Each household has several switches. In each room, we operate them to turn one or more light sources on and off, for example, and electronic devices and everyday items are turned on or off at the touch of a button. But also in the car or on motorcycles are the most diverse types of switches, which sometimes we do not notice directly.
Switches all work according to the so-called all-or-nothing principle: By operating in one direction or the other, the circuit is either opened or closed. They are differentiated according to the various categories, for example, the type of operation, the design or the design features. Most important to the purchaser are the electrical characteristics, also known as rated specifications, which describe the suitability of a switch for certain voltage and current ranges and the environmental conditions.
Differentiation according to actuator
Mechanically actuated switches can be operated either manually, ie by man, or via devices. It is differentiated for the reason that humans can co-determine the control loop: If one operates a switch, then the desired effect occurs, for example the turning on of a television. If this does not happen, you can get to the root cause of it. An example of the operation of a switch by a device are electric blinds. In case of failure, the device should ideally itself ensure that no danger arises.
Furthermore, a distinction is made between direct and indirect switch actuation. The directly operated switches include, for example, toggle switches, pressure switches, slide switches or rotary switches. Indirect switches include, for example, twilight switches or motion detectors.
Most widely used: The toggle switch
A mechanically directly operated switch is the toggle switch that is most commonly found. Representing this design, the light switches are often called. Within the housing is a movable contact, which is moved depending on the switch position in another position. This encounters an immovable contact and closes the circuit; If you put the switch back on the contacts are loosened and thus the circuit opened. Due to their simple operation, toggle switches usually have a very long life.
In the car you will find toggle switch also as a light switch. Above the center console, the light can even be switched to three different types of lighting: permanently switched off, permanently switched on and those that only light up when the car door is open. Here, the toggle switch is still combined with a door contact switch.
The door contact switch monitors the condition of all doors and the boot lid in the car. If the doors and the flap are closed, then the circuit is closed. If the circuit is still open when starting the engine or when starting, this is indicated either by an audible or a visual signal; usually it is even the combination of a beep and a signal light.
Actuation according to temperature: The temperature switch
Part of each thermostat is the temperature switch. Most of these include a bimetallic plate; The two metals containing different thermal expansion coefficients. Sometimes a bimetal strip is also used here. If this bends now, a jump switch is activated. The switch opens or closes the circuit, thus initiating or stopping a process. This can be for example a cooling or heating.
Temperature switches are also used in kettles, but in an automatic form: once the boiling temperature has been reached, the cooker shuts itself off automatically. The same thing happens with the toaster.
Temperature switches are also available in combination with liquid. They use the thermal expansion or the evaporation just that. This type of temperature switch is used for temperatures from -20 degrees Celsius to +300 degrees Celsius. An example of this is a refrigerator thermostat; The desired temperature range is set via a rotary knob. Contact thermometers are in principle temperature switches of this type, but are not referred to as such.