View source for Rotary switch

{{short description|Device}}
{{for|the Rotary Machine Switching System telephone exchange|rotary system}}
{{one source|date=February 2024}}
{{no footnotes|date=February 2024}}

[[File:rotaryswitch.gif|thumb|360px|Three-deck rotary switch allows controlling three different circuit functions.]]

A '''rotary switch''' is a switch operated by rotation. These are often chosen when more than 2 positions are needed, such as a three-speed [[fan (implement)|fan]] or a [[CB radio]] with multiple [[frequency|frequencies]] of reception or "channels".

A rotary switch consists of a [[spindle (tool)|spindle]] or "[[Rotor (electric)|rotor]]" that has a contact arm or "spoke" which projects from its surface like a [[Cam (mechanism)|cam]]. It has an array of terminals, arranged in a circle around the rotor, each of which serves as a contact for the "spoke" through which any one of a number of different [[electrical circuit]]s can be connected to the rotor.  The switch is layered to allow the use of multiple poles; each layer is equivalent to one pole. Alternatively the rotation can be limited to a fraction (half; third etc.) of a circle and then each layer can have multiple (two; three etc.) poles.  Usually, such a switch has a [[detent]] mechanism so it "clicks" from one active position to another rather than stalls in an intermediate position.  Thus a rotary switch provides greater [[Switch#Contact terminology|pole and throw]] capabilities than simpler switches do.

Rotary switches were used as channel [[Switch|selectors]] on television receivers until the early 1970s, as range selectors on electrical metering equipment, as band selectors on multi-band radios, etc.

Modern rotary switches use a "star wheel" mechanism to provide the switching positions, such as at every 30, 45, 60, or 90 degrees. Nylon cams are then mounted behind this mechanism and spring-loaded electrical contacts slide around these cams. The cams are notched or cut where the contact should close to complete an electrical circuit.

Some rotary switches are user-configurable in relation to the number of positions.  A special toothed washer that sits below the holding nut can be positioned so that the tooth is inserted into one of a number of slots in a way that limits the number of positions available for selection. For example, if only four positions are required on a twelve position switch, the washer can be positioned so that only four switching positions can be selected when in use.

==Gallery==
<gallery mode="packed" class="center">
File:Twelve position rotary switch contacts view.jpg|Bottom view of a 12-position rotary switch showing wiper and contacts
File: Rotary switch base.jpg|Rotary switch circuit
File: Rotary switch head with pins 0.jpg|Rotary switch handle as seen from below

<gallery>
IEEE 315 Contacts, Switches, Contactors, and Relays Symbols (84).svg | Schematic symbol for 1P3T, break-before-make, nonshorting style
IEEE 315 Contacts, Switches, Contactors, and Relays Symbols (86).svg | Schematic symbol for 1P4T, break-before-make, nonshorting style
IEEE 315 Contacts, Switches, Contactors, and Relays Symbols (88).svg | Schematic symbol for 1P4T, make-before-break, shorting style
</gallery>

==References==
* {{Cite web |date=3 February 2023 |title=A Complete Guide to Rotary Switches |url=https://uk.rs-online.com/web/content/discovery/ideas-and-advice/rotary-switches-guide |url-status=live |archive-url=https://web.archive.org/web/20230321215109/https://uk.rs-online.com/web/content/discovery/ideas-and-advice/rotary-switches-guide |archive-date=21 March 2023 |website=RS}}

==See also==
{{Commons category|Rotary switches}}
* {{annotated link|Commutator (electric)}}
* {{annotated link|Control knob}}
* {{annotated link|Rotary encoder}}
* {{annotated link|Rotary system}}
* {{annotated link|Stepping switch}}

{{switches}}
{{authority control}}

[[Category:switches]]

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