Last Updated on October 22, 2023 by Kevin Chen
When you think of electromechanical switches, the first things that probably come to mind are momentary buttons and toggle switches. While these are two of the most commonly used and most recognizable switches, they’re not the only ones out there. There are many other electromechanical switches with unique properties and applications.
These include rotary switches, which are a special type of double-throw switch that has a varying number of positions instead of two on-or-off states like a toggle or pushbutton switch. Even if you don’t have much experience with different types of mechanical switches, this article will give you everything you need to know about rotary switches and how they work.
What is a Rotary Switch?
A rotary switch is an electromechanical switch with a rotating actuator (the part you press) and multiple positions, unlike toggle or momentary push buttons that have two positions (on or off).
You may have also heard rotary switches referred to as rotary dials, as they often appear on telephones with rotary dials that allow users to manually enter telephone numbers.
Rotary switches are either single-throw or double-throw. Single-throw switches have only one set of contacts, whereas double-throw switches have two sets of contacts that rotate between when the actuator is moved. Double-throw switches are the most common type of rotary switch.
Different Types of Rotary Switches
Wafer rotary switches
These switches are very small, with a diameter of about 1.5mm and a height of about 2.5mm. They are commonly used in watches, calculators, and electronic devices where size is important but the switches must still be able to fit into the device.
Wafer switches are available in both single-throw and double-throw varieties, but will usually have only one position.
Multi-position rotary switches
These are the most common type of rotary switch because they have two or more positions (like a toggle switch) and can be used for both on/off functions as well as for other functions like adjusting the volume or turning on/off an LED light.
High current rotary switches
As the name suggests, these switches are intended to be used in high current applications. They are usually made of metal and can withstand high currents.
Miniature rotary switches
These are the smallest type of rotary switches available and can be used to replace the switches on small electronic devices. They are usually made of plastic and have a diameter of less than 2mm.
Momentary rotary switches
These are used in applications where the switch needs to be held in a particular position (usually for a period of time) and then released. They are usually made of plastic and have a diameter of less than 2mm.
Resonant rotary switches
These switches usually have two or more magnetic poles and when actuated, they oscillate back and forth, with each push or pull causing the switch to move slightly further along its travel path. This type of switch is often used on watches, calculators, and other electronic devices where size is important but the switches must still be able to fit into the device.
Components of rotary switches
-Stator-Actuating Mechanism: The stator-actuating mechanism is the mechanism that turns the actuator of a rotary switch. It’s composed of a stationary part that turns and a movable part, the stator, that is attached to and turns the actuator.
-Rotary Actuator: The rotary actuator is the part of the switch that you press, and is located between the stationary stator and the movable stator that turns the actuator. The actuator can be a knob, a ratchet wheel, or any other type of mechanism that can be rotated to turn the switch between its positions.
-Conductive Contact Areas: Conductive contact areas are the parts of the rotary switch that contact the stationary and movable stator when the actuator is in a given position.
How Do Rotary Switches Work?
We have just seen that there are different types and configurations of rotary switches. Despite these differences, all of them tend to have the same working formula. This is because a typical rotary switch has three components that guide its work; a rotor/spindle that has a protruding spoke.
The stator is attached to the stationary part of the switch and moves when the actuator is turned. The contact areas are located on both sides of the stator so that when the rotary switch is turned, one side of the stator will touch one contact area and then another side of this stator will touch another contact area.
Rotary Switch Operation
When you rotate a rotary switch, its actuator turns with it. As you turn, each side of the stator turns with it and touches different conductive contact areas in turn. The diagram below shows what happens as you rotate a rotary switch through its positions.
Each time you move to a new position, you will be connecting two different output terminals together through two different sets of contacts. This means that each time you move to a new position, your output terminal will connect to a different input terminal or vice versa.
In other words, as you turn your rotary switch through its positions, your input terminals will be connected to different output terminals each time.
Rotary Switch Positions
In addition to the described rotary switch working principle, it is vital to know that there are different positions for this switch. Let’s look at some of them:
-3-position rotary switch: This type of rotary switch has three terminals. This switch is the simplest one and it has no center position. The terminals are connected in a different way in each of its positions.
-6-position rotary switch: This type of rotary switch has three terminals. It also has a central position and this means that the switch can be turned to one of the two positions on either side of the center.
-12-position rotary switch: This type of rotary switch has four terminals. It also has a central position and this means that the switch can be turned to one or two positions on either side of the center.
In most cases, these switches are used for controlling circuits in which there are more than three states, for example, circuits for controlling a light bulb or other appliances which require more than three settings to be controlled.
Benefits of Rotary Switches
– Versatility: A rotary switch can have one position or several, depending on the type of switch used. Rotary switches are often used in applications where the number of positions needs to be manually entered, making them ideal for use in telephone systems, computer systems, and other settings where manual input is required.
