Exploding Capacitor: Wrong Polarity & LED Damage?

[david90]

exploding capacitor :(

I got my electronic lab today and start playing with the 470 uf capacitor. I connected to a 9v source and it exploded . The casing went across the room. what happened? The capacitor was an electrolytic capacitor. Can having the wrong polarity be the cause? If so, why?

Also, i think I busted one of my LED on my kit by not checking the polarity.

 

[Guybrush Threepwood]

Originally posted by david90
Can having the wrong polarity be the cause? If so, why?

you bet
welcome to the world of capacitor killers

Well, the college days are long gone, but I think the explanation was that when he wrong polarity is applied, the capacitor acts as a resistor, heats, gas bubles are formed in the electrolite and thus results a "pretty" explosion.

http://www.rubycon.co.jp/en/faq/alumi.html

 

[david90]

regarding transistors (3 prongs), does the Base require a resistor in series to prevent burn out? I think I shorted one out because it smells weird...

 

[wimms]

Though, you can't blow up capacitor with 9V battery. So you must be using quite powerful supply. Hopefully DC not AC?
Suggestion: DON'T take fist-sized electrolytic capacitor with low voltage rating and connect it directly into the mains.. It WON'T be pretty If you'll survive, it'll take weeks to cleanup.

Transistors allow max 1V across its base to emitter. If there is no resistance in series, then it acted like a short circuit to the power. If you applied 9V powerful source to it directly, you are lucky that it didn't go ballistic.

Man, I think you could use a helmet for a start

 

[Coughlan]

ok then, so if a capacitor takes such low voltage does that mean we can jack up the amps, and really have fun? -- I have a helmet AND goggles

 

[david90]

I'm using dc 9v and yes it did exploded! It was like a firecracker. Luckly the casing didn't hit me in the face. I assume it is safe because the electronic project kit is made for 10 or older. Wtf. Maybe I should call the company and complain. Who says I was using a hand size capacitor? The one i was using was a 470uf so it was small.


// Though, you can't blow up capacitor with 9V battery. So you must be using quite powerful supply. Hopefully DC not AC?
Suggestion: DON'T take fist-sized electrolytic capacitor with low voltage rating and connect it directly into the mains.. It WON'T be pretty If you'll survive, it'll take weeks to cleanup.

Transistors allow max 1V across its base to emitter. If there is no resistance in series, then it acted like a short circuit to the power. If you applied 9V powerful source to it directly, you are lucky that it didn't go ballistic.

Man, I think you could use a helmet for a start //

 

[Momosaida]

Do capacitors grow?

Do capacitors grow before it explodes or does it just explode?

 

[trambolin]

Apart from the voltage applied if the capacitor is saturated, a shunt or short circuit will also do it.

 

[Mike Cookson]

The effect of a connecting an electrolytic the wrong way across a power supply is usually fair instantaneous.

 

[berkeman]

You guys are like bulls in a china shop! Geeze! Your TA must be a wreck.

 

[dlgoff]

You never blow up a cap before berkeman?

 

[berkeman]

You never blow up a cap before berkeman?

Well, to be honest, yes. But never on purpose, and the couple times it's happened, it's scared the bejeezus out of me. Sounds like a gunshot going off

When we do serious Surge testing of prototypes, the protos are under a protective plastic enclosure, and we are standing back and generally ready for the noises when something fails (MOVs are loud too).

When I work with open assemblies that have electrolytic caps on them, and I'm doing any kind of circuit work that could cause a problem (like power supply work where the supply might go unstable and overvoltage), I always at least wear safety glasses, just in case one of the EL caps lights off. Oh, and I try not to have them pointed at me for any length of time...

Be safe out there kids!

 

[Corneo]

I just blew one up at work yesterday. Scared the crap out of me. The cap was on the bottom side of the board and I was poking along the top side.

 

[Ouabache]

Berkeman reminds me of some of my earlier experiments; I fired up a power supply circuit using some filter caps the size of a peanut butter jar. I needed that size capacitor, because it was for low frequency work. I had it set up in a copper shielded room and had just walked out, when BANG . There were few professors on my hall, who I am sure, not only woke them up, but gave them a chuckle All the white electrolyte spilled out too. What a mess to clean up.. So the moral is, double check your wiring to be sure you've got the correct polarity on your electrolytics.

 

[Ouabache]

I assume it is safe because the electronic project kit is made for 10 or older.

I recommend sticking with the projects in the kit and try to understand how they work. There are sound reasons why components are wired up as they show you. If you have questions about those circuits, ask them here. It will be fun discussing them..

 

[edmondng]

FET's blowing up are one of the nastiest. Not only it is loud and take crap out of you but may affect other active components so probably have to change them all.

 

[hxtasy]

Electrolytic's Do not like current in their "wrong" direction for long periods of time. Some people are mistaken though when they think that an electrolytic will not work where there is an oscillating circuit going through them, they are still capacitors, they work like any other typical capacitor, they just have longevity problems when too much current is going through them the wrong way.


Also you will notice on the top of most electrolytics, they have a crimped pattern where if the pressure gets too high they will open up through that route. If you get worried about working with them, just aim them away from your face!

always where safety glasses!

 

[Momosaida]

Would capacitors still explode if it's in the right direction but the voltage is over the limit?

 

[Corneo]

Would capacitors still explode if it's in the right direction but the voltage is over the limit?

Yes. Caps have rated voltage.

 

[Keep_i_real]

lol yeah :D I've never blown a capacitor before, but had my fair share of transistors before I learned to bias them properly! Theyre boring though, they just stop working... no explosion.
All transistors should contain a little gelignite to let you know when you've messed up!

 

[Mike Cookson]

The best you get with smaller transistors and FET's are things like little pits where there was a tiny explosion inside. You can get more but yea it's usually pretty unspectacular, however I try to avoid making any electronic components explode where possible :P

 

[zeitghost]

The smell of burning epoxy is peculiarly offensive.

 

[Mike Cookson]

Very true, also you can get burn marks or power after one burns out coming to think of it.

 

[Adz]

I remember back in college, a mate of mine descovered how to blow up capacitors for the first time... He ran 2 long wires to a capacitor underneath someone's seat. Back at his desk he had the cap connected the wrong way then half way through class he turned on the psu! hahahaha college days !