Sciencemadness Discussion Board
Not logged in [Login ]
Go To Bottom

Printable Version  
 Pages:  1  
Author: Subject: Blowing up a resistor at the end of 100m of wire
Deceitful_Frank
Hazard to Self
**




Posts: 82
Registered: 5-11-2005
Member Is Offline

Mood: Pensive

[*] posted on 29-1-2009 at 15:31
Blowing up a resistor at the end of 100m of wire


Hello again guys.

Today my new toy arrived via eBay, an 820uF 450V radial capacitor with screw terminals, very cool!

My plan is to charge it to full energy (82J) and then dump all the juice in to an 1/8W resistor on the end of a length of thin cheap speaker wire up to 100 metres long, with the hope that the resistor will EXPLODE. Not just overheat but disintegrate with great violence.

The rules of this board prevent me from saying why I want to achieve this but I am sure many of you could figure it out.

I have a few queries.

I plan to use the circuitry from a disposable camera to charge the capacitor. It kicks out 330V using a 1.5V AAA. Would the tolerances of the circuitry allow me to feed in 2.4V (2 rechargable AAs) for a 500V+ output and simply moniter the voltage across the capacitor and simply charge untill it reaches 450V?

Also, I have been shocked a few times by photoflash caps at 330V 150uF and didn't really enjoy the experience of 8J through my fingers. How would 82J compare and how dangerous is this capacitor to a healthy adult male?

I figure that 100m wire there and back is around 10 ohms so if I use a 100 ohm resistor I can say that 400V will be across it yes?

...I guess that this will force the 1/8W resister to try to dissipate 1600W. Would its destruction be suitably violent?

Also I am considering a bleed resistor to go permanently across it and gather that after 5 time constants it will be safe eough to handle. I wont ask to be spoon fed here as I can do the math but what do you guys feel is appropriate for one time constant for a bleed resisiter? 1 min, 5 mins.... ten?

Lastly would the 100m or speaker wire act enough like a capacitor to hinder the voltage rise across the resistor that I am hoping to destroy? If so are there any solutions besides using thicker wire or just seperating the twin flex over the entire length?

I know these are a lot of questions but sensible guidance would be appreciated!

Thanks and regards!
View user's profile View All Posts By User
dann2
International Hazard
*****




Posts: 1523
Registered: 31-1-2007
Member Is Offline

Mood: No Mood

[*] posted on 29-1-2009 at 18:12


Hello,


Googleing 'exploding wires' gets some info. which may be helpful.

There is a Thesis here on exploding wires (could you believe it), all 27mB of it.
http://etd.caltech.edu/etd/available/etd-08022006-104759/unr...

When attempting fast discharges the inductance of the wires (and even the capacitor construction methods) make a difference. Photo flash caps. have low inductance to give fast discharge. Perhaps you already know that.

Dann2

Hope your not trying to blow up a car. A dude tried that over here and burned his lips on the exhaust pipe.............
View user's profile View All Posts By User
Xenoid
International Hazard
*****




Posts: 775
Registered: 14-6-2007
Location: Springs Junction, New Zealand
Member Is Offline

Mood: Comfortably Numb

[*] posted on 29-1-2009 at 18:22


Well, I have a variety of rocket motor ignition systems based on charging up photoflash capacitors and discharging them into resistors. My largest has 2 capacitor banks, each comprising 4 120uF 330V capacitors. I use one capacitor bank with a single 330 ohm 1/4 watt carbon resistor and both banks (960uF) for 2 resistors in parallel for dual ignitions.

When the full 960uF is discharged into a 100 ohm 1/4 watt resistor (not sure if it is carbon or metal) there is a crackling noise, bright flashes and the resistor bursts into flame for a few seconds. This is with the resistor connected directly across the output terminals of the ignition unit.

