Micro Switches

Micro-switches can be equipped with different control elements. The most common models are available with a push button or with a hand lever. But there are also, for example, so-called roller actuators that switch from the moment the used roller has wound off a predefined distance.

Micro-switches can be mounted in very different ways. There are models for soldering on a circuit board, for mounting via a screw mechanism or for plugging on a breadboard.

An important purchase criterion for a microswitch is the maximum switching current and the switching voltage . The indication 250 V/AC 10(4)A indicates that switches can operate an resistive load of maximum 10 ampere and an inductive load of maximum 4 ampere at an operating voltage of maximum 250 VAC. You must therefore ensure that consumers do not exceed these load limits after the switch.

The value of the actuating force indicates how much physical force is required in Newton to trigger the switch and thus change the switching state. The release force indicates how much force is released when the switch is released.

The type of contact material to be selected essentially depends on the desired service life of the microswitch. You can choose between the materials gold, silver, brass and nickel as well as various alloys.

The maximum switching frequency indicates how often a switch can be operated at a maximum of one minute. An operation here comprises a complete shift cycle, from the initial actuation to the return to the rest position of the control element. This is specified in " Switching cycles per minute ".

Labels such as on/(off) or on/(on) indicate the switching behavior of a pre-wired microswitch. The first specifies the behavior in the rest position, the second in brackets determines the behavior when the switch is pressed.

For a microswitch labeled on/(off), the contact is closed in the rest position. When the switch is pressed, the contact is interrupted. The switch is an "opener".

For a microswitch labeled off/(on), the contact is open in the rest position. Only when the switch is pressed will the contact be closed and a current flow possible. The switch is a "normally open" switch.

A switch labeled/(include) closes a contact in both states and is used to alternately supply two different circuits with power. One of the two terminals N/O and N/C is always supplied with power. The switch is a "changer".

A microswitch can combine several controls . Thus, a microswitch with the switching function 2x off/(one) can have about two operating levers that must be operated simultaneously in order to enable a continuous closing of a contact. The microswitch has two separate contacts that can be switched with two different control elements.

The switching function of the microswitch indicates its contact type. Basically, a distinction is made between the NC and the NO . The normally closed contact interrupts the circuit when it is opened, i.e. connects the C terminal to the N/O terminal by default. As long as the switch is in its rest position, a contact is made. This type of switch is therefore also called a normally open contact.

A normally open contact, on the other hand, only closes the circuit when it is actuated. In its rest position, it connects the C terminal to the N/C terminal. Since the normally open contact does not contact the N/O terminal until it is activated, a normally open contact is also called a normally open contact.

Depending on the switching state, a changeover contact closes the contact with either the N/C or the N/O terminal, but always supplies power to one of the two branches.

The service life indicates the minimum number of switching cycles within the specific values. It depends on a number of factors, including

• Height of switching current and switching voltage
• Load (e.g. resistive, inductive, capacitive or lamp load)
• Choice of materials for actuator and actuator
• Operating type and speed
• Switching frequency (in switching cycles per minute)
• Forward and follow-up travel
• Environmental factors such as climate or harmful gases in the environment

A distinction is also made between mechanical and electrical service life . The mechanical life indicates how often a switch can be operated without electrical load. The electrical life indicates the life of the switch below rated voltage, rated current and resistance load at 23 °C ambient temperature.

The minimum and maximum temperature limits define the upper and lower limits of the ambient temperature in which the switch can be operated properly. Most microswitches can be operated well below freezing and well above boiling point of water.

The choice of housing material contributes to the robustness and thus to the service life of the microswitch. Most microswitches are supplied with fiberglass housings. Rubber, for example, is particularly resistant to shock and vibration and is therefore often chosen in demanding operating environments.