| rajkumar |
I found this MH bulb with 15 degree beam and am thinking of trying this out. Looks like the bulb has internal reflector and a small condensor like set up on the top which spreads light at 15 degree beam. Unfortunately no other data- physical measurement etc. found on the site. Any suggestions?
Link:
http://www.lighting.philips.com/nam...yhid.php?id=125 |
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| rajkumar |
Yes...its huge I found out when I searched on philips PDF files. I like MH175/RSP that you have..Looks perfect size for my project.
donsbulbs ran out of it do you suggest any other place where I can buy this bulb?
Rajkumar |
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| Rolm |
http://www.atlantalightbulbs.com/
$89, but that's about as good as you'll get. I know they have them in stock, because they had to order a case to get the one bulb I ordered =)
This is a 16deg lamp. They have a flood version that's $20 cheaper. I went with the 16deg lamp, because I figured a more tightly focused beam would mean more light directed out the apeture. I hope. |
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| rajkumar |
Thanks for the bulb suggestions. I will order it soon..looks great. Is it true that its rated for 60k lumens!! (on the weblink you gave). Thats really bright so even if we dont capture a whole lot of light we sould be fine..
Which ballast are you using. I am thinking of buying IceCap electronic ballast which can run "any" 175 w bulb at the following for $115 - that the cheapest I found. Any suggestions?
http://www.aquatictech.com/lighting.html
Thx. |
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| Rolm |
I went with a non-electronic ballast, 'cause it's so much cheaper ($40) :
BS/MH0175MT
http://www.1000bulbs.com/
(enter the part # in the search box)
It's a little harder to wire up, and a tiny bit noisier, but I got burned with a bad electronic Magnatek M57 ballast off ebay, so I needed a cheap solution. Esp. after laying out $80 for the bulb.
Not gonna be here til 02DEC, tho... |
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| Rolm |
Also, AFAIK, the output is, indeed, 60K (peak). There is a pdf on the Philips site listing the bulb properties that supports this. However, there is probably a warm-up time before it gets to peak output. Usually not more than a few minutes.
I've become a little concerned that the 16deg beam may be a little _too_ tight. I've been toying with feeding different lights thru the optics of an OHP, and with a tight beam you lose the sharp edges of the projected image.
This is, of course, speculation until I get the ballast and can test it. |
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| rajkumar |
I was wondering about the same over the weekend. I found the following formula to measure the distance between the lamp and LCD panel based on the beam angle of the bulb. I am not good at solving these kinds of equations so need some help. Here is the link and the formula. My LCD panel is 10.4 diagonal and considering the 16 degree beam angle I came up with 37 inch distance between LCD and LAMP (if I did the correct math) - Thats too far but I think a frasnel lens can be used - dont know what kind though! Any help appreciated.
http://www.highend.com/news/lightingfaq.html |
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| Rolm |
My calculator doesnt have an arctan button. You could look at it as half the 16deg triangle and just use
tan(alpha) = OP/ADJ
Since you want ADJ (your 'L' in the diagram),
ADJ = OP/tan(alpha)
or
ADJ = 5.2/0.14054 = 36.9999
So you're right.
A fresnel lens essentially takes light and gets it all moving in the same direction to make a narrower beam:
<img src ="http://www.lanternroom.com/fresnel/_images/fresnel02.jpg">
(the image is of a curved lighthouse fresnel, but you get the idea).
So there may be a problem with this 16deg lamp being too narrow. I don't know about that, tho, because the light source for my OHP passes it's light thru a 1.25" apeture, so there's obviously something else going on.
In any event (for me, anyway), I already have the bulb and am just waiting for the ballast so I can test it. I will post the result as soon as I have it. Worst case is I have to buy the 50deg flood, which, in your case, would reduce your depth to 11.58". This actually sounds much more sane for OHP optics, which is what most of the projectors around here are based on. |
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| rajkumar |
I am glad my numbers were correct! The problem with MH 175 RFL(Flood) is that its not as bright as the RSP (10 K lumen v.s. 60K) but the beam angle is 65 so the distance I calculated is around 9.16 inch which will work out best sizewise. Since most of the 10K lumens are actually usable I dont think it will be a huge problem for the brightness.
I am planning on cutting the bottom my spare OHP and see if I can mount the lamp upright in a small enclosure before building a custom box. |
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| Rolm |
Yeah, that was kinda why I went with the 16deg; that, and I was laboring under the (maybe false) assumption that I wanted the light in a tight beam to begin with.
Seeing as I had planned to mount this new light source on an existing OHP, I hope that my distance does not need to be 37". I'm gonna give the 16deg bulb a chance. After that, I'm either going to have to use a lens to spread the beam, or design a rear-facing mount and cold mirror setup to increase the bulb-to-stage distance (eg hack it up), or give it up and use the bulb to **** off my backyard neighbors instead.
If this fails, I will probably try the "wider pipe" approach with an unfocused 400W MH; I had my eye on the $90 rig that some guy builds and sells on ebay. It would be a tight fit on the back of the OHP, but it would probably pump out enough light to overcome the problem. |
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| rajkumar |
Placed an order with atlantalightbulbs.com for the RFL lamps and they said its out of the stock and will take 2 weeks or more time to get it...They do have RSP (16o beam) in stock (since they order a case for your order) and am curious to see how it works out for you..
I also checked my 3M (model ?) OHP and the light is mounted on the back side wall in a separate compartment with a 1 1/2 inch opening pointed down diagonally at a cold mirror which bounces it to the OHP stage. Similar arrangement might work with a narrow beam MH RSP lamp that you have since the halogen light is going through a 1 1/2 inch aparture and its spread evenly on the OHP stage. So I am back to the idea of using the lamp you have - even if I cant use all the available 60K lumens, I should be fine with what ever passes through that 1 1/2 inch aparture..
I also found the GE made MH bulb with elliptical syle reflector with up to 9K lumens still unable to loacate an online dealer.. Here is the link:
http://www.gelighting.com/na/business/pl3_hid_cmh.html
- I tried my LCD panel Z255, 800 X 600 16 M color, on a regular 3M overhead with 360W Helogen bulb and was able to get a corner to corner crisp and balanced image and was very happy (and so was my wife!). I watched a DVD last night and it was fun. I am using XGA theater TV4000 from avtoolbox where you can change the resolution from 480 x 600 to 800 x 600 with a remote and can adjust brighness, etc too. The panel has built in Hi-Fi speaker which was enought for a trial run. I need to figure out how to make the fan on the panel quieter...
So I think MH RSP lamp should work with a narrow beam even without using any thing to spread the light - just by bouncing it off a cold mirror. Did you do any more tests with your OHP set up?
thx. |
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| Rolm |
I also have a 3M OHP with the same light setup. I'm just worried that the beam spread might not be enough.
Also, I examined the bulb that goes in the OHP, and IMHO it appears to be an ellipsoid reflector. That has a great deal of bearing on what we're doing:
http://ourworld.compuserve.com/home..._reflectors.htm
If it is indeed an elipsoid, then the 1" apeture in front of the light is probably roughly at the focal point of the beam. Then the beam reverses itself and spreads out.
With our parabolics, there would be no need for this apeture. On the down side, the beam may be too tight and not spread out enough to cover the entire LCD. Or, it might enter the fresnel at a different angle than the original light source, and therefore throw off the final image. I think that this could be remedied with a simple spreader lens, but I don't know. I have a number of lenses that I got in a parts auction, so hopefully I can spread the beam if it proves to be too tight.