– Restoration: The rotary switch actuator can be turned by hand to return the switch to any position it was in previously. This can be helpful when the switch is not being controlled by another system and needs to be restored to a known position manually.
– Customization: Rotary switches can be customized to have any number of positions that are appropriate for the application. For example, rotary switches are often used in telephone systems to allow users to manually enter telephone numbers. The number of digits in a telephone number is different for every location, making custom rotary switches ideal for this application.
Applications of rotary switches
-Telephone Systems – Rotary switches are often used in telephone systems to allow users to manually enter telephone numbers. Telephone systems with rotary dials are still sometimes used today, although they are mostly being replaced by systems with pushbutton dials that allow users to enter numbers using pushbuttons.
-Computer Input – Rotary switches are often used in computer systems to allow users to manually enter data. For example, rotary switches are often found on computer keyboards, allowing users to manually enter a letter when pressing a single key is not enough to enter a complete word.
-Electronic Circuits – These switches are used in various electronic circuits, such as in radio receivers that receive signals from remote controls, timers, and other electronic devices.
-Mechanical Switches – Rotary switches are also sometimes used in mechanical systems, such as in doorbells, where they are used to control the ringing of a bell by turning a shaft that causes the bell to ring.
-Lighting Control – Rotary switches are often found on lighting control panels, where they are used to manually turn lights on and off.
-Rotary switches in speed fans: Speed fans are devices that are used to cool computers or other electronic devices. They are often controlled by rotary switches that allow the user to manually control the speed of the fan.
Limitations of rotary switches
Sensitive to Dirt and Grime – For rotary switches to work properly, they must be kept free of dirt and grime. Dirt and grime can interfere with the rotation of the actuator and the movement of the stator, preventing the switch from completing a circuit.
Another limitation of rotary switches is that some are limited to a single direction of motion. This means that the user cannot move the switch in multiple directions, meaning that the user must always know whether or not the switch is in one of two possible positions.
Rotary switches are also sensitive to heat and vibration. Heat can affect a rotary switch, causing it to fail. Vibration can also cause a rotary switch to fail, as vibrations may interfere with its operation by causing it to not rotate properly.
Physical specifications of rotary switches
So you are about to buy a rotary switch? You should strive to know several specifications that determine its configurations when installed in real-world applications. The physical specifications include;
-Mechanical life: This defines the life expectancy of a rotary switch. The longer the life of the switch, the better. Mechanical life can be measured in terms of how many rotations the switch can withstand before it fails.
-Resistance: Resistance is the most important physical specification for rotary switches. The lower the resistance, the better. Typical resistance for current-carrying rotary switches is 10 MΩ or less.
-Switch force: The switch force determines how much pressure is required to activate a rotary switch. A typical switch force for a current-carrying rotary switch is 1 N or less.
-Actuator length: The actuator length of a current-carrying rotary switch determines how far away from a printed circuit board (PCB) it can be installed without affecting signal integrity and signal quality when used with PCBs and other electronic components that have signal paths near them. Typical lengths are between 1 and 2 inches (2–5 cm).
-Actuator diameter: The actuator diameter of a current-carrying rotary switch determines how big the switch can be. Typical diameters are between 0.2 and 0.5 inches (0.5–1.2 cm).
-Number of poles: This spec defines the number of poles that can be activated at any single time. A single pole rotary switch has only one contact. A double pole switch has two contacts. A triple pole switch has three contacts.
-Number of blades: This spec defines the number of contacts on a rotary switch’s shaft. The number of blades defines how many different positions the shaft can be rotated into, in a single revolution.
-Angle between positions: This spec defines the angle that the shaft can be rotated through as it is turned. For example, a 4-position rotary switch has a 90 degrees angle between the positions.
-Contact resistance: This spec defines the amount of force needed to make a contact click. A rotary switch with a high contact resistance will not move much if at all when activated, making it unsuitable for use in hard-to-reach places where small movements are needed.
-Diameter of the switch’s shaft: This spec defines the diameter of a rotary switch’s shaft in inches.
-Number of decks: This is the maximum number of decks that can be attached to a common shaft at any given time. These decks come in two main configurations, single-deck, and Multi-deck. Single-deck rotary switches have a single deck which is used for all of the switches in that group.
Where to buy rotary switches
Rotary switches are available from a variety of sources, including electronics and hardware stores, electrical distributors, and online retailers. You should also consider buying a rotary switch directly from the manufacturer or supplier in China. This way, you can be sure of getting original and quality switches at a reasonable price.
And where can I find such manufacturers? You can use a sourcing agent. Most of them are very professional and can serve as a very important source of information. For instance, we at ICRFQ will provide you with the best suppliers in China.
As rotary switches come in many different types and sizes, it’s important to select the right switch for your application before purchasing one. Before you make a purchase, make sure to select a rotary switch that is suitable for your application.
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