Plastic capacitor for camera flash tube?

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.

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.

In an isolated corner of a developing country where online shops are still mostly a joke.

Would you mind explaining the 'too small' part? I do have some film caps of a few microfarads rated up to 630VDC and some 275V AC ones. I thought the joule capacity was sufficient for what I want to do and was more concerned about the caps' ESR and their ability to withstand repeated high-current discharge.

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.

"Dontspam"

... Phil

A film cap will work fine. Mylars have pretty good energy density. For high-power, short-pulse flashing, it was sort of traditional to use an oil-filled paper cap at fairly high voltage, a kilovolt or so.

I used to fire military surplus coiled-tube flashtubes (used to be runway lights) at 5 KV or so from a few uF of oil cap. At 6-7 KV, they would fire without a trigger. Short linear tubes, like from a camera, will self-fire at lower voltages.

Can you use an LED instead?

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.

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.

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

Late at night, by candle light, "Dontspam" penned this immortal opus:

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

- YD.

"Dontspam"

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

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

.... Phil

"David Eather"

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

.... Phil

--- 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.

-- JF

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).