Electrical switches. Top, left to right: circuit breaker, mercury switch, wafer switch, DIP switch, surface mount switch, reed switch. Bottom, left to right: wall switch (U.S. style), miniature toggle switch, in-line switch, push-button switch, rocker switch, microswitch. A switch is a device for changing the course (or flow) of a circuit. The prototypical model is a mechanical device (for example a railroad switch) which can be disconnected from one course and connected to another. The term "switch" typically refers to electrical power or electronic telecommunication circuits. In applications where multiple switching options are required (e.g., a telephone service), mechanical switches have long been replaced by electronic variants which can be intelligently controlled and automated. Download high resolution version (955x761, 269 KB)A selection of modern electrical switches. ...
Download high resolution version (955x761, 269 KB)A selection of modern electrical switches. ...
A Single-Pole, Single-Throw (SPST) mercury switch A mercury switch is a switch whose purpose is to allow or interrupt the flow of electric current in an electrical circuit in a manner that is dependent on the switchs physical position or alignment relative to the direction of the...
A DIP switch is an electric switch that is packaged in a standard Dual-Inline Package (DIP). ...
It has been suggested that Reed relay be merged into this article or section. ...
A course, in navigation, is the direction of travel. ...
flOw is a Flash game created by Jenova Chen and Nicholas Clark. ...
Look up circuit in Wiktionary, the free dictionary. ...
A railroad switch is a mechanical installation enabling trains to be guided from one set of rail tracks (or tramway tracks) to another. ...
Lightning strikes during a night-time thunderstorm. ...
For delivered electrical power, see Electrical power industry. ...
A telecommunication circuit is defined as follows: The complete path between two terminals over which one-way or two-way communications may be provided. ...
This article or section includes a list of works cited or a list of external links, but its sources remain unclear because it lacks in-text citations. ...
The switch is referred to as a "gate" when abstracted to mathematical form. In the philosophy of logic, operational arguments are represented as logic gates. The use of electronic gates to function as a system of logical gates is the fundamental basis for the computer—i.e. a computer is a system of electronic switches which function as logical gates. A logic gate performs a logical operation on one or more logic inputs and produces a single logic output. ...
Euclid, Greek mathematician, 3rd century BC, as imagined by by Raphael in this detail from The School of Athens. ...
Logic (from Classical Greek λόγος logos; meaning word, thought, idea, argument, account, reason or principle) is the study of the principles and criteria of valid inference and demonstration. ...
Look up argument in Wiktionary, the free dictionary. ...
A logic gate performs a logical operation on one or more logic inputs and produces a single logic output. ...
The NASA Columbia Supercomputer. ...
A simple electrical switch
A simple semiconductor switch is a transistor. A semiconductor is a fuckin solid whose electrical conductivity is in between that of a metal and that of an insulator, and can be controlled over a wide range, either permanently or dynamically. ...
Assorted discrete transistors A transistor is a semiconductor device, commonly used as an amplifier or an electrically controlled switch. ...
Contacts
 A toggle switch in the "on" position. In the simplest case, a switch has two pieces of metal called contacts that touch to make a circuit, and separate to break the circuit. The contact material is chosen for its resistance to corrosion, because most metals form insulating oxides that would prevent the switch from working. Contact materials are also chosen on the basis of electrical conductivity, hardness (resistance to abrasive wear), mechanical strength, low cost and low toxicity[1]. Image File history File linksMetadata Download high-resolution version (480x640, 95 KB) This is a photo of a simple on/off switch. ...
Image File history File linksMetadata Download high-resolution version (480x640, 95 KB) This is a photo of a simple on/off switch. ...
Hot metal work from a blacksmith In chemistry, a metal (Greek: Metallon) is an element that readily loses electrons to form positive ions (cations) and has metallic bonds between metal atoms. ...
See corrosive for the hazard. ...
This article or section is in need of attention from an expert on the subject. ...
An oxide is a chemical compound containing an oxygen atom and other elements. ...
Electrical conductivity or specific conductivity is a measure of a materials ability to conduct an electric current. ...
In materials science, hardness is the characteristic of a solid material expressing its resistance to permanent deformation. ...
