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Old 15th December 2002, 11:16 AM   #1021
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I was very blessed to find a 5" Sharp LQ6NC01 240x720 for around $45 on E-Bay (not including shipping).

If I didn't get that, I would probably go with the small 2" spy-monitor TFT from Hong Kong -- those look really cool. My goal is silent, cool, small, and portable. I want to try and stay away from fresnels if at all possible.

Just out of curiosity, how many LED bulbs do you think I would need? I have a hard time converting from watts to mcd to lumens and all else.

Thanks!

--Clint
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Old 15th December 2002, 05:56 PM   #1022
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Default zardoz!

zardoz- You mentioned that you found some HID lights/ballasts at a local building wrecker... I am also in Nova Scotia. Mind giving up exactly where you came across these lights?? Thanks.

Axeman
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Old 15th December 2002, 06:50 PM   #1023
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Default Re: zardoz!

Quote:
Originally posted by Axeman
zardoz- You mentioned that you found some HID lights/ballasts at a local building wrecker... I am also in Nova Scotia. Mind giving up exactly where you came across these lights?? Thanks.

Axeman
Hi Ax..try happy harry's in Burnside, he's a bit expensive tho. There is another guy very near him also but I dont know his name. I have a few transformers and such, missing mogul bases but as far as I know they work. If you are interested let me know, I got my "reflector" from Saan's (big SST bowls...tested one last night with good result) I'm debateing over 2 choices till I get my panel this week. What do you have for gear? Maybe we can help each other out and get something accomplished. I have a few optics/electrics but am actively seeking more, and may part with some of the stuff I do have.

zardoz
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Old 15th December 2002, 07:00 PM   #1024
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Default Well...

So anyway, I won the auction for the 5.7 inch LCD $45 for a 240x740 Sharp is good for my first experimental LCD.

http://cgi.ebay.com/ws/eBayISAPI.dll...944678193&rd=1

However, considering that I want to use LED's as my light source, I probably can't use fresnels because of the light loss. Therefore, I need to keep with normal optics. However, this is a problem. It wouldn't be so bad if it was a normal 5" LCD as advertised, but it's 5.7 inch. I knew that before bidding, but I didn't realize or something that I needed to have 6 inch diameter high-power double-concave lenses. I'm thinking my best bet is likely to find 6 inch magnifying glasses, although they are hardly projection optics quality, they may have to do. However, I haven't been able to find any of them anywhere. Does anyone else have experience with using completely non-fresnel optics, and where do you find big ones? I'd like to spend <$50 for all my optics, although I'm not sure that's possible.

Thanks alot! Keep up the great work guys!

--Clint
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Old 15th December 2002, 07:11 PM   #1025
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Default Re: Well...

Quote:
Originally posted by HanClinto
So anyway, I won the auction for the 5.7 inch LCD $45 for a 240x740 Sharp is good for my first experimental LCD.

http://cgi.ebay.com/ws/eBayISAPI.dll...944678193&rd=1

However, considering that I want to use LED's as my light source, I probably can't use fresnels because of the light loss. Therefore, I need to keep with normal optics. However, this is a problem. It wouldn't be so bad if it was a normal 5" LCD as advertised, but it's 5.7 inch. I knew that before bidding, but I didn't realize or something that I needed to have 6 inch diameter high-power double-concave lenses. I'm thinking my best bet is likely to find 6 inch magnifying glasses, although they are hardly projection optics quality, they may have to do. However, I haven't been able to find any of them anywhere. Does anyone else have experience with using completely non-fresnel optics, and where do you find big ones? I'd like to spend <$50 for all my optics, although I'm not sure that's possible.

Try surplus shed they have some big (7 inch plus ) PCX lens's

zardoz

Thanks alot! Keep up the great work guys!

--Clint
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Old 15th December 2002, 08:28 PM   #1026
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Default Thanks!

