[Boards: 3 / a / aco / adv / an / asp / b / biz / c / cgl / ck / cm / co / d / diy / e / fa / fit / g / gd / gif / h / hc / his / hm / hr / i / ic / int / jp / k / lgbt / lit / m / mlp / mu / n / news / o / out / p / po / pol / qa / qst / r / r9k / s / s4s / sci / soc / sp / t / tg / toy / trash / trv / tv / u / v / vg / vp / vr / w / wg / wsg / wsr / x / y ] [Search | Home]
How much power does a led emitting 6000 mcd...
Images are sometimes not shown due to bandwidth/network limitations. Refreshing the page usually helps.

You are currently reading a thread in /sci/ - Science & Math

File: piceds.jpg (659 KB, 2197x1463) Image search: [iqdb] [SauceNao] [Google]
659 KB, 2197x1463
How much power does a led emitting 6000 mcd of 465 nm blu light in a 20 degrees angle converts into luminous energy (Watts)? All the light the led emits is captured, so I don't care how wide the beam is, just how many watts I can gather.
I tried searching for led efficiency but all I find is lumen/watt. The problem is that it is calculated for 550 nm light, and I don't know how to calculate that for blue light. Any ideas?
>>
Anyone has some advice?
>>
Just give me an advice
>>
>>
https://en.wikipedia.org/wiki/Candela#Explanation
<--wavelength dependent formula
>>
>>7809043
According to my math, one of these leds https://www.adafruit.com/products/301 outputs only 0.01 W. Is this even possible?
>>
>>7809811
yes, most commong 5mm leds are 0,01W/0,25W/0,6W/1W
>>
>>7809818
Are you talking about the power they use or about the power they output?
>>
>>7809825
if you tried to integrate the emitted wavelengths to find out the power it emits 0,01 sounds like a reasonable result.
>>
>>7809867
just write down or screencap what you're trying to find out and i'll help. also post a pic of your calculations
>>
>>7807680
>I don't know how to calculate that for blue light.
It's not a calculation; light follows aberrant quantity rules. Detection depends on the composition of the measuring body, wattage inclusive.
>>
>>7809887
I'll explain everything:
According to this paper ( http://emedicine.medscape.com/article/1894477-overview#a4 ) I need 10 mW/cm^2 of blue light at 458 nm (I found those 465 nm blue led: https://www.adafruit.com/products/301 ), over an area of 0.10 m^2 (30 * 30 cm).
Now I can't tell how many leds would I need to get those 10 W.
If every single of those leds output 0.01 W I'd need 1000 of them, but that seems overkill.
Anyway this is how I calculated it:
6 cd / (683 * 0.1).
I got the last number from this site ( http://www.cvrl.org/lumindex.htm ) for 465 nm light.
That gives me 0.1 W/sr.
In the leds vendor page the viewing angle is listed to be 20 degrees (10 + 10).
So it covers a solid angle of (assuming a sphere of radius 1): PI * (sin 10°)^2 / (1^2), which is 0.1 sr.
It follows that the total power that a single led emits is 0.1 W/sr * 0.1 sr = 0.01 W.
Did I get it wrong?
>>
>>7809894

>>7809043
>>
Help?
>>
>>7810365
Me!
>>
>>7809927
i tried this for 555nm and checked with this website to make sure i did everything correct.. then i did the same calculation for 480nm and i got 0,012W which is either correct or we are both idiots. http://www.translatorscafe.com/cafe/EN/units-converter/illumination/9-11/lumen%2Fcentimeter%C2%B2-watt%2Fcentimeter%C2%B2_%28at_555_nm%29/
>>
>>7811317
>>
>>7811703
Thank you, for some reason it didn't show me your reply. That is a lot less than what I was hoping.