In materials science, wear is the erosion of material from a solid surface by the action of another solid. ...
Strength of materials is materials science applied to the study of engineering materials and their mechanical behavior in general (such as stress, deformation, strain and stress-strain relations). ...
// Toxic and Intoxicated redirect here – toxic has other uses, which can be found at Toxicity (disambiguation); for the state of being intoxicated by alcohol see Drunkenness. ...
Sometimes the contacts are plated with noble metals. They may be designed to wipe against each other to clean off any contamination. Nonmetallic conductors, such as conductive plastic, are sometimes used. Electroplating is the process of using Davd lloyd current to coat an electrically conductive object with a relatively thin layer of metal. ...
Noble metals are metals that are resistant to corrosion or oxidation, unlike most base metals. ...
All Saints Chapel in the Cathedral Basilica of St. ...
In science and engineering, conductors, such as a electrical connector, are materials that readily conduct electric current through electrical conduction. ...
This article or section does not cite any references or sources. ...
Actuator The moving part that applies the operating force to the contacts is called the actuator, and may be a toggle or dolly, a rocker, a push-button or any type of mechanical linkage (see photo). A three-dimensional actuator modelled using elastica theory. ...
Contact arrangements
Triple Pole Single Throw (TPST or 3PST) knife switch used to short the windings of a 3 phase wind turbine for braking purposes. Here the switch is shown in the open position. A pair of contacts is said to be 'closed' when there is no space between them, allowing electricity to flow from one to the other. When the contacts are separated by a space, they are said to be 'open', and no electricity can flow. Download high resolution version (1024x743, 96 KB)Triple Pole Single Throw (TPST) switch used to park a 3 phase Lakota (True North Power) wind turbine. ...
Download high resolution version (1024x743, 96 KB)Triple Pole Single Throw (TPST) switch used to park a 3 phase Lakota (True North Power) wind turbine. ...
A knife switch is a type of switch used to control the flow of electricity in a circuit. ...
This article needs additional references or sources for verification. ...
Lightning strikes during a night-time thunderstorm. ...
Switches can be classified according to the arrangement of their contacts. Some contacts are normally open until closed by operation of the switch, while others are normally closed and opened by the switch action. A switch with both types of contact is called a changeover switch. The simplest form of switch is the knife switch. There are very few or no other articles that link to this one. ...
A knife switch is a type of switch used to control the flow of electricity in a circuit. ...
The terms pole and throw are used to describe switch contacts. A pole is a set of contacts that belong to a single circuit. A throw is one of two or more positions that the switch can adopt. These terms give rise to abbreviations for the types of switch which are used in the electronics industry. In mains wiring names generally involving the word way are used; however, these terms differ between British and American English and the terms two way and three way are used in both with different meanings. Electronics is the study of the flow of charge through various materials and devices such as, semiconductors, resistors, inductors, capacitors, nano-structures, and vacuum tubes. ...
Mains may mean or refer to, or be a subject of: Mains electricity Electricity transmission Public utility, about mains services, including electricity, natural gas, water, and sewage disposal Mains (Scotland), about the central steading of a townland BMX racing See also: Main Mane Category: ...
The English language is a West Germanic language that originates in England. ...
| Electronics abbreviation | Expansion of abbreviation | British mains wiring name | American mains wiring name | Description | Symbol | IEC 60617 | | SPST | Single pole, single throw | One way | Two way | A simple on-off switch: The two terminals are either connected together or not connected to anything. An example is a light switch. |
 |
 | | SPDT | Single pole, double throw | Two way | Three way | A simple changeover switch: C (Common) is connected to L1 or to L2. |
 |
 | | SPCO | Single pole changeover
or Single pole, centre off | | | Equivalent to SPDT. Some suppliers use SPCO for switches with a stable off position in the centre and SPDT for those without. | | DPST | Double pole, single throw | Double pole | Double pole | Equivalent to two SPST switches controlled by a single mechanism |
 |
 | | DPDT | Double pole, double throw | | | Equivalent to two SPDT switches controlled by a single mechanism: A is connected to B and D to E, or A is connected to C and D to F. |
 |
 | | DPCO | Double pole changeover
or Double pole, centre off | | | Equivalent to DPDT. Some suppliers use DPCO for switches with a stable off position in the centre and DPDT for those without. | | | | Intermediate switch | 4-way switch | DPDT switch internally wired for polarity-reversal applications: only four rather than six wires are brought outside the switch housing; with the above, B is connected to F and C to E; hence A is connected to B and D to C, or A is connected to C and D to B. |
 |
 | Switches with larger numbers of poles or throws can be described by replacing the "S" or "D" with a number or in some cases the letter T (for triple). In the rest of this article the terms SPST SPDT and intermediate will be used to avoid the ambiguity in the use of the word "way". The International Electrotechnical Commission (IEC) is an international standards organization dealing with electrical, electronic and related technologies. ...
