR30 reflector it´s made to handel 10mm arc-sizes. |
Yes there are diff halogens. Example. Standard halo flood light 100watt is around 1400 lumens 4k hour bulb, no special coated reflector. Now like you said diff gasses BUT more importantly the ENH uses Tungsten filiment. Which can be very small and run very hot meaning small reflector (under 2") with higher lumen per watt output. Tungsten and xenon halo's arent house lights also as you said. They (PJ bulbs) burn out faster, this one in 150hours (vs 4k from standard) due to more heat from higher output. The pj bulbs reflectors remove IR/UV they are actually a FS dichrotic cold mirror. MUCH better then hot mirror for removing heat from visible light. I dont know why ALOT here think heat mirrors are the answer. Heat mirrors not only dont remove as much heat from light, most only doing a 25% diff to pro ones doing upwards 60% but they loose more of the visible spectrum due to passing through mirror coating. Better to reflect needed light and avoid absorbtion. Most ALL pro projectors use cold mirro arrays to handle heat in small enclosures. It "can" depending on grade of mirror reflect on avg. 90% visible and remove upwards 85% heat per mirror! They incidently do get "hot" but were named cold mirrors for their ability to remove MORE heat then HOT mirros do. And cause they reflect cooler visible light more efficient. Hot mirrors are toys for laser guro's primarily. Sorry long post. LOL.
:smash:
Good read for the diff in bulb types.....
http://www.pti-nj.com/obb_lamps.html
"Tungsten Lamps
Technical lamps consist of a coiled tungsten filament mounted in a precision glass envelope. The envelope may have a vacuum or, more commonly, be filled with an inert gas such as argon or krypton. Typical technical lamp operating parameters are 2.5 to 12 volts and .02 to 1 amp. Color temperature ranges from 2,200 to 3,000 degrees Kelvin; lamp life may be as high as 30,000 hours.
Tungsten-Halogen lamps feature a tungsten coil filament mounted in a quartz glass envelope that has been filled with an inert gas plus a trace of halogen (normally bromine). This gas creates the “halogen cycle”: tungsten that has evaporated from the filament combines with the halogen gas. Convection currents within the bulb carry this gas to the quartz wall where it is cooled and then returned to the proximity of the filament. The heat of the filament causes the tungsten and bromine to separate, and the tungsten is then deposited on the cold portion of the filament.
This regenerative process prolongs the life of the filament considerably, and also eliminates blackening of the bulb by preventing the evaporated tungsten from condensing on the envelope. The Halogen lamp color temperature runs from 2900 to 3400 deg. Kelvin and are available in wattages from 10 to 250 at operating voltages from 6 to 24; lamp life ranges from 10 to 2500 hours. Luminous efficiency is approximately 22 lumens per watt.
Tungsten-Halogen lamps must be operated at voltages that maintain an envelope temperature between 250 and 350 deg. C. Cooler temperatures will not allow the halogen cycle to take place, thus causing bulb blackening and shorter life; higher temperatures will cause oxidation of the conductors and lead to premature lamp failure."
So Tungsten is similar to Xenon output per watt just aimed at lower watt range. Makes sense. Cept Halo doesnt emit UV and need that filtering. Xenon more color correct but be carefull with it. The guys link I posted earlier that listed enh spec was dead wrong. Which I can agree with I couldnt believe it myself. thats what my 175watt mh gives! Anyhow even though lower lumen its controled heat removed and focusable. So overall what gets to screen TONS brighter. The light engine is lots smaller too. So...at 22lumen per watt. Enh is 5,500 lumens. By reg. tungsten watt rating that is. Sorry for any confusion. I hate specs that are WRONG.
:bigeyes: |
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| ace3000_1 |
Hmmm you might want to run up a few tests for yourself on the cold mirror, i have some here thats far more efective then any dichoric reflector ive owned, and thats testing with a pro reflector as i posted a couple of posts ago. A dichoric reflector will only cool the light that it reflects, thus being not all so a large quantity of heat still comes from the light source, now if you run all of your light onto a cold mirror and reflect the visible light to the lcd, all of the light from the source is filterd and yealds a much cooler light.
How to run a cold mirror cold? well dont have a metal backing plate on the back of it as sujested by manny leading manufactures, so the heat doesnt build up on the metal plate at the back of the mirror, redirect it to a metal plate 2inches behind it and the mirror will just get warm, the metal plate will only get hot which u can easily cool with a fan or convection.
Trev |
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| ace3000_1 |
| quote: | | When it comes to do the same on a UHP-lamp modul, I can only say one thing, forget it. The reflector in a UHP-lamp is really small mine is 37mm (1.45") wide and 37mm (1.45") high and the cdm-t lamp is 20mm (0.78"), not so very much left of the reflector after you have cut a 21mm hole in it. |
Yeah those new small ones u cant do anything with lol.
And yeah, its definatley eliptical, works fine with a condenser although its focal is abit long for my needs.
Trev |
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| Altec |
"Hmmm you might want to run up a few tests for yourself on the cold mirror, i have some here thats far more efective then any dichoric reflector ive owned, and thats testing with a pro reflector as i posted a couple of posts ago. "
I agree cold mirrors are best. I already have 5 here to test with. One is in now and planning on staying there. hehe.:) But what you mean by they are better then dichrotic mirros I dont understand. They are a dichrotic mirror. So are hot mirrors. And many other types of special mirrors. Dichrotic just means its multiple layers of diff metal on glass in such a way that it filters and reflects. If you look into it or through it you see the multi colors of reflector from different fine metal layers that are imposed staticly to the glass. Dichrotic simply mean-multi colored. The ENH has a cold mirror reflector now. But I also have it aimed at another 4 3/4" one.
"How to run a cold mirror cold? well dont have a metal backing plate on the back of it as sujested by manny leading manufactures, so the heat doesnt build up on the metal plate at the back of the mirror, redirect it to a metal plate 2inches behind it and the mirror will just get warm, the metal plate will only get hot which u can easily cool with a fan or convection."