(std OHP optics sans various mirrors)
<img src="http://members.cox.net/rolm/images/ohp_optics.jpg">
<OHP optics with a parabolic light source)
<img src="http://members.cox.net/rolm/images/ohp_optics2.jpg">
The pictures suck, but you'll probably get the idea: if the beam angle coming out of the light source in the lower image is not broad enough (or does not spread enough), it could be fed thru a lens to broaden it.
I dunno, this is all academic until I can build the new light source and feed it thru the OHP. |
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| rajkumar |
I could not find any online source for the flood style (RFL) MH 175 W so far so am thinking of buying the RSP lamp like yours and work on spreading the tight beam. Looking for suggestions on how to spread that 16o beam using some sort of lense. While reading online on how the beam angle is measured I found out that the beam angle is spread from center to the edge where the light intensity is 50% of the center. If that's the case than we may end up with a hotspot issue. (see drawing).
Also, how about using a magnifying mirror (cheap $10 used for makeup) which may be able to bounce and spread light at the same time which may reduce the length of the light path.
I am very curious to see your results when you get the ballast and test the lamp. I am still waiting for the reply from GE regarding their MH 100 watt lamp with elliptical reflector. I will post the link on that lamp later today. |
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| Rolm |
I actually just got done wiring up my test kit and running some initial tests for the lamp.
The bad news is that you are right: this bulb has a terrific hotspot at the center. In side-by-side comparison, it at first appears that the MH bulb is putting out about as much light as the 360w halogen in the OHP. But if you look closer, you can see that there is a brilliant hotspot that is about 4" diameter at 6'. This, I am sure, is where they measured the 60K lumens. If we could come up with a lens to spread this hotspot, then this might be a viable solution.
I also experimented with some masks for the bulb, and came to the conclusion that the beam, as it emanates from the bulb, is just too narrow for us to use.
My last experiment was to direct the bulb thru the optics of the OHP. This cinched it: there was one hotspot at the center of the image, and dim light around the prerimeter.
The bulb appears to put out a phenomenal amount of light for it's wattage, but I don't think it's usable without mucking with the beam.
I took images with my digital camera, but the hotspot was so bright as to interfere with the image. I'll give you an example: the attached image is one where the OHP and the MH are side-by-side. The horizontal lines are interference.
<img src="http://members.cox.net/rolm/images/sidebyside.jpg">
Your mirror idea may work, but my approach (at least) was to leave as much of the internals of the OHP alone and instead to alter the light source.
I'm going to experiment with some of my lenses tonight to see if I can spread the beam a little more.
Note to self: wear sunglasses when messing around with this light. I came upstairs 2 hours ago and I still have spots in front of my eyes... |
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| rajkumar |
Rolm,
I was very anxious to find out the test results and am disappointed to know that the beam is too narrow for our use (atleast without too many optics involved) and the hotspot is an issue.. 60K lumens is indeed illusive as I originally suspected. Well, I will have to try with the Flood style lamp (still unable to find online!) and post the test results..
If I cant find the MH 175 RFL lamp by the end of today, i am going to get two MH 100 W lamps from bulbs.com (Flood style with 60o beam) and use it with a dual MH ballast (used in growlight set up) and see if I can use two lamps with some sort of mirror arrangement to bounce light to the LCD. I am working on the drawing rightnow.
I also found this interesting setup for auto headlight with elliptical reflector and am looking for the sources to find/buy this. Here is the link (page six center diagram)
http://www.osram.se/pdf/produktblad/Xenarc.pdf |
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| Rolm |
Yeah, after further experimentation I think I have to call the MH175/RSP a bust. I was able to spread the hotspot using a 2x5 glass fresnel, but that showed me that there was an anomoly in the bulb on one side, resulting in a serious color difference. This anomoly is most likely a result of the inner workings of the bulb (the elements used to create the arc).
Mocking it up on the OHP, I was able to get about the same image brightness as with the 360w halogen bulb. About as bright, but uneven and dim around the edges.
My next move is to try to adapt a higher-wattage non-PAR bulb. I ordered a 400w Mh with a 16" x 8" reflector. I plan to polish the reflector and probably try removing the inner light stage from the OHP to move as much light as possible.
Another idea was to take a page from uvodee and try installing multiple fluorex bulbs. Admittedly, the light is about as unpolarized as you can get, but if you can generate enough of it you might be able to overcome that.
Either concept is going to cost about $100 to try out. I've already blown about $150 on bulb, ballast(s) and shipping, and I'm back to square one.
Ellipsoidal reflectors are most likely the way to go with this, but the difficulty lies in the size: either a reflector that's large enough to use a std MH bulb, or a MH bulb that's small enough (and affordable) to fit a common ellipsoidal reflector. I've seen docs similar to the one you linked, but the xenon bulbs don't put out enough light for our purposes, and MH bulbs small enough to fit that reflector are either limited to 150 watts or are very expensive. In any event, they would be one-ended bulbs, and probably suffer from the same anomoly as the PAR bulb that I have now.
As a side note, this is one of the reasons that production LCD projector bulbs are so expensive. MHs are great for pumping out huge amounts of light for not much watts, but getting a clean, focused beam out of them is hard by itself, and even harder as you make the bulb smaller.
I think that the answer will either lie in figuring out how to get a semi-focused beam from a common (read: cheap) ~400w bulb, or from using double-ended HQI bulbs (which are expensive). |
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| rajkumar |
After spending several hours to read the forum I have concluded the following:
1. Point source light (Fluorex are not suitable even if you have two of them - other people have tried them with not so impressive results)
2. Ellipsoidal reflector to focus all the light and redistribute evenlly on the panel
3. MH 250W+ is the start point higher W is better if heat issues can be resolved (Low E glass barrier, Fans, etc.)
4. Line doubler or similar device helps (I have tv 4000 and my test results shows excellent sharp image at 800 X 600 resolution (Nview z255 panel). Also, TV 4000 has a remote which helps to change brighness/contrast etc while watching movies. I show pre-recorded Alias from my VCR yesterday on 6 X 6 Da Lite screen last night (with lights off in living room) and after adjusting brightness etc.. My wife and I were very happy with the image quality. Than we played a DVD in wide screen format and it was awsome.
5. Based on the room dimension, OHP optic may not be suitable. I had to put my OHP at about 10 feet to get the image to fit on my 6 X 6 screen. I need atleast a 15 feet throw distance to get the similar size projection so am looking for some lenses.
What bulb/reflector you are looking into? 16 X 8 reflector sound a little big but still manageable. Is it ellipsoidal or parabolic? I have a friend who is into glass blowing and I talked to her yesterday she can make a reflector from glass if I provide her proper dimension and I am looking into how to make one. I know Gunwan has some theory and drawing on his website at
http://gwidijanto.fcpages.com/reflector.htm
I also found this interesting info on elliptical reflector at:
http://www.phys.ncku.edu.tw/optics/...%20Tutorial.pdf |
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| Rolm |
Yes, I reached pretty much the same conclusions. However, I think that the reason uvodee is having success with his fluorex lights where no one else has is that he _doesn't_ try and treat the light as a point-source that needs to be focused into a beam. He has chosen instead to just let the light pass thru the apeture as it is. As such, he is probably not getting as efficient use of the light as possible, but it obviously works for him.
I think that there is going to be a fundamental problem with the use of "standard" MH bulbs: the internal elements of the bulb get in the way of creating a clean, precise beam.
<img src="http://members.cox.net/rolm/images/mh_bulb00.jpg">
This uneven placement of the point source of the light makes it difficult to use a standard conical reflector (either parabolic or ellipsoidal) to get a clean, even beam.
