I'm powering a solenoid from a battery, so I want to spend the minimum amount of power to get the job done. In this case the solenoid doesn't even have a return spring, so as soon as the armature has moved a couple of millimeters, the job is done. Can I measure the current draw or another electrical property to see when the armature has moved? I haven't been able to find a plot of how the current draw behaves in response to a step voltage.
As I understand it, the inductance of a solenoid's coil changes significantly as the armature moves. If it doesn't result in a clear change in the current draw as I feed it DC (or a falling voltage from a charged capacitor), would it be feasible to measure the momentary inductance by modulating the supply current with some AC signal?
If all this fails, I can certainly fall back to driving it with just a timed pulse and experimenting to see what the required time is.