Hard Disk Voice Coil

A hard disk voice coil assembly, also called actuator, is a linear control device within a hard drive responsible for positioning the read / write heads. It consists of a copper coil wound around a former and a permanent magnet.

Linear Control - Voice Coil

The voice coil assembly is reliable as there are few mechanical components required. Majority of the problems tend to be with the driver electronics associated with it.

Occasionally the pivot bearing can wear out, but more often data recovery ‘engineers’ over tighten the pivot screws.

In the past manufacturers used motors, which produced slow seek times. All modern hard drive designs use the voice coil assembly to position the head, because it is the fastest mechanism for linear control.

Neodymium Magnet

The actuator typically consists of a large neodymium magnet securely bolted to the chassis, with an iron plate of the same shape secured from the top to focus the magnetic field.

These neodymium magnets are incredibly powerful. Back in 2005, my firm scrapped a bunch of 20 MB hard drives and I was able to salvage the magnets to build a wind powered electricity generator. The voice coil mechanism makes a wonderful loudspeaker as well.

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