Hi, I have a device that will trigger on a +3V to +45V signal, and send an SMS text message. The application is a boat & motor alarm/tracker. I would like to place a wire going from the boat to the outboard motor. If this wire is cut (they normally just cut off all wires/cables to save time), someone is stealing my motor.
My problem is to turn this "the wire has been cut"-signal into a +3V to +45V signal for the device. To complicate matters, I have +12V readily available, but no other voltages. I require minimal power consumption while the device is in standby.
A voltage divider + a logic NOT gate seems like a good starting point, but I'm concerned about getting a good signal when the input goes from HIGH (connected) to "float" (not connected, not even to ground).
Better ideas, please? :-)