Hi I'm working on a green house water mister controller, I'm trying out a simple monostable 555 mode to pulse a short output of 5v when the trigger goes low when a reed magnetic switch is closed, this 5volts is to actuate a solenoid to close a water valve. The problem I have is that the reed switch in this project can remain closed for around 15 minutes which would keep the 5v output going all that time draining the battery I've tried the circuit with just an LED and when you press the switch and leave it on the LED stays on all the time which is not what I want. Can anyone suggest how I can just achieve a 1 second pulse of 5v even if the trigger is set to low for a period of time . The circuit runs on a 9 volt supply