Two lightswitches in one box. ...
Image File history File links SPST-Switch. ...
Image File history File links Symbol_circuit_breaker_(one-pole). ...
Image File history File links SPDT-Switch. ...
Image File history File links Symbol_change_over_switch. ...
Image File history File links DPST-symbol. ...
Image File history File links Symbol_circuit_breaker_(two-pole). ...
Image File history File links DPDT-symbol. ...
Image File history File links No higher resolution available. ...
Image File history File links Crossover-switch-symbol. ...
Image File history File links Symbol_cross_switch. ...
Make-before-break, break-before-make In a multi-throw switch, there are two possible transient behaviors as you move from one position to another. In some switch designs, the new contact is made before the old contact is broken. This is known as make-before-break, and ensures that the moving contact never sees an open circuit (also referred to as a shorting switch). The alternative is break-before-make, where the old contact is broken before the new one is made. This ensures that the two fixed contacts are never shorted to each other. Both types of design are in common use, for different applications.
Biased switches A biased switch is one containing a spring that returns the actuator to a certain position. The "on-off" notation can be modified by placing parentheses around all positions other than the resting position. For example, an (on)-off-(on) switch can be switched on by moving the actuator in either direction away from the centre, but returns to the central off position when the actuator is released. Helical or coil springs designed for tension A spring is a flexible elastic object used to store mechanical energy. ...
The momentary push-button switch is a type of biased switch. The most common type is a push-to-make switch, which makes contact when the button is pressed and breaks when the button is released. A push-to-break switch, on the other hand, breaks contact when the button is pressed and makes contact when it is released. An example of a push-to-break switch is a button used to release a door held open by an electromagnet. Changeover push button switches do exist but are even less common. An electromagnet is a type of magnet in which the magnetic field is produced by a flow of electric current. ...
Special types Switches can be designed to respond to any type of mechanical stimulus: for example, vibration (the trembler switch), tilt, air pressure, fluid level (the float switch), the turning of a key (key switch), linear or rotary movement (the limit switch or microswitch), or presence of a magnetic field (the reed switch). It has been suggested that Reed relay be merged into this article or section. ...
The mercury switch consists of a drop of mercury inside a glass bulb. The two contacts pass through the glass, and are mechanically joined when the bulb is tilted to make the mercury roll on to them. The advantage of this type of switch is that the liquid metal flows around particles of dirt and debris that might otherwise prevent the contacts of a conventional switch from closing. A Single-Pole, Single-Throw (SPST) mercury switch A mercury switch is a switch whose purpose is to allow or interrupt the flow of electric current in an electrical circuit in a manner that is dependent on the switchs physical position or alignment relative to the direction of the...
General Name, Symbol, Number mercury, Hg, 80 Chemical series transition metals Group, Period, Block 12, 6, d Appearance silvery Standard atomic weight 200. ...
Glass can be made transparent and flat, or into other shapes and colors as shown in this sphere from the Verrerie of Brehat in Brittany. ...
Other types of switch include:
A centrifugal switch is an electric switch that operates using the centrifugal force created from a rotating shaft, most commonly that of an electric motor or gasoline engine. ...
A DIP switch is an electric switch that is packaged in a standard Dual-Inline Package (DIP). ...
