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 or a

CB radio Citizens band radio (CB radio) is a land mobile radio system, a system allowing short-distance one-to-many bidirectional voice communication among individuals, using two-way radios operating near 27 MHz (or the 11-m wavelength) in the high freq ...

with multiple

frequencies Frequency is the number of occurrences of a repeating event per unit of time. Frequency is an important parameter used in science and engineering to specify the rate of oscillatory and vibratory phenomena, such as mechanical vibrations, audio ...

of reception or "channels". A rotary switch consists of a spindle or "

rotor ROTOR was an elaborate air defence radar system built by the British Government in the early 1950s to counter possible attack by Soviet bombers. To get it operational as quickly as possible, it was initially made up primarily of WWII-era syst ...

" that has a contact arm or "spoke" which projects from its surface like a

cam Cam or CAM may refer to: Science and technology * Cam (mechanism), a mechanical linkage which translates motion * Camshaft, a shaft with a cam * Camera or webcam, a device that records images or video In computing * Computer-aided manufacturin ...

. 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 An electrical network is an interconnection of electrical components (e.g., battery (electricity), batteries, resistors, inductors, capacitors, switches, transistors) or a model of such an interconnection, consisting of electrical elements (e. ...

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 pole and throw capabilities than simpler switches do. Rotary switches were used as channel 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.

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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 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

See also