<img src="http://members.cox.net/rolm/images/mh_bulb01.jpg">
The MH- driven OHPs use a double-ended MH bulb to get around this. Double-ended means that they can precisely place the point-source because there is none of the U-turn nonsense in the element. The downside is that the high-wattage double-ended bulb is very expensive.
Another idea is to create a rectangular or tubular reflector and mount the bulb on it's side instead of head-on:
<img src="http://members.cox.net/rolm/images/floodzilla.gif">
This makes it much easier to place the point-source at the center of the reflector. It is possible to also add angled reflectors on either side of the bulb to scavenge even more light.
I, being the cheap bastard that I am (and having blown about ~$150 on a failed attempt to use a MH PAR bulb) am now trying to do something like the rectangular setup:
<a href="http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category=3186&item=2077089289">
<img src="http://abacus.sj.ipixmedia.com/abc/M28/_EBAY_27e84836ec902925a92c4b45d5/i-1.JPG">
400w light from ebay
</a>
The reflector is not ellipsoidal, but it's a start, and it's a bulb, socket, ballast and metal reflector for $100. This is kind of taking a page from uvodee and trying to make as much light as possible available, and hoping that enough of it goes in the right direction. If I get promising results from this, then I'll begin trying to make a decent ellipsoidal rectangular reflector.
I guess I'm opting for the bigger hammer here, rather than the more refined technique of trying to make a custom glass reflector (which would be awesome if you could pull it off). I'm just concerned that you might sink an awful lot of time and effort into making said reflector, only to be unable to locate a bulb that will allow you to truly center the point-source of the light.
I'm also trying to divide and conquer: rather than trying to create a good, bright light source AND come up with a good optics system, I'm re-using the optics from the existing OHP and just trying to solve the light problem. If I solve the light problem, then I'll consider rearranging the optics of the projector.
Your TV-4000 sounds a LOT better than what I have. I just bought the $80 cheese-box, mainly because (at the time) the OHP that I had was only capable of 640x480. However, it sounds like I should have bought what you bought. Oh well, nothing a little more money won't fix... just wish I had some... |
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| rajkumar |
thats pretty cheap price for the bulb, ballast, and reflector set up.. I remember seeing on ebay before and he has several of them which is good.
Uvodee has used two fluorex lamps but If I remember correctly his panel is 5' so it works well...I think for large panels we might get dark corners.
I talked to my friend again about making the reflector and he said it would be easy to make it in ceramic than glass if I provide him with the measurements..They make several style bowls in ceramic and they are very cheap (<$10 each). Now the question is how to make the inner surface reflective... I am looking for tiny mirrors from craft stores and planning on sticking them inside the ceramic reflector. The other idea is to paint the surface with some sort of metalic reflective paint.. I am not sure how the heat is going to affect mirrors/paint though.
The offcenter set up of MH should not be a problem since I can mount the lamp a little bit off center so that the lighting element falls in the center of the reflector.
If I decide to use the home made reflector than I will be looking for tubular metal halide than the round one so it fits well in the reflector. |
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| rajkumar |
I forgot to include this in my last post..
The other idea I am pursuing (in the interim basis) is to use the following lamp by GE. Its rated for 1000 hours but comes to about 12 cents an hour (affordable for watching DVDs). What I liked about it is the dimensions. Its less than 2 inch tall and very narrow diameter. My other OHP (EIKI) has a small bowl shaped reflector (i think its parabolic) sitting at the bottom of OHP and the current halogen lamp is mounted in such a way that the light center of the bulb falls in the center of the reflector which bounces it upward on the fresnel. It seems like if I use this MH lamp I would be able to use all the existing set up without twiking too many things..The lumens are not that great but almost all the light will be used so worth giving a try. Also, the lamp is very small so I can use other types of readymade reflectors too.
The ballast type is M81 so I am searching for the ballast right now. |
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| rajkumar |
| here is the attachement |
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| Rolm |
Now THAT'S the kind of bulb that I wish we could find, just in a higher wattage. One of my early ideas was to try to use a bi-pin MH lamp in a very small (~2" diam) conical reflector, possibly even cutting out the center bulb of an ENX projector bulb. I could never find them either cheap or of decent wattage. Which is a little odd, since they make 600w bi-pin halogens for use in stage lighting.
If you're considering this kind of bulb, you might want to look into PAR56 or PAR64 reflectors. PartsExpress sells just the reflectors with a bi-pin base (I believe it's G12, though), but it's a parabolic reflector rather than an elliptical. Perhaps with a little sleuthing you could turn up an ellipsoidal PAR56 reflector that would work.
I'm a little wary about the tiny-mirrors-glued-into-a-bowl idea. On the one hand, if you look at an ENX or FXL halogen projector lamp, that's exactly how the reflector is formed. On the other hand, it would be a heck of a lot of work, and if the mirrors are not small enough (or don't abut perfectly) you could end up with a faceted beam that would not serve your purpose (think lots and lots of hotspots). Someone on this board tried this approach a while ago, and abandoned it very quickly when they ascertained how much work was going to go into getting it just right.
If you were going to try something like this, I think I would try to find some highly reflective substance to paint the inside of the bowl with instead. Or try getting some tinfoil as flat and seamless as you can on the inside. Me personally, I plan to polish the aluminum reflector to a mirror finish, which takes a little time but yeilds the best results.
I don't mean to shoot you down, I'm just offering my opinion on it. It's more work that I think I would want to undertake, especially if there is an easier alternative out there somewhere. |
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| stinky |
I have used two florex lights like udovee and had some sucess with them. But I would like to make the image bright and not have to worry about using so tons of optics. I know that the Florex design works on just creats lots of light and letting it pass though the LCD.
I was thinking about making the lcd the only part where light could escape from my light/reflector. So far I have come up with this disign. I just ordered a 400w MH fixture and a high power fan for my set up. |
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| rajkumar |
| What size LCD are you using? 5 inch or regular overhead panel (around 10 inch diagonal) - Just curious. |
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| stinky |
| 10.4 laptop screen, because of the nature of the laptop lcd it will allow the most light through the screen. It will be hooked up to a laptop that has a USB tv tuner witch allows an S-Video input as well as coxial cable. |
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| rajkumar |
Mirrors reflect light straight so may not be suitable for a point source light. When the light comes from a point source and needs to be equally distributed on a large surface (10 inch panel), you might be better off with a curved reflector of some sort.
Check out:
http://gwidijanto.fcpages.com/reflector.htm |
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| stinky |
| I planned for that, I have a high quality glass fresnel lens from an over head projector to distribute the light. |
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| Rolm |
Fresnels don't just magically straighten out light that is not in a semi-coherent beam. First you should try to set up your light source to direct as much light as possible in one direction, and then put the fresnel in that path.
You never manage to capture 100% of the light. If you did, you would have, in effect, created a laser.
IMHO, the only flaw in your design is that you rely on the light source itself and two 45degree mirrors to direct light towards the fresnel. If you were to set up some sort of curved reflector (as we have been talking about), you would direct FAR more light than you will with flat mirrors placed at 45deg angles behind the light source.
Here's a really bad illustration of what I'm talking about:
<img src="http://members.cox.net/rolm/images/compare_reflectors.jpg"> |
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| rajkumar |
I hate this people selling bulbs online.. They have fancy websites with all kinds of bulb listed with individual price. My order for the small 150 MH bulb directly from GE company has been cancelled this morning...They sale by case only. I think its better to call and talk to these online retailers first before placing online purchase order.
On a side note, I was looking into theater/stage light suppliers online they have decent zoomable spot/flood light set up with elliptical reflectors.
