Need project ideas for camera flash charging circuits and parts.

[XOIIO]

Hey all, a few years ago at least I went to a photo shop in town and got a box with around 100 (I think 105) disposable cameras for free, which I harvested the capacitors from in a project to make a capacitor bank for a small coil gun (which was proven futile as one large cap I got a year or two ago had much more storage, and I didn't ever get around to making it. There was also the issue of charging the caps). It was a lot of work to crack them all open and get the caps but a good chore while watching TV.

Anyways I have this shoe box full of them, not quite sure how many left, still a lot, so I'm trying to think of something to do with them. Making tiny shockers out of them using a few of the parts is somewhat entertaining, though quite a few have little neon lights which light up using the high voltage so that's a bit more interesting. I'm also tempted to get all the flash tubes and hook them together connected to some larger caps and see how much of a flash I can make out of them.

Anyways, do you guys have any ideas?

[T3sl4co1l]

As far as multi-flash goes, I wonder how many flash tubes you can trigger from one transformer (and how many actually fire as a result).  Probably quite a few.  You'd want to use one capacitor per tube to do this, but otherwise, the charger could be one or many, with the caps connected by resistors (use at least a few kohm metal oxide 1-2W+ for this).

You could make a sequential flash, ala bullet time, where each one goes off in succession.  Use a clock generator, counter, and as many 1-of-N decoders as you need, and wire them to the trigger circuits.  If all the flash tubes are just kind of in a pile, you'll have a regular strobe light, with a total repeat rate much higher than an individual circuit can handle.  This could have further options as a weird hacked strobe light, say you applied a music beat detector from an Arduino (or rPi depending on how sophisticated you want it..).  Or just good old analog, like a light organ, but only on bass beats (and something about them, like peaks, or zero crossings, or in a narrow band, or...).

You can run them from higher voltage (3+?) and see what happens.  There's probably a voltage regulator in there (possibly related to the neon light), which you'll want to modify to see the effect.

A number of those look pretty big (I see a large yellow one, a trigger coil I think, and a blue and ferrite blocky one, an inverter I expect), which could probably be driven to much higher current (and possibly voltage) than they're being used at.

More esoteric uses might include digital logic or frequency divider type applications, taking advantage of the negative resistance of the neon lamps; the flash tubes could be used for "power amplification", shall we say, so that the result can be read off the residual charges of a series of capacitors, or blinked out as a binary series of flashes, or something.

You *might* be able to do a sort of low power, single-pulse Tesla coil, using the flash lamp to deliver power, but I don't think the capacitor will have low enough ESR to be able to run a power RF oscillator this way.  (Offhand, I don't know how suitable the xenon arc is for negative resistance purposes.)

Tim

[miguelvp]

Some people use these to make "joule thiefs"

But careful with the caps, 300v and no matter how long they've been in that box, they can shock you badly!

[XOIIO]

Some people use these to make "joule thiefs"

But careful with the caps, 300v and no matter how long they've been in that box, they can shock you badly!

The caps have all been removed actually.

[flextard]

Hello...

The maximum number of flashtubes I've been able to reliably trigger from the same capacitor bank is 3, and that only if they are stacked (in a triangular shape), to ensure trigger pulse and power is delivered to the 3 at the same time.

I think I have now figured a way to make a flash strip, however, without increasing circuit voltage into the 1000VDC+ and arcing multiple tubes in series.

I'm connecting 4 tubes anode-to-anode and cathode-to-cathode, to be able charge 2 capacitors from the same transformer and have a much shorter current path from capacitor to flashtube than capacitor to capacitor - preventing multiple capacitors from being discharged into only one or two flashtubes.

It works, but it's not 'really' safe without the high power resistors T3sl4co1l mentioned to link the capacitors, so the circuit can become unstable if I increase the capacity further.

Ring flash possibility? That's where I'm heading.

I'll keep experimenting, and let you know if I come up with something more.

[Richard Crowley]

An amusing project from years ago was to use a step-up transformer (like those in the flash units) with an oscillator to make an object that would deliver a mild (but unexpected) shock if someone picks it up.  Of course that probably wouldn't be considered "safe" by today's standards.