Micro switches are widely used in household appliances, automatic control and other industries. Micro switches use tiny external force to connect or disconnect the static contact and moving contact inside the switch. Because of the small external mechanical force and small action stroke, they are named micro switches or sensitive switches.
Internal diagram of normally open, normally closed and changeover switches
There are many ways to classify micro switches. Household appliances generally classify micro switches into three categories according to their uses: normally open, normally closed and conversion. Before external force is applied, the static contact and the moving contact are connected, which is a normally closed micro switch, otherwise it is a normally open micro switch. Normally open and normally closed micro switches have two terminals.
The transfer switch can control two paths. One of the paths will be connected before and after the moving contact piece moves, and only one of the paths can be controlled. As can be seen from the diagram, the transfer switch can replace the normally open or normally closed switch and is usually used in scenarios where the loads cannot be turned on at the same time.
Taking the normally open micro switch as an example, the main structural parts are as follows:
When force acts on the switch, the moving contact begins to approach the static contact. When the reed moves to the critical point, the deformation produces instantaneous action, and the moving contact is quickly connected with the static contact to prevent ignition and arcing. When the external force is removed, the reaction force of the spring acts on the moving contact piece to complete the quick disconnection action.
Therefore, to determine whether the micro switch is normally open or normally closed, you only need to use a multimeter to measure the connection between the two terminals before and after the switch is closed. To determine whether the micro switch is damaged, use a multimeter to observe the switch before and after it is closed. If only one path is conductive, the micro switch is normal. If both paths are conductive or disconnected, the micro switch is damaged.
Of course, the structural design and material requirements of micro switches are very high, and there are many types of switches and application scenarios. When designing the product, it is necessary to consider the switch's operating environment, electrical performance, action characteristics, switch life, etc.