120,000mcd leds

Just In KY 2002 · 27th December 2005, 01:41 PM

I found some leds that are [typical] 120,000mcd w/30* viewing angle (80ma,3.7volt,10mm

I can purchase 100 of these for $70.

The approximate lumens per led are 25.691 lumens with the calculator found here: http://led.linear1.org/lumen.wiz

If I was to use 100 of these, would I have sufficient light in a dark room for a 90-100" screen size?

I've used 9 14,000mcd 20* leds to project a dark slide in a slide projector 10 feet with success in a dark room. This is only 110 lumens or so.

Do lumens add up, or multiply with the formula? For example:

I'm assuming that 100 leds @ 120,000mcd @ 20* = 2569.132 lumens.

I could also pulse the leds to get as much as 200ma, but would have to play with the refresh rate of the monitor to see if this would work.

mikyd1954 · 27th December 2005, 05:38 PM

well, don't forget that the LCD eats about 94% (on average) of your loumens into the lcd so that = about 125 lumens...however.... its not total lumens into the LCD that counts, its the lumens that actually make it to the triplet that count(thats why we use a collimating fresnel)...with a 30 degree spread on each , very little light will be projected... you can try it, but unless you just want to play with it and have 70$ to blow, I wouldn't.... I think the critical angle past which the light rays won't hit the triplet is 7 degrees....

Just In KY 2002 · 28th December 2005, 04:37 PM

To those who have said it cannot be done...Look what I found!!!

http://www.lumenlab.com/forums/index.php?showtopic=9136

This guy used a 7" screen with 896 white 12,000mcd leds, and it was just a slight bit dimmer than a regular mh bulb.

Chinese version here:
http://diy2005.aa.topzj.com/viewthre...=44145&fpage=1

His LEDs had a wide viewing angle and worked fine. The color output was fine. Although his starting lumens were way less than a mh bulb, the picture was just slightly darker. The conclusion on this was that ALL of the lumens from LEDs makes it forward into the LCD, but only some of the lumens from a mh bulb will make it into the lcd screen. Also there is a loss when using the first fresnel lense, which leds do not use.

This made me more interested, that's for sure! Thanks Tian!

27th December 2005, 01:41 PM	#1
Just In KY 2002 diyAudio Member Join Date: Dec 2005 Location: Louisville, KY	120,000mcd leds I found some leds that are [typical] 120,000mcd w/30* viewing angle (80ma,3.7volt,10mm I can purchase 100 of these for $70. The approximate lumens per led are 25.691 lumens with the calculator found here: http://led.linear1.org/lumen.wiz If I was to use 100 of these, would I have sufficient light in a dark room for a 90-100" screen size? I've used 9 14,000mcd 20* leds to project a dark slide in a slide projector 10 feet with success in a dark room. This is only 110 lumens or so. Do lumens add up, or multiply with the formula? For example: I'm assuming that 100 leds @ 120,000mcd @ 20* = 2569.132 lumens. I could also pulse the leds to get as much as 200ma, but would have to play with the refresh rate of the monitor to see if this would work.

27th December 2005, 05:38 PM	#2
mikyd1954 diyAudio Member Join Date: Jul 2005 Location: IL, USA	well, don't forget that the LCD eats about 94% (on average) of your loumens into the lcd so that = about 125 lumens...however.... its not total lumens into the LCD that counts, its the lumens that actually make it to the triplet that count(thats why we use a collimating fresnel)...with a 30 degree spread on each , very little light will be projected... you can try it, but unless you just want to play with it and have 70$ to blow, I wouldn't.... I think the critical angle past which the light rays won't hit the triplet is 7 degrees.... __________________ Battles fought, hearts won, honor defended, tires rotated and chickens plucked

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28th December 2005, 04:37 PM	#3
Just In KY 2002 diyAudio Member Join Date: Dec 2005 Location: Louisville, KY	To those who have said it cannot be done...Look what I found!!! http://www.lumenlab.com/forums/index.php?showtopic=9136 This guy used a 7" screen with 896 white 12,000mcd leds, and it was just a slight bit dimmer than a regular mh bulb. Chinese version here: http://diy2005.aa.topzj.com/viewthre...=44145&fpage=1 His LEDs had a wide viewing angle and worked fine. The color output was fine. Although his starting lumens were way less than a mh bulb, the picture was just slightly darker. The conclusion on this was that ALL of the lumens from LEDs makes it forward into the LCD, but only some of the lumens from a mh bulb will make it into the lcd screen. Also there is a loss when using the first fresnel lense, which leds do not use. This made me more interested, that's for sure! Thanks Tian!

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