DO NOT use this for any other reason then self defense.
How it works:
The capacitor charging circuit from a camera is used to charge a small capacitor. Not the electrolytic capacitor from the camera. A different one.
When the capacitor reaches X volts then a spark gap which arcs at X volts will arc across and dump the capacitor through a high voltage coil.
The high voltage coil then puts out a very high voltage spark on the other side.
The capacitor loses its charge, the spark gap stops conducting and it all starts again with the camera circuit charging the capacitor.
All that will happen about 20 times a second.
First you need the capacitor charging circuit from a disposable camera. Any will do but the easiest way is to get a Kodak Fun Saver camera. The Wedding and Custom Kodak cameras are the same thing by the way.
Get the battery out of it, and short out the capacitor before removing the circuit:
Chop off just that corner with the charging circuit on it:
The rest is plug and play. These are what you need:
The spark gap in this example is a 350V gas discharge tube (so it will arc at ~350V). You may also get by with an open air gap as commercial stun guns use which is two strips of metal crossing each other separated by a thin insulator.
To assemble follow the video:
Finally, pack it up into a practical size:
This circuit produces tens of thousands of volts. Be extremely careful with the output, it can and will jump gaps of several centimetres.
Ideally, use a momentary switch so that if you do get electrocuted by it, it's easier to switch it off.
The capacitor will store a voltage of several hundred volts even when the circuit is turned off, short it out before working on the circuit.
The high voltage sparks are VERY likely to cause interference and damage to nearby sensitive electronics even if the sparks do not make contact. Don't run it near an expensive phone or computer...
Bear in mind the sparks cause ozone and nitrogen oxides to be produced as they ionise oxygen and nitrogen in the air.
Both gases cause irritation and damage to eyes and lungs. Try to be in a ventilated room or outside if allowing it to spark for any notable length of time. A small closed room is not ideal.
Prepping For The Worst is not responsible for any injury obtained with this information. This is a self defense tool used in a SHTF situation only.