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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Build a Foam Cutter Right Now

Cutting foam is difficult with traditional methods. The best way is with a hot wire. If you read Hackaday, it is a good bet you can figure out how to use electricity to make a wire hot without any help. However, there’s something  clever about [MrGear’s] minimal build.

As you can see in the video below, he uses a 9V battery, a clip, some popsicle sticks, and the wire from a ballpoint pen. He also used a switch, but we couldn’t help but think that was unnecessary  since you could just unclip the battery to turn the device on and off. Since he used hot glue to attach the switch to the battery, replacing the battery would be a pain.

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Hackaday Links: February 2, 2014


[Michel] was in need of a 9V battery connector, and in a brilliant bit of insight realized 9V batteries will plug directly into other 9V batteries (just… don’t do that. ever.) Taking a dead 9V, he tore it open, was disappointed by the lack of AAAA cells, and soldered some wires onto the connector.

Sometimes a project starts off as a reasonable endeavour, but quickly becomes something much more awesome. [Wallyman] started off building a hammock stand and ended up making a giant slingshot. We’re not one to argue with something that just became a million times more fun.

We’ve seen solder stencils made out of laser-cut metal, photoetched metal, plastic cut on a vinyl cutter, laser-cut plastic, and now finally one made on a 3D printer. It’s a pretty simple process – get the tCream layer into a .DXF file, then subtract it from a plastic plate in OpenSCAD.

Apple loves their proprietary screws, and when [Jim] tried to open his Macbook Air with the pentalobe screwdriver that came with an iPhone repair kit, he found it was too large. No problem, then: just grind it down. Now if only someone could tell us why a laptop uses smaller screws than a phone…

[Victor] has been playing around with an RTLSDR USB TV tuner dongle for a few months now. It’s a great tool, but the USB thumb drive form factor wasn’t sitting well with him. To fix that, he stuck everything into a classy painted Hammond 1590A enclosure. It looks much cooler, and now [Victor] can waterproof his toy and add a ferrite to clean things up.