Rewound And Rewired BLDC Makes A Half-Decent Generator

November 8, 2018 by Dan Maloney 18 Comments

What’s the best way to turn a high-powered brushless DC motor optimized for hobby use into a decent low-RPM generator? Do you take a purely mechanical approach and slap a gearbox on the shaft? Or do you tackle the problem electrically?

The latter approach is what [GreatScott!] settled on with his BLDC rewinding and rewiring project. Having previously explored which motors have the best potential as generators, he knew the essential problem: in rough terms, hobby BLDCs are optimized for turning volts into RPMs, and not the other way around. He started with a teardown of a small motor, to understand the mechanical challenges involved, then moved onto a larger motor. The bigger motor was stubborn, but with some elbow grease, a lot of scratches, and some destroyed bearings, the motor was relieved of both its rotor and stator. The windings were stripped off and replaced with heavier magnet wire with more turns per pole than the original. The effect of this was to drive the Kv down and allow better performance at low RPMs. Things looked even better when the windings were rewired from delta to wye configuration.

The take-home lesson is probably to use a generator where you need a generator and let motors be motors. But we appreciate [GreatScott!]’s lesson on the innards of BLDCs nonetheless, and his other work in the “DIY or buy?” vein. Whether you want to make your own inverter, turn a hard drive motor into an encoder, or roll your own lithium battery pack, he’s done a lot of the dirty work already.

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Tilt-Rotor Plane Needs Flight Controller Hack To Get Airborne

November 6, 2018 by Dan Maloney 6 Comments

Part of the charm of quadcopters is the challenge that building and flying them presents. In need of complex sensors and computational power to just get off the ground and under tremendous stresses thanks to their massively powerful motors, they often seem only barely controlled in flight. Despite these challenges, quadcopter flight has been reduced to practice in many ways, leaving hobbyists in search of another challenge.

[Tom Stanton] is scratching his creative itch with this radio-controlled tilt-rotor airplane that presents some unique problems and opportunities. Tilt-rotor planes are, as the name implies, able to swivel their propellors and transition them from providing forward thrust to providing verticle lift. With the rotors providing lift, the aircraft is able to hover and perform vertical take-off and landing (VTOL); switched to thrust mode, wings provide the lift for horizontal flight.

[Tom]’s realization of this design seems simple – a spar running through the wing holding BLDC motors and props is swiveled through 90° by a servo to transition the aircraft. Standard control surfaces on the wings and tail take care of horizontal flight. Actually getting an off-the-shelf flight controller to deal with the transitions was tricky. [Tom] ended up adding an Arduino to intercept the PWM signals the flight controller normally sends directly to the servos and speed controls to provide the coordination needed for a smooth transition. Full details in the video below, and some test flights which show that an RC VTOL is anything but a beginner’s plane.

[Tom] is proving himself to be quite the Renaissance man these days. Between air-powered piston engines, over-balance trebuchets, and popping the perfect wheelie, he seems to have covered all the bases and done his best to keep our tip line stocked.

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Building An Electric Scooter That’s Street Legal, Even In Germany

October 23, 2018 by Dan Maloney 47 Comments

Sometimes a successful project isn’t only about making sure all the electrons are in the right place at the right time, or building something that won’t collapse under its own weight. A lot of projects involve a fair amount of social engineering to be counted as a success, especially those that might result in arrest and incarceration if built as originally planned. Such projects are often referred to as “the fun ones.”

For the past few months, we’ve been following [Bitluni]’s DIY electric scooter build, which had been following the usual trajectory for these things – take a stock unpowered scooter, replace the rear wheel with a 250 W hub motor, add an ESC, battery, and throttle, and away you go. Things took a very interesting turn, however, when his street testing ran afoul of German law, which limits small electric vehicles to a yawn-inducing 6 kph. Unwilling to bore himself to death thus, [Bitluni] found a workaround: vehicles that are only assisted by an electric motor have a much more reasonable speed limit of 25 kph. So he added an Arduino with a gyro and accelerometer module and wrote a program to only power the wheel after the rider has kicked the scooter along a few times – no throttle needed. The motor stops after a bit, needing another push or two to kick it back on. A brake lever kills the motor, as does laying the scooter on its side. It’s quite a clever design, and while it might not keep the Polizei at bay, you can’t say he didn’t try.

