| Mitch |
Hi guys,
How bad would a 100:1 contrast ration be? it sounds pretty bad considering Sony has a screen that has a 3000:1 ratio... |
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| Mario007 |
| 100:1 ratio is not bad. The highest sharp projection panel is 150:1 (QA-2500). Sony may have a screen with 3000:1 ratio but that could be counting each pixel and multplying that by 3. 3000:1 is a bit excessive I think. Although more is always better I sure don't want to pay the price for that sony. :) |
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| thelaw |
Hello ppl, just wondering if any of you could help me out with something.
I have an NView Spectra Pro. When using it with my ohp, there is a small (but quite irritating) white spot in the middle of the screen (about 2inches wide on a 2metre screen diag)
I think that this is an image of the filament projected, however it must have something to do with the polarizers on the lcd. When i turn the panel over, the spot disapears. I have a rear-projection setting on the panel so inversing the picture is not a problem.
My question is, will operating the panel like this damage it? Is there some kind of heat blocking substance at the back?
One other thing, took the panel apart today out of interest, seems the lcd module inside is manufactured by sharp :) i do have a sharp panel after all :))
If anyone has a Sharp QA-2500 for sale, please email me |
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| prjctr_builder |
If anyone interseted, i accept offers for my QA-2500. good condition, no scratches, and all the specs that it came with. Has a hard case, Vga cable, remote.
thanks:) |
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| woneill |
Hi Aleksey,
What went wrong? You seemed so happy with it.
Bill. |
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| thelaw |
| Ditto. How come u dont want it anymore? |
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| prjctr_builder |
1. i love this panel, but i have nowhere to watch movies with it, the rooms are kinda small, i used in garage, but it is getting cold in there, and iwanna have a cozy place.
2. no time = school, work
3. no money = car
thanks
P.S. hard to be 16 |
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| woneill |
Aleksey,
If cost is an issue, why not go for a cheaper option: Spectra C and $30 OHP from ebay. If you looked around, or called Inventory Solutions direct, you could probably do the whole thing for $100. (Small rooms = small screen = brighter image from cheaper bulbs...)
At least, that way you stay in the game...
Bill.
P.S. You're doing good for 16. |
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| noodles |
| When I go to the Inventory Solutions site, they have Spectras for $100-$150!!! That's crazy. No job (unless you count web designer), school, no car, 15. |
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| devenfore |
Wouldn't it be a lot easier (and cheaper) to simply take a used Slide projector, and insert a small LCD screen (such as one from a $100 hand-held tv) where the slide would normally sit. I know that some of the wiring for the lcd would be a little tricky. Anyways, just a thought.
- deven |
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| noodles |
| Where's the fun it that? :D |
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| devenfore |
I have been trying to find out the easiest and cheapiest way to build a home theater, and I thought that would be the best. So far a have:
Sony 5.1 Reciever - $20 off ebay, becuase of bad relays.
RCA Progressive Scan DVD Player - $25 off ebay, needed laser alignment.
My TV, Speakers, Subs, VCR, DishNet Receiver, ect.
only thing that is missing is a Projector. So I thought something like:
$20-40 for an old slide projector off ebay or somewhere.
$20-100 for an lcd screen w/a tv tuner.
I dont know, becuase I dont have a lot of experience with optics, it is relativly new to me. Anyway, I was wondering if anyone had any good reasons why it wouldn't work / wouldn't work well.
Thanks for the replys - deven |
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| thelaw |
This has been discussed at much length on the DIY small panel projector thread of this forum.
The main problem is resolution. TV panels commonly have 340x240 or similar resolutions. My LCD panel has 640 x 480 and I can still vivdly see pixels. Believe me, its not worth throwing your money on something unproven. Get yourself an OHP and panel, and you will be happy :)
cya, |
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| eebasist |
devenfore......did you lie when you posted saying you searched the forum before posting?
Look at the DIY small panel projector. or DIY projector 1. THe answer you seek lies within......i'll sum it up for you......you can strip a lcd tv to fit inside the slide projector....but don't go asking for a long life or high resolution as the heat will eventually kill the panel. |
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| Gunawan W |
Hi jco9w,
You should put the fresnel 12" in front of light spot (point where you burned the cardboard), with this setup you get parallel rays come out from fresnel panel.
For condenser lens, you should find lens with short fl, shorter is better, because it can spread the light widely at short distance from fresnel.
Actually, if your reflector can produce small enough lightspot, you can put your fresnel directly 12" in front of the lightspot and you get the same result.
Hi Redevil,
So with my drawing#2 setup (fresnel-LCD-fresnel) the result was not good compared with your original setup?
Even with Woneill suggestion (fresnel direction and fresnel distance from LCD)?
thanks. |
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| braxton |
I think I know why aleksey might be selling his panel and overhead
see page 22 of this thread...
not good |
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| woneill |
Hi Noodles,
Yup, that's what I saw when I checked out their site. However, I bought a Laserdisk from them through Ebay, and asked what hi-res panels they have (I had seen some good reviews of them on the earlier thread).
They had no high-res ones available, but threw in a Spectra C for $75. The price might have gone up recently, but give them a shot - they seem to be good guys.
Bill. |
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| daveb |
I've found a reflector for the 400 W MH bulb. It's an A15 highbay reflector, which certainly puts much more light in a single direction. I also found that if I lower the bulb deeper into the base of the reflector, light output is significantly better.
But my screen image is still very dim. Something's very wrong. I feel that I've got all the right components to do this right, but using them wrong.
The Focal lenght of the Fresnel is about 8.5" (the distance from the panel to a surface where the image of the sun is tightest)
The focusing distance for a 12' throw is about12.5" from the LCD to the lens head.
Here's a pic of the revised set up. Any ideas? Suggestions? Obvious oversights?
