"Internal protection"? Where in the world do you get that?
It's just a plain, ordinary LED, yanked out of some phone-answering machine, VCR or something. No "protection". (You can see right through the diode and see plainly that there's only the usual LED die in there.)
Sheesh; everyone's trying to come up with explanations of why this can't possibly work. All of which makes me all the more want to do it!
As I said, I'll be reporting back periodically to say "it's still working: I told you so!".
We're both in the world right? So it must have came from somewhere in the world.
"Sheesh", you dont want to listen to the most experienced people here so go ahead and blow out some more LEDs.
Nobody said it will never work, they just said it should not work. There's no transient current limiting and nothing to limit the reverse voltage which kills LEDs.
If the LED does survive, then it probably has something special about it like internal protection of some sort, which could be by design or by coincidence because most LEDs will burn up. I suspect that it has a built in reverse diode.
Also, it doesnt matter how long it runs for. Tomorrow the power could go out, then come back on, and that's the end of your "long life" LED.
If you are UNLUCKY (note i said 'unlucky' not 'lucky') it will burn for several months and you'll get the wrong idea about experiments like this.
Good design techniques do not come up by inventing your own specs for devices (like LEDs). Good design techniques involve knowing what is good practice as well as what the manufacture specs are for a given device. I think you understand the specs, but i dont think you understand what good design practice is.
Of course it's nice to experiment, and i think you will learn something from this if this LED burns out too.
Also, it doesnt help as much to experiment with an unknown part number because we can not know the manufacturers specs. Like i said, they may have made it special for some reason.
After all is said and done, what if this LED burns for hours on end, maybe weeks or months. How will you apply the results of this experiment to future designs?
Are you going to practice hooking up LEDs and blowing them out until you find one that doesnt blow out? (little chuckle there sorry)