Question

I'm trying to design a short light pole with a height of 1 ft (0.3m) to light up an area of 9 $m^2$ [length of 10ft (3m) and width of 10ft (3m)] using an ARRAY of LEDs. In order to do that, I need to use MATLAB to calculate the intensity of each LED. However, I have an issue where I don't know how to calculate the light intensity of a single LED at each angle when it hit the surface (assuming no bump or anything, just flat). By that I mean when the LED hit the surface straight down, I will get the most intensity. As it spreads further and further away, it will get dimmer and dimmer and at one point, I will not receive a light at all. The LED can only spread in ONE DIRECTION (not ALL DIRECTION. This means the light will NOT spread 360 degrees. This is what gave me the most trouble). PLEASE HELP!! (NO MATLAB CODE NEEDED. I JUST WANT TO KNOW HOW DO YOU COME UP WITH AN EQUATION TO CALCULATE THE LIGHT INTENSITY)!!!

Answer 1

First you need to find the wattage of the LED.

sphere aree 41r2 intensity at surface of sphere IL source strength 4Ir2 2r 3r

Then use the above formula

Since you are using LED that only spreads in forward direction, use 2 pi instead of 4 pi in the denominator

Also, the angle does not affect the intensity. It just depends upon the distance. So, if you want to include the angle, you need to use trigonometry in the formula.

r is distance of the point you are considering from the center of LED array.

put x = rcos@ and you will now have formula in terms of angle.

Here x is the horizontal distance. (distance of the point from the bottom of the array)