Were thinking the same! My pj is doing just that. No backing to cold mirror. Just a 50cfm (HOLLY COW!) fan behind bulb drawing out. I have cool air intake flow directed so it must pass cold mirror first and the hot backside at that. Should work. Yes? I will know tonight, Im THAT close to done. I'll be happy with a bright 5-6' image. From there its on to rear pj with same light engine.
:D |
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| ace3000_1 |
| quote: | | But what you mean by they are better then dichrotic mirros I dont understand |
Hmmm was like a kind of figure of speech:xeye: lol well what i meant to say is that a cold mirror can more efficently cool the light from a source at 45deg as all of the light from the source (reflected and non reflected light) is filterd by the mirror, compared to just having a dichoris reflector that wikll only filter just the reflected light bouncing from the reflector.
All your setup sounds good bud, to give you a helpful idea, why dont you rivet a heatsink on the metal plate thats taking the heat from the back of the cold mirror? this will help keep things cool:) .
Trev |
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| [RPD]-Killer |
As no one is looking into the other thread, I post it here again:
Controller for UXGA resolution:
Datasheet
Manual
But that won't help me because I'm searching for a WUXGA-controller for the mighty 16:10 display...
As I found out, the only chipset capable of this resolution is the new gm1601 from Genesis Microchip Inc. and I'm sure as hell, that this is the controller used in the Dell notebooks as Dell mentioned Genesis as their primary provider on this stuff. But there are no freaking controllers with this chipset on the market. I already mailed Dr. Berghaus aka Kontron but I didn't get any reply by now.
Those Kontron guys are already using chips by Genesis in their existing controllers and I hope they will introduce a new one with the gm1601 soon!
Optional TV-controller:
Datasheet
You can find this stuff here:
http://www.dr-berghaus.de/frame_start.html |
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| Tiarb |
Hi!
I haven't been reading the posts on this site for a long time cause my own project has been on hold after the last freakishly hot, kind of yellowish (and relatively dim compared all the problems it produced) 250W halogen blew up after its lame 300h lifetime. Well, I'm getting 150W HQI TS/NDL HID bulb and ballast from a friend (should be here monday), and decided to come here and read a bit.
And what do I see, still a lot of stuff about the paraller light beams and point sources...
Um.... I've tested this with many kinds of screens that are illuminated (and also with tv) that if you put a projection lense in front of any kind of illuminated or bright surface, it will be projected. The brighter the image, the brighter the projection.
Would someone care to explane why does the light before the LCD have to be in any kind of specially directed beams or point source, I somehow dont seem to get it? Maybe I am stupid. Isn't it all the same what kind of light it is before the lcd if the LCD gets lit up as brightly and evenly as possible?
With the halogen I did lots of experiments with reflectors and lamp positioning, and although I got a bit brighter image with reflectors it wasnt a huge difference, and also the position of the lamp and the reflector didnt seem matter much, if the lamp was in a position that most of its light got to direction of the lcd's and optics the image appeared and was ok :B Of course it could be that the optics in the projector which I am retrofitting fixed the light or something, but I dont think so as the original lamp had such a specially designed reflector.
These are just some of my thoughts, comment and answer if you like but I do understand that as I am just retrofitting the projector it might differ from those projects where you build a projector from a scratch, so these thoughts might not have anything to do with those.... I dunno....
Regards
HB |
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| Tiarb |
Also, I might add that there are people on this site who use soup ladles as reflectors, and myself I have some metal bowl I found in my kitchen :B
Works nicely and I am pretty sure those reflectors mentioned have nothing to do with accurate controlling of light or making beams paraller, they just reflect more light to the general direction of the lcd :B
Regards
HB |
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| mrmonopoly |
Dear All
I have been following this project for a very long time now , and i am very amazed at the dedication and persistance of your goals in this project , and I was hoping that maybe i could become part of your wonderfull idea. I have been looking into the light source side of things for the last few weeks here in the UK. The super bright LED which you have been looking at are very cheap here in the Uk. You are looking at around £5 for a pack of 10.
So for £50 (which isnt much when u count cost of bulbs) you can get 100 of these beutys producing a serious amount of light. 1000 luminas is easily achiveable from the LED at a angle of 10% or less. I have several firms in the Uk working on my idea for a light source at the moment , and will post my findings on here if you so wish. My project is only going to be a rather small one comprising of a 2.,5 inch STN screen and a few odds and sodds i found around the house. (normal still cameras have nice lenses on them). If I can be of any assistance with electronics or information then please drop me a line i would be pleased to help in any way i can
Kind Reagrds
David |
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| Tiarb |
MrMonopoly, sorry to break this to you :B
"The super bright LED which you have been looking at are very cheap here in the Uk. You are looking at around £5 for a pack of 10."
Um, that's not very very cheap...
"So for £50 (which isnt much when u count cost of bulbs) you can get 100 of these beutys producing a serious amount of light. 1000 luminas is easily achiveable from the LED at a angle of 10% or less."
... especially if you compare that with about £50 you can get a 150W MH and ballast that gives you over 10000 luminas and doesnt need lots of cooling...
"I have several firms in the Uk working on my idea for a light source at the moment , and will post my findings on here if you so wish."
We most definetly wish. Many (me too) have been wondering if LEDs could be used and about everyone have decided not to even try them after doing few calculations. You might wanna search the forum for posts about leds. Although it would be great if you'd try the led way and report the results to everyone, and I myself do really hope that all the calculations made before would be proved wrong by you.
Regards
HB |
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| Tiarb |
MrMonopoly:
In addition to the first answer I might add that there is a reason why it might be possible to use LEDs. If you calculate lumens you end up with the answer "naah, thats not enough, no way", but there is the issue of the angle. The light comes out of led like from a spot light, you can use about all of the light if you position it correctly. With other bulbs there has to be reflectors, condenser lenses and so on to get the light on the right direction, with leds there just might be a change they are not needed.
How much does this have effect on the matter? Probably not 90% (which you'd need to get the same amount of light on the wall than with a 150WMH), but if the LEDs stay cool (they probably wont if theres that many :( ) and last long and you get even 200 ANSI lumens, that'd be a nice little projector.
