Community hub
0 subscribers8 pages, 0 posts
Recent from talks
All channels
Be the first to start a discussion here.
Be the first to start a discussion here.
Be the first to start a discussion here.
Be the first to start a discussion here.
Contribute something
Welcome to the community hub built to collect knowledge and have discussions related to Rotary switch.
Nothing was collected or created yet.
Rotary switch
View on Wikipediafrom Wikipedia
 | This article relies largely or entirely on a single source. (February 2024) |
 | This article includes a list of references, related reading, or external links, but its sources remain unclear because it lacks inline citations. (February 2024) |
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 with multiple frequencies of reception or "channels".
A rotary switch consists of a spindle or "rotor" that has a contact arm or "spoke" which projects from its surface like a 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 circuits 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.
Gallery
[edit]-
Bottom view of a 12-position rotary switch showing wiper and contacts -
Rotary switch circuit -
Rotary switch handle as seen from below -
Schematic symbol for 1P3T, break-before-make, nonshorting style -
Schematic symbol for 1P4T, break-before-make, nonshorting style -
Schematic symbol for 1P4T, make-before-break, shorting style
.svg)
.svg)
.svg)
References
[edit]- "A Complete Guide to Rotary Switches". RS. 3 February 2023. Archived from the original on 21 March 2023.
See also
[edit]
Wikimedia Commons has media related to Rotary switches.
- Commutator (electric) – Device for changing direction of current
- Control knob – Rotary device used to operate mechanical or electrical device system
- Rotary encoder – Electromechanical device
- Rotary system – Electromechanical telephone switch
- Stepping switch – Electromechanical multi-pole switch controlled by a chain of pulses
 | This electricity-related article is a stub. You can help Wikipedia by expanding it. |
Rotary switch
View on Grokipediafrom Grokipedia
A rotary switch is an electrical switch that operates by rotating an actuator, such as a knob or shaft, to select one or more positions for controlling electrical circuits, providing a compact alternative to multiple individual switches.[1][2]
In its basic construction, the switch features a rotating spindle or rotor with a protruding spoke that aligns with fixed terminals at specific angular intervals, such as 30°, 45°, or 90°, to make or break electrical connections; a detent mechanism often provides tactile feedback and prevents unintended movement between positions.[1] Key components include the spindle, terminals for circuit attachment, and sometimes multiple stacked wafers or decks to enable simultaneous switching across several circuits.[1]
Rotary switches are classified by their pole and throw configurations, such as single-pole single-throw (SPST) for simple on-off functions, double-pole double-throw (DPDT) for more complex routing, and multi-deck or cam-operated types for high-current or sequential operations in industrial settings.[1][2]
Common applications span consumer electronics, including audio volume controls and guitar pickup selectors; industrial controls like HVAC systems and motor speed adjustments; and instrumentation such as multimeters and test equipment, where their reliability and ability to handle multiple positions make them essential.[1][2]
These switches offer advantages in durability for harsh environments, precise position selection, and versatility in both low-power signal switching and higher-power loads up to several amperes, depending on the model.[2]
Overview
Definition
A rotary switch is an electromechanical device that enables the selection of one or more electrical circuits from a set of multiple options through the rotation of a spindle or knob actuator. This rotation aligns a moving contact with fixed terminals to establish or interrupt connections, allowing control over various circuits with a single mechanism.[1][2] Key characteristics of rotary switches include their support for multiple discrete positions, typically ranging from 2 to 12 or more, which facilitate sequential or selective circuit engagement. They incorporate tactile detents—mechanical stops that provide audible or haptic feedback to confirm position alignment—ensuring reliable operation without unintended shifts. Unlike continuous variable controls such as potentiometers, rotary switches are designed for discrete selection, making them suitable for applications requiring fixed, predefined states rather than analog adjustment.[3][4] In comparison to linear or toggle switches, which generally offer only two positions (on/off) and require separate units for multiple functions, rotary switches provide a more compact solution for handling numerous positions in limited space, reducing wiring complexity and panel footprint. This design efficiency stems from their circular arrangement of contacts, enabling higher circuit density without extending linearly.[5][6]Basic Operation
A rotary switch functions as a multi-position selector by rotating its spindle, which drives a wiper or spoke mechanism to sweep across a series of fixed contacts or terminals, thereby establishing or breaking electrical connections in a controlled manner.[1][7] This rotational motion allows the switch to transition between discrete positions, where the wiper aligns with specific terminals to route current through selected paths.[8] The positions are arranged at fixed angular intervals, commonly 30°, 45°, 60°, or 90°, enabling a precise number of selectable states depending on the total rotation range—for instance, a 360° rotation at 30° intervals yields 12 positions.[1] To maintain these positions and provide tactile confirmation during operation, detent mechanisms—often involving spring-loaded components or notched wheels—engage at each stop, offering resistance and haptic feedback while preventing unintended movement.[1][7] Electrically, in any given position, the wiper bridges designated poles (input terminals) to corresponding throws (output terminals), closing circuits for the active paths and leaving others open.[1][8] This configuration facilitates circuit selection, such as directing a single input to one of multiple outputs, with open states isolating unused terminals to prevent current flow and closed states completing the intended electrical pathways.[7][8]History