If I cant locate the GE bulb by the end of the day, i am going to buy a MH retrofit kit from hellolight with Iwasaki 250W lamp (6500K) ;
http://www.hellolights.com/25methalbalk.html
I like the idea electronic ballast and relatively small diameter of the tubular lamp - easy to fit in the reflector. |
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| Rolm |
Yes, I found the same by-the-case-only problem as well.
I've been doing some thinking about this, and I think I've come to the conclusion that the MH bulbs with a U-turn element will not be able to create a clean, focused beam if they are end-mounted in a "conical" reflector. This has to do with the uneven distortion caused by the glass of the bulb a result of the point-source being mounted off-center in the bulb. And, to a lesser exent, the presence of the returning element on the other side of the bulb.
Consider that all glass distorts light to some extent. Assuming an even thickness on all points of the glass, this distortion can be calculated as a product of the angle of the beam of light relative to the surface of the glass. Therefore, an "ideal" bulb is a perfect sphere with a 0-diameter point-source in the exact center. That way, the angle of every beam emanating from the point-source is 90deg, therefore no distortion.
Move the point-source away from the center, and now almost _every_ beam emanating from it strikes the bulb glass at an angle other than 90deg, so almost every beam suffers from varying degrees of distortion. Another terribly inaccurate illustration:
<img src="http://members.cox.net/rolm/images/bulb_distortion.jpg">
If you imagine this offset bulb mounted end-on in a conical reflector (even if you manage to offset the bulb to put the point-source in the exact center of the reflector), you can see how the resulting beam will not be even. Since the source of the light is distorted, there is no way the focused beam can be even. This is part of what I ran into iwith the MH175RSP, because it uses a U-shaped element; even spreading the 60K-lumen hotspot resulted in an uneven beam.
If you look at MH floodlights using standard (U-shaped element) bulbs, they ALL mount the bulb sideways in a "rectangular" reflector. This rotates the distortion so that the reflector is reflecting complementary "distorted" beams rather than uneven distorted beams.
Ok, that description was a little hard to follow. But if you imagine this:
<img src="http://members.cox.net/rolm/images/bulb_distortion1.jpg">
It appears that the sideways-mounted bulb could give you a much cleaner beam than the end-mounted bulb.
The popularity of the U-shaped element probably means that it is the cheapest to mass-produce, and the most stable design. This would explain why the bi-pin and HQI bulbs are so expensive and limited to >=250W, while there are 1000W bulbs with the U-shaped element.
What do you think? |
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| rajkumar |
I finally order the following bulb and compatible ballast:
http://store.yahoo.com/elights/methal40unbu1.html
It seems like this bulb has the element centrally located compared to the other I researched. Also, the size is more managable than 10 inch plus lamps.
I have not worked with any MH bulb so far so I am not sure how the placement of element affects the distribution of light - but I will find out as soon as I get the bulb and ballast delivered.
Since the dimension of LCD is more rectuangular than round I am thinking of building rectuangular reflector based on the elliptical reflector theory ( I had posted a link earlier) - basically two circles one for the length of the panel and the other for the width and then fuse them together.
I am not going with the spider style reflectors - used for the acquarium lighting.
I am also looking into the Iwasaki 6500K 250W bulb (double ended - small unit) - that's sold with IceCap electronic ballast etc. for around $250. I still believe that If I have a small bulb, I may be able to get a ceramic reflector made. The bulb I have ordered has 5 inch light center length from the base and is Universal so I can mount is at any angle. I am thinking on mounting it horizontal with the arc facing the reflector side to reduce possible hotspot effects.
Since I will have to use the large bulb, I dont thik I can use the existing OHP set up so am thinking of working on the box design while waiting for the bulb/ballast. |
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| rajkumar |
While waiting for the lamp and ballast.. I am thinking of working on the box and reflector.
Thoughts on ellipsoidal reflector.
Since I am going to use the fresnel, I think I dont need to build an ellipsoidal reflector. Let the fresnel collect and focus the light. All I think I need to do is feed straight light to fresnel.
The first diagram shows how to bounce point source light straight and the second shows my design using the measurements of the bulb I am going to use. THe only thing I can think is that I have three inch room between the bulb element and the reflector surface (see my design) - that might be too narrow.
If this design is true, than I am going to draw a 6 inch radius circle and cut a half round of the circle in cardboard. Once I have that I can take that with me and look around for ceramic/glass/stainless steel/pyrex/etc bowls that can resemble similar curve. If not, I can have a friend make a ceramic half round with same radius that I can use for the reflector.
Any input? |
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| Rolm |
So, you're not going to try for the "conical" (ie bowl-shaped) reflector? By "half-round", do you mean that it will be a "rectangular" reflector (like a tube cut in half)?
If so, you might save a little time and effort and visit your local Home Depot (or the local equivalent). There are very sturdy cardboard tubes with a 12" diameter that are used to pour concrete footings. Cut one in half (you'll need a hacksaw, that's how sturdy they are) and layer the inside with aluminum flashing (also at Home Depot, comes in 12"x10' rolls, and it's usually almost as reflective as a mirror), and I think that'll be a good beta version of your design. If I understand your "half-round" design correctly, that is.
As far as the design itself, I'm not immediately aware of a reason why it _wouldn't_ work. It seems like a sound idea to me. If the reflector is large enough, and your trig is right, then you should end up with a large enough "parallel" beam. The only problem is that there's a pretty big margin of error in lining up the bulb and the reflector just so. I would make sure that I have some "wiggle room" to make some pretty large adjustments.
My light should be here tomorrow (according to UPS tracking), so I may have more results to post soon. |
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| rajkumar |
Rolm,
I think I didnt explain my design correctly. I am not looking into the tubular half round because it wont work for the light escaping on sides - it will only bounce light in the center of the tube. The reflector I am thinking is like a half of the hollow ball. Imaging a 12 to 15 inch ball thats used in bowling and cut it in half - something like that - the only thing is its hollow so I can put some sort of reflective film/aluminum sheet inside.
The placement of lamp inside should not be a huge deal since it has to align with the center of the lcd and at half the radius of the overall radius of the ball. |
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| Rolm |
Ok, so a conical (or, more accurately, hemispherical) reflector.
Hm, if you could go smaller than the 12" diameter you mentioned, you might try this:
<img src="http://www.homedepot.com/cmc_upload/HDUS/EN_US/asset/images/pii/9/8/2/2/A22289_2.JPG">
6' Cord Clamp Lamp with 8-1/2" Shade
Model: #010-HD277-894
SKU: #277894
The aluminum reflector is 8-1/2" diameter, and it sells for about $8. With a standard incandescent bulb, it throws a pretty even expanding beam. This was going to be my next test if the reflector that comes with my MH light isn't good enough.
The shade is rough-spun aluminum, so there are ridges inside the reflector that would have to be sanded down before you could polish it. It's easy to do, just get some wet sandpaper in 200, 400, and 600 grits (comes in a combo pack for about $5), and then spend an evening sanding down the shade, starting with the roughest grit to get rid of the ridges, and then progressing to the finer grits in stages. After it's as smooth as you can get it with the 600, use some Mothers Mag Polish (aluminum polish from an automotive store) to polish it to a mirror surface.
Er, come to think of it, it's an awful lot of effort just to see if it works. And then it might still be too small for you to use...
