I installed a plunger in my cab recently. It's really a bizzare mecanism, which is why I didn't write it up. I happened to have an in-ground lawn sprinkler head that was exactly the length of the plunger, and when I took it apart, it had a hole in one end that just fit the plunger rod and the hole in the cap perfectly fit a Happ button. So I installed a vertical button (a horizontal one would probably cream the microswitch with the plunger hits) in the cap, ran the plunger rod through the sprinkler body, and screwed on the cap with the top of the button on the inside; the plunger rod holds down the button firmly. I wired to the NC (Normally Closed) terminal instead of the usual Normally Open, so the button triggers when it's released, not pressed. The whole assembly isn't affixed to anything, just held on by the force of the plunger spring, so when the plunger hits the button the whole assembly pulls away from the plunger and the shock of the impact is absorbed by the spring. Physics then resets the whole thing. It's truly truly bizzare.