[Bitluni] has quite a range of builds, from software-defined television to bad 3D-scanners to precision wine glass whacking. You should check out his stuff. Continue reading “Building An Electric Scooter That’s Street Legal, Even In Germany” →

Homebrew Linear Actuators Put The Moves On This Motion Simulator

October 4, 2018 by Dan Maloney 32 Comments

Breaking into the world of auto racing is easy. Step 1: Buy an expensive car. Step 2: Learn how to drive it without crashing. If you’re stuck at step 1, and things aren’t looking great for step 2 either, you might want to consider going with a virtual Porsche or Ferrari and spending your evenings driving virtual laps rather than real ones.

The trouble is, that can get a bit boring after a while, which is what this DIY motion simulator platform is meant to address. In a long series of posts with a load of build details, [pmvcda] goes through what he’s come up with so far on this work in progress. He’s building a Stewart platform, of the type we’ve seen before but on a much grander scale. This one will be large enough to hold a race car cockpit mockup, which explains the welded aluminum frame. We were most interested in the six custom-made linear actuators, though. Aluminum extrusions form the frame holding BLDC motor, and guide the nut of a long ball screw. There are a bunch of 3D-printed parts in the actuators, each of which is anchored to the frame and to the platform by simple universal joints. The actuators are a little on the loud side, but they’re fast and powerful, and they’ve got a great industrial look.

If car racing is not your thing and you’d rather build a full-motion flight simulator, here’s one that also uses DIY actuators.

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Single-Rotor Drone: A Thrust-Vectoring Monocopter

August 31, 2018 by Dan Maloney 54 Comments

We’re not entirely sure what to call this one. It’s got the usual trappings of a drone, but with only a single rotor it clearly can’t be called by any of the standard multicopter names. Helicopter? Close, but not quite, since the rotor blades are fixed-pitch. We’ll just go with “monocopter” for now and sort out the details later for this ducted-fan, thrust-vectored UAV.

Whatever we choose to call it — builder [tesla500] dubbed it the simultaneously optimistic and fatalistic “Ikarus” — it’s really unique. The monocopter is built around a 90-mm electric ducted fan mounted vertically on a 3D-printed shroud. The shroud serves as a mounting point for the landing legs and for four servos that swivel vanes within the rotor wash. The vanes deflect the airstream and provide the thrust vectoring that gives this little machine its control.

Coming to the correct control method was not easy, though. Thanks mainly to the strong gyroscopic force exerted by the rotor, [tesla500] had a hard time getting the flight controller to cooperate. He built a gimballed test stand to work the problem through, and eventually rewrote LibrePilot to deal with the unique forces on the craft and tuned the PID loops accordingly. Check out the results in the video below.

Some attempts to reduce the number of rotors work better than others, of course, but this worked out great, and we’re looking forward to the promised improvements to come.

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Remote Controlled Electric Snowblower Sports FPV For Safety

August 7, 2018 by Dan Maloney 27 Comments

As summer scorches the northern hemisphere, here’s something to cool your thoughts: winter is only four months away. And with it will come the general misery and the proclamations that “It’ll never be warm again,” not to mention the white stuff and the shoveling. Or perhaps not, if you’re lucky enough to have a semi-autonomous electric snowblower in the garage.

The device [Dane Kouttron] describes is a strange beast indeed, and one that came to him under somewhat mysterious circumstances. It appears to be a standard Ariens two-stage blower, the kind normally driven by a fairly beefy internal combustion engine so as to have enough power to run the auger, the impeller, and the drive wheels. But a previous owner had removed the gas engine and attached a 4-kW brushless motor to run the auger and impeller. Realizing the potential of this machine and with a winter storm heading his way, [Dane] used the old engine mount to hold giant LiFePO₄ batteries from a cell tower backup battery, slapped a couple of electric wheelchair motors onto the drive wheels, mounted a motor to swivel the exhaust chute, and added control electronics from a retired battlebot. Setting such a machine loose in the wild would be bad, so an FPV system was added just in time for storm cleanup. Upgrades for version 2 include better weight distribution for improved stability and traction, and of course googly eyes. Check out the video below to see it flinging snow and moving around faster than any snowblower we’ve ever seen.

We’ll never get lucky enough to have such wonders gifted on us as [Dane] did, but we applaud him for picking up the torch where someone else obviously left off. And who knows; perhaps the previous maker took inspiration from this remote-controlled snowblower build?

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The Current Advances Of PCB Motors

May 12, 2018 by Brian Benchoff 9 Comments

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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