In any event, this is probably what I'm going to have to do with the reflector I'm getting. |
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| rajkumar |
Seems like a decent set up for a cheap price. I have seen similar but smaller reflectors in home depot/IKEA etc.. I just ordered a PAR56 reflector with bipin base from partsexpress. Also, I found a retailer for that GE bulb I was refering before. Its around $62 each with 1000 hr. life. 10K lumens. Its very small (<1.8 inch length and <1 inch diameter) and can burn in universal position. The arc is fairly centrally located so it may work with the reflector from part express or even with my EIKI OHP built in reflector. So, I am going to order that bulb and another ballast for 150W set up while waiting for my 400W metal halide bulb/ballast. Hope in between this two set up one will work.
10K lumen seems lower but a proper reflector may help. If its three times brighter than my junky 3M projector (3K lumens), I will be happy since I dont have to build a box for the bigger bulb setup for now. I will continue working on 400W MH set up in a box with custome made reflector and a long throw projector lense. |
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| Rolm |
Grrr.
I received the MH setup today, and UPS chipped the bulb. So I can't test it until I replace that.
Attached is an image. The metal ruler at the bottom of the image is 24" long, so it gives you an idea of the size of this thing. |
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| Rolm |
| <img src="http://members.cox.net/rolm/images/Img.jpg"> |
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| rajkumar |
Sorry to hear about UPS thing. Seems like the whole set up is HUGE.. I think you gonna have to make a custome box for the projector it will not fit in the standard IKEA box that several people are using to build the projector unless you replace the reflector..
I have placed two orders, one for 150W Metal halide set up (bulb 4 inch long Tubular, less than 1 inch diameter 12K lumen with electronic ballast) and the other 400 W set up (5 inch long bulb). After placing order for the 150W bulb, I have been looking for the GY 12 base (BiPin ceramic base for the bulb) and have not been able to find one..its not readily available online..see what happens.
I did get a response for my original 150W GE bulb (tiny bulb <2 inch long and <1 inch diameter) from one online retailer so I am going to order that as well since I can use my 150 ballast for that. If I will get the GE bulb that I would be able to retrofit my OHP.
While waiting for the bulb set up I am working on the screen and a long throw projector lens to fit in my living room set up. |
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| Rolm |
Yes, it's gigantic. On the upside, it looks like it might be a half-decent fit for the back of the OHP. I dunno, I have to fiddle with it, and will probably make a mating panel.
It's a shame that the smaller (physically) bulbs are so expensive. I was thinking that a multiple-bulb setup might work pretty well for small bulbs. And since 2 x 150w = 300w, that would play nicely to what we're trying to do.
As it is, I'll be happy if I can get this big honkin bulb working. I'm not bothering with trying to file a claim with UPS, I'm just going to go buy another bulb (they're only about $20). Impatience gets the better of me... |
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| rajkumar |
I have been thinking about the two lamp set up using two small 150 W lamps (100 hrs life, 12K lumens, $63 each) and finally found a retailer online right in my own city (san francisco!). I ordered two of them with GY 9.5 bases ($12 each). They do have base on stock so I will pick it up tomorrow and the bulbs will be available in a week or so. The measurements for the bulb is 1.62 inch long, 3/4 diameter and the light center length is 1.2 inch which is almost identical to the Halogen lamp I have in EIKI OHP with a separate reflector at the bottom. I wish I would have known this before since I already ordered a 150W metal halide electronic ballast and its shipped. I later found out that I could have bought magnetic dual ballast that can run two of this lamps and the cost is same as single electronic ballast.. oh well. will buy the dual as well.
Since the bulbs are really tiny, I am thinking of putting two of them side by side with two reflectors and see how that will work out. I only have one reflector from EIKI OHP and am looking for another reflector.. it looks pretty much like a small half round 3.5 inch bowl.. may me a small stainless steel bowl of that size can do the trick.. Will post some pictures later showing the EIKI setup.
I also ordered a PAR reflector from partsexpress with GY 9.5 base and waiting to see how it works. |
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| Rolm |
Okay, it looks like I'm going to have to abandon my idea of not messing with the basic OHP. The bulb is too large to allow itself to be placed where I need it to be, and that enormous reflector is not properly shaped to give me the clear light that I need.
I was able to essentially re-make the OHP by making a new stage to mount the fresnel in and suspending it above the enormous reflector. The problem is that the reflector is decidedly not elliptical (ie the beam just gets wider after the reflector) and it's already wider than the fresnel (let alone the LCD), so I'm wasting probably more than half my light even if I put the stage right on top of the reflector.
The answer is unfortuately a step backwards: make my own reflector. With the size of this bulb (11" long and 4-1/2" diam), it's going to have to be elliptical and rectangular.
I'm going to use the pencil-and-string method from the page you linked to make a reflector that will probably be 1.5X to 2X the height of the LCD (since the LCD is only about 6" high). I plan on only making the one dimension at first (ie like a half-pipe). If I end up with a distorted beam then I'll make the second.
There are images of my tests, but I'll probably wait to post them (since they're only images of unsuccessful tests :( ) until later. Or I'll make a webpage-o-shame of my mistakes. |
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| rajkumar |
Rolm,
Retrofitting OHP is viable only if you have small lamp/reflector set up. I got my ballast (150/175 W electronic from hallolight) a few days ago, picked up GY 9.5 and G 12 sockets from Buhl Distributors in SF yesterday, PAR 56, 64 reflectors are in the mail and so as two 150W lamps. I am going to IKEA tomorrow to pick up APS toy chest for $9.99 and will start building the box. I am working on both (OHP retro and Custom Box) approaches side by side.
While searching for the reflectors, I found out that elliptical reflectors are used in car fog lights - I am not sure if they are plastic, glass or metal but I am looking for them. Example and links enclosed.
Auto Fog lights with elliptical reflectors:
http://www.jcwhitneyusa.com/catsubpic.jhtml;$sessionid$CO5EXEAAAABD2QSNDV1CFFCCJUOXKIV0?CATID=3219&BQ=jcw2
Custom box for MH 400 with reflector:
http://users.erols.com/martinm/gaffs/diyprojector.htm |
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| Rolm |
: small bulbs vs. large bulbs.
Yes, I realize this, but I was trying to break that barrier. I started out looking for the smallest bulbs possible, but soon realized that it was not really within my budget to do so. Then, somewhere along the line of trying to find a good midpoint of cost vs. size, I got onto the cheap-as-possible kick. And that means going with the big honking 11x4.5" bulbs, which can be had for $20. I bought the $90 setup off ebay because (a) I thought I could use the reflector, and (b) it came with the socket, wiring, and a nice quiet F-can ballast. The ballast, bulb and socket would have run me close to $90 by themselves, so I'm consoling myself on the failure of the reflector by the fact that I kinda got it for nothing. Of course, I could have bought a 400w magnetic ballast for about $40, but I try not to think about that.
: elliptical driving lights
Hmm, a possibility. How do the dimensions of an H3 halogen bulb match up to the dimensions of your bulb? And how much modification would you have to do to the reflector to accomodate this?
I drew up the curves for two different elliptical reflectors last night: one with a 16" focal depth (for placing the LCD before F2) and one with a 6" FD (for placing the LCD after F2). I think either one would work, but the 6" one will probably more closely mimic the original halogen light pattern. At this point, the materials for making the "rectangular" reflector are cheap enough that I will probably make both just to see how they turn out.
If I were working with the smaller 400w bulbs, I might try that 8-1/2" reflector I pointed out earlier. But that's not the track I'm on right now...
I still plan on more-or-less mimicking the OHP setup, with the light on the bottom, a stage with a fresnel above that, LCD on the stage, and a 90deg lens/mirror setup on top. The main difference will be that I will not employ a mirror to reflect light from behind the projector to the stage above. This may cause cooling problems, but I'm going to try to overcome those with airflow. |
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| rajkumar |
Rolm,
Can you tell me where did you find this ? Offline or online? I would love to try that for my large 150W lamp.