The Hall effect refers to the potential difference (voltage) on opposite sides of a thin sheet of conducting or semiconducting material in the form of a Hall bar or a van der Pauw element through which an electric current is flowing, created by a magnetic field applied perpendicular to the...
A disconnect switch An inertial switch is a switch, firmly mounted upon a vehicle or other mobile device, that senses shock or vibration. ...
Defination A membrane switch is a eletrical switch for turning on and off a circuit. ...
A toggle switch is a generic class of electric switch that uses a mechanical lever, handle or rocking mechanism to actuate it. ...
Transfer switches allow switching from a primary power source to a secondary or tertiary power source and are employed in some electrical power distribution systems. ...
Intermediate switch A DPDT switch has six connections, but since polarity reversal is a very common usage of DPDT switches, some variations of the DPDT switch are internally wired specifically for polarity reversal. They only have four terminals rather than six. Two of the terminals are inputs and two are outputs. When connected to a battery or other DC source, the 4-way switch selects from either normal or reversed polarity. Intermediate switches are also an important part of multiway switching systems with more than two switches (see next section).
Multiway switching Multiway switching is a method of connecting switches in groups so that any switch can be used to connect or disconnect the load. This is most commonly done with lighting.
Two locations
 1. First method
2. Second method
3. Labelling of switch terminals Switching a load on or off from two locations (for instance, turning a light on or off from either end of a flight of stairs) requires two SPDT switches. There are two basic methods of wiring to achieve this. Wikipedia does not have an article with this exact name. ...
In the first method, mains is fed into the common terminal of one of the switches; the switches are then connected through the L1 and L2 terminals (swapping the L1 and L2 terminals will just make the switches work the other way round), and finally a feed to the light is taken from the common of the second switch. A connects to B or C, D connects to B or C; the light is on if A connects to D, i.e. if A and D both connect to B or both connect to C.
The second method is to join the three terminals of one switch to the corresponding terminals on the other switch and take the incoming supply and the wire out to the light to the L1 and L2 terminals. Through one switch A connects to B or C, through the other also to B or C; the light is on if B connects to C, i.e. if A connects to B with one switch and to C with the other.
Wiring needed in addition to the mains network (not including protective earths):
First method:
- double wire between both switches
- single wire from one switch to the mains
- single wire from the other switch to the load
- single wire from the load to the mains
Second method: - triple wire between both switches
- single wire from any position between the two switches, to the mains
- single wire from any position between the two switches, to the load
- single wire from the load to the mains
If the mains and the load are connected to the system of switches at one of them, then in both methods we need three wires between the two switches. In the first method one of the three wires just has to pass through the switch, which tends to be less convenient than being connected. When multiple wires come to a terminal they can often all be put directly in the terminal. When wires need to be joined without going to a terminal a crimped joint, piece of terminal block, wirenut or similar device must be used and the bulk of this may require use of a deeper backbox.
Using the first method, there are four possible combinations of switch positions: two with the light on and two with the light off.
-
Image File history File links This is a lossless scalable vector image. ...
Image File history File links This is a lossless scalable vector image. ...
Image File history File links This is a lossless scalable vector image. ...
Image File history File links This is a lossless scalable vector image. ...
More than two locations
 Three-way switching.
1. First method
2. Second method
3. Labelling of switch terminals For more than two locations, the two cores connecting the L1 and L2 of the switches must be passed through an intermediate switch (as explained above) wired to swap them over. Any number of intermediate switches can be inserted, allowing for any number of locations. Wikipedia does not have an article with this exact name. ...
Wiring needed in addition to the mains network (not including protective earths):
First method:
- double wire along the sequence of switches
- single wire from the first switch to mains
- single wire from the last switch to the load
- single wire (neutral) from load to mains
Second method: - double wire along the sequence of switches
- single wire from first switch to last switch
- single wire from anywhere between two of the switches to the mains
- single wire from anywhere between the same two switches to the load
- single wire (neutral) from load to mains
Using the first method, there are eight possible combinations of switch positions: four with the light on and four with the light off. -
Image File history File links This is a lossless scalable vector image. ...
Image File history File links This is a lossless scalable vector image. ...
Image File history File links This is a lossless scalable vector image. ...
