Just get a reed switch that is rated for the current and voltage input for the Dynatorch .....its probably something like 15 volts DC at 100 milliamps....but that's just a guess...you need to check with Dynatorch. Epoxy the switch inside a piece of black iron or steel pipe...the pipe id should be close to the od of the reed switch. I would wrap maybe 3 turns of the WORK cable (the cable that goes from power supply to the plate)....and tye wrap it securely. When the arc transfers to the plate you should see the reed switch contacts lose....they will remain closed until the arc shuts off. More turns will make it more sensitive.
Jim |