Using Motors As Encoders

If you have a brushless motor, you have some magnets, a bunch of coils arranged in a circle, and theoretically, all the parts you need to build a rotary encoder. A lot of people have used brushless or stepper motors as rotary encoders, but they all seem to do it by using the motor as a generator and looking at the phases and voltages. For their Hackaday Prize project, [besenyeim] is doing it differently: they’re using motors as coupled inductors, and it looks like this is a viable way to turn a motor into an encoder.

The experimental setup for this project is a Blue Pill microcontroller based on the STM32F103. This, combined with a set of half-bridges used to drive the motor, are really the only thing needed to both spin the motor and detect where the motor is. The circuit works by using six digital outputs to drive the high and low sided of the half-bridges, and three analog inputs used as feedback. The resulting waveform graph looks like three weird stairsteps that are out of phase with each other, and with the right processing, that’s enough to detect the position of the motor.

Right now, the project is aiming to send a command over serial to a microcontroller and have the motor spin to a specific position. No, it’s not a completely closed-loop control scheme for turning a motor, but it’s actually not that bad. Future work is going to turn these motors into haptic feedback controllers, although we’re sure there are a few Raspberry Pi robots out there that would love odometry in the motor. You can check out a video of this setup in action below.

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RC Boat Goes Brushless For Speed & Reliability

Remote control boats can be great fun, and come in all manner of forms. There are unpowered sailcraft, speedboats that scream under the power of internal combustion, and of course, those that move under electric power. The brushless motor revolution of the past 20 years in particular has proven capable of creating some exciting RC watercraft, and [Matt K] decided he wanted to get on board.

[Matt] had owned a Kyosho Jetstream 1000 for several years, but found the nitro engine to be temperamental and not the most fun for high-jinx down at the lake. An old-school brushed motor setup with mechanical speed control similarly failed to excite. However, after experiencing the power of brushless in RC planes, [Matt] knew what he had to do.

Using an online calculator, [Matt] determined that his earlier nitro powerplant was putting out roughly 900 watts. When it came to going brushless, he decided to spec a Turnigy powerplant with twice as much power, along with the requisite speed controller. There was some work to do to integrate the new motor with the original propeller driveshaft and water cooling system, but in the end [Matt] ended up with a much faster boat that is a lot less hassle to set up and run.

Perhaps though, your RC boat needs brains, over brawn? Perhaps it’s time to look at autonomy…

Video after the break.

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Semi-automated Winder Spins Rotors for Motors

What’s your secret evil plan? Are you looking for world domination by building a machine that can truly replicate itself? Or are you just tired of winding motor rotors and other coils by hand? Either way, this automated coil winder is something you’re probably going to need.

We jest in part, but it’s true that closing the loop on self-replicating machines means being able to make things like motors. And for either brushed or brushless motors, that means turning spools of wire into coils of some sort. [Mr Innovative]’s winder uses a 3D-printed tube to spin magnet wire around a rotor core. A stepper motor turns the spinner arm a specified number of times, pausing at the end so the operator can move the wire to make room for the next loop. The rotor then spins to the next position on its own stepper motor, and the winding continues. That manual step needs attention to make this a fully automated system, and we think the tension of the wire needs to be addressed so the windings are a bit tighter. But it’s still a nice start, and it gives us some ideas for related coil-winding projects.

Of course, not every motor needs wound coils. After all, brushless PCB motors with etched coils are a thing.

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Flat Pack Generators

We just wrapped up the Power Harvesting challenge in the Hackaday Prize, and with that comes some solutions to getting power in some very remote places. [Vijay]’s project is one of the best, because his project is getting power in Antarctica. This is a difficult environment: you don’t have the sun for a significant part of the year, it’s cold, and you need to actually get your equipment down to the continent. [Vijay]’s solution was to use one of Antarctica’s greatest resources — wind — in an ingenious flat pack wind turbine.

There are a few problems to harvesting wind power in a barren environment. The first idea was to take a standard, off-the-shelf motor and attach some blades, but [Vijay] found there was too much detent torque, and the motor would be too big anyway.

