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Is it possible to use the guts from a flash disposable camera as a high voltage square wave generator? Answered

Is it possible to use the guts from a flash disposable camera as a high voltage square wave generator? I know that in order for the transformer to work it must use AC voltage so the 1.5 DC is changed to some high voltage AC but I'm not sure if it is square wave or just regular sine wave. And I'm also not sure at what point the AC is changed back to DC for storage, any help? A schematic or some diagram would be much appreciated!


The charging circuitry of a flash looks something like THIS.  If you remove the rectifier diode and take the output directly from the secondary of the main coil you will get high voltage AC.  Not too sure what it would look like but I'm guessing it would be positive and negative going spikes with an exponential decay.
What's the application you need a square wave for?

 thank you, the square wave would be for an inductive transfer unit...

I'm no expert on inductive transfer, but I'd have thought a camera flash isn't going to be a lot of use.  Maybe someone with more knowledge will post here, but I'd think you need a low voltage high current source (positive and negative) and to drive the transmitting coil with a push-pull amplifier type circuit.

Someone HERE has done quite a bit of work on this, but he's using a single ended power source rather than switched both ways.

How much power are you trying to transfer, over what distance?

 As it turns out, you can! I did exactly what you said and it works great, I got a new multimeter for christmas and it measured in at about 20 kHz and about 45% duty cycle! Its around 100 volts too.
Thanks for your help!!

Great - I've got a feeling that if you try to load that with an inductive coil the current will drop off to almost nothing, but I'm quite happy to be proved wrong.
Post back if you get good results with it.

 Ya, actually measured the amperage not long after that last post, and it is phenomenally low...  I'm trying to decided how to get around it...

What you need is one of THESE.  High current and low voltage, just substitute your induction coil for the ignition coil.  (It would be wise to put a chunky diode across the coil and another from rail to ground to kill the switching spikes.)  Of course, if you want to have a play with EHT sparks, just use the ignition coil ;¬)

Ya, I actually tried making one very similar, almost identical, but I couldn't get it to work for some weird reason... I'll probably have to go back and remake it...

 ya, im not an expert on it either, I will definitely have to read up on it... 
The amount of power, I'm kind of indifferent on, it just depends on what the source of the square wave generator I decide to use uses, and as for the distance, thats really the reason I'm making it, I kind of want to experiment with it...

I think the answer to the question as asked is "no"; I would expect the photoflash's DC-to-DC converter to generate sine waves at the high voltage (but very little current) because that's what can be stepped up most efficiently.


8 years ago

What transformer?
The last time I tore one apart, and it's been a long time, It had a 6 volt flat battery pack and a capacitor to discharge into the flash bulb. Probably Xenon. If there was any circuitry at all, it was microscopic.
Six volts can charge a capacitor to throw a spark a pretty good distance in the right atmosphere...like through 3/8" of Xenon gas in a tube.
What do you really want to accomplish? That might steer you in a better direction.

 ya, in the newer ones, they have a transistor that gets it to AC then there is a very small but very powerful transformer, then it goes i guess into a rectifier diode, then into the capacitor, when the shutter is pressed, depending on the camera it either gets changed back to AC, goes through another transformer then through the flash tube, or just skips that last part, and goes straight through the tube, the square wave generator would be for an inductive transfer unit.