Contrary to expectations there is not a lot of difference between resistors in the range 1K to 100 ohms, they all burst into flame. I use 330 ohm carbon resistors because they give a reliable hot flame with 480uF without resorting to pyrolytic coatings, the carbon and paint are sufficient.

In general the resistor tends to open circuit before the capacitor fully discharges and the 200V to 300V is not enough to bridge the gap. Metal resistors are worse in this respect.

I haven't tried 1/8 watt resistors but I think you will be dissapointed if you are thinking of using them as detonators.

BTW I believe a single photoflash discharge across the chest is capable of killing someone with a weak heart, so a bank is certainly deadly! The ON/OFF switch on my units is wired so in the OFF position a 3.3 K ohm (7 watt) resistor discharges the capacitors.

My earlier ignitors used photoflash components, rewired onto stripboard but later versions use components from old portable fluorescent lights. These have more "grunt" and run off 6 volts (4AAs).

Edit: Forgot to mention I use a TYN816 (800V, 16A) SCR for triggering the discharges.
Edit: Added that 3.3K resistor is rated 7 watts - see Pantone's post below!

TAKE CARE WHEN EXPERIMENTING WITH THESE CAPACITORS - :o

[Edited on 29-1-2009 by Xenoid]

[Edited on 30-1-2009 by Xenoid]
View user's profile View All Posts By User
Twospoons
International Hazard
*****




Posts: 1209
Registered: 26-7-2004
Location: Middle Earth
Member Is Offline

Mood: A trace of hope...

[*] posted on 29-1-2009 at 19:18


Photoflash caps are definitely capable of killing you. 82J cap discharge will definitely damage you severely, will most likely kill you. I've had 25J arm to arm, and count myself lucky to still be here. It was extremely painful, left holes in my fingers, and I couldn't stop shaking for an hour. An experience I plan never to repeat.

Bleed resistor is essential! Also put a 'tell-tale' across - an LED with series resistor and series 25V zener diode, which will glow down to 26V at which point the cap can be considered safe.

Build yourself a 'chicken stick' too - a wood or plastic stick with a shorting bar or low value power resistor on the end for discharging the cap.

Again: the capacitor you have is extremely dangerous - treat it, and anything connected to it, with utmost respect.




Helicopter: "helico" -> spiral, "pter" -> with wings
View user's profile View All Posts By User
pantone159
International Hazard
*****




Posts: 572
Registered: 27-6-2006
Location: Austin, TX, USA
Member Is Offline

Mood: desperate for shade

[*] posted on 29-1-2009 at 21:21


Quote:
Originally posted by Xenoid
The ON/OFF switch on my units is wired so in the OFF position a 3.3 K ohm resistor discharges the capacitors.


Is that number right? I didn't do any analysis, but a resistance only 3.3 times something that reliably bursts into flames sounds iffy for something to slowly bleed power...
View user's profile Visit user's homepage View All Posts By User
Xenoid
International Hazard
*****




Posts: 775
Registered: 14-6-2007
Location: Springs Junction, New Zealand
Member Is Offline

Mood: Comfortably Numb

[*] posted on 29-1-2009 at 22:21


Quote:
Originally posted by pantone159

Is that number right? I didn't do any analysis, but a resistance only 3.3 times something that reliably bursts into flames sounds iffy for something to slowly bleed power...


Well I can't be bothered with the maths either! It's not a bleed resistor permanently wired across the capacitors, but a DISCHARGE resistor which is switched in when the switch is turned to OFF.

In practice the capacitor bank charges to 310 volts. The discharge resistor was just chosen by trial and error, it's actually 7 watts and discharges the capacitors to 25 volts in about 10 seconds. I should have actually used a lower value resistor, for a faster discharge, but this was on hand and it fitted into the cramped case nicely.

Remember the resistors bursting into flame are only 1/4 watt, the discharge resistor is 7 watts, 28 times the power handling, spread over about 10 seconds verses say about .1 seconds for the 1/4 watt ignitor resistor.