- -----------------------------------------------
Hm, if you could go smaller than the 12" diameter you mentioned, you might try this:
6' Cord Clamp Lamp with 8-1/2" Shade
Model: #010-HD277-894
SKU: #277894
--------------------------------------------------------
I was thinking about the two designs of elliptical reflectors and IMHO the second design (LCD outside of F2) will probably give hotspot free even light beam.. particularly when using fresnel before LCD. In order to do the first design, I think you will have to start with a very large reflector so that when you place lcd between F1 and F2, it covers the whole panel..the beam will narrow towards the F2 and you probably need to keep atleast 6-7 inches distance between the lamp and LCD to avoide hotspot/heat issues..considering that distance and counting approx. 10 inch diagonal distance for LCD, your reflector diameter will come around 20inch minimum - just a rough estimation. Now, 20 inch diameter reflector could be hard to make/find. I could be wrong about the reflector diameter calculation but just a thought. |
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| Rolm |
: 8-1/2" reflector
I bought mine at Home Depot, but any self-respecting hardware store should carry them. It's nothing more than a plastic bulb socket attached to a clamp, and the reflector screws onto it.
: short-FD vs long-FD elliptical reflectors.
I had something of an epiphany while I was tracing the reflector curves: if you follow the curve all the way around to draw a complete ellipsoid, then you can see that F1 and F2 are equadistant from points on the ellipsoid corresponding to the horizontal axis.
<img src="http://members.cox.net/rolm/images/complete_ellipse.jpg">
From this, you can see how the height of the ellipsoid relates to the FD and the height at F1 and F2: the shorter the fd, the smaller the height, up until FD == 0, at which point you have a sphere with diameter == (height at F1).
Academic rather than practical, and pretty simple geometry when you think about it, but it's an interesting illustration. For me, anyways.
Or maybe I have too much time on my hands... :/ |
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| rajkumar |
Very interesting observation..
I didnt complete the ellipsoidal so missed that part! Simple geometry makes an interesting observation. If the observation is correct (which I think is) than I think the best approach is to go with the design #2 where lcd is outside the F1 and F2 points since hight decreases with FD increase and the idea is to cover the entire LCD within the beam path. |
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| Rolm |
Well, I built a design2 model, with the LCD after F2. Results were so-so. It's a little brighter than the std OHP, but not greatly so. I can hold a piece of paneling above the reflector and verify that my focal point is where I expect it to be, and the light at the stage/fresnel is quite bright. But not that much more than the OHP.
<img src="http://members.cox.net/rolm/images/mhohp_design_1.jpg">
One possible reason for this is that I have created an elliptical reflector with a too-small FD (I went for 6"), and therefore too great of an angle of beam spread, and the fresnel isn't able to cope with the expanding beam. This theory is supported by the fact that the stage/fresnel throws an awful lot of ambient light into the room (ie light NOT directed upwards), even with a narrow internal apeture.
I'm reconsidering design1, and abandoning the fresnel altogether. I have enough components to construct it, so I think I'll just give it a try. Undream had a similar idea (http://www.dreamlash.com/DIY/may13-2.html), and it looks like it's working pretty well for him.
I have more pictures of the progress, but I'm having a hard time motivating myself to make a page until I have something to show off... |
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| rajkumar |
HOw did you make your elliptical reflector? Is it just the one curve (length or Width) based on gunwan's design? just curious.
I found a source (theaterical supply) in SF where I can possibly find some ellipsoidal reflectors made for stage lights. I will go there Monday and hunt for some thing pre made.
Part-express reflector arrived - Its a typical parabolic shape and I dont this it will help with my project but I will try anyway when my lamp arrives.
I was reading about various screens and found out that the glass bead screens are not suitable for LCD projection - less contrast. White matte is the best and if you apply a thin coat of gray color (5%) mixed with gesso (clear) with another coating of some transluscent gesso, the screen gives more contrast (due to gray) and 3D effect (clear coat). I will have to try that. |
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| Rolm |
Yes, my reflector was just the one curve, based pretty much on Gunwan's method. I experimented with adding side reflectors as well as using a flexible mirrored plastic, but nothing really improved the brightness too much. This lead me to my conclusion that there was something fundamentally wrong with my setup.
I have constructed another much deeper elliptical reflector, this time with a 26" FD. I've made the reflector, but haven't mounted the lamp yet (I hope to do that tonight). I'm trying for design1 on this one. The challenge is to make the reflector large enough to reduce the angle that the light enters the LCD without making the entire projector 6 feet tall. It would be easy to do: due to the diameter of the bulb (4-1/2"), I am forced to make very wide reflectors (this one is 18" wide). Even so, my beam angle is close to 55deg. In this case, F2 is only 5" above the theoretical placement of the 7"-high LCD. This may be too shallow.
The trouble is that trying to increase this height is difficult: I can only do this by either increasing the FD or decreasing the ellipse height. The difference in F2 height above the LCD when I went from a 20" FD to a 26" FD was only 3/4". And the 4-1/2" diameter of the bulb forces me to make the ellipse taller as I increase the FD. If I went with the smaller ($30) 2-1/2"-diam bulb, I could reduce the width of the reflector to around 12" and increase the angle of light passing thru the LCD dramatically, and probably raise F2 another 5". But that means shelling out more $$$, which I'm not willing to do yet.
Hmm, a theatrical store... I'd be interested to know what they have to offer in the realm of elliptical reflectors.
Screens are an area that I have read a fair bit about but haven't experimented that much with: once I get the projector working well, then I may have time to mess with that. |
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| rajkumar |
Finally, I got the reflector from the theater supply store. Its indeed a piece of art (see pics) has more than 700 flat mirror like surfaces and according to the literature can reflect up to 90% of the light. Its about 6 inch diameter and around the same height and comes with the cover with approx. 3 inch opening where the beam focuses.
They also had a glass reflector (same dimensions) which reflects all the light but transmit heat so that the bounced light is not hot -if this aluminum reflector works I might upgrade it to the glass one later. Glass reflector can transmit almost all the light and according to the theater people has a very sharp focused beam since it does not have small flat mirror like surfaces of the aluminum one.
Finding F1 for the elliptical reflector was fun. See the next post. |
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| rajkumar |
| To see how the reflector works and where the F1 is, I used a salvaged ballpoint pen with LED light and tryied to mimic the dimension of the MH lamp I plan to use (still have not received - more than a week overdue). The reflector is amazing - I can get a very focused beam (about 2 inch diameter) at the F2 and if I look inside the reflector from F2 I can pretty much see the LED on most of the mirror surfaces. The pictures are not sharp enough since I took them with available light holding the reflector with one hand and my heavy digital SLR on the other so kind of blurry but you can get the idea. |
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| rajkumar |
| Here is my version of the MH lamp using LED light from a ball point pen (freebie from western union!) to find the F2 and observe the beam behavior. |
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| rajkumar |
Now I have the reflector and the lamp is on its way, I am thinking of looking into how to expand the focused beam from the reflector. I know other people on the forum have been using a condensor lens to expand the focused light on to the frasnel. In my 3M overhead, it has a halogen lamp with elliptical reflector and the focused light goes through a narrow iris on to the mirror and bounced on the frasnel.
My question is is it necessory to use condenser lens or let the beam to expand itself (like the 3M ohp setup). I dont have anything close to the condensor lens that I can try so any other suggestions? |
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| Rolm |
WOW! That's a pretty kick-A reflector! Nice job figuring out the F1/F2, also.
