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Plastic capacitor for camera flash tube?

Discussion in 'Electronic Basics' started by Dontspam, Oct 3, 2012.

  1. Dontspam

    Dontspam Guest

    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.
     
  2. Baron

    Baron Guest

    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.
     
  3. Dontspam

    Dontspam Guest

    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.
     
  4. where are you located?

    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.
     
  5. Dontspam

    Dontspam Guest

    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.
     
  6. Charles

    Charles Guest

    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.
     
  7. Phil Allison

    Phil Allison Guest

    "Dontspam"
    ** Yep, they will work fine.
    ** X2 caps are regularly used in party strobes etc.


    .... Phil
     
  8. Dontspam

    Dontspam Guest

    That gives me a starting point. Thanks.
    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.
     
  9. Dontspam

    Dontspam Guest


    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.
     
  10. bw

    bw Guest

    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
     
  11. Dontspam

    Dontspam Guest

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

    YD Guest

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

    - YD.
     
  13. Phil Allison

    Phil Allison Guest

    "Dontspam"

    ** 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
     
  14. Phil Allison

    Phil Allison Guest

    "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
     
  15. tuinkabouter

    tuinkabouter Guest

    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).
     
  16. Dontspam

    Dontspam Guest

    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.
     
  17. Phil Allison

    Phil Allison Guest

    "tuinkabouter"

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


    ** Nah, that happened billions of years ago.

    WTF is this raving loon on about ??



    ..... Phil
     
  18. want me to ship you some charged caps?
     
  19. Dontspam

    Dontspam Guest

    Now there's an idea.
     
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