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In my basic electronics class we've covered LEDs and other semiconductors in detail, but never how they get destroyed, because we're not supposed to bias them in ways that cause them to be destroyed. We always used current limiting resistors when dealing with LEDs. 
I've accidentally burnt out a transistor once though, and from there I think I can form a theory.
Once you reach breakdown voltage, current through the semiconductor increases dramatically. P = (I^2) * R, so the power dissapated by the semiconductor increases as current does at an exponential rate. This rush of current probably heats up the semiconductor junction on the order of hundreds of miliwatts to a tiny junction which couldn't possibly dissapate it all. The heat probably expands the solid plastic inside the LED, shattering the plastic, and the smell is probably caused by the chemical reactions as the junction burns to a crisp.
That's just a theory, mind you. I don't know for certain. I'll ask one of my instructors on monday for a good reason.
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Quote:Zack Wrote:TheDarkJay Wrote:[wild guess] too much electricirty flowing through it for it to control, the electricity built up and when it escaped it did so with such force it blew up the whole thing
like i said that is just a guess and most likely wrong
The electricity "escapes", "built up"...where and how?
Nath: Right. I was thinking on those lines, but more that the excess heat caused an ignition with a chemical/material in the semiconductor itself, and that exploded.
like i said, i was only guessing, i am only 13 you know. I just turned 14 myself. Age doesn't matter.  Besides, I don't know how you picked up negative intentions in my comments, I even included a smiley and everything.
Aeth: C'mon, I didn't know it was going to blow up. I just figured it would stop working. It wasn't one of those tiny LEDs, it was a chunky one, although I don't suppose that's a very good indication of it's breakdown voltage.
Also, AFAIK capacitors won't blow up unless they're electrolytic capacitors wired in reverse polarity to how they should be.
BTW I'd like to make my own capacitor. I tried, with a two small squares of aluminum foil seperated by a square of wax paper. I tried to charge it with a 9-volt, and then connected a very small electric motor to it. It didn't appear to have taken enough charge to have the motor move at all. Any tips on creating a functioning capacitor that will stay charged for a few seconds and with enough capacitance to hold a signifigant voltage?
SJ: Yes, I was thinking along those lines, too.
f only life let you press CTRL-Z.
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Freebasic is like QB, except it doesn't suck.
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the AL and wax paper cap doesnt hold much of a charge
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I did the foil-and-paper thing when I was younger...didn't work so great.  I don't think wax paper makes a very good dialectric. But this reminds me of this summer camp I went to years ago...the teacher hooked up wall current to a huge capacitor (much larger than the ones you find in televisions, the thing looked like a giant grenade), let it charge for one second, then shorted the leads using a plastic rod which had a nail attached to its end. Sparks EVERYWHERE. Scared the hell out of most of the other kids.
I'd knock on wood, but my desk is particle board.
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Oh!
I was going to write a tutorial on making your own capacitor!!!
I'm too lazy to explain.
Yes, the capacitor has to be a dielectric, but it's become more common for capacitors to be dielectric. Oh, the way they fizz and spew out toxic gases and the lot when they blow up
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Eh? So it HAS to be a dielectric capacitor to blow? I thought it had to be electrolytic. In fact I was SURE... :-?
Ado: Yeah, the massive ones are great. Read up on some capacitor-bank experiments. Hand-grenade-size capacitors? Ah, no...try 10 size-of-computer capacitors, wired together. The wallop that they pack is not only lethal, as the Powerlabs website says, but it's known to blow bits off people that come in contact with it.
f only life let you press CTRL-Z.
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Freebasic is like QB, except it doesn't suck.
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Zack, I really dont understand how the LED blew up. The plastic casing of the LED isnt supposed to have even the smallest trace of air. At the most it may have an inert gas if there is a cavity. Unless you have something that will rapidly expand on heating it is impossible to get an explosion. The diode should've just melted, not exploded.
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Argh sorry Zack, I made a mistake.
In fact, now I am confused.
It is the electrolytic capacitors that do that, not dielectric. I was real doozy then.
A dielectric capacitor uses that - a dielectric...mica or paper or even air or something, whereas an electrolytic capacitor is a different way...with liquids.
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yup, though it is possible to blow up a capacitor which uses air as the dielectric medium. And I have blown up an electrolytic one in my face :roll:
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Yeah.
So any ideas on how to build a capacitor? I'm not using an electric motor anymore to test if I have a charge: I bought a multimeter which will work better to indicate votages.
f only life let you press CTRL-Z.
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Freebasic is like QB, except it doesn't suck.
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