A time switch (also called a timer switch, or simply timer) is a

timer A timer is a specialized type of clock used for measuring specific time intervals. Timers can be categorized into two main types. The word "timer" is usually reserved for devices that counts down from a specified time interval, while devices th ...

that operates an electric

switch In electrical engineering, a switch is an electrical component that can disconnect or connect the conducting path in an electrical circuit, interrupting the electric current or diverting it from one conductor to another. The most common type ...

controlled by the timing mechanism.

Intermatic Intermatic Incorporated is an American manufacturer of time switches headquartered in Spring Grove, Illinois. Intermatic was founded in 1891 in Chicago, Illinois as the ''International Register Company'' to produce fare registers. The compan ...

introduced its first time switch in 1945, which was used for "electric signs, store window lighting, apartment hall lights, stokers, and oil and gas burners." A consumer version was added in 1952. The switch may be connected to an electric circuit operating from mains power, including via a

relay A relay Electromechanical relay schematic showing a control coil, four pairs of normally open and one pair of normally closed contacts An automotive-style miniature relay with the dust cover taken off A relay is an electrically operated swit ...

or contactor; or low voltage, including battery-operated equipment in

vehicle A vehicle (from la, vehiculum) is a machine that transports people or cargo. Vehicles include wagons, bicycles, motor vehicles ( motorcycles, cars, trucks, buses, mobility scooters for disabled people), railed vehicles ( trains, trams ...

s. It may be built into power circuits (as with a

central heating A central heating system provides warmth to a number of spaces within a building from one main source of heat. It is a component of heating, ventilation, and air conditioning (short: HVAC) systems, which can both cool and warm interior spaces. ...

or water heater timer), plugged into a wall outlet with equipment plugged into the timer instead of directly into the power point; or built into equipment.

Types

Sleep timer

A sleep timer is a function on many modern

television Television, sometimes shortened to TV, is a telecommunication Media (communication), medium for transmitting moving images and sound. The term can refer to a television set, or the medium of Transmission (telecommunications), television tra ...

s and other electronic devices that shuts off the power after a preset amount of time. The setting is usually made either from the

remote control In electronics, a remote control (also known as a remote or clicker) is an electronic device used to operate another device from a distance, usually wirelessly. In consumer electronics, a remote control can be used to operate devices such as ...

of the device or the device's menu. They are intended to allow viewers to watch as they fall asleep. The mechanism may be mechanical (e.g.,

clockwork Clockwork refers to the inner workings of either mechanical devices called clocks and watches (where it is also called the movement) or other mechanisms that work similarly, using a series of gears driven by a spring or weight. A clockwork mec ...

; rarely used nowadays), electromechanical (e.g., a slowly rotating geared motor that mechanically operates switches) or

electronic Electronic may refer to: *Electronics, the science of how to control electric energy in semiconductor * ''Electronics'' (magazine), a defunct American trade journal *Electronic storage, the storage of data using an electronic device *Electronic co ...

, with

semiconductor A semiconductor is a material which has an electrical conductivity value falling between that of a conductor, such as copper, and an insulator, such as glass. Its resistivity falls as its temperature rises; metals behave in the opposite way. ...

timing circuitry and switching devices and no moving parts. The timer may switch equipment on, off, or both, at a preset time or times, after a preset interval, or cyclically. A countdown time switch switches power, usually off, after a preset time. A cyclical timer switches equipment both on and off at preset times over a period, then repeats the cycle; the period is usually 24 hours or 7 days. For example, a central heating timer may supply heat for a specified period during the morning and evening every weekday, and all day on weekends. A timer for an unattended slow cooker may switch on automatically at a time and for a period suitable to have food ready at mealtime. Likewise, a coffee maker may turn itself on early in the

morning Morning is the period from sunrise to noon. There are no exact times for when morning begins (also true of evening and night) because it can vary according to one's lifestyle and the hours of daylight at each time of year. However, morning stric ...

in time for awakening residents to have fresh

coffee Coffee is a drink prepared from roasted coffee beans. Darkly colored, bitter, and slightly acidic, coffee has a stimulating effect on humans, primarily due to its caffeine content. It is the most popular hot drink in the world. Seeds of ...

already brewed for them. Timers may do other processing or have sensors; for example, a timer may switch on lights only during hours of darkness, using a

season A season is a division of the year based on changes in weather, ecology, and the number of daylight hours in a given region. On Earth, seasons are the result of the axial parallelism of Earth's tilted orbit around the Sun. In temperate and po ...

algorithm In mathematics and computer science, an algorithm () is a finite sequence of rigorous instructions, typically used to solve a class of specific problems or to perform a computation. Algorithms are used as specifications for performing ...

or light sensor. Combining the two allows a light to come on at sundown and go off at midnight, for example.

