I recently got into an argument with a friend over what the correct implementation of a safety switch for a motor with a spark gap is.

So for intents and purposes, here is the simplified schematic with the engine generator, the fly-back transformer and the spark plug.

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Here is what I think the wiring should be for a safety switch

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I think it should be this way because any modification would cause the engine to not start, which I think is essential.

My friend thinks that an E-stop should be wired like so:

enter image description here

with the rationale that a faulty switch wouldn't cause an engine out.

In this case, what is more correct, and why?

  • \$\begingroup\$ What is the point of an E-stop if the engine can run with a faulty E-stop? \$\endgroup\$ – DKNguyen Nov 11 '19 at 2:14
  • \$\begingroup\$ @DKNguyen presumably to stop the engine \$\endgroup\$ – tuskiomi Nov 11 '19 at 2:17
  • \$\begingroup\$ But if it's faulty. Why should the engine be allowed to run at all? E-stop failures would just go unnoticed...until the E-stop is needed most. \$\endgroup\$ – DKNguyen Nov 11 '19 at 2:43
  • \$\begingroup\$ @DKNguyen that's my reasoning, but I think the other side has merit too \$\endgroup\$ – tuskiomi Nov 11 '19 at 2:52
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    \$\begingroup\$ Why would you show a DC motor driving a transformer, knowing that would saturate the core and short out the motor? \$\endgroup\$ – Tony Stewart Sunnyskyguy EE75 Nov 11 '19 at 5:07

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