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I need to buy a few tantalum capacitors for a serial port (together with a MAX232 RS232 driver). When reading up on ceramic or Tantalum capacitors, I stumbled over this:
Quote: With a reverse voltage applied, a reverse leakage current flows in very small areas of microcracks or other defects across the dielectric layer to the anode of the electrolytic capacitor. Although the current may only be a few microamps, it represents a very high localized current density which can cause a tiny hot-spot. This can cause some conversion of amorphous tantalum pentoxide to the more conductive crystalline form. When a high current is available, this effect can avalanche and the capacitor may become a total short.
This tempts me to experiment with Tantalum capacitors a little. As far as I know, they don't explode when they short out. They go up in flames. How long does this take? Is reverse polarity of the standard voltage enough or does it take a little more?
The Huey might get firing rockets after all. 
I have lived with several Zen masters - all of them were cats.
His last invention was an evil Lasagna. It didn't kill anyone, and it actually tasted pretty good.
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CodeWraith wrote: The Huey might get firing rockets after all.
Yes, but can the tantalum capacitors short on command? Or will the Huey fire the rockets at undetermined times?
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I think the they will randomly fire as detailed below!  though...
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Yes, of course. If the few volts from a microcontroller I/O pin are sufficient and the capacitor does not need to fry for an hour to finally short out.
I have lived with several Zen masters - all of them were cats.
His last invention was an evil Lasagna. It didn't kill anyone, and it actually tasted pretty good.
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They short out when you apply a voltage with reverse polarity. The question is how long it takes for this to happen after you apply the voltage.
I have lived with several Zen masters - all of them were cats.
His last invention was an evil Lasagna. It didn't kill anyone, and it actually tasted pretty good.
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My experience Tant's don't like getting hot (found this out by coming across one of our bits of kit that died when a Tant got cooked by being too close to a heat sink). The thing is they catch fire like you say but I have found it a little random... But cool idea for the Huey... I think it's down to the actual chemistry in the them the electrolyte can be spread in different concentrations in certain area's. While it is possible to get matched sets they are pricey.
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I have heard that the dielectric in the capacitor chemically has a resemblance to thermite[^]. It does not burn as hot (which probably is good), but also takes far less energy to ignite. The spark when the capacitor shorts out should be sufficient.
Edit: Thermite / termite, sounds like a pun waiting to happen. Talk about fire ants 
I have lived with several Zen masters - all of them were cats.
His last invention was an evil Lasagna. It didn't kill anyone, and it actually tasted pretty good.
modified 30-Oct-19 9:55am.
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Well a quick look at the Wiki page and it sounds not a million miles away from electrolytic. Controlling the when & how big a bang is the issue...if memory serves you can get a bigger bang from a low voltage cap when over volted, or you get a fizzle. One of my first designs was for a 'gun' that fired caps across the school lab! Also the name Termite-Thermite name was used for a USB packet reader I worked on... (based on the Termite comms program)
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I can get 11.1 out of the flight battery, but lithium polymer does not react kindly to shorts.
I have lived with several Zen masters - all of them were cats.
His last invention was an evil Lasagna. It didn't kill anyone, and it actually tasted pretty good.
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Oh, The Evil Soul!
I never thought to apply a reverse voltage to poor tantalum capacitors.
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Electric starters for model rockets would do too, but they are kind of expensive: Estes Modell Rakete Starters (6) Es2302 | eBay[^]
I would need 14 of them for every flight. And there also still is the tiny matter of getting sufficiently tiny rockets and preventing the 3D printed launchers from melting away.
I have lived with several Zen masters - all of them were cats.
His last invention was an evil Lasagna. It didn't kill anyone, and it actually tasted pretty good.
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It depends on the voltage. When I was quite a bit younger we would hook them up to an AC line and they would explode instantly. We had a lot of fun with those little bombs. At least, we thought it was fun at the time.
"They have a consciousness, they have a life, they have a soul! Damn you! Let the rabbits wear glasses! Save our brothers! Can I get an amen?"
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Every time I come across a mention of tantalum I think about some projects I did a few jobs ago involving chemical processing. We were making systems called "wetbenches" and this one particular variety of them was used to strip the oxide from the monitor wafers used in a deposition furnace. The wafers had to be cleaned with phosphoric acid that was VERY hot : around 150C. The only material we found that could stand up to that was tantalum so that's what the tanks were made from. I think they held on the order of ten gallons or so. Tantalum is very, very dense and that tank was really heavy. It took four guys to lift it into place. One curious thing - water and phosphoric acid is an exothermic reaction so when we wanted the acid bath to be hotter we would add cold water to it. That defies most logic but because it is an exothermic reaction it actually did raise the temperature.
"They have a consciousness, they have a life, they have a soul! Damn you! Let the rabbits wear glasses! Save our brothers! Can I get an amen?"
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They'll throw a tantrantum!
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Is a rasp used on flowers considered a petal-file?
| Ravings en masse^ |
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| "The difference between genius and stupidity is that genius has its limits." - Albert Einstein | | "If you are searching for perfection in others, then you seek disappointment. If you seek perfection in yourself, then you will find failure." - Balboos HaGadol Mar 2010 |
modified 30-Oct-19 7:44am.
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Double bacon cheeseburger w/ large fries?
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Well, that certainly serves the puzzle part. The obvious answer, of course, is "seven".
| Ravings en masse^ |
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| "The difference between genius and stupidity is that genius has its limits." - Albert Einstein | | "If you are searching for perfection in others, then you seek disappointment. If you seek perfection in yourself, then you will find failure." - Balboos HaGadol Mar 2010 |
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W∴ Balboos wrote: The obvious answer, of course, is "seven"
No. LIQUID NITROGEN.
Software Zen: delete this;
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For a very short while, yes.
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Batman, Batman!!! The Riddler is here!
I have lived with several Zen masters - all of them were cats.
His last invention was an evil Lasagna. It didn't kill anyone, and it actually tasted pretty good.
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Are you kidding us?
I, for one, like Roman Numerals.
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Just some minor amusement.
| Ravings en masse^ |
|---|
| "The difference between genius and stupidity is that genius has its limits." - Albert Einstein | | "If you are searching for perfection in others, then you seek disappointment. If you seek perfection in yourself, then you will find failure." - Balboos HaGadol Mar 2010 |
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One quarter of just about roughly near the ballpark (13)
Chaps and Chapesses: I have to go out for a couple of hours - one of those weeks - so I won't be giving "right / wrong" decisions for a while. I'll be back as soon as I can...
"I have no idea what I did, but I'm taking full credit for it." - ThisOldTony
AntiTwitter: @DalekDave is now a follower!
modified 30-Oct-19 5:24am.
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approximative ? only guessing and hope it's wrong 
"We can't stop here - this is bat country" - Hunter S Thompson - RIP
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Good guess - but wrong.
"I have no idea what I did, but I'm taking full credit for it." - ThisOldTony
AntiTwitter: @DalekDave is now a follower!
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