SATA Cable Replaces DC Motor Brushes as Macgyver Looks On

[dmalhar] was digging around in his bins for motors and found one with missing brushes. Being resourceful (and not able to find another motor), he managed to tear apart a SATA cable and form the pins into brushes with just the right amount of spring. Yes, this looks like a cheap motor, but in the moment of necessity availability wins, and this hack is truly commendable. If he had used a paperclip, MacGyver would have been proud, but the SATA cable pins make us proud.

Normally the brushes of DC motors are made with a graphite or some other material which provides a small amount of resistance so that when the motor is spinning the brushes will provide a gradual shift of current from one commutator to the next. Also, the softness of the carbon makes the brush wear down instead of the commutator, and in large motors the brushes are replaceable. In cheap motors the engineers design the brush material around the expected lifetime of the product. In [dmalhar’s] case, the motor just got its lifetime extended by a while.

EZ-Spin Motor Spins “Forever”

Now this isn’t a perpetual motion machine, but it’s darn close. What [lasersaber] has done instead is to make the EZ Spin, an incredibly efficient motor that does nothing. Well, nothing except look cool, and influence tons of people to re-build their own versions of it and post them on YouTube.

The motor itself is ridiculously simple: it’s essentially a brushless DC motor with a unique winding pattern. A number of coils — anywhere from six to twenty-four — are wired together with alternating polarity. If one coil is a magnetized north, its two neighbors are magnetized south, and vice-versa. The rotor is a ring with permanent magnets, all arranged so that they have the same polarity. A capacitor is used for the power source, and a reed switch serves as a simplistic commutator, if that’s even the right term.

As the motor turns, a permanent magnet passes by the reed switch and it makes the circuit. All of the electromagnets, which are wound in series, fire and kick the rotor forwards. Then the reed switch opens and the rotor coasts on to the next position. When it gets there the reed switch closes and it gets a magnetic kick again.

The catch? Building the device so that it’s carefully balanced and running on really good (sapphire) bearings, entirely unloaded, and powered with high impedance coils, leads to a current consumption in the microamps. As with most motors, when you spin it by hand, it acts as a generator, giving you a simple way to charge up the capacitor that drives it. In his video [lasersaber] blows on the rotor through a straw to charge up the capacitor, and then lets it run back down. It should run for quite a while on just one spin-up.

The EZ Spin motor is absolutely, positively not perpetual motion or “over-unity” or any of that mumbo-jumbo. It is a cool, simple-to-build generator/motor project that’ll definitely impress your friends and challenge you to see how long you can get it running. Check out [lasersaber]’s website, this forum post, and a 3D model on Thingiverse if you want to make your own.

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Hackaday Prize Entry: DC Motor Controller

There are a lot of cheap Chinese CNC machines out there with okay mechanics and terrible electronics. The bearings aren’t complete crap, but the spindle of these CNC machines is a standalone PWM controller with a pot to control the speed. This means you can’t control the spindle speed with LinuxCNC or Mach3.

For his Hackaday Prize entry, [SUF] is building a DC motor controller for a Chinese spindle motor that doesn’t use any kind of encoder. The first part of that project is fairly easy; [SUF] has already built a high current driver. The second bit is a little it harder – because these spindles don’t have an encoder, [SUF] will have to read voltage spikes on the motor poles, giving him the RPM of the spindle. From there, it’s a bit of PID code to get this spindle running at a desired RPM and connecting it to a CNC control box.

So far, [SUF] has a second version of his board waiting for assembly. In the first version of the board, the switching time for the MOSFET was a little slow, but that’s all corrected in the current revision. It’s a great project to extend the capability of these cheap CNC machines, and perfect project for the Hackaday Prize.

The 2015 Hackaday Prize is sponsored by:

Closed Loop Control For 3D Printers

One of the bigger problems with any CNC machine or 3D printer is the issue of missed steps when moving the toolhead. If a stepper motor misses a step, the entire layer of the print – and every layer thereafter – will be off by just a tiny bit. Miss a few more steps, and that print will eventually make its way into the garbage. [Misan] has the solution to this: closed loop control of DC motors for a 3D printer.

Most printer firmwares use an open loop control system for moving their motors around. Step a few times in one direction, and you know where the nozzle of a 3D printer will be. Missed steps confound the problem, and there’s no way for the firmware to know if the nozzle is where it should be at any one time.