Regards
HB |
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| diylabs |
| I did an experiment a while back with a cluster of 20 - 16,000 mcd 10 degree LED's. My findings were that the light produced was of extremely poor color quality, and though the light was absolutely blinding to look into, it wasn't nearly enough to drive an LCD projector. The experiment was to put the tightly packed cluster behind a projection panel and then attempt to project that small region of the image onto the wall. The image was very dark and there wasn't enough image color detail to make the image usable even if it were bright enough. |
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| mrmonopoly |
| Thanks for the speedy responces and suggestions. I have told the company I am working with at the moment what the project was for. They do infact sell clusters of special LED to power the outside light that shines onto buldings. They cpme complete with the lenses fitted. Now these type of lights must be very powerfull indead. I am holding Hi hopes that together with this optics company we can in fact come to a solution to the problem. So bare with me , I am working on it :). if it turns into a totall disaster then nothing ventured nothing gained. Watch this space :). |
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| diylabs |
| well if they are bright enough for outdoor lighting, then that is indeed impressive! Perhaps the lens that they fit to the front of the assembly holds some key to collecting more light that I was able to get. I hope that my comments previously didn't seem overly critical - in fact I hope that your LED clusters do work because LEDs could help make our projectors more energy efficient, smaller, and run cooler and quieter ... that would be most excellent! |
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| ace3000_1 |
| quote: | | well if they are bright enough for outdoor lighting, then that is indeed impressive |
Heya Allan, outdoor led lighting has been around for some time, and is found easiest on ebay.
Trev |
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| diylabs |
| i was imagining something a little more industrial like the metal halide kits they use to illuminate the outside walls of tall buildings at night time. The LED's for outdoors that I was able to find on eBay were those landscaping lights, which are nowhere near bright enough for sure. |
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| ace3000_1 |
| quote: | | i was imagining something a little more industrial like the metal halide kits they use to illuminate the outside walls of tall buildings at night time. The LED's for outdoors that I was able to find on eBay were those landscaping lights, which are nowhere near bright enough for sure. |
Lol, yeah those things, they arent bad though, you need to make a cluster from them to be able to work, keep searching, cos they have driveway industrial leds too wich are much bigger and more powerful.
Trev |
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| rmccoll |
| Is the anyway to fix the lines that be in lcds screen. I have screen that has lines in it when you turn it on. I can here sound,but the video is scrambled. If you know a way to fix this problem please help me. |
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| ace3000_1 |
Heya buddy, check the fcc cable conections on the fcc cables that run from the lcd to its controller card/cards.
Trev |
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| rmccoll |
| I checked the cable and looked for dry solder but they still appear on the screen. |
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| ace3000_1 |
Are you using vga or video in?
Trev |
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| rmccoll |
| I'm using video in |
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| ace3000_1 |
Sounds to me its a controller card issue, or a flex cable problem, more then likely a flex cable one.
Trev |
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| Yazan24 |
| Hey all, I need a little help, for a school project im building a video projector Im wondering if I put an LCD screen a bit elevated with all the necessary output jacks, on a Regular Projector would it work? |
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| diylabs |
| what do you mean by "regular projector"? If you mean using a projection panel on an overhead projector, then yeah that would be fine (most people started off that way). |
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| Diragono |
| That was total spam |
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| Orochi |
I just ordered 100 20000mcd LEDs for $25. No, Im not kidding, or full of ****, a factory in hongkong is selling them direct on ebay at about 1/10 the cost of what youd pay if you ordered a similar part from mouser or something. I didnt really belive they where legit at first, but after checking out all the good feedback they have gotten, I have to assume that they are indeed reputable. Just do a search for "20000mcd" to get their listings.
For those who may not be familiar (although I would assume most of you on this forrum probably would be) with what "20000mcd" means; I am told that in order to roughly convert candela to lumens, you multiply by 12.57. So basicly, each LED being 20 candela (or 20000mcd) can put out about 251 lumens. Now, granted, that is their most optimistic rating, their minimum rating is 140000mcd, which would translate to about 175 lemens per LED.
So, just to be conservative, lets assume that you are getting the minimum posible lumens from each LED, and that you will need 5000 lumens to get a good picture from your projector. That would mean that you need about 30 of these pupies to make a projector lamp. Considering that I payed $0.25 each for them, that means you can make a 5000 lumen lamp that will last a very conservative 50,000 hours for arround $7.50.
Is it just me, or is this the bloody freakin holy grail of do it yourself projector building? And to top it all off, I found lots of 10 3v (same voltage as the LEDs) lithium Ion photo batteries with a capacitiy 1300mah each, for as little as $9.00. ****, I mean, what is to stop us from making completely portable hand held projector for a few hundred dolars?
If somone could point me in the direction of a reasonably priced, decent (aka 1024x768) 2 to 5" inch LCD, and driver, as well as a good source of innexpensive optics, and the plans neccesary make a nice transmissive style projector (I am assuming that a transmissive set up would be optimal in this case, considering I can keep the lcd so close to the lamp without it over heating like an incandecent bulb would do) I would be very greatfull.
-Orochi |
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| ace3000_1 |
| quote: | | I am told that in order to roughly convert candela to lumens, you multiply by 12.57 |
Try devide lol and thats why we dont use leds, i dont even think devide is right, its somthing like 2lumens per led.
Trev:) |
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| tgreenwood |
According to the good folks at the University of North Carolina and the scientific dictionary they have .....
millicandela (mcd)
a unit of light intensity equal to 0.001 candela. The intensity of the light-emitting diodes (LEDs) used in electronics are stated in millicandelas.
lumen (lm)
the SI unit for measuring the flux of light being produced by a light source or received by a surface. The intensity of a light source is measured in candelas. One lumen represents the total flux of light emitted, equal to the intensity in candelas multiplied by the solid angle in steradians (1/(4·pi) of a sphere) into which the light is emitted. Thus the total flux of a one-candela light, if the light is emitted uniformly in all directions, is 4·pi lumens. "Lumen" is a Latin word for light.
Looks like Orochi is right.
