DIY Video Projector Part II - Page 53

eebasist · 2nd August 2002, 02:39 PM

oh well time to take apart one of my crt projector and find out what lenses inside are of any use to me, if any.

biteon · 2nd August 2002, 06:53 PM

some one give me the perfect dimmintions to a parobolic relfector and ill try to make the out of alum. and sell them to you guys through ebay for cheap that of cource if they work out.where i work has alot of tools etc. that i can work with. but if this dose work out im only making a limited amount just for u guys. nonprofit work sucks after a while. we see how it gose.

Mitch · 2nd August 2002, 11:15 PM

Hey, thanks guys. You just saved me about $40.00.
As far as the Lights of America goes, they are 8,000 lumens and they are color corrected (I don`t know if color corrected is better or not). But I think 8000 lumens is bright enough...isn`t it?

Mitch

Mario007 · 2nd August 2002, 11:54 PM

8000 lumens is not enough I think. You would defiently have to have a good reflector even then it would be dim. Use a metal halide although they are a bit more expensive they have good color tempature and are very bright. Most people are using 400 watt metal halide which seems to be good size. They output 40,000 lumens. ROTFLMAO on icculus comment that his pictures look like a video bagel.

woneill · 3rd August 2002, 09:00 AM

Hi Guys,

Where (and whose) was the post a few days back about using a cardboard cutout to create a solid elliptical dome out of plaster/clay that could be used as a mold to build an elliptical reflector around using aluminium foil/sheet?

I remember reading it a week or so ago, but it seems to have been lost in the weeds...

Having seen the commercial reflectors from stage lights, I am sure that this is the answer to the reflector problem.

A suitably cut (like petals on a flower) aluminium disc could be wrapped around this dome, fastened in place, and its inside surfaces polished. It would be cool!

I THINK a suitably set-up elliptical arrangement would also eliminate the center hotspot situation that affects many who have used a parabolic reflector, or cylindrical + fresnel combination. But, then again, I might be wrong...

Bill.

mycamel · 3rd August 2002, 01:23 PM

Quote:

Originally posted by woneill
A suitably cut (like petals on a flower) aluminium disc could be wrapped around this dome, fastened in place, and its inside surfaces polished. It would be cool!

Bill,
The plaster mold idea is here on this page.

I liked your idea of the thin - petal approach, but wonder how easily it would conform to the shape required. The better the specular surface, the worse any imperfections will affect the light reflected off of it.

I still think it would be easier to use thinner, easily formed metal like foil, built up in many layers to obtain the wall strength needed. Sort of like paper mache, but using foil instead of paper. The sticking point (bad pun alert!) I think would be glue.

Biteon had suggested melting the aluminum together, but I don't think that would work unless you formed a complete mold and did a pour like a foundry. Otherwise you'd be essentially trying to weld it, and as far as I know, aluminum doesn't cooperate around oxygen.

Any adhesive experts among us? What sort of heat does super-glue handle? Would it start producing toxic fumes after we'd been watching our TV a while? Are there any epoxies made for automotive repair that could handle the heat?

remp · 3rd August 2002, 02:03 PM

Maybe something like that black gasket goo they use for auto engines. Gasket cement. Gasket replacemnt. May need highish pressure to work properly.

thelaw · 3rd August 2002, 04:48 PM

Quote:

Originally posted by cowanrg
possibly. i have the site done, and hosting done, it just got pulled because of some disputes with my hosting over traffic...

this site pulls a LOT of people when its up. i think i was doing like 4K page visits a day near the end. i forgot how much bandwidth was used, but its more than a cable/dsl can handle for sure. it was in the multiple GB/month range.

ill get it back up and see if i need a mirror. where you located?

I wouldn't be to sure cowan.

I host a very popular forum on my DSL line (512k/256k) I have ~13000 members and usually around 30 connected at any one time. Traffic wise this costs me around 700MB a day, on busy days though its usually around 1GB, recently it came up to 2.5GB in one day.

Beleive me, a well configured server on a dsl line can handle a hell of a load (this was my problem). I had to upgrade the server for a performance boost, the line was not the bottleneck. In my 2 years experience of home-hosting

the hardest thing is keeping the server running.

Anyway, back to projection

Im all setup, sorry I havent posted pics yet, im still trying to get hold of a camera. I have an Elite Vision 4000 OHP that takes EVD Lamps, and my panel is a Spectra Pro (different to Spectra C)

I never thought i would get such a good projection on such a budget. It's amazing, the best thing i have ever purchased for home cinema is this panel and ohp. I had it setup yesterday on my outside wall, the picture was about 14ft diagonal. Amazingly it was still crisp and bright (this was about 11pm

)

I am aiming to fit my ohp with a new MH setup though because i have a few problems::

1. The panel gets EXTREMELY HOT (REALLY REALLY HOT

)

2. There is a small spot in the middle of the picture (the tungsten filament.

3. It would be nice to have a brighter image for ambient lighting

4. Im worried that in this state it would be a fire hazard to roof mount.

Also, I would like to upgrade the panel to an XGA QA-2500 and have emailed ISI to ask them to keep one reserved if they get a few in. If anyone is selling a Sharp QA-2500 please send me a private message.