Thanks Zardoz! They've got some great-looking 7.5" diameter 20" FL magnifying lenses that look like they'll do the trick.

I stayed up all night (literally) looking at this stuff and trying to figure it out. I know I can calculate the lens focal points and such once I get the right layout that I need. I drew a quick picture to see if this is right, but I don't think it is. I think this would give me a point on the screen. But if it's larger, wouldn't it just be an image out of focus? I know you need to have the focal point on the spot that you're projecting to. I'm sorry, I'm just very confused at the moment.

Geocities hates image re-referencing. Here's the picture.wronglayout.JPG
Thanks for your help!

--Clint
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Old 15th December 2002, 08:55 PM   #1027
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Default HanClinto

I'm using a 12 inch laptop panel that hasnt arrived yet. I myself still dont have a really good handle on the optics I'm going to need. I do have a number of elements that I took from CRT lens packs, but not sure if I have anything that I can use. I saw the big PCX from surplus shed and am fairly sure I'll be getting a couple of them. At their prices I might get some other stuff just to have around to experiment with.

zardoz
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Old 15th December 2002, 09:29 PM   #1028
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Default LED Light calculation update

Here's an update on calculations that I've made for the feasability of using the lights available on http://www.superbrightleds.com/1157.htm

Going off the spec-sheet for the bulbs... the axial luminous intensity (lv) unit is in mcd (I'm assuming millicandles). A candle is the same thing as a lumen (according to my Pocket Ref), and each bulb is 78720 mcd, or 78.720 lumens.

78.72 lumens = .11808 Watts

12 bulbs costs $84 ($89 shipped)... which is roughly my limit on lighting at this point.

12*.11808 = 9.918 watts

$84 for a perfectly cool and silent 10 watt bulb... that sounds like nothing compared to these 400 watt systems that people are running. These bulbs have a viewing angle of 12 degrees though... I imagine that means that most of the light is within a 12 degree cone. Would the direction of the light help that much? I can't imagine directed light helping out more than doubling the effective brightness, so that would still mean it's like a 20 watt bulb. That's nothing. That's a very dim reading light for my clip-on. *sigh*. Am I doing my math right? It looks like I might be using a LOA worklight afterall.
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Old 16th December 2002, 06:41 AM   #1029
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Default A lens vs fresnel question

What is everyone's experience with fresnel lenses versus using a large cvx lens. I can buy a fresnel for my 5.6" screen for less than $10, or I can buy a 7" cvx lense for $30. I can't imagine that fresnels have great optical charictaristics, and it seems that the light would refract much better with a real cvx lense... but I really don't know if the difference is noticable. Thoughts from anyone?

--Clint
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Old 16th December 2002, 07:03 AM   #1030
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mcd is <a href="http://physics.nist.gov/cuu/Units/candela.html">millicandela</a>, not straight candlepower. <a href="http://www.schorsch.com/kbase/glossary/luminous_intensity.html"> A candela is 1 lumen per steradian.</a>

Careful of the difference btw <i>spherical</i> candela and <i>beam</i> candela. Most contemporary lights are measured in spherical cd, whereas LEDs are measured in beam cd.

Calculation for lumens from beam cd is :

<a href="http://dcwi.com/~nybarra/LED.html">( 1 - cos(beam_width/2)) * 2pi * cd </a>

so, for 78,720 mcd ...

( 1 - cos(6) ) * 2pi * 78.72 = 2.71 lumens

This sounds weak because it's calculated on the basis of the width of the beam. This measurement may be inaccurate, tho, because the "beam_width" is supposed to be the width of the beam at half-power. IOW, it's the radius at which the intensity of the beam is half of it's maximum.

Also, with a 12deg beam, your distance to the panel would have to be:

tan( beam_width/2 ) = ( panel_diagonal/2 )/ depth

so for an 8.4" diagonal panel, you would have to place the 12deg light source almost 40 inches away (39.96, TBE).

As always, your mileage may vary, but that's the math as far as I know.
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