What is a solenoid, and why should I care?
A “solenoid” is a coil of wire that, when electricity is sent through it, becomes a magnet. The resulting magnet is attracted to iron objects. Being able to turn a magnet on and off allows you to exert a pull or push from a distance, and under electronic control. The most common haunt application for a solenoid is to activate an air valve, controlling a pneumatic animated prop. But even by themselves, solenoids can be quite useful. Gallery of assorted solenoid pictures This is a large “pull” solenoid. When energized, it pulls in the bar. You can also get solenoids that push the bar when energized. Note that the bar has a slot cut into the end to attach it to whatever needs pulling. This is a slightly smaller solenoid. When energized, the bar pulls in. When the power is removed, the external spring pushes the bar back out. This is a “rotary” solenoid. When energized, the black tab on the top rotates approximately 45 degrees. This page from the All Electronics catalog (#203, Spring 2003)