Thanks ppl
cya,

woneill · 3rd August 2002, 10:07 PM

Hi Mycamel,

Awesome original idea!!!

I was thinking that something like 1mm aluminium sheeting would be robust enough to hold its shape once formed, but ductile enough that it could be "forced" using blunt implements (and a small hammer - hammers are always fun)

to conform to the curve of the dome.

The petals would overlap each other to some extent, and a solution as crazy as pot-riveting near the exit apeture might be good enough to hold them together in place without disrupting the output beam too much (the rivets would probably need to be applied from inside the reflector). The holes could be drilled through the reflector petals while they are still on the mold.

Even a crude and simple arrangement such as this would be better than most of the existing reflectors out there, and once polished, would probably be equal to many of the stage-lighting ones.

If nothing else, it would dramatically increase the amount of usable light from the big 400W MH bulbs.

Bill.

woneill · 3rd August 2002, 10:11 PM

Mycamel,

Your foil idea is definitely a good alternative, though! High-temperature epoxy would be your best bet - it is what is used by the Xenon car headlamp manufacturers to glue the base to the bulb.

I don't know what the heat characteristics of normal epoxy are, but I too would be wary of superglue - it contains cyanide compounds. Not good!!!

Bill.

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2nd August 2002, 02:39 PM	#521
eebasist diyAudio Member Join Date: Apr 2002	oh well time to take apart one of my crt projector and find out what lenses inside are of any use to me, if any.

2nd August 2002, 06:53 PM	#522
biteon diyAudio Member Join Date: May 2002	some one give me the perfect dimmintions to a parobolic relfector and ill try to make the out of alum. and sell them to you guys through ebay for cheap that of cource if they work out.where i work has alot of tools etc. that i can work with. but if this dose work out im only making a limited amount just for u guys. nonprofit work sucks after a while. we see how it gose.

2nd August 2002, 11:15 PM	#523
Mitch diyAudio Member Join Date: Jul 2002 Location: Indiana, USA	Hey, thanks guys. You just saved me about $40.00. As far as the Lights of America goes, they are 8,000 lumens and they are color corrected (I don`t know if color corrected is better or not). But I think 8000 lumens is bright enough...isn`t it? Mitch

2nd August 2002, 11:54 PM	#524
Mario007 diyAudio Member Join Date: Jul 2002 Location: Portland	8000 lumens is not enough I think. You would defiently have to have a good reflector even then it would be dim. Use a metal halide although they are a bit more expensive they have good color tempature and are very bright. Most people are using 400 watt metal halide which seems to be good size. They output 40,000 lumens. ROTFLMAO on icculus comment that his pictures look like a video bagel.

3rd August 2002, 09:00 AM	#525
woneill diyAudio Member Join Date: Jun 2002 Location: Somewhere in Sunny NJ	Hi Guys, Where (and whose) was the post a few days back about using a cardboard cutout to create a solid elliptical dome out of plaster/clay that could be used as a mold to build an elliptical reflector around using aluminium foil/sheet? I remember reading it a week or so ago, but it seems to have been lost in the weeds... Having seen the commercial reflectors from stage lights, I am sure that this is the answer to the reflector problem. A suitably cut (like petals on a flower) aluminium disc could be wrapped around this dome, fastened in place, and its inside surfaces polished. It would be cool! I THINK a suitably set-up elliptical arrangement would also eliminate the center hotspot situation that affects many who have used a parabolic reflector, or cylindrical + fresnel combination. But, then again, I might be wrong... Bill.

3rd August 2002, 02:03 PM	#527
remp Account Disabled Join Date: Nov 2001 Location: New Zealand	Maybe something like that black gasket goo they use for auto engines. Gasket cement. Gasket replacemnt. May need highish pressure to work properly.

3rd August 2002, 10:07 PM	#529
woneill diyAudio Member Join Date: Jun 2002 Location: Somewhere in Sunny NJ	Hi Mycamel, Awesome original idea!!! I was thinking that something like 1mm aluminium sheeting would be robust enough to hold its shape once formed, but ductile enough that it could be "forced" using blunt implements (and a small hammer - hammers are always fun) to conform to the curve of the dome. The petals would overlap each other to some extent, and a solution as crazy as pot-riveting near the exit apeture might be good enough to hold them together in place without disrupting the output beam too much (the rivets would probably need to be applied from inside the reflector). The holes could be drilled through the reflector petals while they are still on the mold. Even a crude and simple arrangement such as this would be better than most of the existing reflectors out there, and once polished, would probably be equal to many of the stage-lighting ones. If nothing else, it would dramatically increase the amount of usable light from the big 400W MH bulbs. Bill.

3rd August 2002, 10:11 PM	#530
woneill diyAudio Member Join Date: Jun 2002 Location: Somewhere in Sunny NJ	Mycamel, Your foil idea is definitely a good alternative, though! High-temperature epoxy would be your best bet - it is what is used by the Xenon car headlamp manufacturers to glue the base to the bulb. I don't know what the heat characteristics of normal epoxy are, but I too would be wary of superglue - it contains cyanide compounds. Not good!!! Bill.

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