Also known as bi-stable valves, latching valves take a momentary electrical signal and deliver a maintained pneumatic output, until a second momentary signal is applied. They use a permanent magnet within the solenoid. When current flows through the solenoid in one direction the armature moves into the permanent magnetic field, shifting the valve stem to one flow state (port 1 > port 2). The force of the permanent magnet is sufficient enough such that the armature “latches” after current is removed. When current flow to the solenoid is applied in the opposite direction, the force of permanent magnetic field is effectively “neutralized”. The return spring then can shift the valve to another flow state (port 2 > port 3).
A 50 millisecond minimum pulse of electrical current to the solenoid will shift and secure the armature into the desired state.