This device was purchased by a friend and passed to be for a quick safely check. I don’t really know if these devices provide any benefit to the user, but their workings are quite interesting.

The general idea of the device is to generate a high voltage at a high frequency at very low current to cause stimulation of nerve endings. Note that the frequency is so high that muscles do not react. The current limiting device is a glass tube filled with a gas that will glow violet when ionised by the high voltage. The glass tube is pushed into a handheld wand which actually contacts a step-up transformer.

The internals of the device reveals little to the untrained eye. Just a few coils and a rheostat. There is however, quite a bit more going on in there. After a lot of looking at different angles, lights and mirrors, the following circuit diagram was discovered.

The left hand part of the diagram is where mains electricity is connected. The right hand part shows the step-up transformer in the wand handle. The aerial symbol top-right, is where the glass tube is attached.

Live mains is fed into the circuit via two chokes (which are presumably to prevent high frequency energy travelling along the mains wiring of the home.

The mains current flows through the vibrator circuit, which is comprised of a solenoid coil and normally-closed contacts, through the rheostat and the primary winding of the output transformer then back to the supply. This will cause the solenoid to close and open very quickly, emitting a buzzing sound.

So far, so boring, this isn’t really much different to and old buzzer circuit. What is really good, is what is happening in the moments while that contact is open.

while it is closed, a magnetic field builds up in the solenoid coil until it fully charges up and opens the contact. Because the current stops flowing very quickly, a large voltage is created across the coil as the magnetic field collapses. The large 4000v 0.1uF capacitor charges up from this high voltage.

When the contacts are closed, the capacitor and the primary winding of the output transformer form a tuned circuit and oscillate at a high frequency using the high voltage energy that was previously captured.

The turns ratio of primary to secondary of the output transformer is such that several tens of thousands of volts high frequency AC will be present at the output, where the glass tube attachment will be connected.

The vibrator keeps the capacitor tank circuit topped up with high voltage pulses. While the tank circuit turns these into a high frequency decaying sine wave.

See the video below for a demonstration!