Thanks,
dave. |
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| daveb |
The Top surface of the OHP I'm using is a frame with the fresnel mounted about 1" below a plate glass surface, upon which the LCD lies.
Gunwan instructed me to put the LCD as close to the Fresnel as possible. Is this 1" an issue? Because it's part of the original OHP setup, I was thinking it's OK to keep this configuration.
And another thing... The fresnel itself is plastic, so I'm concerned about keeping it too close to the light source (heat...)
And yet another thing... The recent discussion around condenser lenses is interesting, but I'm confused by those that say the best thing is to have a set of fresnel/condenser from a single OHP. My OPH doesn't seem to have this condenser lens. The head is a pari of lenses, about 1/2" apart, but I thought the multple lens setup is just to reduce spherical abberations.
More thoughts???
dave. |
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| woneill |
Hi Dave,
Is your reflector elliptical or parabolic?
It looks paraboic(ish) and I am assuming that it is throwing out a parallel beam of light.
If this is the case, then don't put anything (except some decent UV & possibly IR blocking glass) between the light source and the LCD. The first measurement to make with this arrangement is to see how much light is getting through the LCD. There should be loads.
Next: use a single fresnel lens (not the fresnel doublet from an OHP - they are designed to focus a point source of lifght back to another point source; you only need to beam parallel light into a cone).
If you put this on top of your LCD as close to the LCD as is possible without getting moire, the light from the LCD should all get beamed into a cone without much distortion at the corners etc. Generally, you want the rough side of the fresnel facing the panel, and you want the fresnel to have as long a focal length as possible while being compatible with your objective. The ones from OHPs have the right focal length, but I'm not sure of their optical quality...
Ok, with your fresnel in place, take a piece of paper and find the apex of the light cone. This is where your objective should go (roughly). You want it so that as you move the objective up and down to focus it, the light from the cone stays within the diameter of the lens. As soon as the diameter of the cone at the point where it hits the lens is bigger than the diameter of the lens, you are losing much light.
If the fresnel and objective are compatible, then you will be able to achieve this easily. If they are mismatched, then one or other will have to change (or, you could put corrective lenses in between, but this gets messy...)
An alternative to this, assuming your reflector is parabolic, is to put the top half of a fresnel doublet under the LCD as if it were a regular OHP. Depending on your panel characteristics, you might get less light or contrast or both.
The caveat about matching the fresnel and objective still applies though... (If your optics are from an OHP, then no problem.)
The thing about condensers only applies to the use of an elliptical reflector to produce a point source of light - a virtual bulb - that is more efficient than using the bulb alone.
Here, a condenser is needed at the focal point of the elliptical reflector to produce divergence characteristics that are compatible with the fresnel DOUBLET. (You DO use the full doublet in this case to re-converge the diverging rays from the reflector/condenser back to the objective).
Hope this helps.
Bill. |
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| prjctr_builder |
There's nothing wrong with my Panel or Overhead....NOTHING, they work together as well as it is possible, they image i got on page 22 was because the panel was not centered on the OHP, and after i raised it about 3 mm off the fresnel, that effect disappeared.
I believe that i need an LCD, a really good, Small, and high res. ( at least SVGA) lcd, to keep me going in this field. Before a NEW LCD is released, there's no point of trying new designs, they all will be huge.
I know Marklar and Undream got nice results, mine were not worse. But their designs are a bit too large for me. VERY nice work though, keep it up, guys!!
And if anyone else is still in doubts about my panel or Overhead, i can take screen shots, but i will need to get a digital camera, and so on and so on...
thanks
aleksey |
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| Undream |
I'm *still* stuck on the reflector, unfortunately. I just plain and simple can't find one. I need some help! I've exhausted all the local electrical supply stores looking for something reasonably priced, and have come up empty handed. Maybe someone else out there with more local resources can help me out?
Under preliminary tests of my roughly made cut mirror reflector that I spent 8 bucks on, I don't think its going to work well enough. |
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| woneill |
Hi Undream,
Why not try out Mycamel's idea of creating (using a simple template) a plaster mold and then either build up a reflector from layers of tinfoil wrapped around it and epoxied together, or, use a bit of brute force to wrap a suitably cut sheet of 1mm aluminium foil into something suitable that could be held together again by epoxy, or bolts or even pot rivets?
Alternatively, there seem to be plenty of reflectors from stage-lights etc on ebay. The 6" ones are too small for the big 400W MH bulbs, but you might be able to find an 8" one that would fit.
Bill. |
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| woneill |
Also, what is your light path? If you are trying to duplicate Marklar's setup, the demands on a reflector will be much higher than if you want to use a more parallel beam of light:
The Marklar setup used an elliptical reflector + condensor to emulate a virtual bulb. This allowed him to use his conventional OHP optics.
This elliptical arrangement is not easy to make unless you ter Mycamel's arrangement. A roughly parabolic reflector would be much easier to get going. This would get the light going in a roughly parallel beam. As long as the lighting is even, this is enough.
Then, all you need is a SINGLE fresnel lens - either above or below your panel - depending on taste. The single fresnel will take the parallel beam and converge it into a cone.
The doublet fresnel from an OHP is purely designed to take a point source of light, and focus it back into a point image. If you are using a doublet, and your reflector arrangement is not generating a compatible point source, then that is your problem.
Check out my previous reply to daveb for more details on the setup.
Bill. |
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| Forrest |
No-one here probably remembers me but nevermind....
