Brushless HDD Motor Driver from 9V and Painter’s Tape

Hard drives work by spinning platters full of magnetized data while a read/write head very quickly harvests or changes bits as needed. Older (or perhaps cheaper) drives spin at 5400 RPM, better drives spin at 7200 RPM, and elite drives (that mortals like you never shell out for) spin in the 10k-15k RPM range. This spinning is thanks to a sweet combination of a bearing and a brushless DC motor.

Unfortunately you can’t drive a brushless motor without a brushless motor driver. Well, of course that’s not absolutely true — and [Tommy Callaway] has certainly hacked together a crude exception to the rule. He’s using a 9-volt battery and some blue painters tape to drive a brushless motor.

Brushless motors do their thing by placing permanent magnets on the rotor (the part that spins) and placing multiple stationary coils of wire around it. Brushless motor drivers then energize these coils in a vary carefully timed pattern to continuously push the rotor magnets in the same direction.

[Tommy] wired up his 9V to one of these coils and observed that it holds the rotor in position. He then began playing around with different ways automatically break the circuit to de-energize the coil at just the right time. This means using the spinning center of the hard drive as part of the circuit, with blue painter’s tape in alternating patterns to create the timing. Is this a brushless motor driver, or has he just re-invented the brushed motor?

If this workbench trick leaves you wanting for some hardcore BLCD action, you can’t go wrong with this $20 offering to push motors at very high speeds.

[via /r/ECE]

24 thoughts on “Brushless HDD Motor Driver from 9V and Painter’s Tape

  1. That is pure genius, making a brushless motor work, by adding a brush, he should patent that…

    Perhaps next he will use the motor as a generator and record the pulses onto tape then put that into a loop and play it back to drive the motor, or something similar that almost works.

        1. Sure they are! Or, to be more precise, they were, because now are hard to find.

          Instead of simple coils, inside the cassette-like shaped device there was another stereo play-head that sit in front of the boom box play-head. The play-head from the cassette was fed with the stereo audio from a 3.5mm jack.

          1. Dollar Tree still has them here.

            I think they appeared shortly after portable CD players, so you could use them in the car.

            Still keep browsing the cheapy China sites hoping a low buck bluetooth one will turn up though.

          2. RW’s comment got me curious since i use a usb bluetooth adapter connected to 3.5mm cassette converter. One google search later, and i found they have one without all the wires called the ION bluetooth cassette. $20 at walmart. I was however disappointed that it runs on battery instead of being powered by the constantly spinning cassette spindle.

          3. I guess $20 isn’t too painful. The advantage of not being spindle driven is that a lot of players have age weakened drive mechanisms, and if you wanna use it in an original 80s boombox, you’ll probably have to rebuild the thing first. If it’s battery powered, tape mech doesn’t even have to move, if it won’t, still works as long as the head is live.

          4. I have one of these dangling out of the cassette player in my `02 Wrangler just because I’m too lazy to pull the player and look for points to add an aux input jack (though I’m sure there likely is one).

  2. Avoid the brush by running current for the motor through a light sensitive device close to a reflective portion of the disk and use tape (or Paint) to interrupt reflection of light off the disk. Further control the flow of current to the motor by manually blocking some variable portion of the reflected light, to fine tune speed of disk rotation.

    1. There’s not a lot of point, really. If he’s going to implement an actual circuit, rather than a bit of wire, he may as well use an actual motor driver. This is just pissing about. Still fun, but no practical use.

  3. He’s only powering and unpowering a single winding, whereas most brushed motors have multiple windings that also reverse in polarity. And, of course, the BLDC in a hard-disk usually has three windings, as well. Nice simplification-job, here.

  4. That wire will wear out. Something like a graphite pencil or carbon rod out of an old battery would last longer. Maybe spring loaded it to keep contact and… oh wait a minute…
    Actually I do like the hack.

  5. “Older (or perhaps cheaper) drives spin at 5400 RPM”

    What do you mean “perhaps”? If you don’t know anything about a piece of hardware, don’t write comments about it.

    There’s also 4200RPM hard drives, FIY. It’s not about age, it’s about price/power/heat.

    1. I think the “perhaps” is because Mike doesn’t know if the hard drive in question is old and therefore spins at 5400RPM or is new and cheap and spins at 5400RPM because sometimes it’s about price, and sometimes it’s about making a comment in a desperate attempt to appear knowledgeable.

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s