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A rotary solenoid is an electromechanical device that uses solenoids to create rotational torque. There are several applications for these rotary solenoids in fields as diverse as security, medicine and industry. Compared to other forms of creating rotational torque, a rotary solenoid offers several distinct advantages. Being relatively compact devices, however, these types of solenoids also have some disadvantages that intensify as the devices age and lose their power.
Solenoids are often made of copper wires wrapped around a magnetic core that create 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 that can then be connected with the machinery requiring rotational movement. Variable torques can be produced through this effect and often depend on the size of the solenoids and the rotating mechanisms.
Applications that use a rotary solenoid are considered diverse, because many machines and devices require specific rotational forces. Security mechanisms, for instance, often use rotary solenoids to activate or deactivate complex locks such as those found on vaults. Medical instruments also can make use of rotary solenoids, perhaps to control fluid pressures or activate pumps; dialysis machines, for example, often incorporate these types of solenoids. Using a rotary solenoid is often considered most common within industrial applications such as assembly lines and automated machinery.
There are several advantages to using a rotary solenoid compared to other rotating mechanisms. They are often considered relatively cheap, providing the necessary torque without being overly expensive. Generally, these types of solenoids also consume less power than some other mechanisms that provide the same torque. A rotary solenoid also may last longer than some other mechanisms, which is a major benefit for long-term industrial machinery. Some types of rotary solenoids also rotate both ways with the same torque, which is considered a difficult task to achieve with low-power mechanisms.
Disadvantages to using a rotary solenoid limit how many applications can make use of these devices. Rotary solenoids are often limited in torque unless combined with other methods of creating the necessary forces. The rotating mechanisms can wear out eventually, which can shorten the service life of a solenoid. Additionally, the starting torque of many rotary solenoids is less than some similar devices, a fact that can restrict their use to applications that can afford a weaker starting rotation.