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.
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.
Phil did you mainline those meds? This last post seemed, well.... normal. Mikek
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.
With a strobe, you don't need it to be blindingly bright to be noticeable. Typical disco-type strobes (that go really really fast) use a 1 uF polyester cap. The tradeoff is between the charge time and how much energy you want to put through your flashtube.
But for 2 Hz, I wouldn't use anything anywhere near 200 uF! Do you have a junque box? I'd try different value caps, starting at about 1 uF, and going up in value until you're happy - the thing to look for is the lowest possible ESR (equivalent series resistance), so that the current can go through the flashtube really quickly, and make a nice sharp strobe. I think it's the fast rise and fall times that stimulate the rod cells of your retina.
Good Luck! Rich
Some Caps from not to old PC-Powersupplys will do that without problems. Don`t forget the voltagebalance-resistors if you connect theese caps in series
btdt
Dischargecount for several buildt units stopped at 15,000 because the unit (flash-trigger-transformer and sourounding pcb) we need to test needs only survive 5,000 events...
hth
- Michael Wieser
Thanks. Nice to hear about an actual experience. As I explained in reply to someone else, I doubt that my unit will ever need to fire much more than 1000 times. It's a temporary solution that will probably be replaced with a better one in a couple of years, and used at roughly 10-20 sequences an hour, 3-5 hours a day, 1 or 2 days in a year. I'm already thinking about the replacement.
Thanks. I've already experimented with a Chinese-built 12V strobe meant as a car decoration light. It uses a 2uF cap and flashes at roughly the same frequency, but the output is nowhere near bright enough. Maybe it's restricted by the charging circuit which I haven't analysed yet. I also tried out the idea with the flash of my Panasonic FZ30 camera which is fairly powerful for a built-in unit. It was barely acceptable.
The idea of starting out with a smaller cap is a good one. But I think something like 10uF will be a better starting point. Placing the flash in a shaded area should make a big difference, but that's not practicable.
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