driving a NIDEC 1857-43mx-10 HDD motor with an Arduino UNO

I opened an ancient JTS harddrive and it has a NIDEC 1857-43mx-10 motor with a little bit of flex cable coming out of it with 4 conductors.

If I measure the resistance between the rightmost wire to the other three I get about 2 ohms. The resistance between all the others is a mixture of slightly larger resistances.

How do I figure out what kind of motor this is and how do I drive it with an Arduino UNO? I'm hoping you can drive this with nothing but transistors/darlingtons and that you don't need something like an H-Bridge.

They are usually star-would BLDCs I believe - here the rightmost wire will be the common winding.

You can drive as a unipolar 3-phase motor using the common wire, or from a full 3-phase bridge directly (ignoring the common wire) - this is more complex.

Given the low winding resistance you probably want to use quite a low PWM duty cycle to start with, fed to each winding in turn. 3 darlingtons or MOSFETs to ground, common to V+ (which is usually 12V for a disk drive). The PWM frequency may need to be a lot higher than the Arduino default - it would be nice to know the winding inductance to estimate that.

This video seems to be on-topic: https://www.youtube.com/watch?v=CMz2DYpos8w&spfreload=10

That video was quite helpful.

I got my motor spinning. It’s not terribly useful and has almost no torque but it works :slight_smile:

What do you expect from a small motor with no gearing? Torque is limited by
motor volume, roughly speaking.

MarkT: What do you expect from a small motor with no gearing? Torque is limited by motor volume, roughly speaking.

I never expected it to be like a stepper but it can't even spin when the HDD platters are attached. It only spins when it's bare.

I'm not doing anything with this motor, I just wanted to see if it was possible to make it spin.