Solenoid

A solenoid is a electromechanical device that either pushes or pulls a rod when powered. The linear motion of the solenoid is achieved by using an electromagnet that surrounds a steel or iron rod, and when powered, attracts the rod.

The motion of the solenoid is binary in motion. It is either fully engaged, or not. Under-powering a solenoid will not cause it to only engage half way, but will simple reduce the force at which it engages.

By placing a magnetic rod within the windings of a solenoid one can shift the rod's position by introducing a current through the wire. The direction of movement will depend on the current flow through the wire as well as the polarity of the object placed within the solenoid. One such configuration is the solenoid valve.

Solenoid valves are a popular use of solenoids providing in most cases a simple open/close valve along a process line. In most practical application solenoids are used in a binary state of either charged or uncharged. Some solenoid valve use a spring to return then to a defined state upon discharging.