Image File history File links This is a lossless scalable vector image. ...
Image File history File links This is a lossless scalable vector image. ...
Image File history File links This is a lossless scalable vector image. ...
Image File history File links This is a lossless scalable vector image. ...
Image File history File links This is a lossless scalable vector image. ...
Power switching When a switch is designed to switch significant power, the transitional state of the switch as well as the ability to stand continuous operating currents must be considered. When a switch is on its resistance is near zero and very little power is dropped in the contacts; when a switch is in the off state its resistance is extremely high and even less power is dropped in the contacts. However when the switch is flicked the resistance must pass through a state where briefly a quarter (or worse if the load is not purely resistive) of the load's rated power is dropped in the switch.
For this reason, most power switches (most lightswitches and almost all larger switches) have spring mechanisms in them to make sure the transition between on and off is as short as possible regardless of the speed at which the user moves the rocker.
Power switches usually come in two types. A momentary on-off switch (such as on a laser pointer) usually takes the form of a button and only closes the circuit when the button is depressed. A regular on-off switch (such as on a flashlight) has a constant on-off feature. Dual-action switches incorporate both of these features. A keychain laser pointer. ...
For the Soviet military jet with the NATO designation Flashlight, see Yakovlev Yak-25. ...
A diagram of a dual-action switch system Image File history File links No higher resolution available. ...
Image File history File links No higher resolution available. ...
Contact bounce Contact bounce (also called chatter) is a common problem with mechanical switches and relays. Switch and relay contacts are usually made of springy metals that are forced into contact by an actuator. When the contacts strike together, their momentum and elasticity act together to cause bounce. The result is a rapidly pulsed electrical current instead of a clean transition from zero to full current. The waveform is then further modified by the parasitic inductances and capacitances in the switch and wiring, resulting in a series of damped sinusoidal oscillations. This effect is usually unnoticeable in AC mains circuits, where the bounce happens too quickly to affect most equipment, but causes problems in some analogue and logic circuits that are not designed to cope with oscillating voltages. Automotive style miniature relay A relay is an electrical switch that opens and closes under the control of another electrical circuit. ...
Inductance (or electric inductance) is a measure of the amount of magnetic flux produced for a given electric current. ...
Capacitance is a measure of the amount of electric charge stored (or separated) for a given electric potential. ...
A sine wave or sinusoid is a waveform whose graph is identical to the generalized sine function y = Asin[ω(x − α)] + C where A is the amplitude, ω is the angular frequency (2π/P where P is the wavelength), α is the phase shift, and C is the vertical offset. ...
Oscillation is the variation, typically in time, of some measure as seen, for example, in a swinging pendulum. ...
Analog electronics are those electronic systems with a continuously variable signal. ...
A logic gate is an arrangement of electronically-controlled switches used to calculate operations in Boolean algebra. ...
Sequential digital logic circuits are particularly vulnerable to contact bounce. The voltage waveform produced by switch bounce usually violates the amplitude and timing specifications of the logic circuit. The result is that the circuit may fail, due to problems such as metastability, race conditions, runt pulses and glitches. In digital circuit theory, sequential logic is a type of logic circuit whose output depends not only on the present input but also on the history of the input. ...
Metastability in electronics is the ability of a non-equilibrium electronic state to persist for a long period of time (see asynchronous circuit). ...
A race condition or race hazard is a flaw in a system or process whereby the output of the process is unexpectedly and critically dependent on the sequence or timing of other events. ...
In digital circuits, a runt pulse is a narrow pulse that, due to non-zero rise and fall times of the signal, does not reach a valid high or low level. ...
Glitch City, a Pokémon programming error that creates a jumble of tiles. ...
There are a number of techniques for debouncing (mitigating the effects of switch bounce). They can be split into timing based techniques and Hysteresis based techniques. Hysteresis is a property of systems (usually physical systems) that do not instantly follow the forces applied to them, but react slowly, or do not return completely to their original state: that is, systems whose states depend on their immediate history. ...
