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A rotary solenoid is an electromechanical device that uses solenoids to create rotational torque. There are many applications for these rotary solenoids in areas as diverse as security, medicine, and industry. Compared to other ways of creating rotational torque, a rotating solenoid offers several distinct advantages. However, being relatively compact devices, these types of solenoids also have some drawbacks that intensify as the devices age and lose their power.
Solenoids are usually made of copper wire wound around a magnetic core that creates a magnetic field when energized. These solenoids act on a rotating mechanism like bearings and create torque through magnetic forces. In many cases, this rotation is directly connected to a rotating armature which can then be connected to machinery that requires rotational motion. Variable torques can be produced through this effect and are often dependent on the size of the solenoids and the rotating mechanisms.
Applications using a rotary solenoid are considered diverse because many machines and devices require specific rotational forces. Security mechanisms, for example, often use rotating solenoids to activate or deactivate complex locks such as those found on safes. Medical instruments may also make use of rotating solenoids, perhaps to control fluid pressure or activate pumps; Dialysis machines, for example, usually incorporate this type of solenoid. The use of a rotary solenoid is often considered the most common in industrial applications such as assembly lines and automated machinery.
There are several advantages to using a rotary solenoid compared to other rotary mechanisms. They are often considered relatively inexpensive and provide the required torque without being too expensive. Generally, these types of solenoids also consume less power than some other mechanisms that provide the same torque. A rotary solenoid can also last longer than other mechanisms, which is a great benefit for industrial machines in the long run. Some types of rotary solenoids also rotate in both directions with the same torque, which is considered a difficult task to achieve with low power mechanisms.
The disadvantages of using a rotary solenoid limit how many applications can make use of these devices. Rotary solenoids are often torque limited unless combined with other methods to create the required forces. Rotating mechanisms can eventually wear out, which can shorten the life of a solenoid. Also, the starting torque of many rotary solenoids is lower than some similar devices, a fact that may restrict their use to applications that may allow weaker starting rotation.