Finally finished uni, saved up and bought some bits and pieces, current set up:
LCD - Infocus 550LS (640x480 though it actually seems to do 800x600)
LIGHT - 400w Metal Halide (tubular bulb) with a SON T ballast
Lenses - 2 Fresnel and 2 glass lenses
Not sure what the lenses are called, lens one is flat one 1 side and curved on the other while lens 2 was from an OHP
It goes LIGHT - LENS1 - FRESNEL - LCD PANEL - Fresnel or LEN2
using the second fresnel i get a brighter image and it's bloody huge though a little out of focus in places (i'll try and get photos)
Lens 1 has the curve facing the bulb, i though this would disperse the light out in all directions.....
a little bit lost so any help, pointers or just plain taking the **** would be appreciated :)
Thanks |
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| Forrest |
| lenses look like this |
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| woneill |
Hi Forrest,
Check out your alignments and light path.
The light coming from your first fresnel (assuming it is a singlet) should be parallel. The second fresnel should be as close to the LCD as possible - check out which way round you have it. If it is close, and it is the right way around, there should be no distortion.
If your image is too big, then you might have an issue with focal length - even if the fresnel & objective are matched (see prev posts), if the focal lengths are too short, you will get mega zoom.
You might want to try a concave lens close after your objective to reduce zooming a little.
Bill. |
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| Mario007 |
| You do realize that forrest is using a lcd projector and not a panel right? It is an older infocus and from what I've read it only does 640*480 res which is still pretty good. The replacement bulbs for it should be fairly cheap as it just uses a 400w halogen bulb. Although replacing it with a small metal halide would be cool. |
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| ap0the0sis |
Has anyone thought of using the reflector side off a automotive fog light as their reflector? Just think of the times you get blined by them when you drive down the street. Now, Imagine it with a metal halide bulb in it.
I've been looking at these reflectors and they seem like they would work well since they are very reflective and they are available anywhere from 3" to 8" across (baja style) or even larger.
My SHARPVISION projector uses a 6.4" screen (800x600) and the reflector from the metal halide buld assembly is no larger than 3" across and the lens the light shines through is no larger than 2" so I dont think you need to use huge bucket style reflectors.
just a thought
ap0the0sis |
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| eebasist |
| The reflector in a fog light will do one of two things.....melt or be ****. Most nowadays are plastic with a chrome interior finish......and are rated for 100W tops....even the baja ones. The metal ones will have the same problem.....they are thin guage metal and the mirror surface isnt as good as commercial reflectors. Again they were designed for lower wattage bulbs. Where are you going to get a 400W MH bulb to put in one? I havent seen any 400 watters compact enough to fit in a fog light to begin with......the enclosure will most definitly melt or at the least deform. |
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| Gunawan W |
Daveb,
You said that your objective lens to LCD distance is 12.5" and your fresnel fl. is 8.5", supposed your reflector is parabolic type, you will get parallel light coming out from it, then it hits the fresnel, light output coming out from fresnel will be condensed to small point at fresnel focal length=8.5" in front of it. Your obj. lens is at 12.5", it's to far!
The best lens position is shorter than 8.5", try it with white hard paper as small screen, draw a circle on it with diameter=lens dia., put it in front of the fresnel, move it back and forth until the light beam covered the circle, that is the best location for your lens.
Since you already had the reflector,
first, adjust the light bulb up&down, until the light beam covered all side of the fresnel panel and
second, adjust fresnel panel position, until the light beam covered the whole objective lens.
Hope it will work. Good luck.
Woneill,
OHP fresnel can do parallel light to cone, just think it as a doublet lens, parallel beam will be focused to it's focal length.
OHP fresnel has shorter fl. than one face fresnel. (usually 12"). We can use all type of fresnel as long as it has a tight and tiny groove circle (means good quality)and a focal length we need.
Guys,
Is this the perfect reflector setup we need?
Correct me, if I'm wrong. |
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| woneill |
Hi Gunawan,
Your setup looks good to me!!!
For the fresnel thing, though, there is a problem using two fresnels as a DCV lens: Fresnels are usually specifically designed to have the light source and image at specific points that are fixed within a small margin. These points are called conjugates.
If you take a fresnel that is designed to have parallel light hitting one face (conjugate at infinity), and instead place a point source at its focal length, it will work, but there will be distortion and scattering. Similarly, if you take a fresnel that is expecting a point source of light at its focal length (conjugate at its focal length) and hit it with a parallel beam, you will again get a working lens, but with distortion and scattering.
The biggest problem with fresnels is internal reflection. And if they have a wide aperture and short focal length, they must be used as intended otherwise you will lose much quality.
This is the reason why they use two fresnels in an ohp, and is why the rough sides face each other - the flat side is intended to project/receive light at its focal length, and the rough side is intended to project/receive a parallel beam.
Thus in the OHP, the bottom flat side is expecting to receive diverging light from a point source bulb and converge it into a parallel beam which is fed into the rough side of the second fresnel which then converges it into a converging beam.
It WILL work as a regular DCV lens, but it is best used as intended...
See the fresnel-tech PDF for more info on fresnels:
http://www.fresneltech.com/pdf/FresnelLenses.pdf
Bill. |
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| daveb |
Gunwan,
Frustrated with the setup, I took the fresnel outside to the sunlight to reconfirm its focal length. As it turns out, I was finding an IMAGE of the sun (and the surrounding Gazebo) at about 8.5". I thought this is what I needed. But then I remembered all those summer afternoons frying ants on the driveway with a handheld magnifying glass, and thought (hey, shouldn't I be burning a hole in this cardboard?" So I move it a few inches close, and voila! at about 5.5", I'm burning a hole!
So, now I know that one of my problems is that my focal length of the main fresnel is really 5.5".
So I realized that if I'm using the filiment of the 400 W MH bulb as the "point source", I need to have the fresnel 5.5 inches from the filiment. But the bulb iteslf is so large I can't get that close.
So I've taken the reflector off again, put the bulb back to horizontal, and moved the fresnel down to 5.5". Still no brighter.
