Electric Switches

Though all electrical switches are used to open or close electrical circuits, there are many different kinds of electronic switches. Push button and toggle switches are some of the most common electric switch varieties. Push button switches use a recessed, flush or raised button as the actuator. Toggle switches use a lever, handle or rocker as an actuator. Toggle switches are often used for quick switching, connecting and disconnecting in cases when the control devices are mounted very close to one another. Slide switches break electrical circuits by moving linearly from position to position, interrupting the current's flow. They provide at least two switch positions, including "on" or "off," and they are distinguished by their sliding actuators. Rocker switches move when pressed so that one end is raised while the other is depressed. Rotary switches are operated by rotating a control knob. Waterproof switches are enclosed in a watertight housing that is able to resist corrosion, salt, shock, vibrations and other potentially harmful forces. DIP switches are small banks of several switches that are installed in devices like garage door openers and remote controls. When many switches are installed in a single device, that device is often referred to as a switch panel. Switch panels can be composed of several single pole, double pole and other kinds of switches and are used to control multiple electronic circuits.

Electric switches are identified by various factors, including the actuator, which is a mechanism that applies force to the switch's contacts. Switches generally consist of conducting material, wires, terminals and actuators housed in a protective casing; these components vary in quantity and arrangement, but they are similar in that they can complete a circuit by allowing an electrical current to flow through them. Switches can be connected to each other in order to increase the circuit options, or they can be used on their own. Electric switches vary in terms of their complexity; complex switches are able to sense a light or magnetic field and react accordingly, while simple switches require physical contact between the conductors and actuator. Switches also vary in size; some are very small and necessitate a miniature tool to operate; some can be flipped with a finger while others require a strong hand.

Electronic switches are also categorized according to the arrangement of internal components. Single pole switches are general purpose switches that offer two actuator positions: "on" and "off." Single pole switches can be either single throw or double throw, which refers to the number of conducting positions, that is, the number of terminals that will complete the circuit. A double pole switch is an electric switch with a pair of actuators that are either connected or disconnected to a circuit; they may be either single throw (ST) or double throw (DT) depending on how many conducting positions the actuator can be in. Double pole switches are also used to switch appliances using 240 volt circuits to a circuit of a different current. They are commonly are used in devices with multiple mechanical parts that function simultaneously. A switch panel allows users to quickly access a series of mounted electric switches that are arranged in an enclosure. The wires, terminals and other components are hidden within the plastic, metal or wooden housing, while the switches themselves are mounted on the panel's face. A DIP switch is a circuit board with a packaged group of tiny electrical switches. The set is called a dual in-line package; DIP switches are very small manual binary switches and are an inexpensive way to customize an electronic device. They are easy to operate; flipping a switch turns on the component that coincides with that switch.

Electric switches were invented out of necessity. Having an electrical current flow through a circuit is beneficial, but without a safe and easy way to stop and start it, the possibilities are limited. Switches introduced a new way of using electricity. They are relatively simple and yet have been improved since the first basic switches. Smaller components allow the switches to be downsized and to fit in tighter spaces. They do not require much space, and sometimes the entire electronic device with which the switch is used can be made in a smaller size. Better materials and finer machining allow for high quality parts and components that do not wear out as quickly and that can provide the same service for hundreds if not thousands of repetitions during the switches' lifetime. These switches can be used in demanding environments where their functionality is critical. Some switches are used with other switches for precise control of the circuit. Using electric switches also helps conserve energy because unused circuits can be shut off, which saves electricity. Instead of having a device or appliance running constantly, they may be powered on only when in use due to the use of an electric switch. Although switches may seem to be simple and basic to their users today, they remain important parts of the devices on which much of the world has come to rely.

Electric Switches and Electronic Switches Images Provided by APEM Components, Inc.

Types of Electric Switches

• Cam switches have a plastic disk (cam) over which contoured surface a mechanical follower moves, controlling the contacts. The cam is attached to and rotated by a handle shaft. 
• DIP switches are circuit boards with a packaged group of tiny electric switches. The set is called a dual in-line package and is used mainly in programmable electronic devices.
• Double pole switches are electric switches with a pair of actuators that are either connected or disconnected to a circuit. There are at least four terminals in a double pole (DP) switches and these common devices allow two circuits to be either on or off while controlled by a single actuator.
• Double pole double throw (DPDT) switches open or close the connections of two conductors to a pair of separate circuits. DPDT switches, which usually have six terminals, can be set to maintain contact, alternate contact or have momentary contact.
  
• Double pole single throw (DPST) switches open or close the connection of a pair of circuit conductors in a single circuit. DPST switches usually have four terminals.
• Electrical switches are used for changing the flow of a circuit. Electrical switches may be categorized by various factors, such as the type of actuator they use. The actuator is the moving part that applies force to the contacts and may be a toggle, pushbutton, rocker or dial.
• Electronic switches are devices that can interrupt the flow of a circuit. Many electronic switches are binary devices that are either closed to allow the current to pass through the circuit, or they are open, which breaks the flow.
• Enabling switches are similar to safety switches, except they are manually operated. Enabling switches are designed to protect workers in more hazardous environments in which there is heavy machinery.
  
