From time to time I dig up my decades ago constructed technical device for corona photography to make beautiful Lichtenberg figures. This equipment works with high voltage and creates the figures at the edge of conductive objects which can then be photographed (this imaging method is often referred to as "Kirlian photography"). In 1989 I did this with photo paper and chemical development. Of course, digital methods are now available for this.
The circuit consists essentially of a driver and a high voltage source. This is an ignition coil (like a transformer, consists of an iron core with a primary and a secondary winding with a high turns ratio in the order of 100:1) that transforms the pulses of the driver into high voltage (20 - 25 kV), which is then fed to an electrode (insulated copper plate ). The second electrode is the earth or the earth connection on the device. Between the electrodes are the conductive object on which the high voltage discharges in the form of a spark corona and generating ions (you can smell the ozon).
The ignition system produces electromagnetic interfering fields as well as high voltages that are dangerous. Therefore be carefull! 
 Corona device |
 Schematic |
 Corona image |
 Photo - Leaf |
 Photo - Coin |
 Photo - Key neg |
 Photo - Key pos |
