Oudin Coil

The Oudin coil is similar in some resspects to the Tesla Coil, in that it is an air-cored resonant RF trasnformer. It differs from the classic Tesla coil in that it does not have truly separate primary and secondary coils. The primary and secondary form one continuous winding so that the circuit is really a resonant autotransformer.

The tank capacitor forms a resonant circuit with the primary coil. The capacitor charges until the voltage across the spark gap is sufficiently high to break down. When the spark gap breaks down, the capacitor discharges through the coil, producing an oscillatory current at the resonant frequency of the primary circuit. This principal was first descrtibed by Sir Oliver Lodge. The primary oscillating current produces an oscillating magnetic field, which in turn induces a current in the secondary circuit. In the Oudin coil the secondary coil together with the topload is resonant at the same frequency as the primary. Due to resonance effects the voltage produced at the topload is extremely high, in the same manner as in a Tesla coil.

My own versions of the Oudin coil have produced similar size arcs to Tesla coils of similar size, using a tv flyback circuit as the power supply, feeding 10kV DC.

I will be adding pictures shortly, together with more details of the construction of my latest coil.