How does a Cellphone Vibrate?
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How does a Cellphone Vibrate?
Among the many components inside the phone is a small motor.
The motor is built in such a way that it is partially off-balanced.In other words, a mass of improper weight distribution is attached to the motor’s shaft/axis. So when the motor rotates, the irregular weight causes the phone to vibrate.
Rotating unbalance is the uneven distribution of mass around an axis of rotation. A rotating mass, or rotor, is said to be out of balance when its center of mass (inertia axis) is out of alignment with the center of rotation (geometric axis). Unbalance causes a moment which gives the rotor a wobbling movement characteristic of vibration of rotating structures.
There are two basic types of vibration motor.
An eccentric rotating mass vibration motor (ERM) uses a small unbalanced mass on a DC motor, when it rotates it creates a force that translates to vibrations.
A linear resonant actuator (LRA) contains a small internal mass attached to a spring, which creates a force when driven.
The faster the motor spins, the more it feels like a vibration than a wobble. Playstation and Xbox controllers use a similar setup with larger motors to simulate the vibration function.
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