This is getting VERY frustrating. Now, maybe I need to cut back the reflector to accommodate the horizontal bulb, then flip over the fresnel to re-focus the light.
So here's my latest connundrum: You've suggested putting the objective lens inside the focal length of the fresnel. but I belive I'm constrained in this distance: The distnace between the object and the lens MUST be 12.5" in order to cast an image to the wall 12" away. I don't believe I have any latitude in this distance, unless I completely change my objective lens(es).
If it'll help, I'll post a couple of pix tonight of the lens head configuration.
And another question: In your diagram just posted, there's a small convex lens just beside the light bulb: if this diagram is to scale, then it's INSIDE the MH bulb. I don't understand...
dave. |
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| thelaw |
If anyone answer this, i'd be appreciative;
In a commercial LCD projector unit (or the majority of them anyways), how does the unit know if the lamp is on? is there an optical sensor, sensitive to light? or it is measured electronically.
Im asking as I wish to retrofit a LCD projector with a cheaper metal halide.
cheers,
jon |
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| eebasist |
| check out alternative light sources.....we've discussed this a lot in that thread.....some use a simple photocell to determine if its on....other's dont do anything at all. Projectors dont usually go into any elaborate methods for determining it.....usually the ballast is simply switched on via a relay, no complex circuitry is usually needed there. |
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| thelaw |
thank you, thats definately what i wanted to hear :)
cheers,
jon |
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| Forrest |
| quote: | Originally posted by Mario007
You do realize that forrest is using a lcd projector and not a panel right? It is an older infocus and from what I've read it only does 640*480 res which is still pretty good. The replacement bulbs for it should be fairly cheap as it just uses a 400w halogen bulb. Although replacing it with a small metal halide would be cool. |
Mario007, just to clarify it is actually a panel that i'm using, infocus does a 550ls Panelbook and a 550ls litepro or something....exactly the same electronics and LCD but one is housed with a light to make a projector....
my optics seem off people, kinda hard to get stuff in scotland so i'm thinking of trynig to find a busted OHP and steal the fresnel and lens off of that, gonna go hunting tomorrow to see what i can find....
oh, and thanks for your reply Wonneil
Cheers |
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| Marklar |
| Yesterday I got a MVR1000/U/BT-37 lamp OMG its freaking bright 115,000 lumens :0 Im happy now but I still would like to make a smaller projector. I found this today but I dont know much about lasers http://www.lasershow.sk/white.htm it says the color is red,green,blue and it makes a white laser light well to me that sounds like it could work but Im not sure on how the brightness on lasers are measured. a small beam like this would be easy to use on a small lcd panel. |
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| Mario007 |
| Marklar glad for you that you found a bulb that works for you. Does it fit inside your old reflector? As far as a laser goes I'm afraid a white laser would be too expensive. Look at even the smallest one of those units it weighs 25 pounds. |
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| Marklar |
| yea it fit in the old reflector i just had to move it to get the focal point right I made some updates on my site check it out www.hommie.net |
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| prjctr_builder |
MAYBE WE SHOULD TRY MAKING LASERS????
aleksey |
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| Mario007 |
| What excatly do you mean we should try making lasers? Are you speaking of making laser projectors or actually making lasers? |
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| prjctr_builder |
i just feel like burning a hole through my neighbor's house....
hehe;) |
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| Marklar |
| quote: | Originally posted by prjctr_builder
i just feel like burning a hole through my neighbor's house....
hehe;) |
LMAO good idea!! |
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| Spanky_Mcfarlin |
Howdie...I've was wondering if I got totally screwed? Here is a panel that I bid on. It seemed decent enough for a first attempt at projecting. I thought I had stumbled on a great deal...then I saw a line that worried me ( Video PCB not included) I'm not sure what this means but I think it means I have a screen and no way to get a video signal to it. Is this the end of the world?
http://cgi.ebay.com/ws/eBayISAPI.dl...item=1370785894 |
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| remp |
Marklar
A white light laser would be perfect.
Small size
Highly collimated beam
Only need small optics to expand beam
Can be used to burn hole in neighbours house
Instant on - off
Long life
Dont need a reflector
There is just one little small problem
You need about 2 grand and up to buy one.
Try out a cheap red pointer laser. Place it where your light is. Expand beam to fill fresnel. Restrict to small size picture. You should get a very dim red picture.
Large outdoor direct projection laser projectors usually use at least 1 to 5 watt optic power lasers that consumes enough electric power for a small town. Usually 3 phase with water cooling. These new white light lasers are starting to change that. Especially for laser light shows.
Schnieder Co in Germany displayed several prototype large screen projectors at trade fairs using red/green/blue lasers but has gone into receivership.
300mw is good power for indoor direct projection and should give a watchable picture with some lights on. I work with 5 milliwats and can see very small, very dim picture in a dark room. But that is with direct projection. Not through an LCD panel.
Through an LCD panel with the light losses in the panel, I imagine you would need considerable laser power.
Pity high power lasers are so expensive. But you can make your own. See Sams laser site.
Anyone playing with lasers should be aware of safety issues concerning your eyes. |
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| prjctr_builder |
HMMM, i am starting to consider building a DIY laser... you know that at the focal point of DUKANE, the light is so hot, it actually turns the paper black after a awile. If we could condense that light into a thin ray, i believe that it would have enough energy to burn...
