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LRA

LRA stands for linear resonant actuator and rely on a small internal mass attached to a spring, which vibrates in a reciprocating linear motion with an applied AC signal.

In contrast to ERMs, LRAs do not spin. They linearly move a mass (up and down) attached to a spring using a magnetic voice coil. LRAs require a smooth sine wave voltage signal (aka an AC signal) driven at specific resonant frequencies — usually 150-200Hz — which controls how often the mass moves and, therefore, the vibration oscillation. They are increasingly common in smartphones, watches, and trackpads to mimic the feeling of a click.

For example, newer Apple MacBooks and iPhones feature the Apple Taptic Engine, which uses LRA technology. While LRAs are more responsive than ERMs (~15-25ms startup times), their vibration strength is more minimal and the wiring circuitry more complicated. Moreover, their vibration frequency is strongest at a single frequency (the resonant frequency).

LRA types

Most LRA drives are divided into 2 categories:

  • Y-Axis LRA Linear Vibrator
  • Z-Axis LRA Linear Vibrator
Y-Axis LRAZ-Axis LRA
Y-Axis LRAZ-Axis LRA

Applying LRAs

note

There is no strict rules, how to apply different actuators, just a recommendation, based on personal experience.

ERM typeFeedback ForceVestGloveFacial InterfaceOther wearable
Coin LRAWeakest

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