Incidentally, thinking about it, the reason the resistors don't explode is because they are not a solid resistance, but are very thin films around a solid ceramic core. There is so little mass of resistance involved that it just vaporises harmlessly (bursts into flame).
View user's profile View All Posts By User
pantone159
International Hazard
*****




Posts: 572
Registered: 27-6-2006
Location: Austin, TX, USA
Member Is Offline

Mood: desperate for shade

[*] posted on 29-1-2009 at 23:00


Ah, makes sense now. The OP talked of a bleed resistance but that isn't what you have. Thanks.
View user's profile Visit user's homepage View All Posts By User
chief
International Hazard
*****




Posts: 630
Registered: 19-7-2007
Member Is Offline

Mood: No Mood

[*] posted on 30-1-2009 at 05:33


450 Volts @ 10 Ohm cable gives lousy 45 A ; thats lousy, and far from violent !
Then the 100 Ohm-resistor: Alltogether only 4.5 A ... (peak); thats close to nothing ...

For violence at least maybe 1 kA is desirable, better much more ...
View user's profile View All Posts By User
hissingnoise
International Hazard
*****




Posts: 3940
Registered: 26-12-2002
Member Is Offline

Mood: Pulverulescent!

[*] posted on 30-1-2009 at 05:50


Somehow, I don't think an exploding resistor would have the force to initiate anything less sensitive than a primary.
just my tuppence worth. . .
View user's profile View All Posts By User
Deceitful_Frank
Hazard to Self
**




Posts: 82
Registered: 5-11-2005
Member Is Offline

Mood: Pensive

[*] posted on 30-1-2009 at 10:31


Thanks guys for your input. I have posted this thread on three forums and the general view seems to be that in order to get a real shock wave I need KILOvolts across the resistor which is difficult to achieve let alone hundreds of feet away without putting myself in mortal danger. And lets not forget the financial and time cost involved to realise this!

In my time I have conducted many amateur scientific experiments and have been a lapse of concentration away from instant death, even dismemberment a few times but I always try to balance the risk involved against the gains.

This 820uF 450V cap is obviously not up to the task for which it was originally intended and would just in reality be great for firing an e-match... I can do this with a photoflash cap holding a tenth the energy and I know that the penalty for failure is burnt fingers and extreme discomfort at worst. If I fuck up with this big cap I am dead. It only cost me £6 so no great financial loss.

I know to many of you this may sound like a wimpy cop-out but the cemetry is full of heroes.

I will be scrapping the exploding resister idea in favour of heating a length of nichrome wire to dull red heat in the hope of "cooking it off to DDT" Whether or not those five words mean anything to you will depend on which forum you are reading this post in but thats all academic really. I have toyed with this Idea in the past with a view to igniting a simple mx of fuel and oxidiser but this is different.

All I need to do is select the right componants to build a device that will glow the 50mm length of coiled nichrome at 100 metres. The rest would be in the lap of the gods!

[Edited on by Deceitful_Frank]
View user's profile View All Posts By User
chloric1
International Hazard
*****




Posts: 1045
Registered: 8-10-2003
Location: GroupVII of the periodic table
Member Is Offline

Mood: Stoichiometrically Balanced

[*] posted on 30-1-2009 at 11:30


What a cool thread! I will definately look into 'exploding wires" soon. I heard of this 10 years ago but never took the time to study up on it. I love some of the catchy phrases on this thread.

Quote:

Hope your not trying to blow up a car. A dude tried that over here and burned his lips on the exhaust pipe.............
LOL! priceless!:D:D


Quote:

I know to many of you this may sound like a wimpy cop-out but the cemetry is full of heroes.
So true:)

When I went to school for electronics years ago, I used to blow up electrolytics buy deliberately switching the polarity. My Instructer loved it(not). One day I brought in a cap from a television set about the size of a film canister and he said it would go off like a shotgun so I refrained from doing so. I miss those carefree days of young bachelorhood.;)

Seriously though, take care and enjoy. Heck, come to think of it, there is enough fun to be had with high voltage without the chems. Just don't build any EMP's:o:o

[Edited on 1/30/2009 by chloric1]




Fellow molecular manipulator
View user's profile View All Posts By User
hissingnoise
International Hazard
*****




Posts: 3940
Registered: 26-12-2002
Member Is Offline

Mood: Pulverulescent!