• Key lock switches are activated by use of a fitting key. The key is turned to one of several positions, triggering the switch.
  
• Lever switches are activated by turning a lever that is connected to a pivot point. Lever switches typically have three positions.
  
• Limit switches are utilized in monitoring and for the control of machinery and industrial equipment. Limit switches come in many different sizes and configurations.
  
• Maintained switches stay in the selected position when the handle is released.
  
• Miniature switches are used in applications that require compact mechanisms, such as handheld equipment.
  
• Multiple limit switches are used for the positioning and control of industrial equipment and machinery.
  
• Pressure switches convert pressure changes to electrical functions.
  
• Push button switches are so called due to their activation method, which is usually in the form of a plunger that, when pushed down, opens or closes the switch. The configurations of these mechanical switches can be single-pole, single-throw (SPST), single-pole, double-throw (SPDT), double-pole, single throw (DPST), double-pole, double throw (DPDT) or solid state.  
  
• Reed switches feature two contact blades, called ferromagnetic reeds, which are encapsulated in glass. The reeds close when exposed to a magnet. 
  
• Rocker switches are electric switches that are activated by rocking the switch to one side.
• Rope pull switches are triggered when there is tension in the safety cable. Rope pull switches provide safety and monitoring contacts in the printing, food processing and pharmaceutical industries.
  
• Rotary switches have contacts that are arranged in a full or partial circle, which means the mechanism that selects the contact must be turned. Rotary switches, which may be manual or automatic, are used in such applications as automobile distributions or ignition switches.  
  
• Safety switches feature integrated actuators, which serve to protect both equipment and personnel. This is done by monitoring the positions of movable components. 
• Single pole switches are simple electric switches that are either connected or disconnected to a circuit. Single pole switches are general purpose switches that are used in many situations because they are either on or off, a useful and helpful characteristic. Single pole (SP) switches can be either single throw or double throw, which refers to the number of conducting positions, that is, the number of terminals that will complete the circuit.
• Single pole double throw (SPDT) switches, also referred to as "three-way switches," open or close the connection of one conductor with one of two other conductors. SPDT switches often have three terminals and are sometimes used in pairs.
  
• Single pole single throw (SPST) switches, also called a "single-pole switches," open or close the connection of one conductor in a single circuit. SPST switches usually have two terminals. 
• Slide switches are devices that break an electrical circuit by moving linearly from position to position, interrupting the current's flow. It is a common type of DIP (dual in-line package) switch and provides at least two switch positions including on or off.
• Snap action switches are designed to very quickly move their contacts from one location to another. Mouse buttons and appliance settings use such switches. 
• Switch panels allow users to quickly access a series of mounted electric switches that are arranged in an enclosure.
• Toggle switches have only two positions. Light switches and the caps lock key on a computer keyboard are examples of toggle switch applications.
• Waterproof switches are devices that can interrupt the flow of a circuit while operating in a wet environment. Waterproof switches are frequently binary; this means that they either close or open the circuit.

Electric Switches Terms

Actuator - A mechanism that puts something into automatic action. In electrical switch terms, actuators include plungers, plain levers, simulated roller levers and many other examples.
 
Alternating Current (AC) - An electrical current that intermittently changes direction of flow.
 
Ampere-Turns (AT) - A unit of measurement that is used to define switch sensitivity. AT is calculated by the number of turns of the coil in which the switch is tested and the current (expressed in amps) that flows through the coil.
 
Break - The opening of a circuit, the act of which prohibits current flow.
 
Circuit - A closed path along which an electric current flows.
 
Detent - A mechanism consisting of a spring and starwheel that holds a switch in a specified position.
 
Direct Current (DC) - An electric current that flows in only one direction.
 
Drop-Out (DO) - The point at which the switch contacts simply release, expressed in ampere-turns.
 
Ground - The part of an electric circuit connected to the earth that has a zero potential. Most electric switches have ground connections.
 
Latching - The ability of a relay to have its contacts opened or closed upon command and remain in that position until another command is given.
 
Make - The closing of a contact, the act of which permits current flow.
 
Maximum Switching Current - The maximum load, referred to as amperage, that an electric switch is capable of carrying.
 
Normally Closed (NC) - A term that refers to a switch that is closed and connected in its normal position.
 
Normally Open (NO) - A term that refers to a switch that is open and disconnected in its normal position.
 
Plain Lever - A small rigid bar that is attached to a pivot point and is activated by being pushed one way or another. Lever switches normally have two or three positions.
 
Plunger - A type of actuator that is activated with a push or thrust.
 
Pole - An independent electrical circuit of a switch.
 
Set Point - The specific point at which an element of an electrical switch functions, expressed in psi, psia or inches of mercury.
 
Terminal - The position in a circuit at which a connection is normally established or broken.
 
Thermoplastic - A plastic material that can be heated and expanded as well as cooled and stiffened without any significant chemical change. Thermoplastics serve as dedicated housing to some switches.
 
Rating - A specified performance limit given to switches. Volts (V) and amperes (amps) are the standard units for establishing ratings.