Maybe a should start a new thread...
aleksey |
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| Mario007 |
| Aww yes laser beams. There were some people not to long ago who wanted to build laser projectors. Wow that sounds like a big and expensive job. Not only do you have to refresh and draw 320*240 lines of resolution you have to have three colored lasers doing it. White lasers are kind of interesting but still not a practical solution for illuminating the back of a lcd for a decent price as the price you pay for just the laser might as well buy a DLP projector. |
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| noodles |
| quote: | Originally posted by Spanky_Mcfarlin
then I saw a line that worried me ( Video PCB not included) |
That's right, you won't be able to get any video in it. And the PCBs costs upwards of $200 (correct me if I'm wrong). I'd call that a definate screw. Twenty bucks says that over half the people that bought those didn't know what a PCB was. |
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| noodles |
| quote: | Originally posted by prjctr_builder
i just feel like burning a hole through my neighbor's house....
hehe;) |
I always thought it'd be funny if you made a laser so powerful that it could travel around the earth and destroy itself. |
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| barneydd |
I have had a look through the forum and cant seem to see anyone talking bout reflective LCD projectors like the one shown at http://www.audiovisualizers.com/madlab/lcd_proj.htm.
Do they work? I was thinking of trying with a 5.5" LCD and some 24W long-life bulbs (give out 1400 lumens each) to minimise heat build up. Am I dreaming??? |
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| Mario007 |
| Very much so. Your lights are way way way too weak. Plus it would work only with a reflective type lcd. Note the fact that projection panels can't be used with opaque projectors. |
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| barneydd |
Thanks for your feedback Mario007.
I was going to use a car video LCD (see http://www.mp3playerstore.com/stuff...ial/th-5688.htm ) , not one that passes light through such as used for an OHP. The instructions for building it say that you only need two 75-100W globes.
If I used 150W globes and the LCD I mentioned, do you reckon it would work??? |
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| Axeman |
1000W. Wow. Great work so far on your projector.
I would love to see some more shots of your projector showing movies, etc with both bulbs. Mabye in a room with some lights on too just so we can see how bright and clear it really is! If anything, it's a chance to show off! ;) |
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| Gunawan W |
Hi Woneill,
thanks for your explanation and the link, usefull information about fresnel,
Since OHP fresnel used as collector and collimator, I wonder if we can split it up into two individual fresnel and placing the LCD in between them, what do you think?
Hi Daveb,
First try to figure out what type of reflector you have. My suggestion works for parabolic reflector only.
You can't produce good projection without reflector.
If you satisfied with your projected image size, then keep your objective lens.
Below is my rough suggestion, just for testing:
try placing the fresnel between 5.5" and no longer than 11" in front of the "point" light source.
With 5.5" you get parallel light output,
with 11" you get condensed light output.
I think 9" is the optimum distance and you get the whole obj. lens covered with light beam, just try it...
Please have a look at fresnel link that Woneill found below, to know what type of fresnel you have.
http://www.fresneltech.com/pdf/FresnelLenses.pdf
My diagram is not to scale, it just showing how to use almost all of light from the lamp, it depends on 4 factors: reflector size, bulb size, lens size and lens fl.
see you. |
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| eebasist |
Gunawan W
in an earlier post you talked about a 150 watt MH floodlight that could be purchased for 30$, do you have any other info? |
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| barneydd |
Hey ap0the0sis, the plans they are selling on Ebay can be found for free at:
http://www.audiovisualizers.com/madlab/lcd_proj.htm
I was thinking of building the reflective one from the scanned sheets. But have been told that the lights wont be bright enough.
-BD |
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| Spanky_Mcfarlin |
| Just wondering, can any video pcb be used with any screen or would I need a PCB that is designed to work with a specific LCD? |
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| eebasist |
| what exactly do you mean by "pcb" all lcd's require a controller. While some controllers will work with multiple lcd displays, I'm not aware of any 1 controller that will handle them all. This is where the problem is....we can find cheap high quality lcd's on ebay, but finding a cheap controller is out of the question. Good luck. Also you need to be carefull in your choice of lcd's because some have components on the back that simply can't be removed no matter how hard you try |
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| Spanky_Mcfarlin |
| well in a previous post I had wrote how I screwed on a bid on an lcd screen. That was quite cheap but then noticed it said no video PCB included which I assumed is the controler I had already bid on the item...ebayscrewed again... |
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| eebasist |
most likely looking at 200 or more to get one.....www.earthlcd.com
good luck |
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| Spanky_Mcfarlin |
| I emailed them telling them I refuse to pay for something that is such a horrendous ripe off. Thanks for the information... |
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| eebasist |
| you have a link to the auction? No offense unless it says it comes with it, its buyer beware |
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| Spanky_Mcfarlin |
| Well whatever, I feel thats its unfair to hide something like that...so he can complain to ebay all he wants he was purposely trying to deceive people. |
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| woneill |
Hi Guys,
This is going to sound whacky, but it might not be too difficult to build an LCD controller.
From the adverts I have seen recently, and the few data sheets posted on the LCDs, it would appear that there are generic LCD controller chips, usually from Chips & Technologies (remember them???) that can be programmed with the characteristics of the LCD via a ROM.
It is probably not beyond some of the people who frequent this thread (or maybe the other electronics oriented threads) to put something together that would interface to a computer (digitally).
Analogue would be much more difficult, but could probably be done too.
Bill.
(Of course such a project would be more complicated than building the projector itself...) |
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| Mario007 |
| While I have noticed the increase of sellers just selling raw lcd panels and making it seem like they will work with a video source they always seem to put in their in fine print needs a driver board to work Or something to that effect. While I do not agree with the way they are selling it it's not a scam but pretty darn close to it. If anyone has any questions about any lcd panel they are planning on buying ask here first before making a mistake. |
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| ap0the0sis |
If you bid on something on ebay you can just retract your bid (as long as you do it 12 hours before the auction closes). I know its not the best method but it gets you out of buying it. No big deal....
As for my above post. I was showing you that someone on ebay is selling plans to build a DIY Projector. I had a feeling it was gonna happend any day now. I have no intention on buying these plans as I know where to get them for free. HERE!