[*] posted on 30-1-2009 at 11:55


Quote:
Originally posted by Deceitful_Frank

The rules of this board prevent me from saying why I want to achieve this but I am sure many of you could figure it out.


I assumed you simply wanted to detonate a secondary without having to use a (treacherous?) primary.
The filament of a low-wattage bub grossly overloaded by a capacitor-discharge is reputedly hot enough for milliseconds to bring to detonation several (insensitive?) nitrates, e.g. EGDN and HNM.
Nobel himself said, IIRC, that this method was useful for nitro at around the time he developed the modern blasting cap.

[Edited on 30-1-2009 by hissingnoise]
View user's profile View All Posts By User
Deceitful_Frank
Hazard to Self
**




Posts: 82
Registered: 5-11-2005
Member Is Offline

Mood: Pensive

[*] posted on 30-1-2009 at 12:53


Indeed, though 500mg of recrystalized ETN was more what I had in mind. Apparently it can cook off nicely to detonation if heated over 250 celcius. This would need more than a short pulse of energy though I think.
View user's profile View All Posts By User
hissingnoise
International Hazard
*****




Posts: 3940
Registered: 26-12-2002
Member Is Offline

Mood: Pulverulescent!

[*] posted on 30-1-2009 at 13:30


Quote:
Originally posted by chloric1

Quote:

Hope your not trying to blow up a car. A dude tried that over here and burned his lips on the exhaust pipe.............
LOL! priceless!:D:D


I laughed too, chloric 1---that is, after the second reading.
It reminded me of the old joke about the hedonistic IRA "operative" and his visit to a UK brothel to practice the "fun" way of blowing up English cunts.
But I digress---Deceitful_Frank, have you thought about stepping up cap discharge-voltage through a trans just enough so that a hot discharge ~1 mm long could be made within a small quantity of finely powdered ETN or HNM using the detonator body as one terminal.
View user's profile View All Posts By User
hissingnoise
International Hazard
*****




Posts: 3940
Registered: 26-12-2002
Member Is Offline

Mood: Pulverulescent!

[*] posted on 30-1-2009 at 14:55


Quote:
Originally posted by Deceitful_Frank
Apparently it can cook off nicely to detonation if heated over 250 celcius.


A fusing tungsten wire filament reaches nearly 3500*C, but I don't know what metal Nobel used; lightbulbs were but a gleam in Edison's eye at the time.
Davis has described HNM as an almost primary explosive, since it can detonate by the heat of a match-flame.
View user's profile View All Posts By User
dann2
International Hazard
*****




Posts: 1523
Registered: 31-1-2007
Member Is Offline

Mood: No Mood

[*] posted on 30-1-2009 at 16:13


Hello,


Check this out, good reading on exploding wires.
http://www.teledynerisi.com/0products/8td/page03.html

Patent here on exploding foil + 'flyer' as a detonator.
It uses a 'slapper' capacitor,,,,,,,, LOL

http://www.patentstorm.us/patents/6752083/description.html
and here:
http://en.wikipedia.org/wiki/Exploding-bridgewire_detonator
slapper detonator,,,,,,LOL

The guys working on can crushers etc are big into very fast discharge capacitors.
The need for 100 meters of cable in you application rules out fast discharge (at least fast in the sence that these guys speak of).
Can you consider putting the capacator at the business end of the wire? All the advantages of using fast discharge capacators and then running the current pulse through 100m of wire gets lost because of the wire inductance (slows/spreads out the current pusle).
Can crusher stuff:
http://tesladownunder.com/CanCrushing.htm
+ capacitor banks:
http://www.amasci.com/amateur/capexpt.html