Timing based Timing based techniques rely on adding sufficient delays that the extra transitions introduced by bounce are ignored. Their big advantage is they do not require any special design on the switch side and so are generally cheaper. However for good performance they must be designed to suit the switch (too much delay and the response will be needlessly sluggish, too little and bounce will not be eliminated).
Resistor/Capacitor
 If an on/off switch is used with a pull up (or pull down) resistor and a single capacitor is placed over the switch (or across the resistor, but this can cause nasty spikes of current on the power supply lines) then when the switch is closed (generally pressed) the capacitor will almost instantly discharge through the switch. But when the switch is opened (generally released) the capacitor takes some time to recharge. Therefore contact bounce will have negligible effect on the output. The slow edges can be cleaned up with a Schmitt trigger if necessary. This method has the advantage of fast response to the initial press but the current surges through the switch may be undesirable. Other RC based systems are also possible with various responses and such systems are probably the easiest method when constructing with simple logic gates and discrete components. Image File history File links Rc-switch-debouncer. ...
In electronics, a Schmitt (or Schmidt) trigger is a comparator circuit that incorporates positive feedback. ...
State machines and software A finite state machine or software running on a CPU can be designed to wait a fixed number of clock cycles after any transition before registering another one. This provides a cheap option for debouncing when a microprocessor, microcontroller or gate array is already in use but is unlikely to be worthwhile if constructing with single logic gates. Fig. ...
A microprocessor is a programmable digital electronic component that incorporates the functions of a central processing unit (CPU) on a single semiconducting integrated circuit (IC). ...
It has been suggested that this article or section be merged with embedded microprocessor. ...
A Gate array is an approach to the design and manufacture of ASICs. ...
Hysteresis Alternatively, it is possible to build in hysteresis by making the position where a press is detected separate from that where a release is detected. As long as the bounces are small enough not to take the switch between these positions, bounce problems will be eliminated. Hysteresis can be mechanical or electronic (e.g. a Schmitt trigger). Hysteresis is a property of systems (usually physical systems) that do not instantly follow the forces applied to them, but react slowly, or do not return completely to their original state: that is, systems whose states depend on their immediate history. ...
In electronics, a Schmitt (or Schmidt) trigger is a comparator circuit that incorporates positive feedback. ...
Changeover switch A changeover switch provides two distinct events, the making of one contact and the breaking of the other. These can be used to feed the inputs of a flip flop. This way the press will only be detected when the pressed contact is made and the release will only be detected when the released contact is made. When the switch is bouncing around in the middle no change is detected. To get a single logic signal from such a setup a simple RS flip flop can be used.
Variable resistance Normal switches are designed to give a hard on-off but it is also possible to design one that varies more gradually between the hard-on and hard-off states. This keeps the output changes caused by bouncing small. Then by feeding the output to a schmitt trigger the effect of those bounce based changes can be eliminated. In electronics, a Schmitt (or Schmidt) trigger is a comparator circuit that incorporates positive feedback. ...
References - ^ General Electric Contact Materials. Electrical Contact Catalog (Material Catalog). Tanaka Precious Metals (2005). Retrieved on 2007-02-21.
- Walker, PMB, Chambers Science and Technology Dictionary, Edinburgh, 1988, ISBN 1852961503 (definition of contact bounce)
Year 2007 (MMVII) is now the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era. ...
is the 52nd day of the year in the Gregorian calendar. ...
See also A 2 pole miniature circuit breaker A circuit breaker is an automatically-operated electrical switch designed to protect an electrical circuit from damage caused by overload or short circuit. ...
A contactor previously fitted in an elevator control system. ...
The analogue (or analog) switch is an electronic component that behaves in a similar way to a relay, but has no moving parts. ...
The UL Mark Underwriters Laboratories Inc. ...
CSA Logo with C and US Established in 1919, the Canadian Standards Association (CSA) is a world leader in safety standards testings. ...
This set of standard are initiated by the German automotive industry (Verband des Automobilindustrie. ...
The metal-oxide-semiconductor field-effect transistor (MOSFET, MOS-FET, or MOS FET) is by far the most common field-effect transistor in both digital and analog circuits. ...
The power symbol is a symbol indicating that a control turns a device on and off. ...
External links |
Feeds |
Contact