Miniature snap-action switch

Switching happens reliably at specific and repeatable positions of the actuator, which is not necessarily true of other mechanisms.

The first micro switch was invented by Phillip Kenneth McGall in 1932 in Freeport, Illinois, under patent US1,960,020.

A long flat spring is hinged at one end of the switch (the left, in the photograph) and has electrical contacts on the other.

Owing to the geometry, the upward force is proportional to the displacement which decreases as the flat spring moves downward.

Even though the flat spring unflexes as it moves downward, the switch is designed so the net effect is acceleration.

Microswitches have two main areas of application: Common applications of micro switches include the door interlock on a microwave oven, leveling and safety switches in elevators, vending machines, arcade buttons, and to detect paper jams or other faults in photocopiers.

Special low-force versions can sense coins in vending machines, or with a vane attached, airflow.

The snap-switch mechanism can be enclosed in a metal housing including actuating levers, plungers, or rollers, forming a limit switch useful for control of machine tools or electrically-driven machinery.