Electronic – Choosing an LED

brightnessled

a friend has asked me to help them with a LED billboard type of art piece. It's envisioned to basically be ping pong balls cut in half with LEDs mounted under them. She got some jumbo (10mm) LEDs for their brightness specs, and she's happy with the brightness, but not so happy with the specularity (creates a hot spot). I explained to her, somewhat speculatively, that low specularity (wide viewing angle) and high luminous intensity are competing goals,

So on to the question. What are the parameters / characteristics to focus in on for picking an LED that will brightly and evenly illuminate the inside of a ping pong ball? Are there tried and true ways to take a really bright LED and diffuse its light onto a semi-spherical surface? Am I better off getting a wide viewing angle LED at a lower luminous intensity, or a high luminous intensity and using some kind of external diffusion strategy? Any help / advice would be greatly appreciated!

Best Answer

Diffusers are very inefficient ways to spread light at a wide angle. Proper optics can do this with much less loss.

However, if you really want to use the ping pong ball diffusers, one or more surface mount LEDs without lenses will probably be the best. LEDs in 0603 package tend to be the cheapest, so you can compensate for lower overall emission (and the loss introduced by the diffuser) by using multiple of them. A cluster of three or four 0603 LEDs under the ping pong ball should provide more even light, at a wider angle, and still cost less than the archaic thru hole LED you reference. They will cost even less when you consider they can be machine placed.