T. |
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| Orochi |
| quote: | Originally posted by ace3000_1
Try devide lol and thats why we dont use leds, i dont even think devide is right, its somthing like 2lumens per led.
Trev:) |
Ok, I think I see where I got confused , mutiplying the candela by 12.57 seems to be a way to convert to lumens when your light source radiates sphericaly or something (or at least I think thats what they meant, still not sure really), where as leds only cast their light at a particular "viewing angle".
After plugging the brightness of my LEDs into the equation on this site....
http://www.ledproductstore.com/measurement_of_leds.htm
It seems that you would be getting about 10 lumens per LED. Which obviously does change things quite a bit, but it doesnt change that these 20000mcd LEDs at $0.25, are still one hell of a deal compared with the 2000mcd LEDs that cost about $5.00 each no more than a year ago.
So I guess it turns out that my 100 20000mcd LEDs are good for about 1000 lumens on a good day, but hey, I only payed $25 for the lot of em. When you think about it, even if I need 300 to get something comprable to a 3000 lumen metal halide lamp, wouldnt it be well worth it? I mean, hell, they would still produce a lot less heat, and last 50,000 hours.
Anyway, Im no engineer, so I would love to have someone who really knows what they are doing take a look at the specs for these LEDs and let me know exactly what is what.
Heres a link to the LEDs Im talking about, it has all their specs twords the bottom of the page....
http://cgi.ebay.com/ws/eBayISAPI.dl...3840744077&rd=1
Also, Im very curious about something else I found using LEDs that Lamina calls a "Light Engine". They Claim that one of their 8 caviity light engines (about $40 at mouser.com) can produce 1000 lumens, and they sell a light engine that has 39 cavities (about $165 at mouser). Perhaps that would be the way to go?
In any event, here is a link....
http://www.laminaceramics.com/products.htm
Prices at mouser...
http://www.mouser.com/?Ne=400&handl...=59901+59930000
-Thanks
-Orochi |
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| verbose mustafa |
The 12.57 conversion will never, ever, ever, give you the right data. You will actually be getting 7.65 lumens per LED. I wrote a program in c++ based on the proper conversion method posted below. It's just a simple DOS program but eliminates the need to do the math by hand :D.
You Can Download It Here |
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| Orochi |
| quote: | Originally posted by verbose mustafa
The 12.57 conversion will never, ever, ever, give you the right data. You will actually be getting 7.65 lumens per LED. I wrote a program in c++ based on the proper conversion method posted below. It's just a simple DOS program but eliminates the need to do the math by hand :D.
You Can Download It Here |
Yeah, I got the same result once I plugged the correct solid angle into the equation. What a difference 5 degrees makes. It seems that LEDs in general tend to fluctuate between 20 and 25 degrees. At 25 degrees I got about 12 lumens per LED, at 20 I got 7.5. Im guessing that my last assessment of about 300 LEDs would be equivelent to a fairly decent mid range comercial projector. If you think about it though, at $75 it still beats the pants off an incandecent bulb. Yeah, for that price you could get much brighter light sources (I think someone once told me you can get a 10,000 lumen lamp for about $100) but leds will last 50 to 100 times longer, are far more durable, and dont make anywhere near as much heat..
What Im really curious about is that Lamina light engine. If every 7 cavities, really do produce 1000 lumens like they say, then I would more than happily cough up the $160 for a 39 cavity product., 5600 lumens aint to shabby at all, and it would save me the hastle of wiring all those single leds together.
-Orochi |
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| verbose mustafa |
| quote: | | Im guessing that my last assessment of about 300 LEDs would be equivelent to a fairly decent mid range comercial projector. |
Ok, we are all agreed that a 20,000 mcd led with a 20 degree viewing angle will produce about 7.5 lumens of light. I will keep with the tenths place only to stay simple. With 300 LEDs X 7.5 lumens a peice, we are looking at a total gross of 2,250 lumens. That is assuming you can somehow defuse all of the light from each LED in to one general path with no light loss. That is not going to happen no matter how hard one tries.
Once all the light from the leds has been defused and is essentially ready to shine its way through the lcd, there will be a good amount of light loss. What it all comes down to is how good your light kit is. By that I mean not only all the optics involved, but the way it is put together. Something crude like brute force style will not work. You cannot expect to throw a fresnel in front of some leds and go from there. You will need somthing small, well crafted, with little if not no light leaks, and good quality optics. Anyone will tell you the best light kits are made by ace. If you used a highly modfied version of his designs to fit your application, you may get somthing nice.
So assuming you get this really nice light kit made, you're still bound to get some degree of light loss. I can't really throw out a 100% accurate number, but assuming you loose around 30% of the light from the light kit. That means that there would be 1,575 lumens hitting the back of your LCD panel (Becuase I am assuming there would be no way to loose light between the light kit and the lcd).
Your assuming that you will have 10% of the light hitting the back of the LCD actually pass through. That number is a little high in actuality, but since we have a really nice light kit with low loss and there is no way to loose light between that and the lcd, I'll give it the benifit of the doubt. After, 10% of the light passing through the lcd, you would be left with 157.5 lumens of light on the front side of the lcd.
Not taking into account the light lost by the time the image is projected through the lens, accross your room, and onto your wall, that is very roughly a number you might expect on by the time you hit the wall. So you say you would have the results of a mid range commercial projector? About what you would achive IMHO is the brightness a little less then an old, 150 ANSI lumen nView projector, but with the benefit of a much sharper looking picture from your projector. Also, ANSI lumens is not just the % of light after the lcd. It is measured in relation to the size and brightness of the projected image. So, you go for a smaller image, 157 lumens of light passing the LCD might be just right for you (even if oh lets say 80-100 ANSI is your final result).
So! Will LEDs work? IMHO Yes. Seeing the results from placing my delta lens over an unmoddified lcd with the original backlight installed many years ago and seeing a 5 foot projected image on the wall leads me to belive that yes, LEDs will work to a point. How will they will work is up to your engineering skill and the application you want to use the projector. You will not get commercial quality results. You projector will be cripled in the area of size in relation to brightness. I just wanted to make you realize that your aiming your results too high. There is no doubt it'll work (maybe even well). You just need to build the thing to work with what is reasonable. Having the results of a 500 ANSI lumen projector with LEDs is not. Remember, the projector companies are always a a few years ahead of us in technology.
