Safe AC Halloween shock


How to with a few volts [5v] give an alternated current safe shock?

To this Halloween i want to make and door that give a shock, but have to be safe and very lite. Like that pens that when you press, it gives you a shock.

ps.: will be one shock in 3 seconds, durning 015 ms
ps2.: i dont want to kill somebody =]

Best Answer

I would do two things, only produce periodic shocks with reasonable time between them, and make sure the energy of each shock is limited. There are rules for things like electric fences along these lines, but a Halloween gizmo shouldn't produce anywhere near the shock of a electric fence.

The best way to do this electrically I think is similar to a boost converter. A coil is connected between the 5V rail and ground thru a transistor switch. Most of the time the switch is off, no current is flowing, and there is no high voltage. When you want to produce a shock pulse, turn the transistor on for a fixed time to charge up the inductor to just below saturation. When the transistor turns off, the inductor voltage will spike. The total energy will be limited by what the inductor can store. You probaly want to put a clamp on the inductor to limit the voltage to some maximum level. This also limits the voltage the transistor switch sees. That transistor must be rated to at least that voltage.