For all we know it's someone from this forum :o)
As for building your own controller, I think it would be virtually impossible since you would have to get schematics of the LCD panel and find all the necessary parts to build the controller. The effort alone wouldnt be worth it. to much work and trial and error to end up with something that might not work correctly or at all.
Just dish out the $200.00+ for a controller. Look at it this way, once you make that purchase you will have a controller that you can use on other LCD panels as well. (if your lucky)
ap0the0sis |
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| Gunawan W |
Hi guys,
Most OHP setup is like my drawing 1 below, using small spherical reflector to focus light beam into small point close to lamp spark/filament.
With this setup there are lot of waste direct light (light blue color area).
I think using a long-narrow elliptical reflector can avoid this problem (see drawing 2).
What do you think?
Also I correct my previous post that said: most OHP fresnel panel has focal point=12", wrong, actually is between 5" to 6".
Hi eebasist,
sorry not answering your email about 150W MH for $30, I confused, I though, you sent email at the wrong guy or I forgot, may I know at what page I wrote it?
Anyway, my choice of MH lamp is like this:
Double ended MHN-TD 150 W, 12.100 lumens, CRI 85, 4200 K
http://www.gelighting.com/india/metal_halide.htm
http://www.dealec.co.uk/acatalog/De..._Lamps_344.html |
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| Myren |
Hey all. Long time no see.
I may have been silent, but my diy projection hasnt been at a total standstill. it's been slow going - 18 yr old splitting time between friends women school work and thirty some odd pet projects - but its been moving.
spending most of my time doing number crunching now. optimizing lens equations, reducing aberations, trying to get a decent range of distrotions across zoom, all sorts of "fun". *cough* shoot me now *cough*
i think i've arrived at one final piece though, and thats the reflector.
first off, for reflectors: ellipsoidal. keeps me from having to use a fresnel. sends a constant-light-density beam (no faded edges or center hotspots) to a single point, perfect for being thrown through a series of optics to be displayed. no large lenses required. just one big freaking reflector, gathering and focusing the light.
building it large. i've only got a 15 inch panel, but if the reflector works as planned, i will be purchasing a (significantly larger) panel capable of at least 1280 x 1024. plus if i make the mold larger, i can always just cut down the final panel.
not entirely sure how i'm going to build the final mold. previous efforts involved crude plastor molds, wooden braced frames, anything i could do to get something vaguely ellipsoidal. proof of concept work. i'm thinking perhaps a male mold, wood underneath covered by plastor. then heat a large aluminum sheet (i'm going to have to build a custom oven to do so) and bend it over.
the problem is, as Gunawan W illustrated, a good ellipsodial is deep. very deep. i'm going to have over a two foot diameter openning aperature, but that's going to be nothing compared to the nearly three feet of depth i'm building this reflector to.
aluminum really isnt going to like stretching that much. the mold might break. the aluminum might not bend appropriately. i dont know if it will work. i'm skeptical.
probably going to end up throwing a big wad of cash at the problem sometime. get a real metal mold made on a CNC machine. then try some homebrew electro-deposition / electroforming. then ship the resultant reflector off for vaccum deposition. the whole thing reeks of effort.
anyone have suggestions for where to get a gargantuan reflector mold made? my dad's work's CNC machines wont work with things that big, i'm pretty sure.
btw, gunawan, you showed one light path a while back which gathered the light coming from the center of the projector. it wont work, rather, it will, but there'd be a really bright circle in the center of the image. let that unreflected undirected light just diffuse. it wont hurt pq, esp if the reflectors deep enough.
400 w mh is still the way to go. there's also 600 watts available too, if you want something between 1000 (soo much light) and 400 w (a mere metric buttload).
peace + good luck
myren |
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| remp |
Myren
**************
anyone have suggestions for where to get a gargantuan reflector mold made? my dad's work's CNC machines wont work with things that big, i'm pretty sure.
**************
For cheap interim test reflector suggest use lot of strips of material. Pop rivet or PK screw together. I have seen similar fold up reflectors for solar cookers where pieces open out like a giant curved fan.
Stainless steel often avaliable as long thin offcuts for free from metal shops.
SS has good reflective properties. Stainflex is one SS type. Need good drill. Aluminium needs polished and can loose reflectivity over time due to oxidisation. Either one not bad for test setup. I use offcut SS for solar parabolic collector. |
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| the whinner |
anyone tried this?
i think with this setup (two reflectors, light pipe, two fresnels) you can achieve much more efficiensy, meaning less wattage for the bulb! |
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| Gustavo |
Hello Everyone,
I’m Gustavo from Argentina, I been reading all the post for 3 days now, I’m very interested on making a projector myself, first of all I want to tell you that’s great all the effort and all your achievements, I hope I can be able to do it since it’s impossible for me to buy one real projector, we jump from a 1-1 dollar to 1-4 dollar exchange rate (only in my country).
Well here I go, I’m not use to work whit lens but I’m a very understanding man, but I need a little help from you, hope you agree on that.
I’ll go whit a 12.1 inch lcd tft 1024x768 CT:150 from NEC, that’s becouse I can get a Daewoo monitor that comes whit it inside, and I’ll not need to buy the controller board, besides from NEC pdf it seems not to be trouble to take apart the electronics from the lcd, I’ll try to get it for U$s200 in a local auction (it’s U$s260).
Since I don’t know much about optics my first question is about the fresnels,
I found those links and I need to chose one of them
http://www.ec-securehost.com/ila/Ha...Magnifiers.html
Full-Page Magnifier (10” x 12”) $34.95
http://www.officedepot.com/shop/cat...327016&LEVEL=SK
Apollo Full Page Magnifier, 8 1/2" x 11" $6.99
From my calculations either one should work but I’m aware that you are more qualified to opine on that, could be a big quality difference? Should it affect the prject that much?
