Blowing up electrolytic capacitors

You'll get a bigger bang if with more voltage and less capacitance. U = 0.5 * C * V^2 Double the voltage gives you 4 times the stored energy.

Yes, I've had some experience making big bangs with high voltage capacitors. No, I don't want to discuss it. Well, maybe a few hints.

What you experienced with the electrolytic capacitor was a steam explosion where the heat generated by pushing current through the internal resistance of the capacitor produced enough heat to boil the electrolyte. The sealed casing or can provided the necessary confinement. As you get into physically larger capacitors with oil dielectrics, it will be the oil that is headed and explodes.

Please remember that you have only one life to give for your hobby.

I read the above, and my nostrils wrinkled at the memory of that dreadful smell. It must be more than 30 years since I had one go 'bang', but the memory lingers.

At one lab on uni, I remember they had electrolytic caps wired beneath the methacrylate boards. All other components were on top, but this one was beneath the board.

When we asked, they pointed to a stain on the ceiling.

And when some of us volunteered to work as aides the next year, they stressed on us to be very vigilant about when the newbies connected the caps.

Another point to watch were a pot, when connecting to get a variable ac voltage to calibrate a meter.

110v ---\ / \ /<-------- \ / 0C-----\----------

Well, some one connected the 110 (which here is half the mains, as a precaution) on the right hand. And he had a baffled face when it went up in smoke as he turned the spindle :-DD

Thanks for that, Jeff. Yes, one was enough for today! It just struck me that there might be some scope to use this 'phenomenon' as a propellant to blast some cylindrical projectile out of a barrel and measure the energy released (comparative measurement, anyway) by the depth said projectile was able to penetrate a block of wood. There ought to be some formula to convert those factors (projectile weight, cross sectional area, depth of penetration etc) into a credible figure in joules. That way you could more readily compare the energy released by igniting different caps with different voltages and seeing what - literally - gives you the most bang for your buck! Sadly I don't think I'll ever have the time, though as there are too many other pressing tasks I need to get to grips with. So no time for any more fun, sadly. :(

<snip>

Years ago, small electrolytics were used to simulate machine gun fire in films. Typically, a line of such would be wired to a selector switch, and buried in the plasterwork of a wall. The switch would be manually rotated to blow them up in sequence.

Cheaper than pyrotechnics and presumably less paperwork. Film and TV technicians are an ingenious lot.

My first full time job was working in a factory making PA valve amplifiers. After manufacture they were put on a soak test. One had a (very) large electrolytic connected the wrong way around. When that went up the can hit the warehouse roof.

In another job a tantalum bead capacitor was fitted the wrong way around. There was a cherry red glow and some magic smoke. A short time later when examining the PCB the capacitor decided to come apart with a loud pop sending small shards of its ceramic casing across the room.

Also bear in mind that many small electrolytics, particularly the cylindrical surface-mount types, contain an electrolyte which will dissolve copper, and quite likely other things. You don't want that sprayed around.

Using these things above their rated temperature caused the electrolyte to ooze out, which could cause any fault you can imagine, as well as often making the PCB non-repairable (at least, without jumper wires).

Hopefully, it did not strike you very hard.

Sure. Just put the capacitor in a suitable gun like device. Stuff a projectile down the barrel and a capacitor in the chamber. Apply power and the steam or oil explosion will do the rest. Unfortunately, capacitors are not designed for efficient combustion so the useful power might be rather limited. I think the big problem will be the slow recharge time. Charging energy storage caps to kilovolt levels can take something close to forever.

Perhaps if you start with a coil gun. (That's a coil gun, not a rail gun).

You'll probably like ElectroBoom. He make videos of things that explode, electrocute, burn etc and posts them to his YouTube channel.

That's been done for firearms. The result is muzzle energy in ft-lbs.

1 joule = 0.737562 ft-lbs 1 ft-lb = 1.35582 joules Everything beyond the muzzle is called ballistics. There are tables for the energy required to penetrate various materials but I'll pretend not to know anything about those.

All you need it the weight of the projectile and its velocity. There are ballistics tables and calculators that will provide the remaining velocity at a given range.

Good. For a moment, I thought you were serious. Please find something to do which is safer and less destructive.

And that capacitors may contain unpleasant, and possibly even mildly poisonous chemicals. You can end up with a mess that it takes more than just a dustpan and brush to clean up.

I'm not sure if one could build a credible hand-held weapon of the coil gun kind. You'd never get anywhere close to the velocities achieved by convenional firearms. Nevertheless, I guess this is coming down the pike in the near future as supercaps become cheaper or if battery technology makes a quantum leap. That could become a major headache for law enforment agencies in x number of years from now. I'm surprised we haven't had some serious terrorist attacks using drones and lasers before now, in fact.

Yes, I've seen this chap before a while back. It's amazing he still seems to have both eyes and all his fingers - and is still breathing for that matter!

Gladly. As I say, fortunately I don't have the time for indulging in such nonsense!

As a child, I got rid of some dead zinc-carbon batteries by throwing them onto the coal fire in the living room. What a noise and what a mess.

[Picture]

And the reason this happens, is the treatment of potentiometers is poor in Introductory Electronics.

The students end up in the Power Lab, with no practical experience or education about pots.

Basically, the students are given a three terminal device, without knowing the canonical (practitioner) usage forms. And they're sent into Power Lab, to learn about the behavior "at scale" :-) The best way to learn. Nothing reinforces a mistake better, than a cloud of smoke. Right ?

In my Power Lab, one of the student teams, just put the ends of the rheostat across mains (240V). I calculated later, that this mis-step dissipated about 5kW. No reason for the breaker to open of course. And it made a festive Yule Log out of the device, glowing bright cherry red like an "electric fire". The device got hot enough, the coils of wire fell of it. Such a beautiful piece of handiwork. Stu-dentin.

Paul

On 31/12/2023 18:24, Cursitor Doom wrote: I'm still curious to

Not me personally, but a guy who used to work for Marshall amplification said they did...

...once... :-)

True enough.

LOL :-D

Gosh, 5 KW :-)

Ah yes. That ammonium chloride vapour is nasty stuff.