Good luck and please, don't let me discourage you. I'll probably be building one of the guys too :D. |
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| Orochi |
Verbose Mustafa:
No no, I definetly appreciate your input on this. Yeah, I had assumed that the lumen rating of those comercial projectors was a refferance to the light source, I had no idea that the lcd absorbed so much of the light.
I would never have imagined that only 10% of your light gets through to the final image. Damn, that would mean that the metal halide lamps in those commercial projectors, are what, about 20,000 lumens? No wonder they are so expensive, and difficult to keep cool.
In light of this new information, Im thinking those Lamina light engines would no doubt be the way to go if you wanted a solid state light source. The 39 cavity light engine apparently produces about 5500 lumens (yes, they rate it in lumens rather than candela). It would take 4 of them to get that 20,000 lumens, and it wouldnt be cheap at $160 each, but it sure would make for a slick projector.
These things are extremely small too, I think the 5500 lumen product was a little over 2x2 centemetemeters, so youcould probably make it a hand held projector. Which is one of the main attractions to lcds for me anyway. I mean, they are durable, have very low power consumption, and dont produce much heat, which sounds like exactly what youd be looking for in a portable product.
-Thanks
-Orochi |
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| ace3000_1 |
| quote: | | Ok, I think I see where I got confused , mutiplying the candela by 12.57 seems to be a way to convert to lumens when your light source radiates sphericaly or something (or at least I think thats what they meant, still not sure really), where as leds only cast their light at a particular "viewing angle". |
Playing with leds and thier brightness can be tricky, i personally dont fool with leds, Yet! but may do further down the line so realy i have no say on the matter, but what i did know is that 250lumens will never come from a 20000cmd led.
Parabolic reflected lamps are measured like leds aswell, anything with a beam wont be measured in lumens on a manufacturers site, why? not sure, but its to do with the beam angle and there is a way to convert it back.
Regarding light loss, there is a way we can tackle this without a great loss of light, but a few calculations need to be kept in mind, here is the thread where i posted the idea.
http://www.diyaudio.com/forums/show...9580#post459580
Trev:) |
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| elstcb |
My 2c:
A narrower beam may give a lower lumen output per LED but will probably produce less light loss (to the surroundings before the LCD) and give a much crisper picture.
I have yet to see anyone here do any decent pulsing with these white LED's, traditional LED's should take a couple of Amps if it's for a very short period of time giving a perceived increase in brightness. It would be great to find out how much current the cheap white LED's can take and if it made their colour better or worse.
verbose mustafa's calculations look spot on, great work with the dos program by the way. :) |
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| elstcb |
70,000:1 Contrast Ratio (pdf)
No idea how acurate their contrast ratio claim is but it's interesting to see how they've used an LED matrix as a backlight, not quite what we're discussing here but still kinda relevant IMHO. |
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| Guy Grotke |
Personally, I love the new super-bright white LEDs, but there are a few issues that are being ignored here.
1) LEDs are less efficient than MH lamps. That power consumed, but not converted to light, has to go somewhere. Where it goes is... heat! So an LED projector light source will actually get hotter than a same-lumen MH lamp light source. (The heat WILL be spread out more, but you will need more airflow to get it out of the box.) It will also cost you more to power it.
2) This is the killer: All the very bright whites I have seen use a narrow-band blue LED to stimulate a narrow-band yellow phosphor. When we see blue + yellow, the blue stimulates our eye's blue receptors, while the monochromatic yellow stimulates both our red and green receptors. So it looks "white" to us. But it does not look like an even mixture or red, green, and blue to the red, green, and blue filters on the LCD panel! The blue will get through fine, but reds & greens will be very dark. This is why LED projection tests go through the lenses just fine, but look horrible when you pass it through an LCD.
3) There are true RGB LEDs that are used for devices that need to create any color on demand, like paint matchers. But those LEDs are much more expensive and much too dim. The other option is to make your own array of R, G, & B LEDs. Then you would get each color you need, but you would also introduce lots of color artifacts in the image. |
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| Guy Grotke |
They get "70000:1 contrast ratio" by using a backlight made of individual pixel LEDs? But that leads to a more interesting question:
Once you have a full-sized panel of RGB LEDs,why would you put an LCD in front of it? Why not use the LEDs as the display device directly. You could run them at 10% of the power needed to get the same amount of light through LCD filters, etc. |
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| arniel |
| quote: | Originally posted by Guy Grotke
They get "70000:1 contrast ratio" by using a backlight made of individual pixel LEDs? But that leads to a more interesting question:
Once you have a full-sized panel of RGB LEDs,why would you put an LCD in front of it? Why not use the LEDs as the display device directly. You could run them at 10% of the power needed to get the same amount of light through LCD filters, etc. |
Size?
Speed?
Soldering? |
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| Guy Grotke |
>Size?
>Speed?
>Soldering?
My point was that the 70000:1 contrast ratio idea doesn't make much sense. If you have individual pixel backlights, why not just use those as the display device? I don't see what putting an LCD in front of them gets you.
Size: If you have individual pixel LED backlights, then that has to be exactly the same size as the LCD panel. (In fact, they would have to very precisely aligned.)
Speed: LEDs are thousands of times faster than LCD pixels.
Soldering: An LED array like this would have to be fabricated in a semiconductor processing facility, rather like where they make LCD panels. No soldering would be involved, just lots of photo-etching and vapor depositing using very nasty chemicals.
AND it doesn't help us at all, since it would result in a panel with a fixed backlight. Even if you could seperate the backlight from the LCD, the LCD would still be 400:1 max. |
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| mrmonopoly |
Hello all again , i have something which you lot will find very intresting. I have still been followig the project through , and a new LED device has just come into a local electronics store claming this new LED gives more light that a Halogen bulb and is priced at £8 each. Here are the details.
