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'[EE]: Polarity of electronic capacitor when using '
2005\12\22@203622 by

In doing my brushing up on electronics, I am at the point of putting
together a breadboard circuit (this is in a " do it yourself" course).
A friend loaned me a scope, and I am supposed to check the action of the
circuit, and see if it behaves the way the mathematics says it is
supposed to behave.  .

Only thing is, I have read some postings recently where tantalum
capacitors were exploding because of the wrong polarity, and I am
feeling a little bit insecure in what I am doing.  :-(

I have an operational amplifier (op amp) breadboarded up, with +12 volts
and -12 volts.  Each leg of the voltage has a 10 microfarad electrolytic
capacitor going to ground.  On the +12 volts side, I have the minus side
of the capacitor going toward ground.  On the -12 volts side, I have the
plus side of the capacitor going to ground, since ground in this case is
more positive than the -12 volts.

But I worry that I may not be understanding something here, although it
seems right.  Lord knows I don't need any capacitors exploding in the
bedroom!  I would be banished to the basement, at best.

Thanks,
Bill
> A friend loaned me a scope, and I am supposed to check the action of the
> circuit, and see if it behaves the way the mathematics says it is
> supposed to behave.

Of course, the answer is always no ;-)

>
> I have an operational amplifier (op amp) breadboarded up, with +12 volts
> and -12 volts.  Each leg of the voltage has a 10 microfarad electrolytic
> capacitor going to ground.  On the +12 volts side, I have the minus side
> of the capacitor going toward ground.  On the -12 volts side, I have the
> plus side of the capacitor going to ground, since ground in this case is
> more positive than the -12 volts.

That's correct.

Neil
--
http://www.pixpopuli.com

On 12/22/05, Bill Kuncicky <kuncickygmail.com> wrote:
>
> But I worry that I may not be understanding something here, although it
> seems right.  Lord knows I don't need any capacitors exploding in the
> bedroom!  I would be banished to the basement, at best.
>

In my experience, ordinary electrolytics aren't as dramatic as
tantalums when they go.  The vent just opens and they sneeze out the
electrolyte.  A fizzle, not a bang.

Regards,
Mark
markrages@gmail
-
You think that it is a secret, but it never has been one.

>
>
> In my experience, ordinary electrolytics aren't as dramatic as
> tantalums when they go.  The vent just opens and they sneeze out the
> electrolyte.  A fizzle, not a bang.

Yeah, they've improved them.. They used to throw aluminum case and guts all
over the place if properly abused.
At 11:00 AM 12/23/2005 -0500, you wrote:
> >
> >
> > In my experience, ordinary electrolytics aren't as dramatic as
> > tantalums when they go.  The vent just opens and they sneeze out the
> > electrolyte.  A fizzle, not a bang.
>
>
>Yeah, they've improved them.. They used to throw aluminum case and guts all
>over the place if properly abused.

I think only large ones have a vent- the small ones will probably still
blow up good.

>Best regards,

Spehro Pefhany --"it's the network..."            "The Journey is the reward"
speffinterlog.com             Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog  Info for designers:  http://www.speff.com
->> Inexpensive test equipment & parts http://search.ebay.com/_W0QQsassZspeff

On 12/23/05, Spehro Pefhany <speffinterlog.com> wrote:
> At 11:00 AM 12/23/2005 -0500, you wrote:
> > >
> > >
> > > In my experience, ordinary electrolytics aren't as dramatic as
> > > tantalums when they go.  The vent just opens and they sneeze out the
> > > electrolyte.  A fizzle, not a bang.
> >
> >
> >Yeah, they've improved them.. They used to throw aluminum case and guts all
> >over the place if properly abused.
>
> I think only large ones have a vent- the small ones will probably still
> blow up good.
>

Hmm. I think I will have to do the experiment.

Regards,
Mark
markrages@gmail
--
You think that it is a secret, but it never has been one.

On 12/23/05, Spehro Pefhany <speffinterlog.com> wrote:
> At 11:00 AM 12/23/2005 -0500, you wrote:
> > >
> > >
> > > In my experience, ordinary electrolytics aren't as dramatic as
> > > tantalums when they go.  The vent just opens and they sneeze out the
> > > electrolyte.  A fizzle, not a bang.
> >
> >
> >Yeah, they've improved them.. They used to throw aluminum case and guts all
> >over the place if properly abused.
>
> I think only large ones have a vent- the small ones will probably still
> blow up good.

