Demonstrating beat phenomenon and Lissajous figures with hard disk drive voice-coil motors

Abstract

Voice coil motors (VCMs) in mechanical hard disk drives can be used as the adjustable-electric tuning fork driven by alternating signals due to their unique structure and movement. The VCM component is modified to pull the laser or mirror for phase-adjustable simple harmonic motion (SHM). Lissajous experiments using the traditional tuning fork for active vibration can be achieved by VCMs with the help of a laser and a scrollable phosphorescent screen. The demonstrations of beat and Lissajous figures with the double oscillating mirrors method are analysed. The VCM can not only drive the mirror but also drive the laser or another VCM component. Based on this carrying capacity, the demonstration method of a single oscillating mirror has been proposed. Furthermore, one VCM can support another with a laser, which will exhibit the composition of two rotary SHMs more intuitively. The new method is beneficial for students to understand and practice the composition of SHMs from a new perspective.