To Buy or Not to Buy: 5mm LEDs

[Vardarac]

Every now and then when you're looking for an LED, you'll run into a few sites that have discrete LEDs with insane specs. They'll have a relatively low price, yet a phenomenal viewing angle with high intensity and low current requirements. Is it too good to be true? Who better to turn to than other enthusiasts for advice? Post any LEDs with dubious-looking specs that you've seen here and any recommendations you have for or against buying others' posted suggestions.

So for starters, how about this one?

 

[jtr1962]

Pretty much any LED on eBay falls into this category. Thanks to dishonest specs, the only thing you can really do is buy the LED and try it. For what it's worth, according to my lumens testing the bulk of white 5mm LEDs sold these days give 50 to 80 lm/W when driven at 20 mA, so there isn't a big chance of getting a really lousy LED, at least efficiency-wise. Tint is more of a crapshoot. Unfortunately that varies greatly not only between sellers, but even among different batches of the same LED from the same seller.

The specs for that BHK green LED are obviously bogus. That equates to an efficiency of around 250 lm/W. Sure, theoretically possible given the 525 nm wavelength if the conversion efficiency was around 50%, but the best green chips I'm aware of only do about 14%. In most cases sellers tend to exaggerate the viewing angle rather than the brightness. This LED might indeed be 15,000 to 20,000 mcd, but with a 30° viewing angle rather than 70°.

 

[Skywise]

I guess I like the cheap eBay LEDs but I am obviously aware that most of those mcd ratings are "creatively enhanced".

I've also noticed quite a few 5 and 8mm LEDs that are supposed to run on 100mA. I assume those are multi-die LEDs ... how do those LEDs hold up in the sense of lifetime and thermal management? I've ordered a few just out of curiosity, but they are still on the way ...

-Sky

 

[Lightingguy321]

Vishay and Optek make fairly good 3mm/5mm LEDs in both white and color. What I have noticed about these LEDs is that there is no doughnut hole beam pattern and that they evenly illuminate what is infront of them unlike most cheaper 5mm LEDs which have a lot of artifacts and irregularities in the beam.

 

[lctorana]

To buy or not to buy - that is the question
Whether it is nobler in the battery to suffer the spill and throw of outrageous lumens,
Or to take up torches against a sea of darkness
And by opposing, end them?