commutation

3 Articles

Steampunk Brushless Motor Demo Pushes All The Maker Buttons

May 29, 2020 by 46 Comments

We’ll be honest right up front: there’s nothing new in [David Cambridge]’s brushless motor and controller build. If you’re looking for earth-shattering innovation, you’d best look elsewhere. But if you enjoy an aimless use of just about every technique and material in the hacker’s toolkit employed with extreme craftsmanship, then this might be for you. And Nixies — he’s got Nixies in there too.

[David]’s build started out as a personal exploration of brushless motors and how they work. Some 3D-printed parts, a single coil of wire, and a magnetic reed switch resulted in a simple pulse motor that performed surprisingly well. This morphed into a six-coil motor with Hall-effect sensors and a homebrew controller. This is where [David] pulled out all the stops on tools — a lathe, a plasma cutter, a welder, a milling machine, and a nice selection of woodworking tools went into making parts for the final motor as well as an enclosure for the project. And because he hadn’t checked off quite all the boxes yet, [David] decided to use the 3D-printed frame as a pattern for casting one from aluminum.

The finished motor, with a redesigned rotor to deal better with eddy currents, joined the wood and metal enclosure along with a Nixie tube tachometer and etched brass control plates. It’s a great look for a project that’s clearly a labor of self-edification and skill-building, and we love it. We’ve seen other BLDC demonstrators before, but few that look as good as this one does.

Continue reading “Steampunk Brushless Motor Demo Pushes All The Maker Buttons” →

3-Phase BLDC Motor Controller Will Run You $20 In Parts

July 29, 2016 by 33 Comments

If you’re an active shopper on RC websites, you’ll find tiny motors spec’ed at hundreds of watts while weighing just a few grams, like this one. Sadly, their complementary motor controllers are designed to drive them at a high speed, which means we can only hit that “520-watt” power spec by operating in a max-speed-minimum-torque configuration. Sure, that configuration is just fine for rc plane and multicopter enthusiasts, but for roboticists looking to drive these bldc motors in a low-speed-high-torque configuration, the searches come up blank.

The days in the dust are coming to an end though! [Cameron] has been hard at work at a low cost, closed-loop controller for the robotics community that will take a conventional BLDC airplane motor and transform it into a high end servo motor. Best of all, the entire package will only run you about $20 in parts–including the position sensor!

“Another BLDC motor controller?” you might think. “Surely, I’ve seen this before“. Fear not, faithful readers; [Cameron’s] solution will get even the grumpiest of engineers to crack a smile. For starters, he’s closing the loop with a Melexis MLX90363 hall effect sensor to locate the rotor position. Simply glue a small magnet to the shaft, calibrate the magnetic field with one revolution, and–poof–a wild 14-bit encoder has appeared! Best of all, this solution costs a mere $5 to $10 in parts.

Next off, [Cameron] uncovered a little-known secret of the ATMEGA32u4, better known as the chip inside the Arduino Leonardo. It turns out that this chip’s TIMER4 peripheral contains a feature designed exclusively for 3-phase brushless motor control. Complementary PWM outputs are built into 3 pairs of pins with configurable dead time built into the chip hardware. Finally, [Cameron] is pulsing the FETs at a clean 32-Khz — well beyond the audible range, which means we won’t hear that piercing 8-Khz whine that’s so characteristic of cheap BLDC motor controllers.

Curious? Check out [Cameron’s] firmware and driver design on the Githubs.

Of course, there are caveats. [Cameron’s] magnetic encoder solution has a few milliseconds of lag that needs to be characterized. We also need to glue a magnet to the shaft of our motor, which won’t fly in all of our projects that have major space constraints. Finally, there’s just plain old physics. In the real world, motor torque is directly proportional to current, so stalling an off-the-shelf bldc motor at max torque will burn them out since no propeller is pushing air through them to cool them off. Nevertheless, [Cameron’s] closed loop controller, at long last, can give the homebrew robotics community the chance to explore these limits.

Scratch-built Radial Solenoid Engine Is Polished And Professional

May 20, 2016 by 23 Comments

There’s something alluring about radial engines. The Wasps, the Cyclones, the Gnomes – the mechanical beauty of those classic aircraft engines can’t be denied. And even when a radial engine is powered by solenoids rather than internal combustion, it can still be a thing of beauty.

The solenoid engine proves that he has some mechanical chops. If you follow along in the videos below, you’ll see how [Tyler] progressed in his design and incorporated what he learned from the earliest breadboard stage to the nearly-complete engine. There’s an impressive amount of work here – looks like the octagonal housing was bent on a press brake, and the apparently homebrew solenoids are enclosed in copper pipe and fittings that [Tyler] took the time to bring to a fine polish. We’re skeptical that the microswitches that electrically commutate the engine will hold up to as many cycles are they’d need to handle for this to be a useful engine, but that’s hardly the point here. This one is all about the learning, and we think [Tyler] has done a bang-up job with that.

For more radial solenoid engine goodness, check out this engine with an entirely different take on commutation. Or if you need the basics of radial engine theory, this wood mockup might be just the thing.

Continue reading “Scratch-built Radial Solenoid Engine Is Polished And Professional” →