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Plastic capacitor for camera flash tube?

D

Dontspam

Jan 1, 1970
0
I'd like to experiment with a camera flash tube but cannot easily
obtain a proper photoflash capacitor, not even one from an old
flash gun. It's not for photography and I need only a fairly low
flash energy - a few microfarads worth, and the interval between
flashes will generally be minutes, although it may occasionally
be as short as 10 seconds. Will a plastic capacitor - like MKP or
MKT type - be suitable? If so, will an AC x2 cap be more suitable
than a DC cap? Thanks in advance.
 
B

Baron

Jan 1, 1970
0
Dontspam Inscribed thus:
I'd like to experiment with a camera flash tube but cannot easily
obtain a proper photoflash capacitor, not even one from an old
flash gun. It's not for photography and I need only a fairly low
flash energy - a few microfarads worth, and the interval between
flashes will generally be minutes, although it may occasionally
be as short as 10 seconds. Will a plastic capacitor - like MKP or
MKT type - be suitable? If so, will an AC x2 cap be more suitable
than a DC cap? Thanks in advance.

Go grab a used disposable camera ! If you ask one of the D&P shops
nicely they might give you one for free to play with.
 
D

Dontspam

Jan 1, 1970
0
Baron said:
Dontspam Inscribed thus:


Go grab a used disposable camera ! If you ask one of the D&P
shops
nicely they might give you one for free to play with.

Unfortunately, I don't live in a place where they give, sell or
rent out disposable cameras. But you've given me an idea. I'll
see if I can get my hands on an old box film camera with a flash.
In any case, I'd still like to know if plastic capacitors are
suitable for the purpose.
 
C

Cydrome Leader

Jan 1, 1970
0
Dontspam said:
Unfortunately, I don't live in a place where they give, sell or
rent out disposable cameras. But you've given me an idea. I'll

where are you located?

see if I can get my hands on an old box film camera with a flash.
In any case, I'd still like to know if plastic capacitors are
suitable for the purpose.

in short, no. they're too small, unless you can get some giant film caps
in metal cans. Giant means you need two hands to lift and carry the thing.
 
D

Dontspam

Jan 1, 1970
0
John said:
---
If you're just fooling around, any old thing you stick in there
which
will stand off the charge voltage and not blow up the flash
tube will
work.

Is there anything special about your experiments which would
dictate
the choice of capacitor?

I don't have any specific application for it at the moment but
may do so in the future. A few years ago, I built a unit with
ordinary Al caps for charge storage and the result was
disappointing, though not really unexpected.

I suppose I could just go ahead and set up another one except for
a couple of things: 1. I can't think of a simple method of
measuring or estimating the efficiency of the output. The
efficiency may be important for some future application and is
also of academic interest to me. 2. I'd like to have some prior
idea of how well the capacitor will stand up to repeated
high-current discharges.
 
C

Charles

Jan 1, 1970
0
I suppose I could just go ahead and set up another one except for
a couple of things: 1. I can't think of a simple method of
measuring or estimating the efficiency of the output. The
efficiency may be important for some future application and is
also of academic interest to me. 2. I'd like to have some prior
idea of how well the capacitor will stand up to repeated
high-current discharges.

As to measuring output energy, a high-speed op-amp integrator might work.
Use an appropriate voltage divider and current sensor and it might be
doable.

I guess it depends on how serious you are about your efficiency
investigation.
 
P

Phil Allison

Jan 1, 1970
0
"Dontspam"
I'd like to experiment with a camera flash tube but cannot easily obtain a
proper photoflash capacitor, not even one from an old flash gun. It's not
for photography and I need only a fairly low flash energy - a few
microfarads worth, and the interval between flashes will generally be
minutes, although it may occasionally be as short as 10 seconds. Will a
plastic capacitor - like MKP or MKT type - be suitable?

** Yep, they will work fine.
If so, will an AC x2 cap be more suitable than a DC cap?

** X2 caps are regularly used in party strobes etc.


.... Phil
 
D

Dontspam

Jan 1, 1970
0
Charles said:
I suppose I could just go ahead and set up another one except
for
a couple of things: 1. I can't think of a simple method of
measuring or estimating the efficiency of the output. The
efficiency may be important for some future application and is
also of academic interest to me. 2. I'd like to have some prior
idea of how well the capacitor will stand up to repeated
high-current discharges.