I think that people use and "atomoshperic" or "condenser" lens when they want to change the angle at which the beam expands in order to bring F2 closer or push it farther away. My OHP also omittted the condenser lens, so I think that's a pretty common way of doing it.
On the other hand, I don't know whether or not a condenser lens performs other magic on the beam, like evening it out and reducing hotspots. I don't think so, but perhaps.
Unfortunately, the bulb that I'm working with is the el-cheapo 4-1/2"-diameter one, so a 6" reflector is too small. I ended up building 4 different reflectors, each more complex then the last. None of them managed to give me a clean, clear beam: most weren't much better than the bulb with nothing more than cardboard boxing it in.
I think I'm ready to abandon trying to build a "rectangular reflector, because I think they waste too much of the available light. I'm taking a step back and eying the metal bowls like you talked about very early in this thread. I found a source for mixer bowls, which elliptically shaped, and usually about 8-10" in diameter and 10-12" deep. The ones I found are stainless steel, so they should be resonably shiny to start with, and should polish up nicely.
They're cheap (around $20), so I'll order one this week to play around with. I may even pick up a cheap aluminum spherical mixing bowl this weekend to build the alpha test kit.
Again, good job with the reflector. If I decide to go down a bulb size, I think I'll definitely have to find one of those. |
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| zardoz |
I havent worked out the focals ..just some "eyeball" tests. I'm using the giant 4 1/2 inch HID, I located some dirt cheap bowls. The reflector is 13 3/4 wide by about 7 inchs deep $7.00, it seems to give really good direction to the light, the second is 12 1/4 by 6 inchs deep $5.00. The second failed as a reflector, but seeing the stage reflector I'm wondering if there is benefit in using the failed bowl to close the "clam shell" on the out put side of the lamp housing. Also does anyone know how an HID likes to have it's light rays reflected back to it's arc tube? Not to mention cooling...
any thoughts?
zardoz |
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| Rolm |
<b>>clamshell bowls</b>
As far as I know, the clamshell arrangement is only beneficial for an elliptical reflector, where the rearward reflector (where the bulb is mounted) is an elliptical reflector (as opposed to a parabolic or spherical), and the apeture in the forward bowl corresponds to the F2 of the rearward bowl. The second "bowl" serves more to block errant rays that are not in line with the focused beam passing thru F2.
I can't think of of how a clamshell arrangement would benefit a parabolic reflector (where the reflector only serves to spread the beam) or a spherical reflector (where the refl. sends the beam straight out).
Sooo, where'd ya find the cheap bowls? I found a pretty-much elliptical reflector on ebay, in the form of a refubished Kitchenaide mixer bowl. |
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| zardoz |
I got these at the local "bargain department store" Saan's in nova scotia. They are stainless stell and wicked shiny! The larger bowl is somewhat eliptical, I've spent most of my time working out how to feed my laptop panel so havent done a lot of work on the reflector yet. Still learing ;)
zardoz |
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| zardoz |
Well I had a bright idea..I tried it...just hand holding the gear. But the results look very promising. Other than the fact I dont know for a fact where F2 is... Optics will be my struggle in this project I think. Not my strong suit...so I guess I gotta crack a couple of books .
zardoz |
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| rajkumar |
ywh:
The second link with a picture of double ended bulb with a reflector at the bottom is what I have in my EIKI overhead projector and it looks like "parabolic". I think it works pretty well with the halogen bulb I have in overhead projector. As soon as I get my metal halide lamp - I have posted picture earlier in this thread (150W cap style single ended made by GE) - I will try using that with the OHP reflector (parabolic shape). The dimensions seems to be pretty much similar and I dont think of any reason why it should not work.
By the way, I liked your posting and results. Keep on sharing the info and outcome on various aspects. I am glad you can find things in local market. And dont worry about your English! I lived in China (Shanghai - East China Normal University) as an exchange student for a year and liked travelling around. Most of my vacation time was spent in YenCheng (wetland - marshland) watching Migratory birds. |
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| Rolm |
ywh -
Yes, that little reflector back there could be spherical. The advantage there is that the diameter of the reflector is quite small. If I'm not mistaken, that's an "atmospheric" or "condenser" lens that is placed in front of it, for the purposes of spreading out the beam.
For that setup, a spherical reflector works quite well, because you have a very small light source (HQI bulb): approximately 1/2" (~12mm) in diameter. We are dealing with bulbs that are 4-1/2" (~115mm) in diameter, so we end up needing very large reflectors. If the size of a spherical reflector exceeds the diagonal measurement of the LCD, then we're wasting light, since a spherical reflector throws a parallel beam.
Another difference btw your example and what we've been talking about is that what you're showing is an "open" element setup, and we've been discussing "closed" elements, where the reflector encloses the bulb on all sides but one.
That being said, I've seen the pictures of your setup, and I'm jealous: I hope I can get results half as good as yours. |
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| rajkumar |
zardoz:
As rolm said, only elliptical reflector is designed for an end cap with a small apparture. The function of an elliptical reflector is to "collect" light for a point source lamp (F1) and point it to another focal point (F2) where its even and can be redirected to the LCD panel to illuminate the panel evenly. If you read this thread we have pretty good discussion on how this thing works.
I have put a great deal of time reading and thinking about various ways to work with light in the projector set up and IMHO elliptical reflector is probably the best way to avoide potential hotspot and use all the light from the lamp efficiently.
The reflector I have is made for theater lights and landscape lights using metal halide lamps up to 400 W. To find out F1 and F2 in a true or reasonably elliptical reflector should not be an issue. I have done it using an LED light but you can also use meglight with the top reflector part off - jsut the bulb on top and try sliding it back and forth in the reflector from the bottom and observe the beam behavior. |
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| zardoz |
I finally got my hands on a true "eliptical" reflector. Huge differance! Looks like I totalled 2 perfectly good SST bowls for nothing :eek:
Oh well all in the spirit of DIY. This one is alluminum but is painted white, do you think I should chemically strip the paint and pollish it? I'm sure I can get it VERY shiny. It's a prety big reflector, but I can deal with that.
zardoz |
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| Rolm |
You could strip & paint, or you could get some reflective mylar film and glue it to the inside. That should give you an easy mirror finish, as long as you get it nice and flat.
So where'd you get the elliptical reflector? |
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| zardoz |
I got this one from the local building wrecker, it had a 250 watt ballast attached to it. $75.00. I asked if I could buy just the reflector..offered the guy 30 bucks for it..he sold it to me for 25 plus a couple of Sylvania bulbs..total bill 32 bucks and change. I think I like the Sylvania's much better than the GE's I've been experimenting with. The quallity of light seems superior.
zardoz |
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| Rolm |
Yeah, the first GE I got was chipped, which I didn't notice until it blew up. I'm now using a Philips, which some ppl don't like, but I've had no complaints.
A building wrecker, eh? I may have to see if I can find one around here... |
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| ywh |
rajkumar:
welcome to YenCheng again! I live in YenCheng ( guangzhou )
you will to see anything at my overhead projector ,you well to get anything.double ended bulb ,reflector.
"The dimensions seems to be pretty much similar and I dont think of any reason why it should not work."
I don't know what are you talking about
The firster link is
http://photos.gznet.com/photos/1013684/1013684-gMlbjRoQMJQe2qazsk!RZmrALtw6kK.JPG |
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| Rolm |
ywh,
I decided not to deal with the HQI bulbs for 2 reasons:
(1) price. My bulb is about $20, whereas a comparable (400w) HQI is rare; the only one I found was ~$250.
(2) precision. If I deal with a larger bulb, I don't have to be as precise with making the reflector. You and your friend have the advantage of working with a premade system, whereas I am making everything myself.
