An Open Source ESC For Brushless Motors

May 15, 2019 by Lewin Day 18 Comments

For something basic like a brushed DC motor, speed control can be quite simple, and powering up the motor is a simple matter of just applying voltage. Brushless motors are much more demanding in their requirements however, and won’t spin unless driven just right. [Electronoobs] has been exploring the design of a brushless speed controller, and just released version 1.0 of his open-source ESC design.

The basic design is compact, and very similar to many off-the-shelf brushless ESCs in the low power range. There’s a small PCB packing a bank of MOSFETs to handle switching power to the coils of the motor, and a big capacitor to help deal with current spikes. The hacker staple ATMEGA328 is the microcontroller running the show. It’s a sensorless design, which measures the back EMF of the motor in order to determine when to fire the MOSFETs. This keeps things simple for low-torque, low-power applications.

It’s a tidy build, and the latest revision shows a lot of polish compared to the earlier prototypes. If you’re interested to learn more, try building it yourself, or consider building a thrust testing rig for your bench at home. Video after the break.

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Retired Rideshare Scooter Skips The Reverse Engineering To Ride Again

March 19, 2019 by Donald Papp 7 Comments

[Adam Zeloof] (legally) obtained a retired electric scooter and documented how it worked and how he got it working again. The scooter had a past life as a pay-to-ride electric vehicle and “$1 TO START” is still visible on the grip tape. It could be paid for and unlocked with a smartphone app, but [Adam] wasn’t interested in doing that just to ride his new scooter.

His report includes lots of teardown photos, as well as a rundown of how the whole thing works. Most of the important parts are in the steering column and handlebars. These house the battery, electronic speed controller (ESC), and charging circuitry. The green box attached to the front houses a board that [Adam] determined runs Android and is responsible for network connectivity over the cellular network.

To get the scooter running again, [Adam] and his brother [Sam] considered reverse-engineering the communications between the network box and the scooter’s controller, but in the end opted to simply replace the necessary parts with ones under their direct control. One ESC, charger, and cheap battery monitor later the scooter had all it needed to ride again. With parts for a wide variety of electric scooters readily available online, there was really no need to reverse-engineer anything.

Ridesharing scooter startups are busy working out engineering and security questions like how best to turn electric scooters into a) IoT-connected devices, and b) a viable business plan. Hardware gets revised, and as [Adam] shows, retired units can be pressed into private service with just a little work.

The motors in these things are housed within the wheels, and have frankly outstanding price-to-torque ratios. We’ve seen them mated to open-source controllers and explored for use in robotics.

Designing Tiny Motors Right Into The Robot’s Circuit Board

January 1, 2019 by Mike Szczys 10 Comments

Motors are not overly complex, but this one is downright simple. Carl Bujega has been working on a motor design that heavily relies on the capabilities of the printed circuit board (PCB) fabrication processes. His talk at the 2018 Hackaday Superconference covers how he built a brushless DC motor and speed controller into a PCB. You can watch the newly published video after the break.

There are two main parts of an electric motor; the stator is stationary while the rotor spins on bearings. Electromagnetic forces are used to cause that spinning action. In this case, Carl has built the electromagnets as coils on a 4-layer circuit board (six coils on each layer). When electrified, a magnetic field is generated that pushes against the rare-earth magnets housed in the rotor.

A couple of things are really interesting here. First, those coils are usually made of “magnet wire” (enamel covered wire that is very thin) wrapped around an iron core. Using the circuit board instead saves both physical space, and the time and expense of wrapping coils of wire in the traditional way. Second, Carl has been designing with manufacture in mind; you can see in the image show that his motor design is dead-simple to assemble by inserting a 3mm bearing in the PCB, inserting magnets into the plastic rotor and snapping it into place. The end goal is to make robot actuators that are part of the circuit board itself.

The genesis of this idea came from Carl’s interest in drone design, in fact, he jumped right into a drone startup immediately after finishing his EE. The company didn’t last, but his thirst for interesting designs is ongoing. When looking at reducing the total parts necessary to build a quadcopter he happened on the idea of PCB-based coils and he’s followed it to this motor design, and beyond to some very interesting flexible-PCB robot design work which you can check out on his Hackaday.io page, YouTube, and Twitter.

There are of course some trade-offs to this. The motor is low torque since it uses an air core and not an iron core. And he’s had trouble implementing a sensor-less Electronic Speed Controller (ESC) as the back-EMF from the coils appears to be too weak. Not to fret, he added a hall sensor and has succeeded in designing an ESC that measures just 14mm by 8mm. In fact, he’s holding up the ESC and motor in the image at the top of this article!

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Can You 3D-Print A Stator For A Brushless DC Motor?

December 18, 2018 by Dan Maloney 33 Comments

Betteridge’s Law holds that any headline that ends in a question mark can be answered with a “No.” We’re not sure that [Mr. Betteridge] was exactly correct, though, since 3D-printed stators can work successfully for BLDC motors, for certain values of success.

It’s not that [GreatScott!] isn’t aware that 3D-printed motors are a thing; after all, the video below mentions the giant Halbach array motor we featured some time ago. But part of advancing the state of the art is to replicate someone else’s results, so that’s essentially what [Scott!] attempted to do here. It also builds on his recent experiments with rewinding commercial BLDCs to turn them into generators. His first step is to recreate the stator of his motor as a printable part. It’s easy enough to recreate the stator’s shape, and even to print it using Proto-pasta iron-infused PLA filament. But that doesn’t come close to replicating the magnetic properties of a proper stator laminated from stamped iron pieces. Motors using the printed stators worked, but they were very low torque, refusing to turn with even minimal loading. There were thermal issues, too, which might have been mitigated by a fan.

So not a stunning success, but still an interesting experiment. And seeing the layers in the printed stators gives us an idea: perhaps a dual-extruder printer could alternate between plain PLA and the magnetic stuff, in an attempt to replicate the laminations of a standard stator. This might help limit eddy currents and manage heating a bit better. Continue reading “Can You 3D-Print A Stator For A Brushless DC Motor?” →

Plug Your Ears And Hop On This Jet-Powered EBike

November 26, 2018 by Dan Maloney 30 Comments

Ah, the simple pleasures of a bike ride. The rush of the wind past your ears, the gentle click of the derailleurs as you change gears, the malignant whine of the dual electric jet turbines pushing you along. Wait, what?

Yes, it’s a jet bike, and its construction was strictly a case of “Why not?” for [Tech Ingredients]. They recently finished up a jet engine build using a hybrid design with electric ducted fans as compressors and fueled with propane. It was quite a success, and pretty spectacular, but left an embarrassment of riches upon its passing in terms of spare parts. The ducted fans, monstrous 90-mm 12s beasts, along with dual 150A ESCs found their way onto a mountain bike by way of a rear luggage rack. Pannier bags on each side hold the batteries, and a quick control panel went on the handlebar. The video below shows the build details and a couple of test rides, which show just how fast you can go with this setup. It may not be very practical compared to a more traditional hub motor, but it’s nowhere near as cool. Just be sure to wear your hearing protection.

Is this the first jet engine on a bike we’ve featured? Of course not. But for an impromptu build, it’s pretty impressive. Continue reading “Plug Your Ears And Hop On This Jet-Powered EBike” →

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” →