• Very high brightness
• Very high flux per LED
• Very long operating life (to 100k hours)
• Cool beam, safe to the touch
• Instant light (less than 100ns)
• Fully dimmable
• No UV Superior ESD protection
• More energy efficient than incandescent and most halogen lamps
Luxeon star hexagonal modules can be connected and powered in a close packed hexagonal configuration for tight spacing and increased light output per unit area. They are available in white, green, cyan, blue, royal blue, red and amber. Typical applications include passenger reading lights, portable lighting, orientation/emergency lighting, mini accent lighting, decorative lighting, fiber optic alternatives and other appliances. This range of products have a batwing (low dome) radiation pattern and slots in the aluminium-core PCB for M3 or #4 mounting screws. All codes have a viewing angle of 110°
if anyone has any views i be pleased to hear them :) |
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| mrmonopoly |
or there is this one , data sheets are avalible
Luxeon V Emitter Lambertian
• Highest flux per LED family in the world
• Very long operating life (up 100k hours)
• Available in white, green, cyan, blue, royal blue
• Lambertian radiation pattern
• More energy efficient than incandescent and most halogen lamps
• Low voltage
• DC operation
• Cool beam, safe to touch Instant light (less than 100nS)
• Fully dimmable
• No UV Superior ESD protection
Luxeon III is a revolutionary, energy efficient and ultra compact new light source, combining the lifetime and reliability advantages of LEDs with the brightness of conventional lighting.
Luxeon III is rated for up to 1000mA operation, delivering increased lumens per package.
Luxeon emitters give you total design freedom and unmatched brightness, creating a new world of light. |
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| elstcb |
| Luxeons have been looked at several times in the past, the broad viewing angle they give might be good for the numbers but means you'd need a lens for every unit in order to get parallel light. They also tend to be more expensive per mcd than traditional LED's. |
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| Guy Grotke |
I suppose the key to using a diffuse light source would be obtaining a sheet of plastic formed as an array of thousands of PCV lenses. Each lense would "see" the entire light source and converge all the photons it gets from any angle, into a single beam perpendicular to the sheet. This would give you a set of parallel beams that you could send to a field fresnel, either above or below the LCD panel.
That way you could make the most of a diffuse light or even multiple light sources like LEDs or fluorescents. Or even a mixture of light types to give you a better color mix.
Has anybody heard of such a lens array material? |
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| elstcb |
| quote: | | Has anybody heard of such a lens array material? |
It's a nice thought but practically impossible to implement as you'd need to know the divergence of the type of LED you were using, and this is likely to vary slightly between each unit. It would therefore probably have to be custom made and I can't help but think that this reaches way beyond a DIY realm.
A few things to cheer LED lovers up though:
* New reflectors are expected to be introduced into LED's in 2005 whos efficiency is claimed to be 99%. Hopefully this will mean a wider variety of divergence angles as well (source).
* This along with much brightness progress where they are currently acheiving 75 lumens per watt in the lab (source) should give us something serious to play with (I think I'm correct in saying MH is between 70 and 90 lumens per watt). The latter could be a year or two away yet though...
* I still maintain that pulsing LED's produces a much greater perceived brightness than constant current, the danger here is that it could negatively affect the colour temperature of the LED's further towards blue. |
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| Guy Grotke |
Has anybody noticed that you can "borrow" various long focal length lenses for quick experiments by purchasing reading glasses from a local drug store, WalMart, etc. that lets you return things for a refund? The glasses are labelled 1.0 through about 3.0. These are not magnifications, but rather Diopters. (The same as eyeglass prescriptions.)
There is a very simple relationship: D = 1/focal length in meters
So here is a handy table for the standard reading glasses:
D focal length
1.00 = 1000 mm
1.25 = 800 mm
1.50 = 667 mm
1.75 = 571 mm
2.00 = 500 mm
2.25 = 444 mm
2.50 = 400 mm
2.75 = 364 mm
3.00 = 333 mm
When you buy them, make sure you ask if you can return them if they "don't work". (give you a headache, make your eyes hurt, etc.) They aren't very big, and they have a funny shape, but they should do for a quick check before you order a "real" lens. |
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| Orochi |
Maybe we are taking the wrong approach here with LED projectors in general. Everyone keeps talking about how we can make led projectors comprable with MH projectors, but right now it just doesnt look like they really can be, at least without spending far more time/effort/money than its worth. So why not use them for a projetor with a much smaller screen, that is a great deal closer to the source? Do we really NEED an image that is 10 feet wide? Doesnt the brightness increase exponentially as you get the source closer the the image or something? I would be pleanty satisfied with an image that is say the same size as a 70 inch big screen TV. The longer life, small profile, and ability to turn it off without having to worry about the bulb breaking would make it worth considering. I dont know about the colour problems though, if as some people have suggested, a white led wouldnt react the same way with an lcd, then perhaps it is merely a question of adjusting the lcd's colour settings, and accepting a hit on the over all brightness in order to compensate.
I digress though. The major dificulty for me with diy projectors, regaurdlesss of the light source, has been tracking down a reasonably priced lcd. Considering how much more noticable poor resolution is in a larger image, any way you slice it, you need an lcd that is going to do at the very least 1024x768, and if you want to justify not simply going out and picking up a commercialy produced projector, that lcd really cant cost any more than $200 - $300 at the most.
Im curious though, why dont people go with more of an opaque projector like set up, and just stick a run of the mill computer lcd/crt in it? Does the image look to washed out or something? I know people on this forrum seem to think that fresnels are the devil or something, but in combination with other lenses used to ajust the focal length, would they be so bad?
-Orochi |
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| elstcb |
I think there's several approaches been taken by various people to LED backlights, personally I'd love a small projector using something like a PS LCD screen, however using a more standard 14-15" TFT is just as feasible (and the latter is easier to fit more LED's behind). However I'd still want the projected image size to scale up to similar to my current MH projector and, as you say, to get a sensible brightness using LED's this would require a lot of time/effort/money.