[Misan]’s solution to this was a DC motor coupled to an optical encoder. Both the motor and the encoder are connected to an Arduino Pro Mini which receives step and direction commands from the printer controller. The controller takes care of telling the motor where to go, the Arduino takes care of making sure it gets there.

The entire build is heavily derived from ServoStrap, but [Misan] has a very cool demo of his hardware: during a print, he can force the X and Y axes to either side, and the Arduino in each motor will move the print head back to where it needs to be. You can check that out below.

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POV Display Does it on the Cheap


[Sholto] hacked together this ultra low-budget spinning display. He calls it a zoetrope, but we think it’s actually an LED based Persistence Of Vision (POV) affair. We’ve seen plenty of POV devices in the past, but this one proves that a hack doesn’t have to be expensive or pretty to work!

The major parts of the POV display were things that [Sholto] had lying around. A couple of candy tins, a simple brushed hobby motor, an Arduino Pro Mini, 7 green LEDs, and an old hall effect sensor were all that were required. Fancy displays might use commercial slip rings to transfer power, but [Sholto] made it work on the cheap!

The two tins provide a base for the display and the negative supply for the Arduino. The tins are soldered together and insulated from the motor, which is hot glued into the lower tin. A paper clip contacts the inside of the lid, making the entire assembly a slip ring for the negative side of the Arduino’s power supply. Some copper braid rubbing on the motor’s metal case forms the positive side.

[Sholto] chose his resistors to slightly overdrive his green LEDs. This makes the display appear brighter in POV use. During normal operation, the LEDs won’t be driven long enough to cause damage. If the software locks up with LEDs on though, all bets are off!

[Sholto] includes software for a pretty darn cool looking “saw wave” demo, and a simple numeric display. With a bit more work this could make a pretty cool POV clock, at least for as long as the motor brushes hold up!

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Ride, Captain, Ride Aboard Your Arduino-Controlled Autopiloted Sailboat

[Jack], a mechanical engineer, loom builder, and avid sailor wanted an autopilot system for his 1983 Robert Perry Nordic 40 sailboat with more modern capabilities than the one it came with. He knew a PC-based solution would work, but it was a bit out of reach. Once his son showed him an Arduino, though, he was on his way. He sallied forth and built this Arduino-based autopilot system for his sloop, the Wile E. Coyote.

He’s using two Arduino Megas. One is solely for the GPS, and the other controls everything else. [Jack]’s autopilot has three modes. In the one he calls knob steering, a potentiometer drives the existing hydraulic pump, which he controls with a Polulu Qik serial DC motor controller. In compass steering mode, a Pololu IMU locks in the heading to steer (HTS).  GPS mode uses a predetermined waypoint, and sets the course to steer (CTS) to the same bearing as the waypoint.

[Jack]’s system also uses cross track error (XTE) correction to calculate a new HTS when necessary. He has fantastic documentation and several Fritzing and Arduino files available on Dropbox.

Autopilot sailboat rigs must be all the rage right now. We just saw a different one back in November.

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Building a Ball-Balancing Robot


If you want a different kind of feedback systems challenge, ditch the Segway-style robots and build one that can balance on a ball. UFactory is a startup in Shenzhen, and this impressive little guy is a way of showing their skills applied to the classic inverted pendulum. At nearly 18 inches tall and weighing just over six pounds, the robot boasts a number of features beyond an accelerometer and gyroscope: it has both a WiFi module and a camera, and can be controlled via a homemade remote control or a Kinect.

The build uses plastic omni-directional wheels attached to 3 brushed dc motors, which attach to the base of the robot with custom-made aluminum brackets. The UFactory gang constructed the robot’s body out of three acrylic discs, which hold the electronics directly above the wheels. The brain seems to be an STM32 microcontroller that connects up to the motors and to the sensors.

You won’t find the code on their Instructable yet, but according to the comments they have plans to make the entire project open source. If you’re desperate for more details, the UFactory team seems willing to provide source code and other information via email. Make sure you see the video after the break, particularly the end where they demonstrate interference and carrying loads. This isn’t the first ball pendulum we’ve seen; take a trip down memory lane with the BallP ball balancing robot from 2010.

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