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Exploding Caps

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Electric Rain

New Member
I was wondering... just exactly what is an exploding cap? Do the actually explode? Or do they just make a loud popping sound and then are no longer good? And what do I have to do to make them explode? Just apply a large amount of voltage to them? I would like all the details I can get please. :D They sound pretty fun. :twisted: Thanks!

Rain
 

Nigel Goodwin

Super Moderator
Most Helpful Member
Electric Rain said:
I was wondering... just exactly what is an exploding cap? Do the actually explode? Or do they just make a loud popping sound and then are no longer good? And what do I have to do to make them explode? Just apply a large amount of voltage to them? I would like all the details I can get please. :D They sound pretty fun. :twisted: Thanks!

Rain

They do actually explode, one could quite easily take your eye out!. In the past I've seen large metal can electrolytics blast from under their mounting clamps and crush themselves against the TV tube!.
 

Styx

Active Member
yep visious things caps when they blow. Large tank electrolytics are the worst. Also tantilums are noisy buggers for their size but at least they tend to vapourise themselves unlike electrolytics.

Most electronics will tend to explode if you exceed their tolerance. The best explosions I have seen have been from a Eupec IGBT 3ph IGBT module rated at 200A, we accidently turned on all 6 IGBT during a motor regen abt 1000A flowed through all 6 IGBT's and the lid blew off

https://www.jonrb.pwp.blueyonder.co.uk/images/IGBT.jpg

a piccy of the module.

If the cap is a polarised electrolytic just apply the wrong voltage polarity. Otherwise put too much volts, too much ripple current, too high temp. IE exceed any of the maximum ratings.

but PLEASE dont do it if you get a large metal can, you might as well just get a grenade...
 

Dean Huster

Well-Known Member
Exploding capacitors

With 20+ years of teaching, one gets a little liabilty conscious. Students never could understand why it was that I insisted that they always wear safety glasses whenever they were in the lab working with their breadboards. After all, they were little parts, no big deal.

So, one evening after school, I had our media guy come in and set up the big Sony camera and we deliberately blew a few caps. It took a supply with higher current capability and a reversed cap to do the job quickly enough that the media guy didn't get bored waiting, but when they started blowing, it got his attention. These were just little caps. The axial lead variety weren't as bad as both their leads were usually captured by the breadboard. But those little radial lead caps were nasty. They'll shoot out like a rifle bullet and we never did find some of those after they glanced off two or three walls. It would definitely do some eye damage.

We sent the tape to the local TV station to transcribe over to their slo-mo machine so that we could get a good stop-action, frame-by-frame view of the event. In one frame, the cap is there, in the next it's gone. The whole tape was always favorite viewing for the students and gave them a new respect for the parts they were using and a new respect for safety glasses.

And these are just little ones. The big ones, connected into high energy circuits are downright dangerous if they go.

Dean
 

pike

Member
I was told that when you apply current or voltage past the ratings, the electrolyte boils and starts forming hydrogen gases pockets. You can see the caps' starting to bulge from the pressure, and once the cap' gives way watch out...
 

vaineo

New Member
I had one blow in the power supply in my pc. made a loud bang and when i took the thing apart it was filled with little pieces of die-electric stuff.
 

Johnson777717

New Member
Some capacitors, like electrolytics, have the "X" stamped on top of the casing to allow for a more controlled explosion. The X dilberately weakens the metal casing, so the explosion tends to go upward, and not outward.
 

Nigel Goodwin

Super Moderator
Most Helpful Member
Johnson777717 said:
Some capacitors, like electrolytics, have the "X" stamped on top of the casing to allow for a more controlled explosion. The X dilberately weakens the metal casing, so the explosion tends to go upward, and not outward.

Yes, modern ones do, old ones didn't - I once had one 'rocket' off the board, just missing my eye, and punching a hole in the ceiling!.
 

plot

New Member
Dean Huster - Any chance you can put some clips of that online?

Threadstarter - Wouldn't recommend it at all, as everyone else said. Can be very dangerous... All you gotta do is get an electrolytic cap and reverse the polarities. Not good results...
 

Rescue1

Member
I don't recomend this because it is down-right dangerous,but years ago when I was in vocational school/high school we would set up small caps under other students seats.When they sat down we would crank them with over rated voltages...... :lol: .....It never hurt anybody,but it sure was funny.Looking back I realize it was irresponsible,but I was 17 at the time.I am 25 now,and still get a good laugh by thinking about it..... :lol:
 

Electric Rain

New Member
:shock: Wow, those are some pretty scary stories... Soooo... yeah, I'll be triggering these things with a wired remote from about 300 feet away. :lol: No... really.

I'm trying to think of a way to make one of these look cool. You know, like for the 4th of July or something. Sure, just...an explosion is like, :shock: "Wow that was messed up!" :twisted: but really, what then? I need to make some kind of fireworks display with them. That I can remotely trigger from a safe distance away. Any suggestions guys? :?:

I could just have a (REALLY STRONG) box with some multicolored ultra-bright LEDs in it doing some kind of cool pattern sitting on top of a lagre, X-stamped cap. :twisted: :twisted: :twisted: J/k... or is it. :lol: Well, see you guys.

Rain
 

andrew2022

New Member
i eventually found the remains of a cap i blew a few days ago... the metal is dinted and the plastic (?) label has shrunk... been told that was due to reverse polarity
 

spyghost

New Member
so far, i know of two conditions that would pop capacitors...
1 - over voltage
2 - wrong polarity

i terms of popping experience, well i had quite a lot. perhaps the worst i hvae seen was when my friend reversed the polarity of a 3300uF, 50V! he's lucky, the metal cap only hit is forehead and not his eye!
 

stevez

Active Member
It would be good to hear from others but it's my feeling that capacitors can "pop" because of some deterioration or some manufacturing flaw that allowed it to operate for a time, possibly years, prior to failure. I've seen caps fail in commercially produced equipment. I have to presume that the capacitor was appropriately rated and installed correctly. It certainly is possible that the designer failed to recognize the need for a higher voltage rating.

My own personal experience is with the commercial ham radio gear that I've owned. Capacitor pops, I replace it with same value/rating and it never pops again. Most recent scare I got was with 10 yr old computer - turned it on and a tantalum in the power supply let go - wasn't worth fixing.
 

Nigel Goodwin

Super Moderator
Most Helpful Member
stevez said:
It would be good to hear from others but it's my feeling that capacitors can "pop" because of some deterioration or some manufacturing flaw that allowed it to operate for a time, possibly years, prior to failure. I've seen caps fail in commercially produced equipment. I have to presume that the capacitor was appropriately rated and installed correctly. It certainly is possible that the designer failed to recognize the need for a higher voltage rating.

Yes, electrolytic capacitors certainly fail in use, it's probably the largest failure in domestic electronics these days. If you ever look at the full spec on electrolytics they specify their expected lifetime - which is usually pretty low!. Very often you can see where they have leaked electrolite on to the PCB (often causing damage), and often the venting 'cross' on the top will be slpit open.

In the past I've seen large multi electrolytics in valve TV's 'explode', including one which was mounted horizontally under a steel clamp. The force of the 'explosion' forced the back off the TV, and the capacitor 'rocketed' forwards from under the clamp and crushed itself against the back of the CRT.
 
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