Early Development
The rotary switch emerged in the late 19th century amid rapid advancements in electrical engineering and telephony, serving as a key component for automating connections in early electrical devices. Almon Strowger, an American undertaker and inventor, conceived the first practical automatic telephone exchange in 1889 to address perceived biases by human operators, introducing a rotary stepping mechanism that rotated to select circuits based on dialed pulses. This design represented a precursor to dedicated rotary switches by enabling mechanical position selection without manual intervention. Strowger filed for the patent on March 12, 1889, and it was granted as U.S. Patent 447,918 on March 10, 1891, describing an electromechanical system for telephonic and telegraphic exchanges.[9][10] Key milestones in the early 20th century centered on adoption in telephone infrastructure, driven by major telecommunications firms. Around 1910, AT&T's engineering arm, Western Electric, initiated development of rotary switch systems in the United States, later transferring much of the work to its European division for further refinement into motor-driven variants suitable for larger exchanges. The first commercial European installation occurred in Darlington, England, on October 10, 1914, where Western Electric's 7A Rotary System automated an 800-line exchange using non-standard pulse signaling, demonstrating the feasibility of electromechanical rotary automation on a public scale. This event highlighted the shift from Strowger's step-by-step selectors to continuous rotary motion for more reliable switching in telephony networks.[10][11] By the 1920s, rotary switches transitioned into broader electromechanical applications, including channel selection in radios and range adjustment in metering equipment, building on telephony innovations from Western Electric and AT&T. Early radio components, such as the Clapp-Eastham type D receiving transformer circa 1920, employed rotary switches to vary tuning across wave groups, enabling reception of different broadcast signals. These initial non-telephony uses underscored the device's versatility in position-based electrical control, paving the way for standardized electromechanical systems in consumer and industrial settings.[12]Modern Advancements
Following World War II, rotary switch technology advanced significantly, with the invention of the rotary solenoid in 1944 by George H. Leland providing a more compact and reliable mechanism for rotational motion, particularly in applications requiring shock and vibration resistance.[13] This innovation facilitated smaller designs in electromechanical systems, paving the way for broader integration in consumer and industrial devices. In the mid-20th century, rotary switches saw widespread adoption in television channel selectors, remaining common until the early 1970s when electronic tuning began to replace them.[1] They also became staples in audio equipment for volume and tone control, as well as industrial controls for selecting operational modes.[1] During this period, wafer switches—featuring stacked insulating discs with conductive paths—emerged as a key design, enabling multi-pole configurations in compact forms, as exemplified by Centralab's 1945 selector models.[14] Similarly, Yaxley designs, characterized by their durable, multi-wafer construction, gained prominence for reliable switching in radios and early electronics.[1] From the 1980s onward, miniaturization efforts allowed rotary switches to be mounted directly on printed circuit boards (PCBs), supporting the trend toward smaller electronic devices through surface-mount technology.[1] High-current variants, capable of handling loads up to 20A at 14V DC, were developed specifically for automotive applications like battery isolators and accessory selectors.[15] Integration with digital interfaces advanced via encoder rotary switches, which convert mechanical rotation into digital pulses for precise position feedback, evolving from photoelectric models introduced in the 1960s but widely adopted in digital systems by the late 20th century.[16] In the 2000s to 2025, innovations emphasized durability and compatibility with modern demands, including IP-rated enclosures (such as IP67) using sealed housings to protect against dust and water in harsh environments like marine or outdoor industrial settings.[17] Low-profile designs, with bodies as slim as 3.8 mm, enabled integration into space-constrained consumer electronics such as remote controls and portable devices.[18] A shift toward hybrid electro-mechanical rotary switches incorporated digital outputs and sensors for smart devices, allowing seamless connectivity with home automation systems via protocols like DALI-2.[19] By the 2020s, sustainability became a priority, with widespread adoption of RoHS-compliant materials to eliminate hazardous substances like lead, ensuring environmental compliance in manufacturing.[18]Design and Components
Mechanical Structure
