Electric watch
Encyclopedia
Electric watch, which commonly means any watch
Watch
A watch is a small timepiece, typically worn either on the wrist or attached on a chain and carried in a pocket, with wristwatches being the most common type of watch used today. They evolved in the 17th century from spring powered clocks, which appeared in the 15th century. The first watches were...

 that is powered by electricity
Electricity
Electricity is a general term encompassing a variety of phenomena resulting from the presence and flow of electric charge. These include many easily recognizable phenomena, such as lightning, static electricity, and the flow of electrical current in an electrical wire...

, has become a generic term for the first generation of electrically powered watch
Watch
A watch is a small timepiece, typically worn either on the wrist or attached on a chain and carried in a pocket, with wristwatches being the most common type of watch used today. They evolved in the 17th century from spring powered clocks, which appeared in the 15th century. The first watches were...

es which appeared starting in 1957, before the invention of quartz watches in the 1970s. Their timekeeping element was either a traditional balance wheel
Balance wheel
The balance wheel is the timekeeping device used in mechanical watches and some clocks, analogous to the pendulum in a pendulum clock. It is a weighted wheel that rotates back and forth, being returned toward its center position by a spiral spring, the balance spring or hairspring...

 or a tuning fork
Tuning fork
A tuning fork is an acoustic resonator in the form of a two-pronged fork with the prongs formed from a U-shaped bar of elastic metal . It resonates at a specific constant pitch when set vibrating by striking it against a surface or with an object, and emits a pure musical tone after waiting a...

, driven electromagnetically
Electromagnetism
Electromagnetism is one of the four fundamental interactions in nature. The other three are the strong interaction, the weak interaction and gravitation...

 by a solenoid
Solenoid
A solenoid is a coil wound into a tightly packed helix. In physics, the term solenoid refers to a long, thin loop of wire, often wrapped around a metallic core, which produces a magnetic field when an electric current is passed through it. Solenoids are important because they can create...

 powered by a battery. The hands were driven mechanically through a wheel train
Wheel train (horology)
In horology, a wheel train is the gear train of a mechanical watch or clock. Although the term is used for other types of gear trains, the long history of mechanical timepieces has created a traditional terminology for their gear trains which is not used in other applications of gears.Watch...

. They were superseded by quartz watches, which had greater accuracy and durability due to their lower parts count. Recent automatic quartz
Automatic quartz
Automatic quartz is a collective term describing watch movements that combine a self-winding rotor mechanism to generate electricity with a piezoelectric quartz crystal as its timing element. Such movements aim to provide the advantages of quartz without the environmental impact of batteries...

 watches, which combine mechanical technology with quartz timekeeping, are not included in this classification.

Weaknesses

A weak point in early balance wheel electric watches was the switch
Switch
In electronics, a switch is an electrical component that can break an electrical circuit, interrupting the current or diverting it from one conductor to another....

 contacts on the balance wheel, which turned the solenoid on briefly to provide the impulse to keep the wheel oscillating. These wore out and did not operate reliably. Later designs used electromagnetic sensing, with a transistor in the circuit to turn the solenoid on.

Types of electric watches

  • Moving coil system, contact controlled: refers to watches with a balance wheel with integrated coil, fixed magnets and mechanical contacts. Examples of this technology are Hamilton
    Hamilton Watch Company
    The Hamilton Watch Company was originally formed to produce high quality pocket watches and wristwatches mid-range and luxury. Hamilton would become a corporate conglomerate diversified in other operations...

     500 (first electric watch), Epperlein 100, Champion (Ruhla / UMF) and Timex M40.
  • Fixed coil system, contact controlled: watches with a piece of iron attached to the balance wheel, a fixed coil and mechanical contacts. In order to extend the life of the watch, some of these movements included a diode
    Diode
    In electronics, a diode is a type of two-terminal electronic component with a nonlinear current–voltage characteristic. A semiconductor diode, the most common type today, is a crystalline piece of semiconductor material connected to two electrical terminals...

     to minimize sparking on the contacts. Examples of this technology are Lip electronic R 27, LIP R 148, Elgin-electric 722 and Landeron (ESA - Ebauches S.A.) 4750.
  • Transistorized
    Transistor
    A transistor is a semiconductor device used to amplify and switch electronic signals and power. It is composed of a semiconductor material with at least three terminals for connection to an external circuit. A voltage or current applied to one pair of the transistor's terminals changes the current...

     watches with balance
    Balance wheel
    The balance wheel is the timekeeping device used in mechanical watches and some clocks, analogous to the pendulum in a pendulum clock. It is a weighted wheel that rotates back and forth, being returned toward its center position by a spiral spring, the balance spring or hairspring...

    : had a balance wheel, a transistor acting as a switch and no mechanical contacts. Usually the coil was located in the base plate and the magnets are on the balance wheel. Watches using this technology include Timex M87/Laco 882, Citizen
    Citizen Watch Co.
    is the core company of a Japanese global corporate group based in Tokyo, Japan. The company was originally founded as Shokosha Watch Research Institute in 1918 and is currently known as the manufacturer of CINCOM precision lathe machine tools as well as CITIZEN watches. The trade name originated...

     X-8 series and Seiko
    Seiko
    , more commonly known simply as Seiko , is a Japanese watch company.-History and ongoing developments:The company was founded in 1881, when Kintarō Hattori opened a watch and jewelry shop called in the Ginza area of Tokyo, Japan. Eleven years later, in 1892, he began to produce clocks under the...

     Electronic 31A. Another common example example is ESA Dynotron cal. 9150.
  • Tuning fork watches: Instead of a balance wheel, these watches used a tuning fork
    Tuning fork
    A tuning fork is an acoustic resonator in the form of a two-pronged fork with the prongs formed from a U-shaped bar of elastic metal . It resonates at a specific constant pitch when set vibrating by striking it against a surface or with an object, and emits a pure musical tone after waiting a...

     driven by a solenoid
    Solenoid
    A solenoid is a coil wound into a tightly packed helix. In physics, the term solenoid refers to a long, thin loop of wire, often wrapped around a metallic core, which produces a magnetic field when an electric current is passed through it. Solenoids are important because they can create...

     powered by a one-transistor oscillator circuit
    Electronic oscillator
    An electronic oscillator is an electronic circuit that produces a repetitive electronic signal, often a sine wave or a square wave. They are widely used in innumerable electronic devices...

     and no mechanical contacts. The tuning fork had an attached pawl
    Pawl
    Pawl may refer to:* A common component of a ratchet* A part of the adjustable height locking mechanism of an extension ladder* Pawl , a former racing car constructor...

     and 'index wheel', which turned the gear train. The common frequencies used in watches were 300 Hz (ESA MOSABA cal. 9162, 9164 and 9210), 360 Hz (Bulova Accutron
    Bulova
    Bulova is a corporation making luxury watches and clocks. It has its headquarters in Woodside, Queens, New York City.Bulova was founded and incorporated as the J. Bulova Company in 1875 by Joseph Bulova , an immigrant from Bohemia...

     cal. 214 and 218), 480 Hz (Bulova Accutron cal. 2300) and 720 Hz (Omega Megasonic cal. 1220 and 1230). Omega F300Hz and Speedsonics series are common examples of ESA MOSABA based watches.

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