Engine running trigger?

[anguilla1980]

My switch panel has a couple of trigger inputs. I plan on using these inputs to automatically trigger things to go on based on only if the engine is running, that way they don't cause draw during cranking.

The only way to get a signal based on the fact of an engine running that I can think of, would be something like a pulse trigger switch off the tach wire I can calibrate for 600rpm or so (since good mini starter can crank at above 400rpm and my idle is 750).



Has anyone ever bought and set up anything like this? Any recommendations on a pulse trigger switch for this type of application?

I'm also open to other recommendations on how I can get a trigger signal based on only the engine actually running.

Thanks!