Dann2
View user's profile View All Posts By User
chief
International Hazard
*****




Posts: 630
Registered: 19-7-2007
Member Is Offline

Mood: No Mood

[*] posted on 30-1-2009 at 18:35


I have an idea for you, maybe its good:
==> put the to-be-exploded wire in place, and use 2 small 0.20$-capacitors (or less), rated for maybe 500 V;
==> each such capacitor withstands several kV, at least _once_, one is gonna fail first
==> these are paralleled, charged via 100kOhm resistors (on both connections, the resistors close to the capacitors (few cm))
==> so the paralleled capacitors are isolated (100 kOhm from the charging-circuit);
=============
Now: Since one of them is gonna fail first, it will provide path for the charge of the other one too; inside this path the to-be-exploded wire is placed (a thin one, with these small capacitors), and voila: There you have the multi-kA-discharge; inspiration from the design of nitrogen-lasers ...

Of course it's understood that out of each such experiment you will have only one capacitor left of 2 ... ; also: Everything soldered, short and relatively thick wires, everything compact ... for low inductance ...

Use NO electrolytics, because these don't stand much more than the rated voltage !
Maybe you want to use a small glass-diode instead of the wire - such a one may explode violently, because the housing provides some initial inclusion for the plasma; maybe 2 diodes reverse-reverse, so that at least one is in reverse when the capacitor failes, might be more violent ...

Remeber: Energy of capacitor is (capacitance/2) * voltage(squared) ; this makes up for the low capacitance of non-electrolytics: Double voltage == 4 times the energy; but instead of 500 V you may charge such a one to 3 kV or more, before it failes; also the higher voltage provides a much faster path through the circuit, contributing to a much higher peak-power of the discharge too ...

[Edited on 30-1-2009 by chief]
View user's profile View All Posts By User
Xenoid
International Hazard
*****




Posts: 775
Registered: 14-6-2007
Location: Springs Junction, New Zealand
Member Is Offline

Mood: Comfortably Numb

[*] posted on 30-1-2009 at 19:53


Hmmm... I just tried a few small diodes with my rocket motor ignition system, with little effect. Tests used all 8 capacitors and were through about 20 metres of cable about half of which was still on the spool.

A red LED produced a sharp "crack" sound and when examined was still intact but slightly blackened and fractured internally.

A small signal glass encapsulated Si diode (1N4148) produced no visible or audible effect, but when tested was found to be open circuited (needless to say).

An old "point junction" signal diode (not sure if Ge or Si, but has wiggly wire inside and glass encapsulated) produced a bright flash but the glass capsule remained intact.

These low voltages (300V) just don't cut it, I guess the initial current surge open circuits the diode, by which time the voltage has dropped to say 200 - 250 volts and is then incapable of bridging the gap and most of the capacitors energy goes unused!
View user's profile View All Posts By User
Mr. Wizard
International Hazard
*****




Posts: 1040
Registered: 30-3-2003
Member Is Offline

Mood: No Mood

[*] posted on 30-1-2009 at 21:15


You won't get the sudden pop you are hoping for. The big advantage to a large cap is the sudden surge of current with almost no resistance in the source (the cap). By putting 100 meters of wire in the circuit you add in lots of inductance which will slow down the sudden surge you want. The normal DC resistance of the circuit will be significant too when you try to get that high amperage surge. In an ideal situation, your resistor or exploding item will have the same impedance as the line circuit that is feeding it. If you recall the old 300 ohm TV antenna line, it works the same way. If you imagined a pair of wires stretching to infinity and hooked a battery up to them, it would appear to flow current as if it had a 300 ohm impedance. If you used a 300 ohm resistor and a 300 ohm source you would get maximum energy transfer. If you don't, the heat will be dissipated in the mismatched items. You want a pulse, (bang) but what you'll end up with with all that stray inductance is drawn out surge.(whimper).

