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darth radius
10-31-2007, 11:57 AM
I need some help, i am still trying to make a very bright blade and i try that: i am wiring together 7 white leds, each gives 30,000 mcd, actually what is the equivalence between lumens and mcd? How many lumens i can hope to get out of that? Shall i wire them in parallele?
Thank you.

Novastar
10-31-2007, 12:21 PM
This should help you.

http://www.superbrightleds.com/led_info.htm

Don't just read the first page, scroll down and have a go of it. Found in two seconds on an internet search.

darth radius
10-31-2007, 12:34 PM
OK, one led at 30000 mcd (at a beam angle of 20) gives according to the converter 2.864 lumens! that means less than 3 lumens???

Ghostbat
10-31-2007, 01:36 PM
I took an LED class and my teacher summed it all up by saying "These are not lightbulbs, the math doesn't really work the same, don't worry about it."

It's worked for me so far :)

Marsupial
11-05-2007, 10:47 AM
I took an LED class and my teacher summed it all up by saying "These are not lightbulbs, the math doesn't really work the same, don't worry about it."

It's worked for me so far :)

Problem is: luxeon leds are ment to replace lightbulbs...

Ghostbat
11-05-2007, 12:30 PM
I took an LED class and my teacher summed it all up by saying "These are not lightbulbs, the math doesn't really work the same, don't worry about it."

It's worked for me so far :)

Problem is: luxeon leds are ment to replace lightbulbs...

Yes, but they don't work the same way. Light from an LED isn't really the same as light from an incandescent bulb and it was explained to us that in most applications figuring out the lumens was 1) a pain and 2) not really a good indication of how bright the light would look.

I have no idea why, my approach is to try it and see :)

Novastar
11-05-2007, 07:16 PM
Radius wanted the "equivalance"... that is about the best you can do.

I will certainly not stop anyone from buying LED "X" and comparing it to LED "Y". LEDs rated in Mcd are generally not in the league of Luxeon IIIs--for example.

The only other thing I can say is that 100 lumens vs. 120 lumens is pretty inconsequential (when comparing same color, same wavelength, same this, same that).

It takes quite a large "lumens leap" to make an extremely tangible VISUAL difference in most cases. Such as 100 lumens to 160 or 190 lumens.

Eandori
11-09-2007, 08:51 AM
Yeah, it's hard to see the difference between 100 lumens and 120 lumens of the same color. But I have also come to see that's mainly when you are looking at the LED or when the light from the LED is very dense in a small area. When you start spreading that light out over some area I think it becomes easier to see the difference of those extra 20 lumens.

Like in a really well diffused pair of blades. I think if they were next to each other you could tell which one had +20 lumens. But not so much if the sabers flare at the hilt.

Or if you light up a luxeon LED in a dark room and vary the current from 700mA to 750mA. Small change, but you can see the difference on objects in the room some distance away from the LED.

For the most part though, yeah it's really hard to see the differences in small lumen changes.