Portable Jacob's Ladder

Device described on this page is a portable , battery operated Jacob's Ladder which works exactly like the mains powered ones. Here is the video if its operation .

More pictures of the device :

Close-up of the electrodes assembly and the power converter:

Brass power switch :

The Circuit

The circuit used in my portable Jacob's Lader is a double resonant high voltage generator with 100Hz modulator . The "double resonant" configuration means that both the primary and the secondary of the transformer are resonant circuits with the same resonance frequency. Thanks to it the voltage on the secondary is dependent on the input power and the Q factor of the LC circuit rather than the transformer's turns ratio. The resonance frequency of the secondary winding is determined by its inductance and the capacitance of the electrodes. The LC cicuit on the primary side of the transformer improves the power transfer and increases the average power of the discharge. By using a series choke with the LC circuit's drive the voltage on the primary winding is over 20 times bigger than the input voltage .

The driver circuit uses two TL494 chips : one to drive the power MOSFETs with 18 kHz ( resonance frequency of the transformer ) square wave and the second to modulate the first one with 100Hz. Modulator's duty cycle can be set for the best sound effect produced by the Jacob's Ladder .
Here is the schematic of the device ( click the image for pdf version ) :

Some pictures from the construction of the Portable Jacob's Ladder :