Reason (2) is probably why you get such excellent results with a lower wattage bulb. You have a premanufactured bulb holder/reflector/lens that is very precisely made. There is little chance that I'm going to be able to make a precise 2" (50mm) spherical reflector in my home workshop. However, I have been able to make a 12"x14" (30cm X 35cm) rectangular reflector that can focus the light into a 1/2" (12mm) band.
As noted, I have since abandoned the concept of a "rectangular" reflector because it simply doesn't reflect enough of the available light. However, I am still going to try to find a way to use the $20 bulb.
I have a question, perhaps I have missed the answer in some of your other postings: I looked up "3M 1720", and according to all info it uses an ENX bulb. So where did you come up with the HQI bulb holder/reflector/lens setup? I would be VERY interested to find this out... |
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| Wally |
| Hey Rusty, I've got one of those. It's close but no cigar. Not much better than a coffee can. |
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| Rolm |
ywh,
Ok, my research shows that the 3M 1720 uses an ENX bulb like this:
<img src="http://64.95.118.51/images/opti/d1/09/dfe350ca9976b6606d64ea91e64e659c1-resized200.jpg"</img>
But you are using this assembly to replace the ENX assembly:
<img src="http://photos.gznet.com/photos/1013684/1013684-gMlbjRoQMJQe2qazsk!RZmrALtw6kK.JPG"</img>
Where did you get this <b>entire assembly</b>? Not just the bulb, but the <b>whole thing</b>: lamp holder, bracketry, reflector, lens, the entire assembly? Is this the assembly that came with the 3m 1720, and if so did you just add the HQI lamp holder and make a reflector? If so, how did you make the reflector?
The reason I seem so confused is that this assembly appears to be very different from the standard ENX bulb holder, and therefore the <b>entire assembly</b> would be required to replace and ENX lamp with your 150/250W HQI bulbs.
I currently have a 3M OHP that uses the ENX bulb, and my bulb assembly doesn't look anything like this; mine is about 1/4 the size of that one, and doesn't use any lenses at all. |
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| ywh |
3M 1720 uses an ENX bulb like that but has not reflector
My friend get thiat entire assembly at 3M,He give it a new bulb, a lamp holder,the bracketry, reflector, lens came with the 3m 1720, he buy the new bulb, the new lamp holder ,only, |
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| Rolm |
OK, I hope my understanding of you is correct:
All that your friend added to the 3M 1720 was a bulb-holder, the bulb, and the reflector. Other than that, the entire assembly pictured was already in the 1720.
In other words, if I wanted to do the same thing, all I would need is:
(1) 3M 1720
<img src="http://www.unitedvisual.com/jpeg/MM1720.jpg">
(2) an HQI bulb
<a href="http://store.yahoo.com/lamps-now/1510hqidoube.html">
<img width=250 src="http://store2.yimg.com/I/lamps-now_1717_1043712">
</a>
(3) HQI bulb holder
<a href="http://www.hellolights.com/25lamholwitb1.html">
<img width =250 src="http://store2.yimg.com/I/lamps-now_1719_94164">
</a>
(4) home-made ~2" reflector like this:
<img src="http://catalog.sciencekit.com/ProductImageLib/30/30538-75g.eps.jpg">
I would <b>NOT</b> have to buy any parts from some other OHP to make it work, right?
If you can verify this, then I will probably start buying some of these things. I just managed to mangle some of the parts I took from my other OHP, so I'm looking to buy anyways. |
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| ywh |
no !
3m 1720:the bracketry, reflector, lens came
My friend bought the new bulb, the new lamp holder,
your 3m 1720 is not Chinese 3m 1720 !why ?Chinese 3m 1720 is:
http://www.3m.com/intl/cn/office/de...duct_m1720.html
250W HQI bulbs is right for 100" screen.
if 150W £¬dont more than 70"screen,My friend using 250W HQI bulbs
but ,250W is very expensive at HELLOLIGHTS.US$:40 in China |
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| Rolm |
Hm, I suspect you are right, and the Chinese version of the 1720 is different than the western one.
I suspect that your friend's 1720 originally used an EHJ bulb. Am I correct?
OHPs that use the EHJ-type bulbs are probably the ones that are capable of being easily upgraded to a Xenon or MH HQI bulb, because (I am pretty sure) that they all use the apparatus pictured earlier in this thread, with the seperate reflector and lens.
As noted, the western version of the 1720 uses an ENX/FXL style bulb, and therefore has no lens and the reflector is built into the bulb. If an OHP uses an ENX/FXL-style bulb, it is definitely NOT a candidate for this modification, or at least not as easily.
In any event, I've trashed my OHP at this point (I broke the thermal glass that is bonded to the fresnel), so I'm in the market for another OHP. I will try to buy one that uses an EHJ bulb. If, as I hope, that means that it comes with this apparatus, I will try to do the same mod you have done.
Thank you, ywh, for your patience in answering my questions. |
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| rusty42 |
| quote: | Originally posted by Rolm
In any event, I've trashed my OHP at this point (I broke the thermal glass that is bonded to the fresnel), so I'm in the market for another OHP. I will try to buy one that uses an EHJ bulb. If, as I hope, that means that it comes with this apparatus, I will try to do the same mod you have done.
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rolm, i have an elmo HP-A305LV (low intensity version of the solar deluxe, has triplet optics) - 24v/250w EHJ assembly with separate reflector, lamp, and lens.
HTH |
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| Rolm |
rusty42 -
If you're interested in selling it, drop me a line at rolm@cox.net. |
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| rusty42 |
| quote: | Originally posted by Rolm
rusty42 -
If you're interested in selling it, drop me a line at rolm@cox.net. |
heh, not really interested in selling it, as i plan to do a similar mod. but check with inventory solutions, i picked it up there for $45. (you may have to call, as i didn't see any on their website) |
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| Rolm |
NP.
Actually, I've been doing some research into which OHPs have this setup (I'm unsure if this is indeed what "triplet optics" mean). It appears that most that use EHJ, EVD, EYB, and FCS bulbs use the same basic layout, but some of them appear to be missing the condenser lens, which doesn't make sense to me.
The real problem with figuring out which OHPs are candidates for this is that you need to see a parts diagram to know if all the components are there.
I also need to do some more research as to what the least expensive approach to bulbs and ballasts. Optimally (for me) would be a 400w HQI or HMI that can use an M59 ballast (that I already have), but I'm not finding it. |
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| remp |
Rolm
Far as I know triplet refers to how many lens are in the projection head assy. One , two or three.
Two and three are better than one....so they say
My 3m 1705 has a single projection lens and its spot on. |
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| rusty42 |
| quote: | Originally posted by remp
Rolm
Far as I know triplet refers to how many lens are in the projection head assy. One , two or three.
Two and three are better than one....so they say
My 3m 1705 has a single projection lens and its spot on. |
the triplet head assembly is convenient - mine has a rotating lens that focuses, no need to move the entire assembly up and down on the arm.
rolm, check http://www.mbelectronics.com/3M/index.html some of these PDFs have diagrams of 3M OHP internals. |
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| bitbyter |
| This a post directed to Rajkumar from another thread "Not Enough Light". I am using an elliptical aluminum reflector from a high bay light like you would see in a Home Depot (a little big though). I have switched from the 400W Philips Metal Halide because they have a "dimple" in the top of the bulb which interfears with the light (this also might be because my condensor lens is not right on the F2). I am now using a 400W Sylvania Metal Halide with better results. If I have time today I am going to be confirming my F1 and F2 positions to be sure I am getting the maximum light potenial from this light. |
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