Rotary switches are important devices in many machines. They are switches that rely on centripetal force is to create energy or close electrical circuits. Some rotary switches can be traced back to the 1940s. If you intend to create a device that relies on rotary switches, then you need to understand what they are and what to look for when purchasing them.
What is a rotary switch?
A rotary switch is a switch that moves in circular motions. It can have several stopping positions.
What is the main advantage of using rotary switches over standard analog switches? The biggest benefit is that rotary switches are capable of controlling numerous circuits without the need for multiple switches. They can be designed with numerous contact points.
Rotary switches are commonly used in numerous devices, although they are less common than they used to be. They are most frequently used in industrial machinery. However, many consumer devices also use rotary switches. Rotary switches are often used in car fans. They frequently use rotary switches to regulate rotation speeds.
The switches can be rotated in both clockwise and counterclockwise directions. They are manufactured in several different styles, which are determined by different pin arrangements. Four of the most common pin arrangements in rotary switches are listed below:
- One pole with 12 contacts
- Two poles with six contacts
- Three poles with four contacts
- Four poles with three contacts
Design configurations can vary significantly. However, the general principles are consistent across all rotary switch designs.
One of the most important elements is the spindle. Current runs through the spindle as it rotates. The spindle is connected to multiple different rotors. Every rotor has a protruding arm that is capable of contacting with the switch can make numerous contact points in dozens of different positions. Every position it reaches is capable of closing a different circuit.
The precision of positioning is very important. If the spindle rotates to freely, then it will be unable to maintain a closed circuit. The spindle needs to be able to stop at a precise location to ensure circuit connections are properly made.
How are they able to do this? Rotary switches have detent mechanisms. These mechanisms caused the switch to click into a given position. As long as the mechanism is connected, it will not rotate again unless a certain amount of force is applied.
These mechanisms rely on wheels with grooves and notches that have been cut into the outer face and fixed to the rotor. They also have a spring-loaded ball bearing or spring steel component adjoined to the wheel. As soon as the wheel is in a predetermined position, this component will rest in the groove. It will then hold the bearing in place until the rotor is twisted enough to move to the next groove.
What factors should you consider when purchasing a rotary switch?
There are numerous rotary switches on the market. The best ones have their advantages and disadvantages. You will need to choose one that is appropriate for your given application. Some of the factors that you need to evaluate are listed below.
Mechanical life expectancy
One of the most important factors that you need to consider is the mechanical life expectancy. This is a measure of the maximum number of rotations that you can expect the rotary switch to make before failing. You need to keep in mind that the electrical life expectancy often is lower than the mechanical life expectancy. You would need to speak with the manufacture to determine if this is the case.
Rotary switches have different numbers of poles. Four of the most common pole counts are listed above. However, there are many other possible pole counts for rotary switches. You need to know what the pole count is, because that will affect the number of degrees of motion and circuit positions.
The angle between key positions
You also need to look at the angle between different positions. This is going to determine how many different switch positions are possible. If you want to calculate the number of switch positions, you need to divide the angle of throw by 360°. For example, a rotary switch with an angle of throw of 36° will have 10 different positions. A rotary switch with an angle of throw of 120° will have three different positions.
Choose the right rotary switch for your project
There are a number of different types of rotary switches on the market. You need to research them carefully and make sure that you find the right one.