Pumbaa

I saw the stun gun project and thought it was kinda cool although I was wondering if any of u have a smaller plan of a stun gun that dosen't realy stun just zap...say a few hundred volts.

I found a nifty little zapper found in a BBQ lighter and all it was was 2 small round object which looked like batteries (maybe one was and the other wasn't) separated but a space of a few cm inside the plastic case and when u push these "batteries" together they prduce large amount of electricty( probably around 100v)and it zaps. The zap are quite fun after u get use to it. (I wouldn't mind getting zapped by it, infact i kinda like the sensation)

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mechie

I would be suprised if you get a bad shock from this circuit, it will probably give a few hundred volts at best. This is a result of the transformer turns-ratio, you could experiment with different transformers, the small mains-to-low volts types - connected backwards. A 240v to 9v, 100mA unit could be a start point? As the circuit is switching 9v to the transformer you could expect something approaching 240v out. It will be low power (4mA out at best?).

Electric shock severity is a result of its power not its voltage so you want to be developing Joules of energy - a big farm-type electric fence energiser will develop up to 6 Joules and claim a maximum of 10kV :shock: open-circuit. These are safe for humans to touch by design (if a little painful).

The little barby lighter you describe sounds to me like a piezo-electric device - no batteries.
As you squeeze the trigger you will compress a spring, this will suddenly release and strike the crystal with a sharp 'smack' and deform it. The crystal will respond by generating a voltage of a few 10s of kV but with an extremely high impedance so when you touch the terminals the voltage will collapse to something much lower. Open circuit voltage allows for the long (1/4 inch?) spark you probably see when used "normally".

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_4nickando

well, from my old school, when i was in mechanical engineering, in phisics, i learned a not so astonishing, neither electronic way to make an inducted electric charge, to jump between 2 conductors...
Take a look to those old buzzer bells... you see in there 2 coils, and a hammer that is atracted to it, right?
Well, this is very simple: you need one coil, and an specific steel (a long kitchen knife was the sample) that is atracted to one end of the coil! The coil with a steel nucleum is a electromagnetic magnet.
Now here's the trick: the steel is an very high speed switch! it cuts the current when atracted to the magnet, so it stops being atracted and returns to the contact, closing the circuit, and the magnet pulls it again, and the circuit is cuted again... and so on!
This speed depends on the coil, on the steel and on the input voltage! but remember, if you make a coil with lots of insulated wire, and put batteries in parallel, than you can acheive a very strong current!
But there's another nice thing, since you like tho get shocked... try pointing a magnet to any power converter... but don'p be stupid and don't do it for too long!!!

kinjalgp

Hi _4nickando,
The concept of Buzzer-Bell and Stun Gun are completely different. In buzzer bell electric current does not jump from one electrode to other but it operates due to continuous making and breaking of the circuit due to electromagnetic attraction and spring action. This rings the bell and does nothing for generation of high voltages.
While the Stun gun project produces high-voltage between two electrodes using oscillator and step-up transformer.

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mechie

Sorry Kinjal, I don't completely agree...

Any coil (bell, buzzer, dc motor blah, blah) will produce a back-emf as a result of a collapsing magnetic field - the result of breaking the electrical circuit. The magnitude of that back-emf will depend on the strength of the magnetic field and the speed of its collapse. A coil with a soft iron core being infiitely better than an air-core.

A solid-state switch (transistor, etc) must be protected from this effect by flywheel diodes or shunt (parallel) capacitor - look at any motor or relay drive circuit.

I do agree that the probable power from a buzzer-shocker circuit will be less stable, noisier and lower than a well-designed and constucted solid-state circuit but it is possible to get maybe 100v from a 9v buzzer - honest ops:

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_4nickando

Pumbaa is very right! i don't know what voltage it will generate, but even 100v on DC is very, but very... brrrr!!! :?
i think that than, it would be just a question of Ampers!
The one i saw, operetade from a 1,5 AA cell, and the spark had about 1cm of lenght.
As of course, nobody dared to touch it...
But, there is an other way, using a simple electric motor and a rubber belt, but that is a little bit more complicated, but is the same principle as the von-graff generator.
As of course, electronicaly, it would be much better, but sorry for my vision of electonics, as passing from high currents to low... :wink:

kinjalgp

Yes Mechie, you are correct.
Silly me! How could I forget the strange behaviour of Inductor to falling magnetic field. I had just the switching action of buzzer in my mind.

Cheers Mechie.

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sportbank

I need to make a personal protection device and you guys helped me out.
I needed to know how much current the dc/dc converter should have.
I travel alot and get punched at least once a year.
I'm also making a homemade tangent galnavometer from the net to measure sound before it gets played through speakers. (very cheap sound measurement!)