by JMACgyver » Mon Oct 27, 2014 6:24 pm
Perhaps just a self-resetting breaker or thermal fuse rating at just above what the circuit normally draws?
That way, under normal momentary operation the solenoid will trigger like it should. When the button is held for a longer period of time, the solenoid is just building up heat in the coil, and drawing more power, causing the fuse to trip. Then, when the temperature dissipates, or the current draw lowers, the fuse resets and the circuit works normally again.
Maybe you can replace the spring in the switch itself to make it harder or more uncomfortable for people to hold it down for longer than necessary.
Regards,
--Electro--
aka The Other David
"In Theory, the is no difference between practice and theory. In Practice, there is."