For start I would choose RedEvil design for light source, I think the lens he is using is a standard round magnifier, easy to get for cheap. I’ll be wasting a lot of light whit this?
My setup will be: 400w MH - round glass magnifier close to bulb – fresnel – lcd – fresnel – plano convex.\
About the page magnifier, do they all have about the same focal length? 6inch+-, if it so my plano convex should be the same FL? In a local optics, they are able to make me one of them for about 2 dollars whit any specs I want but whit a diameter max of 6cm, I guess for all I read that’s too little, more for 12.1 tft, but I guess I could find it somewere.
Last inquire for now, since some of you have done one of this, whit my setup, witch could be the lumen comparison whit the branded ones? Since I have some frined that have infocus 1000 lumens projectors I could have an idea this way how close can I be.
Thank you and I apologies if my thread is too large.
I ask for excuses if any word or redaction is wrong, but my natural born language is Spanish.
Thanks again.
Gustavo |
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| Redevil |
Gustavo
Good choice.
I put the 2nd fresnel after the pannel, but you can see the circular
linese on the screen. Therefore in my case, putting 2 fresnels after
the magnifying glass reduced the circular lines.
And yes it was cheap for the magnifying glass.
It is about 4 1/2 inch diameter.
Your not going to believe this, but yesterday I picked up a metal halide lamp (400watt 3.4K at 65CRI) and ballast for $80.00.
Couldnt refuse that deal.
Tried it today and man did it ever look good. I would say about
40% brighter. Now I can watch it with lights on. But after a
1/2 hour the case was super hot. Like holy **** man.
Did not have re adjust anything either. This bulb was much larger.
Took it out until I can put more fans in.
It would be much better to use a bulb that is 400w 5Kcolor and at least 75CRI or higher.
If any knows where I can find one, can you please post it.
Make sure you can buy seperate. Most places want you to buy 6 or more
Later |
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| woneill |
Redevil,
The circular lines you mentioned are moire effects. They can be avoided by moving the fresnel about an inch away from the LCD - though this will zoom the image...
Gustavo,
Using fresnels in either Redevil's configuratrion or the standard OHP configuration will, if correctly set-up, beam the light from the LCD into a cone shape. Your 6cm lens might be big enough if its focal length is correct so that when focussed, it is at the apex of the cone, and all the light is beaming through it.
As for brightness - the single RGB panels we use have a maximum theoretical efficiency of about 15% from randomly polarized light. Thus, a projector using a single panel will be significantly dimmer than a "three-panel" design (efficiency of about 45%). DLP designs can be even more efficient...
With a fairly efficient optical path, you should expect an image with about 300-400 lumens from a 400W MH setup. This would be equivalent to the last generation commercial designs that used a single panel. (e.g. Proxima 2800) |
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| woneill |
Hi Myren,
You were commenting that the lens in Gunawan's design might produce a hotspot.
If the lens were too big and its focal length too small, then yes, it would produce a hotspot. However, if it were not there at all, you might find yourself with a "cold-spot" at the center of the beam. (This is actually quite common with many reflectors - elliptical included.)
If the lens is balanced with a suitably small diameter and the appropriate focal length, it would collimate just enough light to balance the beam profile.
Bill. |
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| jvisaria |
well boys and girls --
I've decided i am too lazy to build a from-scratch projector....
however, i think i might try to retrofit an OHP with a 250w-ish MH bulb... how many people have attempted this and was there much success?
Also Bill --
I have looked into building your own controller, and I didnt go through the specifics, but it doesnt look too terribly hard for anyone with a basic foundation in microcontrollers... I never got around to attempting one though, darn school! keeps getting in the way of important things!
Jay |
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| Gustavo |
Redevil, Woneill,
Thanks for the time you took to answer me, you are clarifying my doubts.
About the fresnel, I would like, if you have time, to tell me what will be the one of your choice, since they have a big differecnce of price, I have to buy two of them and 60% taxes when they arrive(impossible to get them here).
Could they be different quality apart of the size? Would it affect the project that much?
http://www.ec-securehost.com/ila/Ha...Magnifiers.html
Full-Page Magnifier (10” x 12”) $34.95
http://www.officedepot.com/shop/cat...327016&LEVEL=SK
Apollo Full Page Magnifier, 8 1/2" x 11" $6.99
Woneill,
Whit the 2nd fresnel 1inch away from the 12.1inch screen, I’ll get a 13inch image or so, maybe the fresnel will have a focal length of 6inch, so the convex lens will have exactly the same focal length(6inch), are you sure that it being 60mm diameter will capture the whole 13inch image?, I’m re asking this to you again because I know nothing about lenses, sorry to be repetitive.
Here’s another concern, I made a little graphic for you to understand my idea. It’s the attached.
If we pivot the lcd in a way we can make the projector cell mounted and correct the trapezoidal image, would it work?
Gustavo |
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| Gustavo |
| Sorry here's the graphic |
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| woneill |
Hi Gustavo,
The mounting you suggest is potentially bad because it will be difficult to focus.
If you were thinking about angling the projector and then correcting for keystone, then htere is a different solution:
Keep everything aligned parallel to the same axis: lamp, fresnels, LCD, objective and screen. This way focussing is simple. Then, to offset the image, you could simply shift the LCD and/or lenses so that the center of the LCD is not aligned with the center of the fresnels/objective.
It is a surprisingly simple and effective way to adjust the output beam without getting the keystoning...
See picture...
As for lens focal length, if you can get lenses fairly cheaply, I would go for a spread between 5" and 8" to match the image size to the desired size of your image, and the length of your room. (The fresnel will move the magnified virtual image away from the objective - further than the LCD itself.)
With a smaller lens, position is crucial to maximise brightness.
Alternatively, if you can get multiple lenses, you might want to try a longer focal length lens exactly at the apex of the cone, and use a second movable lens to actually perform focussing. This is how my main system works.