Maybe somebody that knows more about this than me can explain it better.
View user's profile View All Posts By User
woelen
Super Administrator
*********




Posts: 7805
Registered: 20-8-2005
Location: Netherlands
Member Is Offline

Mood: interested

[*] posted on 1-2-2009 at 01:55


A real explosion cannot be obtained with just a few hundreds of volts. I use the following type of caps for that kind of experiments.

Having a capacitor in my hand:




A capacitor near a standard 300 ml bottle of beer:




This beasts can be charged up to 5000 V (they survive 7500 volts, but it is recommended not to go beyond 5000 V) and their capacity is 40 uF. This makes up for 500 J per capacitor at 5000 V. I have three of them. One such capacitor has a weight of 5 kg.

I must say, that experimenting with these things is very scary, much more so than even the weirdest chemical experiments I have done. One mistake and you're dead, so the last year I hardly did any experiments with high voltages anymore (my wife does not like it at all, actually she really dislikes it and wants me to sell ALL of my HV-related stuff, she has no problems with my chemistry-related acitvities, even better she likes many aspects of it).

Personally I think that very high voltage experimenting (kilovolts) is much more dangerous than chemistry, even when working with stuff like SOCl2, oleum, conc. HNO3 etc. The only exception may be working with pyrotechnics in large quantities, but that is not something I do. Making mistakes in HV-experimenting is fatal!

[Edited on 1-2-09 by woelen]




The art of wondering makes life worth living...
Want to wonder? Look at https://woelen.homescience.net
View user's profile Visit user's homepage View All Posts By User
Mr. Wizard
International Hazard
*****




Posts: 1040
Registered: 30-3-2003
Member Is Offline

Mood: No Mood

[*] posted on 1-2-2009 at 07:46


woelen, I notice from the picture you don't have a shorting wire across those cap terminals. Short them out with a conductor and then leave them stored with a nice wrap of wire around the terminals. These caps can 'reform' a charge after being discharged and when this size can pack a big surprise. Short them out, and put a wire across the connectors when storing them. You may have taken the wire off for the photograph, but people should realize the danger with 'uncharged caps'.
View user's profile View All Posts By User
chemoleo
Biochemicus Energeticus
*****




Posts: 3005
Registered: 23-7-2003
Location: England Germany
Member Is Offline

Mood: crystalline

[*] posted on 1-2-2009 at 08:48


Well many years ago, I paralleled the big capacitors form several old discarded TVs - each had a 500V rating IIRC, and each was as about 3 cm thick and 8 cm high. There were charged to that voltage or higher. I was only able to shortcircuit them a dozen times or so, then they died (no charging possible anymore). But short-circuiting them caused the copper wire in the vicinity of the contact region to vaporise, in a loud bluewhite flash :o

In those care-free days I simply had two insulating pliers, gripped the wires and induced contact that way. But I knew the pliers were safe with 16 kV too, so no fear of short-circuiting through the body :o




Never Stop to Begin, and Never Begin to Stop...
Tolerance is good. But not with the intolerant! (Wilhelm Busch)
View user's profile View All Posts By User
Sedit
International Hazard
*****




Posts: 1939
Registered: 23-11-2008
Member Is Offline

Mood: Manic Expressive

[*] posted on 1-2-2009 at 10:10


Quote:
But I knew the pliers were safe with 16 kV too, so no fear of short-circuiting through the body



If I had a nickle ever time I got zaped thinking that:D
Hell iv gotten so use to it Ill grab an OBIT on a bet now and not have it bother me at all.