Astronomical timer

An astronomical (or astronomic) timer calculates

dawn Dawn is the time that marks the beginning of twilight before sunrise. It is recognized by the appearance of indirect sunlight being scattered in Earth's atmosphere, when the centre of the Sun's disc has reached 18° below the observer's ho ...

and

dusk Dusk occurs at the darkest stage of twilight, or at the very end of astronomical twilight after sunset and just before nightfall.''The Random House College Dictionary'', "dusk". At predusk, during early to intermediate stages of twilight, enou ...

times (tracking the sun position) for each day of the year based on the

latitude In geography, latitude is a coordinate that specifies the north– south position of a point on the surface of the Earth or another celestial body. Latitude is given as an angle that ranges from –90° at the south pole to 90° at the north po ...

and

longitude Longitude (, ) is a geographic coordinate that specifies the east– west position of a point on the surface of the Earth, or another celestial body. It is an angular measurement, usually expressed in degrees and denoted by the Greek let ...

(or just north/central/south and

time zone A time zone is an area which observes a uniform standard time for legal, commercial and social purposes. Time zones tend to follow the boundaries between countries and their subdivisions instead of strictly following longitude, because i ...

on more cheaply made ones), and the

day of the year An ordinal date is a calendar date typically consisting of a '' year'' and a day of the year or ordinal day number (or simply ordinal day or day number), an ordinal number ranging between 1 and 366 (starting on January 1), though year may sometim ...

(month and date), programmed by the user upon installation in addition to the usual

time of day Time is the continued sequence of existence and events that occurs in an apparently irreversible succession from the past, through the present, into the future. It is a component quantity of various measurements used to sequence events, t ...

, except in the case of GPS enabled astronomic timers wherein all programming is fully automatic. This eliminates the need for a photocell (which may be repeatedly triggered on and off by the light which it operates) or for repeatedly re-setting a regular timer for seasonal changes in the length of day or for daylight-saving time. This allows exterior

lighting Lighting or illumination is the deliberate use of light to achieve practical or aesthetic effects. Lighting includes the use of both artificial light sources like lamps and light fixtures, as well as natural illumination by capturing dayli ...

like a

porch A porch (from Old French ''porche'', from Latin ''porticus'' "colonnade", from ''porta'' "passage") is a room or gallery located in front of an entrance of a building. A porch is placed in front of the facade of a building it commands, and form ...

light fixture A light fixture (US English), light fitting (UK English), or luminaire is an electrical device containing an electric lamp that provides illumination. All light fixtures have a fixture body and one or more lamps. The lamps may be in sockets fo ...

to be controlled by simply replacing its indoor wall switch, or doing the same for a lamp in a dark interior corner (away from a

window A window is an opening in a wall, door, roof, or vehicle that allows the exchange of light and may also allow the passage of sound and sometimes air. Modern windows are usually glazed or covered in some other transparent or translucent mate ...

) by simply plugging-in a self-adjusting lamp timer. Time switches can be used for many purposes, including saving

electric energy Electrical energy is energy related to forces on electrically charged particles and the movement of electrically charged particles (often electrons in wires, but not always). This energy is supplied by the combination of electric current and electr ...

by consuming it only when required, switching equipment on, off, or both at times required by some process, and home security (for example switching lights in a pattern that gives the impression that premises are attended) to reduce the likelihood of

burglary Burglary, also called breaking and entering and sometimes housebreaking, is the act of entering a building or other areas without permission, with the intention of committing a criminal offence. Usually that offence is theft, robbery or murde ...

or prowling. Among applications are

(interior, exterior, and

street light A street light, light pole, lamp pole, lamppost, street lamp, light standard, or lamp standard is a raised source of light on the edge of a road or path. Similar lights may be found on a railway platform. When urban electric power distributio ...

ing), cooking devices such as ovens,

washing machine A washing machine (laundry machine, clothes washer, washer, or simply wash) is a home appliance used to wash laundry. The term is mostly applied to machines that use water as opposed to dry cleaning (which uses alternative cleaning fluids and ...

s, and

heating and cooling Heating, ventilation, and air conditioning (HVAC) is the use of various technologies to control the temperature, humidity, and purity of the air in an enclosed space. Its goal is to provide thermal comfort and acceptable indoor air quality. HV ...

of buildings and vehicles. Built-in automatic washing machine controllers are examples of very complex electromechanical and electronic timers cycles, starting and stopping many processes including

pump A pump is a device that moves fluids ( liquids or gases), or sometimes slurries, by mechanical action, typically converted from electrical energy into hydraulic energy. Pumps can be classified into three major groups according to the method the ...

s and

valve A valve is a device or natural object that regulates, directs or controls the flow of a fluid (gases, liquids, fluidized solids, or slurries) by opening, closing, or partially obstructing various passageways. Valves are technically fitting ...

s to fill and empty the drum with water, heating, and rotating at different speeds, with different combinations of settings for different fabrics.

Gallery

File:UK time switch.jpg, A 24-hour cyclical electromechanical UK time switch showing current time 06:15 and set to be on from 07:00 to 07:45 and 20:00 to 22:00. File:Digital In-Wall Timers.JPG, Digital in-wall timer switch with battery for uninterrupted time keeping

References

{{Authority control Switches Energy development Appropriate technology

Types

Sleep timer

Astronomical timer

Gallery

See also

References