Electric switches are, simply put, components that can open or close an electrical circuit. They were invented some time ago, born out of a need to safely and easily control the flow of electricity. While small and quite simple, electric switches are an important part of the modern world. People use them constantly, whether to turn on the bathroom light at night or to control machinery in high-risk industrial environments.
Generally speaking, if an electrical circuit is open, that means it is not connected, disallowing a current transmission, while if it is closed, it is connected and it allows current to pass through. Switches that work like these are known as binary devices, a name that reflects their two states. There are other switches, though, that allow varying voltages to pass through via multiple closed positions that alter the output of that to which they are attached.
Electric switches vary from one another in a variety of ways, but most are made up of conducting materials, wires, actuators, and terminals. Switch conducting materials must be corrosion resistant because metal corrosion results in the buildup of insulating oxides that inhibit proper switch function. Conducting materials are also selected for abrasion resistance, mechanical strength, low toxicity, and, ideally, low cost. An actuator is a moving part that serves switch function by applying operating force.
Actuators, which are housed in a protective casing, may come in the form of any number of mechanical linkages; most commonly, an actuator is a toggle or dolly, a rocker, or a push-button. A terminal is the point at which an electric conductor connects to external circuits. It may be the standalone end of a wire or it may be fitted with a fastener or connector. All of the above components differ in configuration and quantity from one switch to another.
For example, some switches are made quite small and require a miniature tool, like an inkless pen, to be accessed. Others need only the flip of a finger, while others still require special strength. Also, while many switches operate independently, they can also be connected to each other so as to increase circuit options. What’s more, electric switches can also be quite diverse in terms of their intricacy. They range from the simplest operation, requiring a physical touch between the actuator and conductors, or they may be able to open and close by sensing a magnetic field or light. Read More…
One major variable of all electrical switches is the actuator type. Based on this, there are many different kinds of electronic switches, including toggle switches, push button switches, slide switches, waterproof switches, rotary switches, rocker switches, and DIP switches.
Toggle switches are used for applications such as quick connecting and disconnecting, quick switching, and when the application’s control devices are mounted very close to each other. To work, they use a handle, a lever, or a rocker for an actuator.
Next, for an actuator, push button switches engage a flush button, a recessed button, or a raised button.
By moving from position to position in a straight line, slide switches interrupt the flow of a current in order to “break” electrical circuits. Characterized by their sliding actuators, slide switches provide, at a minimum, two slide positions, “on” and “off.”
As their name indicates, waterproof switches are especially designed to resist the negative effects of water, as well as other forces like shock, salt, corrosion, and vibrations. To ensure their protection, waterproof switches are encased in a watertight housing.
Rotary switches are run simply, with a rotating control knob.
Meanwhile, rocker switches are those switches that raise at one end when the other end is pressed down.
Finally, DIP (dual in-line package) switches are manually operated switches that may double as rocker, slide, or rotary switches. Installed in devices such as remote controls and garage door openers, the term “DIP switches” may actually refer to an individual switch, or small banks of several switches. If this is the case, the device in which the switches reside may be referred to as a switch panel.
Switch panels, which are used to control more than one electronic circuit, may be composed several single pole switches, several double pole switches, or a variety of other switches. The internal components of a switch panel are encased inside a housing most likely made of wood, plastic, or metal, while the actual switches can be found mounted on the panel’s face.
The terms “single pole” switches and “double pole” switches refer to switches with specific internal arrangements. Single pole switches, which are used for general purposes, have two actuator positions, “on” and “off.” They can be further categorized as either single throw (ST) or double throw (DT), divisions that reference the number of terminals that will complete the circuit. Double pole switches, on the other hand, operate with a pair of actuators that may be either connected or disconnected to a circuit.
They can also be labeled as either single throw or double throw, based on how many conducting positions their actuators can assume. Double pole switches usually assist the functions of devices that have multiple mechanical parts working at the same time. They also help to switch appliances from 240 volt circuits to circuits with a different current.
Types of Electrical Switches
Below are brief descriptions of some of the more popular and more commonly used electrical switches:
Toggle switches are used to control the flow of electrical power to a device by toggling to one of two or more different positions. The most basic toggle switches simply toggle between off and on, but some more complex toggle switches may have more than two positions. The switch is most commonly comprised of a lever or handle, which is used to switch between the different positions, and an internal spring keeps the lever held tightly in place at each of its set positions. These switches can be used for applications ranging from controlling household lights to industrial machinery, and many switches can handle switching 250 VAC at currents around 1 amp.
Push Button Switches
Push button switches allow for two-position control, which is activated through the pushing of a button. Pushing the button “in” provides a connection in the internal circuit therefore turning on the device to which the switch is connected. A spring within the switch always pushes the button toward its “out,” or off, position, so once the button is released the circuit loses connection, turning off the device. This is especially useful for applications requiring only brief connection or momentary electrical input.
While many other electrical switches are activated by flipping a lever or pushing a button, rotary switches are activated by rotating a knob. This kind of switch is typically used for applications requiring more than just on and off options since they can be rotated to a variety of different positions. Due to this feature, they allow one point to be connected to one of many different points within an electronic circuit. These switches come in a variety of forms, including rotary switches consisting of three levels all connected to a common shaft.
As its name suggests, a proximity switch is activated as it senses an object coming near it. These switches are typically utilized in machinery, and they use magnetic and high frequency electromagnetic fields to sense metallic machinery components as they approach the switch location therefore triggering the switch to close. This effect is accomplished by energizing a coil of wire with a high frequency current, which is then monitored. The approach of a metallic object or component causes the current in the coil to increase, triggering the switch. Not all proximity switches use this mechanism, however. Some instead use an optical mechanism, which utilizes photocells that monitor incoming light. In this case, the switch is triggered when the incident light is blocked or interrupted.
A speed switch monitors the rotational motion and speed of a shaft or other rotating component, and once the speed of the component reaches a set point, the control circuit is switched or energized. The speed switch can monitor the shaft speed in a variety of ways, including a centrifugal weight mechanism, magnetic pick-up mechanism, or optical mechanism.
Temperature switches utilize a strip of bimetallic materials, which is a strip comprised of two metals with differing thermal characteristics combined back to back. Specifically, these metals must have a dissimilar coefficient of thermal expansion. When the strip is heated or cooled, this difference causes the strip to bend one way or the other, and this bending can be used as a contact mechanism. The strip can be oriented in such a way as to make the strip bend and make contact with the circuit when heated and bend away from the circuit when cooled, or vice versa.
Like a toggle switch, a joystick is controlled by a lever. However, the lever in a joystick switch can move in more than one axis, allowing for a larger number of control options. These switches typically contain many contact mechanisms which are not only stimulated by the direction of the lever, but also by how far the lever is pushed in a certain direction. This kind of switch is commonly used in motion control devices and offers both course and fine control.