(Two lenses close together will behave as a single lens with a focal length that is a combination of the two focal lengths of the individual lenses and a factor based on the distance between them. There are examples and spreadsheets to calculate this distributed through the threads.)
Maybe two 12" lenses would suffice. (I am guessing here...)
Bill. |
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| Gustavo |
Woneill,
Thanks, good thinking about moving the lenses to move the picture possition, as I said before I know nothing about lenses and that didn't come to my mind.
About the two links, do you think it could be a big quality difference between the 2 fresnels?
Thanks again.
Gustavo |
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| ap0the0sis |
When adjusting keystone, Gustavo is on the right track.
My SHARPVISION projector uses a rotating fresnel like the one Gustavo drew to adject the keystone. That is basically the way all projectors do it unless they have digital keystone adjustment.
If you point the projector at any agel besides 90 degrees then you will have keystone.
ap0the0sis |
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| Nexzus |
Woneill:
Would that method also work for left-right keystone correction? ie. if the projector was mounted to the left or right of the screen?
Many Thanks |
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| woneill |
Hi Guys,
What I described is not a keystone correction - it is a way of ofsetting the image with respect to the projector. It does not distort the image the way keystoning does - everything stays in proportion. (It works left and right too...)
It assumes that everything is aligned parallel to the optical axis - including the screen. That way, everything stays in focus. (This is also how desktop projectors manage to project upwards and not hit the floor...)
If there is already a keystone issue, then there will probably also be a focus issue too. Then the concept of rotating the LCD will possibly work.
Gustavo,
I checked out the links, and for the price difference, you would probably be better with the one from Staples. I have one, and when properly placed, it gives a very good effect on a 13.3" laptop panel.
I place it about an inch away from the panel to eliminate moire, with the rough side facing the panel. With a projector lens placed at the appropriate point, I can project a crystal clear image from my laptop onto my wall. Of course, there must be no ambient light, and the image is stil dim...
Bill. |
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| Gustavo |
Bill,
Thanks for your answer, I was already thinking on applying both things, your way and a little of mine if it's needed, thanks for the confirmation.
I'm a little concern about the "image still dim", is that so?
Even whit a 400w bulb and RedEvil setup, that seems is working great for him?
Another thing I like to know to be already covered, do I have to take the polarizing filter off the lcd? Remember it's a Daewoo lcd monitor.
About the fresnels, thanks for taking time to check for them, but you put me another doubt, I was thinking after doing the projrctor, if everything goes right, to upgrade the panel to a Viewsonic v150, just for contrast matter, since you are using the small one, I guess the bigger one could be right size for it, do you agree?
Sorry of all my questions, I'm usually not this annoying but I can't afford to make many mistakes, I feel I'm giving nothing and I'm only asking, but I hope to be useful for everybody else once I start, have a little more experience and a little of research myself.
Thank you.
Gustavo |
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| Redevil |
Gustavo
Mitch (where have you gone)
Update
It is now 12:22 AM on a Sunday Knight.
The kids are still playing Zelda on the N-64 for the last 4 hours.
Mark caught a 15 pounder.
Kids love coming over.
The graphics are excellent.
One kid brought his PS2 over and we played Stunt Man.
Looks good with 250W, cant wait to put in the 400W.
Fans will be in tomorrow.
Good luck all.
Later
P.S
Those plastic page manifiers work great.
Paid $11.00 Canadian for mine (Staples). |
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| Undream |
| Redevil, can we please see pictures of your box? |
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| Mitch |
Hey Redevil.
I`ve been here all along, pondering and re-pondering on all this stuff. I am in doubt about using your design because of the space issue. I have less than 8 ft to work with behind the place where my rear screen is going to be. So in that space I have to be able to fit the projector, plus leave room for the throw distance for a 60" dia. screen.
I think it would probably be possible to shrink your design just a tad, but I`m also thinking about the possibilities of just going ahead and using an OHP.
Right now I am in toil over which proj. panel to get. I have no idea of what a 640x480 image is going to look like. Is it clear enough? I know with the limited amount of panels available I can`t be too choosy, but I would like at least to be able to get a picture better than a regular $200.00 TV.
Also, is there anywhere else that I can get a proj. panel other than Ebay? I went to Inventory Solutions and I looked everywhere for panels and I couldn`t find any...maybe I`m just blind.
One other thing. If I`m not going to be using a pc (PC is out of the question here for me) I will probably have to use some sort of TV 3000 thing, right?
Toodles |
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| Mitch |
Gustavo,
Where are you seeing a NEC 12.1" LCD for US $250? Is there a website where I could look at that PDF with the specs?
Thanks,
Mitch |
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| gav |
| hey mitch, go to the wikki and look at the various screenshot links - mine are up there (ovation 820 panel ) the pics are pretty ****** but u get the idea (look ALOT better in real life) |
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| daveb |
I read about this and thought our troubles were over: a 12", true color, good contrast LCD with controller. Wahoo!.
So I wrote to earthlcd with a question:
Dear EarthLCD,
I, along with many other souls worldwide, am interested in building a home theater using lcd projection. My question about this is: could the contoller & lighting panel be removed and swung clear out of the way so that it could be used with an overhead projector?
The response?
No.
So a further question for clarity?
Would cabling and other physical restrictions prohibit it?
The response?
Yes.
So, now the question is, is this the definitive answer, or can it be made to work with some ingenious tinkering?
disappointedly,
dave. |
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| Gustavo |
Daveb,
I hope they are trying to protect themselves against RMA, if you know what I mean.
Anyway I'll try to close the deal for mine today, so I'll let you all know if it's worth.
Gustavo |
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| Redevil |
Undream
I do not have a digital camera.
I will try to borrow one from a friend.
Later |
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