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Moving coil actuators use electromagnetic force to control motion for secondary mechanisms. They differ from solenoids as the coil moves within an array of static magnets, producing bi-directional motion. They can be configured to produce linear and rotary outputs and can be part of a servo system. A common use is in computer hard drives and audio speakers.
A moving coil actuator is an electromagnetic device that provides control motion for secondary mechanisms. Similar in principle to conventional solenoids, it differs in that the actuator coil moves within an array of static magnets. A moving coil actuator is also capable of producing bi-directional motion. Additionally, its output range of motion can be controlled by external triggers and system feedback. Also known as moving coil motors, they can be configured to produce linear and rotary outputs.
The electromagnetic force phenomenon is the cornerstone of a wide range of switching, actuation and control mechanisms in an equally wide range of industries. The most common application of this phenomenon is the simple solenoid. These ubiquitous devices consist of a coil of static wire and a moving plunger used as an output transfer agent. When the coil is energized with an electric current, a strong magnetic field is generated which moves the plunger towards it. This movement is then used to perform the work.
The voice coil actuator also relies on this electromagnetic force to provide its output motion, but it does so in a different way. These actuators feature an array of static magnets and a moving coil used to transfer motion. When an electric current is passed through the coil, a magnetic field is generated around it in the same way as in a conventional solenoid. This field interacts with the static magnet field, attracting or repelling the coil depending on the phase relationship of the two fields. This theory of operation can easily be demonstrated with two small bar magnets pushing towards each other or pulling towards each other depending on which direction they are facing.
In this way, the voice coil actuator, or voice coil motor, as they are also known, can be used to produce a range of finely controlled bi-directional linear motions. The actuator may also be configured to produce a finite rotational motion, typically less than 360 degrees. The voice coil actuator can also be configured as part of a servo system where feedback or inputs from the installation are used to dictate its range of motion. A very common application for moving coil actuators is the read and write head on a computer hard drive.
One of the best known uses of a moving coil actuator, however, is as an audio speaker. The speaker cone is connected to a voice coil and is moved back and forth by the alternating polarity of an audio signal passed through the coil. This, in turn, creates the air pressure waves that produce the speaker’s sound output.
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