| Doon1 |
I've found 15.5" fresnels but do I need 7" fresnels?
do the fresnel grooves need to be closer together for a 7" panel than lets say a 15" panel?
What size lens triplet and condenser is best for a 7"?
I've bought oak 1/2"x1/2" stock and 1/4" for the frame and case. I thought this would be best due to the staitness and rigidity of a hardwood. I have a piece of 1/4" thick aluminium sheet for the base.
I don't plan on using a mirror. I'm just going to run it strait thru the lens to the triplet.
Has anyone use a 12volt lamp assy as a light source?
I'm rather looking foward to this. My brother thinks it would be a great christmas present to him... NOT.
John |
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| Doon1 |
To elaborate about the 12volt light source.
I have a small fog lamp assy from a Mazda Millenium. this lamp is an HP unit that has the reflector, bulb, hemispherical lens, condenser lens, and balast. The total size is approx. 4" square by 5" long. It is incredibly bright. The retail cost for it is $600 so it's not something a DIY'er would run out and buy. I got it for free. The customer that owns the vehicle complained that one side was brigher than the other and it was repaced under warranty. I plan on trying it out on my projector. Before I build it with this light source what should I look for it terms of beam size? Is there a way to measure the color of the light? How about the intensity?
There are no specs with regards this info anywhere that I can find.
More about the fresnel.
I've seen where others have had their larger fresnel cut down to size. wouldn't that tend to make the rings more noticable when using a smaller panel or is this a non-concern?
Thanks
John |
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| Doon1 |
101 look-sees and no answer about Fresnel ring groove pitch with a 7"?
John |
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| Steamer |
John,
Let me preface this by saying I am in no way an expert.
However, Regarding the fresnals, those would work, but you would need to cut them down to size. The exact size, I don't know. They should be slightly larger than the LCD to ensure the light distribution will cover the entire LCD.
The object (projection) lens - or triplet - should match the focal length of the frenal but be slightly shorter. For example, if the frenal's front fl (focal length) is 310mm (typically, most are) then you would want about 1-1/2" to 2" difference or about 51mm shorter fl in your triplet or about 250mm fl on the triplet.
On the condenser, I don't know how to calculate the info but if you go to the DIY Builder Group website. They have a light engine calculator that covers the focal lengths of the fresnals, the triplet , the light reflector, and the condensor
Here is the link to the light engine calculator. It is in excel format:
[http://www.diybuildergroup.com/atta...ttachmentid=123]Diy projection calculator[/URL]
As far as the 12V light, I don't think it is gouig t be bright enough. It may, I'm not sure. I've read other posts regarding regular xenon headlight bulbs but they were not talking about the REAL H.I.D. bulbs. only thing i'm worried about on this is the color temp of the bulb. It may be a little too for on the blue end of the spectrum.
Best regards,
Steamer |
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| Steamer |
Oh yeah,
Regarding the fresnals:
the more grooves, the better the picture quality if your fresnals are the rigid acrylic, then you prolly have the optical acrylic and they are going to have economically the best groove pitch (without spending $80 to $100+)
If and when you cut them down, just be sure you are going to retain the original center or you will be projecting a skewed picture. Review the forums, you will find threads on cutting them properly.
Steamer |
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| machs_fuel |
re - 12v fog light.
sounds like a rather good peice of equipment, but how do you intend to power the light?
if we assume the light is 50W or so, you'll need ~4 amps DC
I was considering this option myself but couldn't find a cheap power suppy |
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