As to measuring output energy, a high-speed op-amp integrator
might
work. Use an appropriate voltage divider and current sensor and
it
might be doable.

That gives me a starting point. Thanks.
I guess it depends on how serious you are about your efficiency
investigation.

Not too serious at the moment, but it may become more so. I have
some vague ideas floating around in my mind about possible
practical applications.
 
D

Dontspam

Jan 1, 1970
0
Phil said:
"Dontspam"

** Yep, they will work fine.


** X2 caps are regularly used in party strobes etc.


Thanks. I take it that that means film caps can be expected to
produce better results than ordinary Al electrolytics, and that
they will not degrade quickly with repeated discharges.
 
B

bw

Jan 1, 1970
0
Dontspam said:
Thanks. I take it that that means film caps can be expected to produce
better results than ordinary Al electrolytics, and that they will not
degrade quickly with repeated discharges.

Your local thrift store will have boxes full of old flash cameras selling
for pennys. Buy a few, take them apart.
Any cheap 35mm from the 1980s is ok, but look for really old polaroid
cameras. They have simple, easily understood circuits.
http://donklipstein.com/donflash.html has all the info you want on flash
circuits
 
D

Dontspam

Jan 1, 1970
0
bw said:
Your local thrift store will have boxes full of old flash
cameras
selling for pennys. Buy a few, take them apart.
Any cheap 35mm from the 1980s is ok, but look for really old
polaroid
cameras. They have simple, easily understood circuits.
http://donklipstein.com/donflash.html has all the info you want
on
flash circuits

Thanks for your interest, but there are no thrift shops where I
live, at least not the kind that sells such stuff.
 
Y

YD

Jan 1, 1970
0
Thanks for your interest, but there are no thrift shops where I
live, at least not the kind that sells such stuff.

Can you get an old microwave oven? They have a large HV cap inside.

- YD.
 
P

Phil Allison

Jan 1, 1970
0
"Dontspam"
Thanks. I take it that that means film caps can be expected to produce
better results than ordinary Al electrolytics,


** There is NO comparison.

Electros of a " few microfarads " will not be suitable at all.

Their internal resistance (or ESR) is way too high.


..... Phil
 
P

Phil Allison

Jan 1, 1970
0
"David Eather"

** Complete nonsense.

An X2 cap may develop an internal short our and smoke and burn if mistreated
or at the end of its life.



..... Phil
 
T

tuinkabouter

Jan 1, 1970
0
"David Eather"


** Complete nonsense.

An X2 cap may develop an internal short our and smoke and burn if mistreated
or at the end of its life.

Ever connected an electrolytic capacitor revere on a 48 volt battery?

I can tel you that is gives a big bang (and a lot of dirt).
 
D

Dontspam

Jan 1, 1970
0
John said:
---
I have a nice assortment of polyester (Mylar) caps and if you'd
email
me a physical address I can send then to, and what voltages and
capacitances you'd like, I'll see what I can do.

Thanks for the offer. I really appreciate it. But I do have some
Mylar caps of appropriate capacitance and voltage and in any
case, given the vagueness of any practical application I have in
mind at the moment, it's not worth the hassle and expense of
international shipping. On top of that, they may just get seized
by overzealous/corrupt customs people at my side.

My questions have been answered clearly and positively -
1. Whether a film cap will dump its charge efficiently into a
triggered xenon tube. I rather expected that it would, and it was
nice to have it confirmed.

2. How well the cap would stand up to the shock treatment: I
didn't know what to expect about that. It's nice to know that it
's likely to take that kind of abuse in its stride.

Thanks to all who contributed to the thread.
 
P

Phil Allison

Jan 1, 1970
0
"tuinkabouter"
Ever connected an electrolytic capacitor revere on a 48 volt battery?


** Ever had your foot caught in a rat trap ?

I can tel you that is gives a big bang ....


** Nah, that happened billions of years ago.

WTF is this raving loon on about ??



..... Phil
 
C

Cydrome Leader

Jan 1, 1970
0
Dontspam said:
Thanks for the offer. I really appreciate it. But I do have some
Mylar caps of appropriate capacitance and voltage and in any
case, given the vagueness of any practical application I have in
mind at the moment, it's not worth the hassle and expense of
international shipping. On top of that, they may just get seized
by overzealous/corrupt customs people at my side.

want me to ship you some charged caps?
 
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