Ceska verze

Jacob's Ladder

     I will not describe in detail what it is Jacob's ladder. The images and video below can describe it much better :). It consists of two high voltage electrodes, on which an arc gradually climbs from the bottom up, then goes out and is immediately re-ignited at the bottom. It is still repeated with a frequency of about 0.2 - 10 Hz. In my case, the electrodes have distance between each other 0.5 - 1 cm at the bottom and 3-4 cm at the top. Their height is 14 cm. Their shape is seen at the pictures.
This device must have a high voltage power supply powerful enough (10kV and at least hundreds of watts of power). The simplest option is to use a neon sign transformer. However, if none is available, a switching HV power supply can be used as a source of high voltage. It's a simple Half Bridge, the same as in induction heating. The output is connected to two HV transformers from TVs (originally designed for use with multiplier), which give each about 5 - 6kV, so 10 - 12kV in series. PRIMARIES are rewound and each have about 50 turns. (Reducing number of turns can increase the output voltage, but there is the risk of secondary breakdown.) Protective bulb in my case 100W + 200W in parallel. Transistors have small heatsink from ATX supply. Potentiometer is set to operating frequency about 18 - 30 kHz (set to the best effect).

     WARNING !!! The device is powered by a powerful source of high voltage! Contact with this voltage can be fatal. The high voltage also can bridge considerable distance or break down the insulation. Arcs produce toxic nitrogen oxides and ozone. Must be ventilated. Everything you do is done at your own risk and any damage to health, life or property I do not take responsibility.

Schematic of the High Voltage SMPS for the Jacob's ladder.

Photography of the ladder with long shutter. Each bar is formed by one half period of the mains (10ms).

The "safe" workplace for high voltage.
That's how it should not look like.


Bright arc from the supply. Length up to 5cm.

Video for download you can find in videos