I'm using a 10kv ignition transformer for a jacob's ladder.

It works great! Currently though I've only tested it on its own circuit. But I would like to have this thing running in my lab. (I know not to run for more than a minute at a time due to ozone generation, and my lab is well ventilated)

However my lab is only one circuit, and I'm worried about the flyback from unplugging it harming my rpis, etc.

How do I isolate this thing / compensate for the flyback?

This transformer is old style, not like a solid state NST.

  • \$\begingroup\$ Shield the RPi’s like a Faraday cage and use line filter if there is any interference and STP sensor cable. It depends how close or shared power. \$\endgroup\$ Jul 26, 2018 at 22:27
  • \$\begingroup\$ I'm not worried about rf, I'm worried about a flyback voltage spike when I unplug my jacob's ladder :) They are on the same circuit and are located about 20 feet away from each other. \$\endgroup\$
    – cat pants
    Jul 26, 2018 at 22:36
  • \$\begingroup\$ Providing your power supply for the Jacobs ladder is well designed, nothing should get back down the mains wires. You do need to protect against RF energy if you have PCBs in the open and close to your display while it's running. \$\endgroup\$ Jul 26, 2018 at 22:55
  • \$\begingroup\$ A line filter will reduce conducted emissions. \$\endgroup\$ Jul 26, 2018 at 22:57

1 Answer 1


Your concern is valid as you are disconnecting an large inductive load. Easy way out is to buy an extension cord (with ground) that has MOV protected outlets, usually 4 to 6 of them. If active noise filtering is included (a X2 capacitor) that is even better.

Don't build what you can buy at low cost. Note that such an outlet may just use the words "Surge Suppression" without much detail. If possible buy one that offers details and is UL or cUL approved. Statements about fuse rating, clamp voltage and/or clamp current help insure quality.

Use this protected outlet to power your Jacob's Ladder. Any surge or back-emf will be stopped there.


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