The mechanical structure of a rotary switch centers on a central spindle, also known as the rotor, which serves as the primary rotating element and typically attaches to an external knob or actuator for user manipulation. This spindle revolves within a shaft, often featuring a protruding spoke or arm that facilitates position changes, and is constructed to ensure precise alignment with fixed components. The detent mechanism, integral to the structure, consists of spring-loaded elements interacting with notches or a star wheel on the rotor to lock the switch into discrete positions, providing tactile feedback and preventing unintended movement between stops. The base or housing encases these elements, offering structural support and mounting points, typically molded for durability and insulation against environmental factors. Rotation mechanics in rotary switches incorporate fixed stops to define the angular travel, limiting rotation to specific increments such as 30°, 45°, or 90° to match the number of positions, while friction or ball-bearing systems ensure smooth, reliable operation without excessive play. Multi-deck stacking allows multiple wafers or layers to be assembled along the spindle, enabling the switch to handle additional circuits through synchronized rotation across decks. These designs often include adjustable washers or spacers to customize the range of motion, supporting configurations from as few as 4 positions up to 24 or more in modular assemblies. Materials selection emphasizes durability and insulation, with insulators commonly made from nylon for its chemical resistance or phenolic resin for high thermal stability and deformation resistance in the housing and base. Metal components, such as the spindle shaft and detent parts, are typically stainless steel, brass, or aluminum to withstand mechanical stress, with heavy-duty variants employing stainless steel shafts and sealed enclosures using elastomers like rubber gaskets for harsh environments such as aerospace applications. Assembly follows a modular approach, integrating the spindle, detents, and base with user-configurable elements like position-limiting stops, allowing customization during manufacturing or installation for specific operational needs.Electrical Elements
The electrical elements of a rotary switch primarily consist of the wiper or arm, which serves as the moving contact that rotates to connect circuits, the fixed terminals or posts that provide input and output connections, and wafers, which are insulating discs embedded with conductive paths or notches for routing signals across multiple positions.[1][3] The wiper, often a protruding spoke on the rotor, slides over the wafer's surface to engage specific paths, enabling the switch's core function of selective circuit routing through mechanical rotation.[1] Contacts in rotary switches are typically constructed from low-resistance materials such as silver alloys or gold-plated surfaces to ensure reliable conductivity and minimize signal loss, with wiping designs that provide self-cleaning action for longevity.[3][20] Wiper configurations vary between bridging (shorting or make-before-break) types, where the contact momentarily connects adjacent positions during transition to maintain continuity, and non-bridging (non-shorting or break-before-make) types, which interrupt the circuit before engaging the next position to prevent unintended overlaps.[3] Electrical ratings for rotary switches generally support voltages up to 250 V AC/DC and currents ranging from 1 mA to 20 A, with power handling capacity determined by factors like contact surface area and material properties— for instance, higher-current models may achieve 12 A at 125 V AC using robust silver contacts.[20] In high-current applications, arc suppression is incorporated through wiping contact mechanisms and material choices that reduce arcing during switching, thereby extending operational life.[3] Multi-deck configurations provide isolation between stacked wafers via high dielectric strength, typically 500–1,000 Vrms, ensuring separation of independent circuits without crosstalk.[20]Types
Pole and Throw Configurations
In rotary switches, poles refer to the number of independent electrical circuits controlled by the switch, with each pole corresponding to a separate input terminal that can be routed to output positions.[21] Throws, often termed "ways" in rotary contexts, denote the number of selectable output positions per pole, enabling the switch to connect each input to one of multiple terminals based on the rotor's rotation.[1] Decks, also known as wafers, are stacked circular contact assemblies that facilitate multi-pole operation by synchronizing the switching action across multiple layers, allowing several poles to operate simultaneously without independent actuators.[1] Common pole and throw configurations follow standard notations like those for other switches but adapt to rotary designs with potentially higher throw counts due to rotational positions. The single pole single throw (SPST) configuration features one pole and one throw per position, using two terminals for basic on/off control of a single circuit.[21] The single pole double throw (SPDT) has one pole switching between two throws, requiring three terminals and suitable for selecting between two outputs from one input.[22] Double pole single throw (DPST) manages two poles with one throw each, employing four terminals to control two isolated circuits in parallel.[22] Double pole double throw (DPDT) extends this to two poles each with two throws, using six terminals for applications like signal routing or polarity reversal.[22] For more complex needs, rotary switches support multi-pole multi-throw (MPMT) setups, such as a 4-pole 12-throw (4P12T) configuration, where four decks synchronize 12 positions per pole to handle extensive circuit selection.[1] In multi-pole designs, the rotor shaft mechanically links all decks to ensure that every pole advances to the corresponding throw simultaneously, maintaining phase alignment across circuits.[1] Rotary switches also differ in contact behavior during transitions: shorting types employ a make-before-break mechanism, where the wiper contact bridges adjacent throws momentarily to avoid signal interruption, while non-shorting types use break-before-make, disconnecting the current position before engaging the next to prevent unintended shorts between outputs.[23] The choice of configuration hinges on circuit requirements; for instance, a DPDT rotary switch is frequently selected for reversing DC motor polarity, as its dual poles allow swapping positive and negative connections across two positions without additional relays.[24]| Configuration | Poles | Throws per Pole | Typical Terminals | Example Application |
|---|---|---|---|---|
| SPST | 1 | 1 | 2 | Simple power on/off |
| SPDT | 1 | 2 | 3 | Dual-output selection |
| DPST | 2 | 1 | 4 | Dual-circuit isolation |
| DPDT | 2 | 2 | 6 | Motor direction control |
| 4P12T | 4 | 12 | 52 | Multi-channel audio routing |