In the 70's we had a computer room (remember them? :-) which had automatic CO2 extinguishing equipment, and
one night a large capacitor (think bean-can size) exploded, and took out the terminal rack it was powering,
frightening the operators, and creating a small cloud of smoke.  Everyone left the room except the shift
leader who rang the operations manager to tell him bout it.  A minute into the conversation it went something
like: "What's that bell ringing?"  "I've no idea, perhaps..." "WHOOOOOOOOSH!  Thump, Crash!"

The bell was the fire system saying that it had detected smoke and was about to trip the extinguishing system.
The Whoosh was the room being filled with CO2 *really* fast, the thump and crash was the operator dropping the
phone, vaulting the handrail that divided off the ramp from the raised floor down to the door, plus opening
the door with his body's momentum!  :-)

There was no actual fire, just the smoke from the demised cap, but apparently the sprayed electrolyte and can
shrapnel was enough to write off the 6U-high PSU and some of the equipment above it, so that plus the lost
computer time and refilling 8 CO2 tanks made it a very expensive capacitor!

Those were the days...

Merry Christmas!

Howard Winter
St.Albans, England

Howard,

I remember the days of a control room where I used to work
back around 1970.  Though I didn't work in the Ctrl Rm I had
frequent occasion to visit it.  From your excellent description
I can picture the whole sequence of events.  I laughed so hard
that you started my day beautifully.  In fact I called my wife
so hard.  She doesn't know what an electrolytic is, but she got
a good laugh from the whole story.  She worked there also.
It's great to reminisce once in a while.  Preserve the great
memory's.

Tom

Howard Winter <HDRWH2Org.demon.co.uk> wrote:
On 12/23/05, Spehro Pefhany wrote:
{Quote hidden}

In the 70's we had a computer room (remember them? :-) which had automatic CO2 extinguishing equipment, and
one night a large capacitor (think bean-can size) exploded, and took out the terminal rack it was powering,
frightening the operators, and creating a small cloud of smoke. Everyone left the room except the shift
leader who rang the operations manager to tell him bout it. A minute into the conversation it went something
like: "What's that bell ringing?" "I've no idea, perhaps..." "WHOOOOOOOOSH! Thump, Crash!"

The bell was the fire system saying that it had detected smoke and was about to trip the extinguishing system.
The Whoosh was the room being filled with CO2 *really* fast, the thump and crash was the operator dropping the
phone, vaulting the handrail that divided off the ramp from the raised floor down to the door, plus opening
the door with his body's momentum! :-)

There was no actual fire, just the smoke from the demised cap, but apparently the sprayed electrolyte and can
shrapnel was enough to write off the 6U-high PSU and some of the equipment above it, so that plus the lost
computer time and refilling 8 CO2 tanks made it a very expensive capacitor!

Those were the days...

Merry Christmas!

Howard Winter
St.Albans, England

Tom Wrighton wrote:
> Howard,
>
>   I remember the days of a control room where I used to work
>   back around 1970.  Though I didn't work in the Ctrl Rm I had
>   frequent occasion to visit it.
Those are nostalgic memories, for sure.  Everyone carrying "IBM" cards
around in their shirt pocket.  We had an IBM 709 vacuum-tube machine,
and whenever we had a power failure the computer operators (who were
students) had to dash madly around the computer-room to pull the panels
off the memory because without air-conditioning the tubes would overheat
and a lot of them would fail.  This would cause a lot of excitement,
because since we had a power failure, there were no lights except for
the glow from the tubes which were fast cooling off.  Even in those days
(early 1960's) the university was an "equal opportunity employer," so we
had both male and female student operators.  Made for a lot of fun,
dashing around in the dark.  :-)

About the same time frame I recall an instance where an electrolytic about
the same size "poofed" in the night. There was only one operator on duty and
his reaction was to get out and call security because the only symptom was
that a door on a tape control unit sprang open with no one around. Of course
there was the crash of the door flinging open. As it worked it was one of a
dozen or so caps in parallel and the system never hiccupped!

John Ferrell
http://DixieNC.US

{Original Message removed}

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