The setup is very simple. It contains:
- the variac. It is important because the voltage on the ignition coils has to be around 1000-1500 vac (more voltage = increased risk to distroy the coils, arcing through the secondary insulation)
- a small MOT (220 V / 2200 V @ 400-600 vac). The higher voltage is a condition for the electric arc stability.
- the current limiting inductance L is a 250 VA ballast from some high pressure Hg fluorescent bulbs. It is essencial reducing the power in the circuit and allowing an easy quenching of the spark gap at each 0 V passing of the AC wave. The voltage has to be high enough to assure the ignition of the arc (1500 vac - 1 mm gap). The current limiting can be used on the HV side also, but i prefered on the LV side.
- the spark gap is made with two carbon electrodes (harvested from some R 1.5 V batteries) mounted in copper supports, allowing easy moving in the support. I know that Poulsen used copper electrode for the anode, but i just used AC current (for DC, the diodes have to be high current rated and this is a big pain ass). The both electrodes are made by carbon, because they have some effect to make the arc runing more stable and smooth.
- the cap is a huge 1 uF @ 6.3 kV oil paper.
- for the inductance I just used my old dual ignition coil setup put in a new and bigger oil bath, which will allow longer spark output. The coils are imersed in a mixture of 2/3 vegetable oil + 1/3 mineral oil (to stop the vegetable oil getting rancid). |
