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.

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Real World Race Track is Real Hack

[Rulof] never ceases to impress us with what he comes up with and how he hacks it together. Seriously, how did he even know that the obscure umbrella part he used in this project existed, let alone thought of it when the time came to make a magnet mount? His hack this time is a real world, tabletop race track made for his little brother, and by his account, his brother is going crazy for it.

His race track is on a rotating table and consists of the following collection of parts: a motor, bicycle wheel, casters from a travel bag, rubber bands (where did he get such large ones?), toy car and steering wheel from his brother, skateboard wheels, the aforementioned umbrella part and hard drive magnets. In the video below we like how he paints the track surface by holding his paint brush fixed in place and letting the track rotate under it.

From the video you can see the race track has got [Rulof] hooked. Hopefully he lets his brother have ample turns too, but we’re not too sure. Some additions we can imagine would be robotics for the obstacles, lighting, sounds and a few simulated explosion effects (puffs of flour?).

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Another Use for Old Hard Drive Parts: Anemometer

So you’ve just taken apart a hard drive, and you’re looking at all the pieces on your desktop. You’re somehow compelled to use them all in different projects. Why not pull out that very high quality bearing that keeps the platters spinning at high RPMs and build this simple anemometer with it? That’s what [Sergei Bezrukov] did, and it looks like a perfect el cheapo project.

The build is fairly low-tech and entirely sufficient. The cups are made from plastic containers that used to contain pantyhose. A Hall-effect sensor and a magnet take care of measuring the rotations, feeding its signal into a PIC that calculates the wind speed from the revolution rate. The rest of the housing is PVC, with some other miscellaneous parts found at the hardware store.

To calibrate the device, [Sergei] made a second hand-held unit that he could (presumably) drive around in a car to get a baseline wind speed, and then note down the revolution rate. Once you’ve got a good reference, holding the portable unit up to the permanent one transfers the calibration.

But the star of the show, that lets the anemometer spin effortlessly, is the sweet bearing that used to spin a hard-drive platter. If you haven’t played with one of these bearings before, you absolutely should. We just ran a post on taking apart a hard drive for its spare-parts goodness so you have no excuse. If you’re feeling goofy, you can mount one onto a board, step on it with the ball of your foot, and spin. They’re quality bearings, and you’ll be surprised how quickly you can spin as you pull your arms in.

Thank [Matt] for the tip!

Hard Drive Disassembly is Easy and Rewarding

Have any dead hard drives kicking around? Hackaday alum [Jeremy Cook] shows how easy it is to disassemble a hard drive to scavenge its goodies. The hardest part is having the patience and the tools to get past all those screws that stand between you and the treasure inside.

The case screws are frequently of the Torx variety. Any self-respecting hacker probably has one or two of these already, but if you’re in the market, [Jeremy] recommends a nice set that looks way better than ours. Once the case is open, you can find rare earth magnets, bearings, and one or more platters.

Those terrifically strong magnets are good for all kinds of projects. Glue a couple of them to the back of an attractive piece of wood, mount it on the kitchen wall, and you have yourself a knife block. Keep a couple on the bench to temporarily magnetize tools. Use them to build a pickup to amplify a cigar box guitar or thumb piano. Or run the pickup into a small amplified speaker and wave it like a stethoscope near your electronics to hear them hum. As far as liberating the magnets goes, [Jeremy] resorted to clamping his in a vise and using a hammer and chisel to pry it away from the actuator hardware.

You’ve no doubt seen clocks made from old hard drives that were kept mostly intact. Many makers including [Jeremy] will extract the shiny platters to use as bases for clock faces and engrave the numbers, etch them, or glue them on. Those platters also make excellent chimes. Even if you just hang one platter off of a finger and tap it with a fingernail, it sounds really nice.

If simple chimes don’t really butter your muffin, there are all kinds of sonic projects for dead hard drives. How about making a microphone or speakers? Maybe an HDD MIDI controller or a synthesizer is more your speed. Speaking of synths, watch [Jeremy] take a hard drive apart to some sweet sounds after the break.

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Software Controlled Hard Drive Solenoid Engine

[Fabien-Chouteau] submitted his interesting solenoid engine. In an internal combustion, steam, or pneumatic piston engine, the motive force is produced by expanding gas. In [Fabien]’s little engine it is produced by the arm of a hard drive. Solenoid engines are usually just for show, and come in all shapes and sizes. If you want to move something using electricity an axial motor is probably a better bet. But if you want a challenge and a learning experience, this is hard to beat.

[Fabien] had some problems to solve before his motor made its first revolution. Just like a piston engine the timing needed to be exact. The arm firing at the wrong time could cause all sorts of trouble, the equivalent of backfire in a combustion engine. A STM32f4 discovery board was coupled with a Hall-effect sensor and a MOSFET. When the board read that the arm has moved back to the most efficient position for firing it sent a pulse through the coil. Just like a regular engine, getting the timing right makes all the difference. Once [Fabien] got it tuned up his motor could spin around at a steady 3000 rpm.

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Disk Hack Creates Persistence of Vision

[Adam Antok] was compelled to create this repurposed hard drive persistence of vision hack after seeing a toy of the same nature.

hdd-display-schematicHe used the frame, disk and motor from a drive and added LEDs under the spinning disk as the light source. The disk has 8 small holes drilled equidistant around the disk, and spiraling slightly toward the center. As the holes pass by the LEDS they are flashed by the ATtiny2313 processor to create images. To determine the position of the platters a Hall effect sensor is monitored by the 2313 to detect a magnet on the underside of the disk. There is room to display ten characters at one time. Each cursor position can scroll through the character set by rotating an encoder. For all the precision needed to coordinate the LEDs with the spinning holes the electronics and software code are amazingly simple. That’s a really nice job, [Adam]!

Persistence of vision hacks are to hackers like flames are to moths. One really nice thing about [Adam’s] project is that you can interact with it while it’s running. Check it out after the break.

For a novel take on POV, check out this slow swinging pendulum clock.

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Macintosh Hard Drive Repair

The Macintosh II was a popular computer in the era before Apple dominated the coffee shop user market, but for those of us still using our Mac II’s you may find that your SCSI hard drive isn’t performing the way that it should. Since this computer is somewhat of a relic and information on them is scarce, [TheKhakinator] posted his own hard drive repair procedure for these classic computers.

The root of the problem is that the Quantum SCSI hard drives that came with these computers use a rubber-style bump stop for the head, which becomes “gloopy” after some time. These computers are in the range of 28 years old, so “some time” is relative. The fix involves removing the magnets in the hard drive, which in [TheKhakinator]’s case was difficult because of an uncooperative screw, and removing the rubber bump stops. In this video, they were replaced with PVC, but [TheKhakinator] is open to suggestions if anyone knows of a better material choice.

This video is very informative and, if you’ve never seen the inside of a hard drive, is a pretty good instructional video about the internals. If you own one of these machines and are having the same problems, hopefully you can get your System 6 computer up and running now! Once you do, be sure to head over to the retro page and let us know how you did!

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