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Picture of Voil Coil Whisker Striker

When building electromechanical sound pieces, I sometimes find solenoids to be too loud for piezo-amplified and coil pickup applications. The voice coil from an old hard drive allows for precise control of a small striker, specifically the thin carbon fiber rod used in this example.

A voice coils act somewhat like a reverse solenoid. Instead of a stationary coil moving a solid metal or magnetic shaft with an applied current, a freely moving coil is propelled through the magnetic field of a stationary magnet. Because the mass of the moving coil in a voice coil is much lower than the shaft in a solenoid, it can move at a much higher frequency and because of that it is the basis for most loudspeakers and electrical dial meters.

In this example, I am using a 9 volt battery to demonstrate the movement of the voice coil, but this can easily be controlled using a switch, relay or transistor. It can also be controlled using a highly amplified audio signal, working like a simple VU meter.

Step 1: Setup

Picture of Setup

Tools and Parts used in this tutorial:
Hard drive
Carbon fiber rod (.033" is a good diameter)
Thin flexible 2-strand cable (the thinnest ones I have found are those for earbud headphones)

Thin solid wire (bus wire or gardening wire, just to hold things in place)
Precision screwdriver set (most hard drives use torx screws)
Small angle cutters
Needle nose pliers
Wire strippers

Soldering iron
Helping hands alligator clip holder
Two-part 5-minute epoxy
Mixing sticks and paper to mix epoxy
Rosin core solder
Super sticky tape (gaffer tape or electrical tape)
9 volt battery
Silver permanent marker

Not shown:
Flat head screwdriver
Hammer and Punch.

Alex in NZ11 months ago

This is an amazing use of an old drive! I've used the platters for art projects, and the magnets for all sorts, but this is awesome! Thank you so much for sharing this :-)