Electrolytic cap in high-discharge application

[Pimpom]

I'm thinking of making a strobe light using a Xenon tube from an
old camera flashgun (tube type unknown). Tentative scheme:
The strobe will fire 4 or 5 times at ~2Hz and then given a rest
for a minute or so before the next cycle. It is to be used for a
few hours at that duty cycle, but only for one day, and then
stored for months until the next time.

I'm thinking of charging the storage cap (maybe 220uF) to perhaps
300-400V from a 12V car battery via a dc-dc converter. I don't
want to go to the trouble of getting some special super-duper
cap - unlikely I can get a specific type here anyway. My question
is: If I use a run-of-the-mill electrolytic, the kind that's used
as a main dc filter in consumer products such as a CRT TV, how is
it likely to fare under the said conditions?

 

[Joerg]

I'm thinking of making a strobe light using a Xenon tube from an
old camera flashgun (tube type unknown). Tentative scheme:
The strobe will fire 4 or 5 times at ~2Hz and then given a rest
for a minute or so before the next cycle. It is to be used for a
few hours at that duty cycle, but only for one day, and then
stored for months until the next time.

I'm thinking of charging the storage cap (maybe 220uF) to perhaps
300-400V from a 12V car battery via a dc-dc converter. I don't
want to go to the trouble of getting some special super-duper
cap - unlikely I can get a specific type here anyway. My question
is: If I use a run-of-the-mill electrolytic, the kind that's used
as a main dc filter in consumer products such as a CRT TV, how is
it likely to fare under the said conditions?

It might not like the peak current. Flash capacitors aren't that
super-duper expensive:

http://www.allelectronics.com/make-a-store/item/PPC-273/PHOTO-FLASH-CAPACITOR-270UF-330WV/1.html

Not sure if you guys in India still use film cameras. In the US there
used to be these disposable cameras where you could take xx photos, then
give the whole camera to a processing place. Which was usually located
inside a drugstore. The cameras were collected in a box there and
(hopefully) recycled. Some people were able to get some of those if they
knew the folks behind the counter well enough. The motivation was often
to pry out that photo-flash capacitor for free

 

[Pimpom]

It might not like the peak current.

That's what I'm afraid of.

Flash capacitors aren't that
super-duper expensive:

http://www.allelectronics.com/make-a-store/item/PPC-273/PHOTO-FLASH-CAPACITOR-270UF-330WV/1.html

That's a steal at $1 but alas, there's no way I can order it from
here. It's not the price I'm concerned about. It's finding a
source. It's not just that I'm in India, I'm in a remote corner
of the country. Indian companies ignore emails 9 times out of 10.
If I call them, they're likely to say "Yes sir, we have just what
you want" and then send the wrong one or simply ignore the order.
:-(

Not sure if you guys in India still use film cameras.

The ratio of die-hard film users to digitals is probably roughly
the same here as in the US.

In the US there
used to be these disposable cameras where you could take xx
photos,
then give the whole camera to a processing place. Which was
usually
located inside a drugstore. The cameras were collected in a box
there
and (hopefully) recycled. Some people were able to get some of
those
if they knew the folks behind the counter well enough. The
motivation
was often to pry out that photo-flash capacitor for free

I've heard about those disposable cameras, but I don't think it
caught on in India - if, indeed, they were introduced at all.

 

[Oppie]

I'm thinking of making a strobe light using a Xenon tube from an old
camera flashgun (tube type unknown). Tentative scheme:
The strobe will fire 4 or 5 times at ~2Hz and then given a rest for a
minute or so before the next cycle. It is to be used for a few hours at
that duty cycle, but only for one day, and then stored for months until
the next time.

I'm thinking of charging the storage cap (maybe 220uF) to perhaps 300-400V
from a 12V car battery via a dc-dc converter. I don't want to go to the
trouble of getting some special super-duper cap - unlikely I can get a
specific type here anyway. My question is: If I use a run-of-the-mill
electrolytic, the kind that's used as a main dc filter in consumer
products such as a CRT TV, how is it likely to fare under the said
conditions?

Capacitors made for the purpose are marked 'photoflash'. Reason is that a
xenon strobe is much akin to short circuiting the fully charged capacitor. A
VERY high current flows while the stored energy is dissipated in about a
microsecond or so. Good for making a plasma in the strobe tube but just as
likely to make a loud noise (and smoke) if the cap isn't up to the task. You
can add a series inductance to the discharge circuit to widen the discharge
time and moderate current rise - air core recommended.
Make sure that you don't exceed the limits of the strobe tube. Too much
energy on each flash and too high a flash rate can kill the tube from
over-temperature.

