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250kv Hand Crank Marx Generator 20 Stage

The aim of this project is to build a hand cranked Marx Generator for display purposes. Where someone can wind a handle a few times and a loud bright snap of lightning ~10cm long accompanied with a cascade of 20 smaller spark gaps flashes at the same time.

An interactive, dangerous and loud electricity display. 

Marx Generator is a very simple and old circuit first described by Erwin Otto Marx in 1924. It generates a very high-voltage by charging a cascade of capacitors wired in parallel, then suddenly connecting them in series using spark gaps. Air breaks down at about 30kV/cm depending on humidity and temperature and when the arc forms it is virtually a short circuit and this is used to join the capacitor in series.  

The project part list so far

  1. The generator in this case will be a 200W 24V DC Motor with a gearbox.
  2. A High Voltage Invertor to step-up a voltage from about 9 to 20VDC to around 10 to 15Kv DC
  3. A 20 stage cascade of high voltage resistors and capacitors 42 x 1M 5Kv 3 Watt Rusian Resistors and 20 x 10nf 15Kv Capacitors
  4. Spark Gaps are 15mm round nickle plated solid brass draw handles x 40
  5. Full circuit diagram here :

HV Invertor  Marx Generator Stages

High voltage Invertor 15KV DC


First rough test of spark cap and RC combo


Second rough test of 2 stages in the correct circuit configuration