It takes the beam angle given by the user and converts it into a solid angle in units of steradians. I just thought it was easier to have the candela as the slider, because that’s the number you get when you measure with your lux meter at 1m distance, and the calculator does the conversion to cd/mm^2 for you when you put in the die area from the datasheet. Than, the luminous intensity Iv (expressed in candelas) corresponds to the luminous flux in a given solid angle (1 cd 1 lm/ster), while the illuminance Ev (. The math behind the wizard is pretty straightforward. If you want to do other LEDs that don’t have lambertian distribution you need to take a screenshot of the datasheet relative intensity graph, overlay it on the desmos calculator with some transparency, adjust the size so that it matches, then use trial and error to modify the cos() function until the orange line matches the image from the datasheet.įor tests done by people like koef3 and others, usually they list luminance (cd/mm^2) instead of directly candela, so you can just manually change the luminance to a number and then change the intensity to “l*s” and then you can adjust the luminance slider instead. Therefore, to convert cd to lm, we multiply the cd value by 12.6. ![]() This calculator gives accurate results for wide viewing angles, such as our LED strips with 120 deg or more. If a light source emits one candela of luminous intensity uniformly across a solid angle of one steradian, the total luminous flux emitted into that angle is. We are told that 1 candela emits 12.6 lumens. All results are for informative purpose only. The unit of this is the lumen per steradian, or candela (cd). ![]() If we do the CSLNM1.TG, we get 324.5 lumens from the calculator, again very close to the rated 325 lumens. To convert cd to lm, we need to know how they are related. This feeling determines the conversion relationship between luminous flux and optical power. Right off the barrel, youll notice there is. Putting that into the calculator then gives 514 lumens, extremely close to the 515 spec. but I have the p320 full size and a compact kit and sub compact module. Here I used cos(1.025*angle) instead of just cos(angle) in order to make the function match the datasheet more closely: ![]() If we put 171cd intensity and 1.59*1.25 = 1.9875mm^2 die size we get 86cd/mm^2 and 537 total lumens.Īs I mentioned earlier this is a slight overestimate because of what you can see in the first image.Ĭorrecting for non-lambertian distribution: By setting the intensity (candela) and LED die size based on test or datasheet info, the luminance is calculated (cd/mm^2) and then you can adjust the min and max angles of light collection.įor example, the CSLPM1.TG has 171cd and 515 lumens at spec.
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