 

[Phil Allison]

"Pimpom"

I'm thinking of making a strobe light using a Xenon tube from an old
camera flashgun (tube type unknown). Tentative scheme:
The strobe will fire 4 or 5 times at ~2Hz and then given a rest for a
minute or so before the next cycle. It is to be used for a few hours at
that duty cycle, but only for one day, and then stored for months until
the next time.

I'm thinking of charging the storage cap (maybe 220uF) to perhaps 300-400V
from a 12V car battery via a dc-dc converter.

** Kiss goodbye to that Xenon tube real fast.

There is a reason why camera lashes take a few seconds between each full
power discharge.


..... Phil

 

[Pimpom]

"Pimpom"


** Kiss goodbye to that Xenon tube real fast.

There is a reason why camera lashes take a few seconds between
each
full power discharge.

Yes, I've had second thoughts about the frequency-energy
combination I first proposed. Maybe ~1Hz with a smaller cap.
However, I'd say that the cycling times of camera flashes have as
much to do with charging limitations as with the need to protect
the tube. Some flashguns are rated to fire several times a
second.

 

[Joerg]

Yes, I've had second thoughts about the frequency-energy
combination I first proposed. Maybe ~1Hz with a smaller cap.
However, I'd say that the cycling times of camera flashes have as
much to do with charging limitations as with the need to protect
the tube. Some flashguns are rated to fire several times a
second.

But they'll sure use bigger tubes, just like the strobes above a fancy
disco dance floor do. My camera also lets off several flashes in one
second but the first ones are of limited energy.

 

[Spehro Pefhany]

But they'll sure use bigger tubes, just like the strobes above a fancy
disco dance floor do. My camera also lets off several flashes in one
second but the first ones are of limited energy.

Wow, best stay away from the later ones. ;-)

 

[Phil Allison]

"Pimpom"

However, I'd say that the cycling times of camera flashes have as much to
do with charging limitations as with the need to protect the tube.

** If you own opinions are all you need then why come here at all ??

Some flashguns are rated to fire several times a second.

** 5 very short flashes (hence low energy) all supplied off one cap charge.



..... Phil

 

[Pimpom]

The lifetime of the bulb will depend on the ratio of the flash
energy
to the explosion energy of the flashlamp. (That's how lamps
are
specified, believe it or not.)

If you stay below about 10% of the explosion energy, you should
get at
least a million shots. Start with a cap about a quarter of
the size
of the one in the flash.

As Phil A points out, you also have to keep the tube reasonably
cool.

Good points. Thanks. I doubt this unit will have to go through
much more than 1000 flashes before it's discarded and replaced
with something else. It's to be a temporary solution that's
unlikely to be used for more than a couple of years at the rate
of perhaps 10-20 flashing sequences an hour, 3-4 hours a day, 1
or 2 days a year.

 

[Pimpom]

"Pimpom"

** If you own opinions are all you need then why come here at
all ??

My original question was about the capacitor. Which is not to say
that an expansion of the topic is not admissible, but that does
not mean that the OP of a thread is under obligation to treat
each reply as gospel.

 

[Phil Allison]

"Oppie

Capacitors made for the purpose are marked 'photoflash'.

** No fooling ......

Reason is that a xenon strobe is much akin to short circuiting the fully
charged capacitor. A VERY high current flows while the stored energy is
dissipated in about a microsecond or so.

** In reality, it's more like a couple of milliseconds.

Good for making a plasma in the strobe tube but just as likely to make a
loud noise (and smoke) if the cap isn't up to the task.

** Electros do not come to any harm by being shorted or suddenly dumping
into a flash tube.

The only thing that harms electros is getting too hot - which could happen
in a strobe flashing rapidly for long periods.

Ones rated for camera flash use have low ESRs and long life expectations -
low ESR electros are almost the norm these days.

Make sure that you don't exceed the limits of the strobe tube. Too much
energy on each flash and too high a flash rate can kill the tube from
over-temperature.

** That is the big worry with the OP's crackpot scheme.


..... Phil

 

[Phil Allison]

"Pimpompous"

My original question was about the capacitor.