Having not really played with LED's behind an LCD enough I have no idea how the colour is affected however because white LED's tend to emit very narrow sets of wavelengths (which the eye interprets to be a broad spectrum white) it may be the case that we're talking about huge light losses, especially through the red and green filters. You are also right in saying that this can be evened out by adjusting the LCD's colour settings however the concern is that this will be a significant loss making it even harder to get a sensible brightness out of a projector.
As for your digression, I use the screen out of a standard Compaq TFT500 computer monitor in my MH setup, it is by no means the best monitor available but does allow 1024x768, with enough colours and a good rise and fall time. The problems with this are:
* that it's a 15" panel and as a result the actual projector box is massive (especially in my small living room).
* That it's a bit awkward to take apart the case of the monitor and refit the panel into a custom design. For this reason people sometimes go with a panel specially designed for projection, especially if it is to be sat on top of an OHP. If you want to use a computer TFT monitor then check out the good panel / bad panel thread to see which are suitable for using.
I'm not sure how you have the impression that people don't like fresnels, every design on here that I've ever seen uses them and IMHO they are paramount to a DIY design. The only problems people have had with them as far as I'm aware is when they have them to close to the focal length of the projection lens at which point their rings can become visible on the projected image. This is easily fixed by moving them up to 1/4" away from the fl.
Hope this clears up a few things,
Steve |
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| Guy Grotke |
The brightness of the screen goes down at the square of the magnification, just by spreading out the same amount of light over a wider area.
One of the reasons I am working on a 15" TFT LCD monitor projector, is that I want to experiment with different forms of lighting. (Also: $200 new from pcclub.com, 300:1 contrast ratio, 30 ms response, 1024 by 768) You can also get a 14" TFT LCD monitor for about $150, but they all seem to have a 50 ms response time.
These monitors are backlit by a single CCFL tube, and have about 10 layers of light spreaders and diffusers the light has to get through before it even reaches the LCD. So I suspect we don't need to use a blinding light source with so much LCD area. I have a 250W MH bulb coming in, but I also want to try a solid array of fluorescent tubes right behind the LCD with a field fresnel above the LCD. Another idea I want to try is a fresnel-free design using a reflector to focus light on the objective lens through the LCD.
I do not plan to try white LEDs, since they are less efficient than MH and have a horrible spectrum. People only think LEDs are ideal because a single LED doesn't generate much heat. But if you put enough white LEDs in your box to match the lumens of a MH bulb, it would generate twice as much heat! (And VERY little red or green in your image.) |
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| Parris1972 |
I'm just tinkering and hunting on the web for information on projectors. At present I work with AV equipment, but don't really have the additional cash flow to purchase expensive equipment for myself, so I make do with an InFocus projector I bought a few years back and a Hitachi I bought on eBay for next to nothing because the seller had NO idea of it's value.
Problem is that I'm sick of shelling out cash every 400 / 500hrs and would probably have been better off buying a 60" plasma by now!
I've read through a few (dipped more like) threads on DIY LCD projectors and frankly, I'm impressed. I read somewhere that white LEDs last 90k hrs. In the time it's taken for these threads to be created, the cost of purchasing a reasonably sized LCD TV has dropped by vast amounts here in the UK.
So, these threads appear to have either moved on, closed down or ground to a halt in Dec 04. Where did everyone manage to get with these projects? Anyone actually put together a decent prototype and create circuit diagrams?
Did anyone have any screenshots worth posting?
curious... |
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| elstcb |
You are quite right, it has gone very quiet around here just lately!
By now I'd imagine there's enough information in these forums for anybody to be able to create their own DIY projector and I'm guessing a lot of people are following pre-made build instructions (e.g. the ones available on http://www.lumenlab.com/ ) rather than experimenting.
You'll find plenty of good pictures around the forum and I'm sure you'll see for yourself that people get stunning results, there's nothing quite like having a 70" screen in your living room!
Most designs use Metal Halide bulbs, I think they're approx. 20k hour lifetime although don't quote me on that one, they're also available for about £20 in the UK if you look in the right places. Last time I looked LED's were still much more expensive than this and less efficient.
In terms of you shelling out for replacement bulbs, you can almost certaintly build yourself a DIY projector for the cost of the next replacement bulb!
If you're contemplating building one then the best advice I can give is read read and read. |
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| Parris1972 |
No doubt good advice. I spent the morning contacting bulb suppliers in the UK, Europe and even in Australia to discover that a replacement bulb (700hrs) for the Hitachi is £300.00 plus P&P (inc 17.5% vat).
Considering I just picked up the Hitachi for £50.00 BIN on eBay (laughs out loud - cheaper than my last set of AV leads) I'd rather not shell out such a silly amount of cash. I knew it was going to be expensive, but prices aren't coming down fast. Don't the manufacturers realise that more people would go for these units instead of plasma if the bulbs cost 50% less and lower. They could do it, the cost of production is measured in £1's.
My InFocus projector has roughly 150hrs left on the bulb, which will not last long and it's started to dim already.
How practical are re-conditioned bulbs? Has anyone on these forums tried? The bulb from the Hitachi looks to me to have died through shock (over heating because of poor venting probably) rather than over use.
As you can see I am new to this side of things as frankly I like to park my ar*e and view films, not spend weeks tweaking. That said, I really want to have a good set-up going.
Cheers.
P.S. I'll look those schematics up as I have built equipment in the past (mostly studio) and wouldn't mind trying my hand at it. |
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| NautTBoy |
Hi I have a portable dvd player that still work but with a bad screen(TFT). Backlight(square tube) went out. I was wonder if it's possible to turn that in to LCD projector. I'm trying to get away from the big box projector (15" screen) I want to try to get it as small as possible as the same size as the real one for $1,000+. I dont really need 150", as long as I have a big enough screen 50"+. Anyone have suggestion?
I haven't had time to upload my plan diagram. |
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| elstcb |
The chances are that the screen will have an appalling resolution, slow response time and poor contrast ratio, however if you think you can live with these then there's no reason not to use it. I'd imagine it would be ok on a small projection screen if you're planning to use it to watch TV, don't expect cinema / theatre quality from it though.
One thing you will need to do is to ensure that any circuitry behind the LCD can be folded out of the way, preferably before destroying your player altogether. You might need to extend an FCC cable (flat small ribbon cable) or two which whilst a bit fiddly isn't too expensive.
