Hard drive voice coil motor demonstration

(Turn on HD video if you can ...)
Hard drives have been using voice coil motors to position the read and write heads for decades now, but it all seems like magic. Here I demonstrate how a hard drive uses varying amounts of current on the voice coil motor to move the actuator across the platters.
A hard drive makes scheduling decisions, deciding how far and how fast the heads need to be moved to intercept the data that is on the spinning platters. That scheduling decision gets turned into current inputs to the voice coil motor, causing movement at the desired speed and distance. The calculations have to be fairly precise, as there are 10s of thousands of tracks per inch on a hard drive from this generation. (Modern hard drives can have 400,000 or more tracks per inch.)
The donor drive is an old Quantum Prodrive LPS. I found the two wires that energize the voice coil and I have soldered two wires to them, allowing me to energize the voice coil with an external voltage source such as a AA battery. While that works, it is hard to control.
For this demo I've gone a step further and I am using a MicroBit embedded computer to control the timing of the voltage pulses to the voice coil motor, demonstrating how small and large movements are made. Small movements are used when streaming data from a large file that is not fragmented. Larger movements are caused by workloads that need data from all over the drive.
Don't try this on a hard drive that you want to use later. :)
For reference: the Python program used on the MicroBit:
from microbit import *
while True:
if button_a.is_pressed() and button_b.is_pressed():
Fast seek: apply about 2.1V
pin1.write_analog(700)
sleep(70)
pin1.write_analog(0)
else:
if button_a.is_pressed():
Slow seek: apply about 0.3V
pin1.write_analog(100)
sleep(200)
pin1.write_analog(0)
else:
if button_b.is_pressed():
Medium seek: apply about 0.75V
pin1.write_analog(250)
sleep(200)
pin1.write_analog(0)
sleep(200)

[@DylanGreen211]

Great video! I'm trying to use old hard drives and the clicking sounds they make as percussion in a computer hardware music project I'm working on, and this was very helpful.

[@shashikantsingh6555]

Excellent video sir.. keep it up

[@f.k.b.16]

0:38 made me nervous! Those things are like having a set mouse trap in your hands! They have made me bleed before 😜

[@TG626]

Once they're "in range" there is NO stopping them.

[@williamwatkins6669]

On which pin did you plug the wires on the HDD?