Electric Switches

About Electric Switches and Electronic Switches Including: Electrical Switches, Pushbutton Switches, Rocker Switches, Rotary Switch & Toggle Switches.

Electric switches, electronic switches or electrical switches are devices used to connect or break an electrical circuit. All switches consist of an operator, contacts and a switch mechanism. The operator actuates switch operation. The contacts are made of low-resistance metal and are used to make or break the electrical circuit. The switch mechanism is linked to the operator and opens/closes the contacts. The function of the switch is designated by the terms pole, throw and break. Pole indicates how many circuits a switch is capable of controlling. Throw refers to how many conductors or paths that a switch is able to control. Break is a term that refers to the breaking or opening of a circuit. The term “position” indicates how many stops a switch will make between its extreme settings.
 
The two most basic switch devices, of which other mechanisms are simply variations, are the slow-make, slow-break (AC base) and the quick-make, quick-break (AC/DC base) mechanisms. The first device is basically a teeter-totter or seesaw design. It is spring-loaded, requiring a very positive force to close the contacts. The slowness of a slow-make, slow-break device provides a slight time delay. This delay allows the AC current wave to nearly instantaneously cycle to zero before the spark is extinguished. Toggle switches, slide buttons, rocker switches or pushbutton switches can operate the mechanism.
 
The operator of a quick-make, quick-break device is similar to a trigger on a gun. It provides an irreversible action when tripped. The almost instant action is suitable in DC applications, as the more rapidly the contacts are separated, the sooner the arc of current is extinguished. The mechanism of a quick-make, quick-break device uses a compression type motor spring to provide the snap action. Quick-break, quick-make mechanisms are smaller and more compact than slow-make, slow-break mechanisms but are more costly. Quick-make, quick-break mechanisms also have self-wiping contacts to prevent corrosive buildup.
 
Although the circuit configuration possibilities for electronic switches are virtually endless, typical circuits include single-throw, double-throw without center off, double-throw with center off and double-throw momentary action with center off. The single-throw switch is the most basic circuit with only two positions: on and off. Double-throw switches without an off position in the center are referred to as ON-ON switches. These manual electric switches are commonly used in selector applications (e.g. 6V or 12V on a battery charger). Double-throw electric switches with a center off position are three-position switches with two independent ON switches, an example of which is the HI-OFF-LOW settings of a kitchen range hood exhaust fan. Three-position double-throw electric switches with momentary action use a spring loading action. As long as pressure is applied to the actuator, the position will be maintained, making these electronic switches operator-dependent.

Electric Switches and Electronic Switches Images Provided by Penn Star Electronics

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.
  
• 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.
  
• Dual inline package (DIP) switches are a set of small-sized ON-OFF switches. DIP switches are used in place of jumpers and in such electronics as garage door openers, personal computers and paintball marker electro-chips.
  
• Electric switches change the flow of electric current.
  
• 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.
  
• Pushbutton 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 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.
  
• Snap action switches are designed to very quickly move their contacts from one location to another. Mouse buttons and appliance settings use such switches.
  
• Toggle switches have only two positions. Light switches and the caps lock key on a computer keyboard are examples of toggle switch applications.

Electric Switches Terms

Actuator – A mechanism that puts something into automatic action. In electrical switch terms, actuators include plungers, plain levers, simulated roller levers, etc.
 
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 which is closed and connected in its normal position.
 
Normally Open (NO) – A term that refers to a switch which 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.