If you find that you can't fold the circuitry out of the way then maybe take a look at the Lilliput screens or the PS2 screen, people on here have managed to get some very good results with them. Again they're fairly cheap and I believe are easy to work with.
Have you looked for other parts yet? You may need to be careful with the bulb dimensions as some can be quite long and therefore would needlessly increase the size of your box. At least if you are only after a small projection screen then you can go with a 250W MH bulb or equivalent.
HTH, hopefully others have some points to add.
Steve |
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| Guy Grotke |
If the LCD is really only 4" diagonal, then you can make a very tiny simple projector using a CRT projection lens. These go for under $15 on eBay and surplusshed.com all the time, and can project up to a 5" LCD. This kind of lens goes right up against the LCD, which makes for a small box.
I would put a 150 Watt double-ended MH lamp behind it with the shortest focal length fresnel you can find (maybe 200 mm?) as a condensor about 25 mm before the LCD. The lamp to fresnel spacing would be the same as the focal length of the fresnel.
Add a spherical reflector for the lamp, some fans, UV and IR filters, and you will have a very small projector that can make a small screen image that will be limited only by your LCD's resolution. But you could start with the $15 lens and a bright incandescent floodlight to see what the image quality will look like before buying any of the rest. |
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| NautTBoy |
Thanks for the advice and suggestion guys. I will try it and learn as i go. These are what i'm working with just to get the idea of projection.
Mintek 5" 4:3 Portable DVD TFT with the player outside the box.
Kodak Lens F:2.8 102mm (heard that it's wrong choice)
Plastic Fresh Snail Len:D
Home Torcheire Halogen Lamps
I like that plan from ....i forgot the ID......5" PS1 LCD screen. I think that's small enough for me.
OH, I put 4" screen instead of 5":D |
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| Guy Grotke |
The one advantage of a CRT projection lens is that you can be pretty sloppy about the lighting, and still get a reasonable image. If you really want to try one of those long skinny halogen tubes, then I would make a beer-can reflector: Cut open an aluminum can by cutting off the ends and then making one neat cut up the side. (Wear gloves! Very easy to cut yourself doing this.) Then open it up and form a two dimensional parabola. You may have to add some wood or metal pieces for the sides to keep the can metal in the right shape. If you put your halogen tube an inch or so from the center of the parabola, you should get a pretty even parallel beam from the whole reflector surface. Play around with the shape until you do.
Put that right behind the LCD and it should work okay without any fresnels at all, as long as you are using a CRT projection lens that is as large as the LCD.
If you want to use a smaller lens, then you will have to use fresnels to condense a point-source lamp's light into the lens.
Either way, a halogen lamp will give you a yellow-tinted image. Not as bad a those parking lot sodium lights, but metal halide lamps look much whiter. |
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| NautTBoy |
| Hey thanks again for the help Guy. I look under "CRT PROJECTOR LENS" on ebay I don't see any under $50. With "BUY IT NOW" filter, I saw $70 plus $30S&H the cheapest price. I went to surplusshed.com and I didn't know what to put in the search because there wasn't "CRT" for me to select. You're probably saying "dang, this boy!" Well, I'm a newbie:xeye: |
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| Guy Grotke |
Here is an expensive example from eBay. I have seen a lot of these go for more like $15 US:
http://cgi.ebay.com/ws/eBayISAPI.dl...5765839493&rd=1
The lens specs would be at least 5" (125 mm) diameter, focal length in the 6" to 8" range (150 to 200 mm). If they only tell you focal length and f-ratio, then diameter = fl / f-ratio. So a 200 mm fl f1.6 would have a diameter of 125 mm.
It doesn't look like surplusshed has any right now, but you could try doing a google (or froogle) search for "CRT projection lens". There was also mention on some thread in this forum about somebody having around 50 of them in his basement. |
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| Mikey p |
| quote: | Originally posted by Guy Grotke
There was also mention on some thread in this forum about somebody having around 50 of them in his basement. |
That would be Curt Palme. If you're interested in that type of lens you can contact him here http://www.curtpalme.com/ |
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| wussboy |
| quote: | Originally posted by elstcb
By now I'd imagine there's enough information in these forums for anybody to be able to create their own DIY projector and I'm guessing a lot of people are following pre-made build instructions (e.g. the ones available on http://www.lumenlab.com/ ) rather than experimenting. |
Are there more websites like this one? I'd like to try this, but am nervous to go it alone. Thanks! |
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| Guy Grotke |
redd38:
That stuff you listed will work fine. If you get a 200 to 220 mm fl condensor (first) fresnel (such as lumenlabs or 3dlens), then put it that same distance from the lamp arc. With this kind of geometry, a pre-condensor lens would not be worth the trouble.
If you get a 330 mm fl condensor fresnel, then the right pre-condensor lens would help gather more light. But, I would just use a 220 and not bother with a pre-condensor lens.
You can pay a lot for an optical-quality spherical reflector from places like Edmonds, but again I would not bother. Try a polished stainless steel mixing bowl from one of the DIY projector sites. They are under $10 precut to fit your Ushio lamp.
Don't forget UV & IR filtering, and one or more fans for forced-air cooling. |
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| jgr |
| hey guy, with a spherical reflector, would you have to not use a condensor fresnel and reflect the front part of the light arc back to the reflector? (kind of like car headlights work) |
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| Guy Grotke |
Car headlights are parabolic, with the lamp filament a bit deeper into the "dish" than the focal point. That makes the resulting beam spread slightly.
A spherical reflector is used with the lamp arc placed at the exact center of curvature. Every ray that hits the reflector is reflected right back through the lamp arc and out the other side. The condensor fresnel "sees" all of this as a single bright point source. If the distance from the lamp arc to the condensor fresnel is exactly the focal length of the fresnel, then parallel rays will come out the other side of the fresnel. A field fresnel can then be used to focus all of those parallel rays to a point inside the projection lens.
There are other possible ways to do it, but any design that can't focus most of those rays into the projection lens will not give you a bright screen image. |
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