Small amounts of RF will slowly degrade the insulation on the pliers and all it takes is a pin hole to ruin your whole day.
Always dischage with a sissy stick, just a nail or something conductive on the end of a stick or better yet a small pice of PVC. Sure beats the alternative when working with a cap that big. You probly wont get a second chance to get it right.
View user's profile View All Posts By User
chief
International Hazard
*****




Posts: 630
Registered: 19-7-2007
Member Is Offline

Mood: No Mood

[*] posted on 1-2-2009 at 23:01


I have 2 capacitors of triple the size of above, each , sice they are for 3 phases. Label says: 40 kVar, isolation voltage 3/15 kV ...
I suspect the 15 kV is towards ground ; once I loaded one of these, don't know the voltage, but below 3 kV: When I shorted it (throwing) aluminum foil onto it and quickly turning away, while the foil was still in the air, it gave such a loud bang, that my ears were ringing ... Probably the loudest thing I ever heard, and I was glad my eardrums survived ...

Such a thing has an energy expressable in grams of TNT, and it unloads even faster ...

Wear ear-protection ! Also parts of metal (wire) may be accelerated to dangerous velocities, so eye-protection is a must too.

One idea: Maybe such capacitors could be used for shockwave-experimentation: One would get around the explosives, by just vaporizing calculated amounts of stuff (1 drop of water-electrolyte, eg., some metal-powder ...) ; so it would be no legal offense (evidently such a capacitor is not a terrorist threat)

Also these big ones, used for storing the energy of whole factories over a 50Hz-halfcycle, should withstand some abuse; within is oil as insulator, so the dielectric is ever-fresh

[Edited on 1-2-2009 by chief]

[Edited on 1-2-2009 by chief]

[Edited on 1-2-2009 by chief]
View user's profile View All Posts By User
Mr. Wizard
International Hazard
*****




Posts: 1040
Registered: 30-3-2003
Member Is Offline

Mood: No Mood

[*] posted on 2-2-2009 at 08:57


"One idea: Maybe such capacitors could be used for shockwave-experimentation: One would get around the explosives, by just vaporizing calculated amounts of stuff (1 drop of water-electrolyte, eg., some metal-powder ...) ; so it would be no legal offense (evidently such a capacitor is not a terrorist threat)

Also these big ones, used for storing the energy of whole factories over a 50Hz-halfcycle, should withstand some abuse; within is oil as insulator, so the dielectric is ever-fresh"

The fact that the cap was used in a big plant to keep the phase angle correct and is oil filled (PCBs ?) is not a safe guide for using it in capacitive discharge applications. The capacitor was made , according to your description, to adjust 50Hz the power factor, which means it would take 1/100th of a second to charge or discharge it's current. This is an eternity compared to the microseconds it takes for some caps to discharge. The faster the discharge, the higher the current, and the higher the magnetic field and mechanical stress. These currents can 'shrink' a conductive coin by the induced magnetic field alone. Imagine the forces placed upon the conductors inside the can!!! Did the designer of the cap plan for this? I seriously doubt they did, unless they were designing the cap for capacitive discharge applications. If they were planning for sudden discharges they would build them a lot stronger and not in a flimsy metal can with oil that will spray over everything in the event of a failure.

I'm not saying not to do it, but realize the cap may decide to become 'the weakest link', and 'roll the darwinian dice' for you. Plan ahead, keep the cap away from you during any discharges, separated by a solid barrier. Plan on how you would clean up an oily mess if the cap 'lets go'. Cat litter does a great job of soaking up oil. Does the cap contain PCBs? You don't want to turn you lab, bedroom, or shop into a haz-mat situation. If you can get to any of the oil in the cap, either through a leak or a hole drilled in the can, put some on a piece of copper wire that you have burned clean in a blue flame of an alcohol or gas flame. A green flame is an indication of halogens when copper is in a flame. It is very sensitive, and will even pick up freon or any halogenated organics. Halogenated oils = PCBs.

I don't mean to be a wet blanket to the fun, but just think ahead a bit and plan for the unintended.
View user's profile View All Posts By User
 Pages:  1  

  Go To Top