The solution to this problem was to wind his own motor that didn’t have the problems of off-the-shelf brushless motors. The design that [Vijay] settled on is a dual axial flux generator, or a motor with a fixed stator with magnets and two rotors loaded up with copper windings. Think of it as a flattened, inverted version of the motor on your drone.

One interesting aspect of this design is that it takes up significantly less space than a traditional motor, while still being able to output about 100 Watts with the wind blowing. Add in some gearing to get the speed of the rotor right, and you have a simple wind generator that can be set up in minutes and carried anywhere. It’s a great project, and we’re glad to see this make it into the finals of The Hackaday Prize.

The Current Advances of PCB Motors

There’s something to be said about the falling costs of printed circuit boards over the last decade. It’s opened up the world of PCB art, yes, but it’s also allowed for some experimentation with laying down fine copper wires inside a laminate of fiberglass and epoxy. We can design our own capacitive touch sensors. If you’re really clever, you can put coils inside four-layer PCBs. If you’re exceptionally clever, you can add a few magnets and build a brushless motor out of a PCB.

We first saw [Carl]’s PCB motor at the beginning of the year, but since then we’ve started the Hackaday Prize, [Carl] entered this project in the Prize, and this project already made it to the final round. It’s really that awesome. Since the last update, [Carl] has been working on improving the efficiency and cost of this tiny PCB motor. Part of this comes from new magnets. Instead of a quartet of round magnets, [Carl] found some magnets that divide the rotor into four equal pieces. This gives the rotor a more uniform magnetic field across its entire area, and hopefully more power.

The first version of this 3D printed PCB motor used press-fit bushings and a metallic shaft. While this worked, an extra piece of metal will just drive up the cost of the completed motor. [Carl] has redesigned the shaft of the rotor to get rid of the metallic axle and replace it with a cleverly designed, 3D printed axle. That’s some very nice 3D printing going on here, and something that will make this motor very, very cheap.

Right now, [Carl] has a motor that can be made at any board house that can do four-layer PCBs, and he’s got a rotor that can be easily made with injection molding. The next step is closed-loop control of this motor. This is a challenge because the back-EMF generated by four layers of windings is a little weak. This could also be accomplished with a hall sensor, but for now, [Carl] has a working PCB motor. There’s really only one thing to do now — get the power output up so we can have real quadcopter badges without mucking around with tiny brushed motors.

[Carl] has put up a few videos describing how his PCB motor works; you can check those out below.
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3000W Unicycle’s Only Limitation Is “Personal Courage”

Electric vehicles are fertile ground for innovation because the availability of suitable motors, controllers, and power sources makes experimentation accessible even to hobbyists. Even so, [John Dingley] has been working on such vehicles since about 2009, and his latest self-balancing electric unicycle really raises the bar by multiple notches. It sports a monstrous 3000 Watt brushless hub motor intended for an electric motorcycle, and [John] was able to add numerous touches such as voice feedback and 1950’s styling using surplus aircraft and motorcycle parts. To steer, the frame changes shape slightly with help of the handlebars to allow the driver’s center of gravity to shift towards one or the other outer rims of the wheel. In a test drive at a deserted beach, [John] tells us that the bike never went above 20% power; the device’s limitations are entirely by personal courage. Watch the video of the test, embedded below.

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Here’s Why Hoverboard Motors Might Belong In Robots

[madcowswe] starts by pointing out that the entire premise of ODrive (an open-source brushless motor driver board) is to make use of inexpensive brushless motors in industrial-type applications. This usually means using hobby electric aircraft motors, but robotic applications sometimes need more torque than those motors can provide. Adding a gearbox is one option, but there is another: so-called “hoverboard” motors are common and offer a frankly outstanding torque-to-price ratio.

A teardown showed that the necessary mechanical and electrical interfacing look to be worth a try, so prototyping has begun. These motors are really designed for spinning a tire on the ground instead of driving other loads, but [madcowswe] believes that by adding an encoder and the right fixtures, these motors could form the basis of an excellent robot arm. The ODrive project was a contender for the 2016 Hackaday Prize and we can’t wait to see where this ends up.