** Red herring.

Which is not to say that an expansion of the topic is not admissible,

** Obfuscation.

but that does not mean that the OP of a thread is under obligation to
treat each reply as gospel.

** Straw man.

Go look the terms up if you have no clue what they refer to.

Dickhead.


...... Phil

 

[mike]

I'm thinking of making a strobe light using a Xenon tube from an
old camera flashgun (tube type unknown). Tentative scheme:
The strobe will fire 4 or 5 times at ~2Hz and then given a rest
for a minute or so before the next cycle. It is to be used for a
few hours at that duty cycle, but only for one day, and then
stored for months until the next time.

I'm thinking of charging the storage cap (maybe 220uF) to perhaps
300-400V from a 12V car battery via a dc-dc converter. I don't
want to go to the trouble of getting some special super-duper
cap - unlikely I can get a specific type here anyway. My question
is: If I use a run-of-the-mill electrolytic, the kind that's used
as a main dc filter in consumer products such as a CRT TV, how is
it likely to fare under the said conditions?

Have you done the math?
According to the back of my "envelope", your biggest problem might be
charging the cap in the half second between flashes.

Here in the states, you can buy used one-time-use cameras with
flash and good batteries for 20-cents each.
If I were doing this, I'd mount 5 flashes side by side,
charge 'em with a 3V supply and fire 'em sequentially.

 

[Pimpom]

"Pimpompous"


** Red herring.


** Obfuscation.


** Straw man.

Go look the terms up if you have no clue what they refer to.

Dickhead.


..... Phil

Whew! That's a relief. For a moment there, I thought you were
losing your touch.

BTW, I'm quite familiar with those terms. Though, as a non-native
user of English, I'm not as fluent in _using_ colloquial terms as
in understanding them.

 

[Phil Allison]

"mike"

Here in the states, you can buy used one-time-use cameras with
flash and good batteries for 20-cents each.
If I were doing this, I'd mount 5 flashes side by side,
charge 'em with a 3V supply and fire 'em sequentially.

** That is what I call a " plan " ...

BTW

I once made myself a simple "ring flash" by mounting 3 such units around a
hole in a piece of cardboard.

The hole was just big enough to poke my SLR camera lens through and the
whole kaboodle hung onto the lens using a large electro capacitor mounting
bracket.

Fired simultaneously, it worked like a charm for taking close up shots of
small items.


.... Phil

 

[Phil Allison]

"Pimpompous"

Whew! That's a relief. For a moment there, I thought you were losing your
touch.

** **** you.

BTW, I'm quite familiar with those terms.

** Sure - they are your stock in trade.

Though, as a non-native user of English, I'm not as fluent in _using_
colloquial terms as in understanding them.

** The terms "straw man" & "red herring" are hardly colloquialisms.

Piss head.


.... Phil

 

[Pimpom]

Have you done the math?
According to the back of my "envelope", your biggest problem
might be
charging the cap in the half second between flashes.

Sort of done the math, in my head. I thought I'd build a fairly
beefy dc converter to do the job, powered by a car battery. The
cap charging current to be limited by a resistor on the
high-voltage side.

Here in the states, you can buy used one-time-use cameras with
flash and good batteries for 20-cents each.
If I were doing this, I'd mount 5 flashes side by side,
charge 'em with a 3V supply and fire 'em sequentially.

Thanks. That would be a good idea except that I have no source of
cheap used cameras and flashes here. Not even at $20 a pop.

 

[amdx]

"mike"


** That is what I call a " plan " ...

BTW

I once made myself a simple "ring flash" by mounting 3 such units around
a hole in a piece of cardboard.

The hole was just big enough to poke my SLR camera lens through and the
whole kaboodle hung onto the lens using a large electro capacitor mounting
bracket.

Fired simultaneously, it worked like a charm for taking close up shots of
small items.


... Phil

Phil did you mainline those meds? This last post seemed, well.... normal.
Mikek

 

[Pimpom]

A capacitor that size, at 300V, stores a lot of energy; do you
need it, when it'll flash again in just a fraction of a second?
It might be better to use an autotransformer-wired flyback
coil (like an auto ignition coil) fed direct from the 12V
source.

Thanks for the suggestion, but will it work that way? The reason
why I wanted a powerful flash is that it has to be clearly
noticeable from a distance of 400m, in broad daylight by people
who are looking in the general direction but not concentrating on
the light. It's to signal a moment in a sporting event.