trying to use motor with 4 pins

i found this motor on an old hard drive (WD Caviar 40g)
it has four wires and strange symbols (see photo)


when i connect it randomly to 3.3v it snaps to a position and does a strange sound (see video)

I'm able to make it turn by steps on the video by changing the connections

i would like to know how to use it with my arduino and what are its capabilities. :slight_smile:

Where in the HDD did You find it? What did it do in the drive? Rotate the disc or move the reading heads?

it was rotating the disk, it has a flat head.

Can you measure the resistance on each pair please.

rafalou38:
it was rotating the disk, it has a flat head.

Okey. RPM control is important for that motor.

Can You look up what voltages that drive used? +5 and +12 I would guess. I wild guess is that the +12 likely would be used for the motor, and likely controlled, PWM is possible.

Try to apply +5 to the wires making the motor move. Observe the motor and don't allow it to run beyond limits.
I think about testing using +12 if the +5 volt test shows vague results, but be careful!

Most HDD spindle motors are BLDC (brushless) motors. They can be driven by a brushless ESC. Cheapest would be to buy hobby RC ESC and drive it by PWM. Something like this would work.

35A means that it can be used to run motors up to that current without damaging ESC. You could find lower current ESC as well (but this one is cheap enough).

ESC consist of three wires, there are no 4 wires ESCs. You need to measure resistance between pairs of wires and connect only wires with higher resistance. One with lower resistance leave unconnected.


here's a picture of the original hdd

for the resistance it changes with the rotation of the motor going from 2 ohm to 0 ohm on each pin pair differently

I guess Western Digital has no interest in answering questions from You...

Details on how to drive are here.....
Amazing how a Google search will bring up almost anything for anyone who wants to try.

Let's hope that Google will not be the data base bringing us WW3.....

Hehe…yes well, search engine may have been more appropriate given Google’s latest…just it’s the normal term around here to Google what you want first up…never know.
I take it you had a quick peek at the video though…??:slight_smile:

Yes, I had a look at the video. Fantastic.
If. I ask Goigle what sometimes makes pain in my back I'm sure they'll have an idea....

A better idea, would be to monitor the signals and voltages on a working spindle before disassembling the drive.

'Reverse engineering' the original PCB (Follow the traces to a driver chip) - looking up the driver chip part number on GOOGLE should give you the pin out, you should be able to work it out from there.

This topic was automatically closed 120 days after the last reply. New replies are no longer allowed.