An Open Source ESC For Brushless Motors

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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Supercapacitors Propel Rocket To The Skies

OK, so this isn’t really a rocket. In the strictest definition, rockets are vehicles or projectiles that propel themselves through jettisoning mass, usually through the combustion of fuel. But with electric motors getting stronger and stronger, folks are building craft that look a lot more like rockets than airplanes. [Tom Stanton] is one such person (Youtube link, embedded below).

We’ve seen “electric rocket” builds before, but where others have used lithium batteries, [Tom] has used supercapacitors instead. Six supercaps are installed in a 3D printed mount, and supply power to a 500 W brushless outrunner motor which gives the rocket the thrust to climb into the sky.

In testing, [Tom] estimates the rocket was able to reach an altitude of approximately 60 m, or 200 ft. That’s not particularly astounding, but it does prove that supercaps can run a high current load in a real world situation. Additionally, their fast recharge rate allows [Tom] to make a repeat flights in just about the time it takes to repack the parachute. Video after the break.

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3D Printing A Water Jet Drive

[Ivan Miranda] is always experimenting with 3D printing, and recently has been taking his work on the water. His latest creation is a racing paddle boat, but its performance left [Ivan] with a need for speed. Cue the development of the 3D printed water jet engine (YouTube link, embedded below).

The basic principle of operation is simple. Water is sucked through an inlet, where it is accelerated by a turbine driven by a brushless motor. This turbine, in combination with stator fins, forces the water through the outlet, propelling the boat forwards in the process.

The first prototype is printed in PLA. Tolerances are good, thanks largely to [Ivan]’s experience and well-calibrated printers. After assembly, the engine is fired up, to great results. After sourcing a series of larger tubs in which to test the device, the engine is finally run up to full throttle and appears more than capable of shifting a serious amount of water.

We’d love to see a proper instrumented thrust test, particularly one that compares the device to other water jet drives on the market. Brushless motors make a great drive solution for RC boats, so we’re sure [Ivan] will be tearing up the lake real soon. Video after the break.

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Brushless R/C Rocket Tests Different Flight Regimes

Quadcopters are familiar, and remote control planes are old hat at this point. However, compact lightweight power systems and electronic flight controllers continue to make new flying vehicles possible. In that vein, [rctestflight] has been experimenting with a brushless electric rocket craft, with interesting results. (Youtube, embedded below.)

The build uses a single large brushless motor in the tail for primary thrust. Four movable vanes provide thrust vectoring capability. To supplement this control a quadcopter was gutted, and its motors rearranged in the nose of the craft to create a secondary set of thrusters which aid stabilization and maneuverability.

The aim is to experiment with a flight regime consisting of vertical takeoff followed by coasting horizontally before returning to a vertical orientation for landing. Preliminary results have been positive, though it was noted that the body of the aircraft is significantly reducing the available thrust from the motors.

It’s a creative design which recalls the SpaceX vertical landing rockets of recent times. We’re excited to see where this project leads, and as we’ve seen before – brushless power can make just about anything fly. Even chocolate. Video after the break.

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Designing Tiny Motors Right Into The Robot’s Circuit Board

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 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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Brushless Motor Thrust Stand Provides Useful Data

When designing model aircraft of any shape or size, it’s useful to know the performance you can expect from the components chosen. For motors and propellers, this can be difficult. It’s always best to test them in combination. However, with the numbers of propeller and motor combinations possible, such data can be tough to come by. [Nikus] decided it would be easier to just do the testing in-house, and built a rig to do so.

The key component in this build is the strain gauge, which comes already laced up with an Arduino-compatible analog-digital converter module. Sourced for under $10 from Banggood, we can’t help but think that we’ve got it easy in 2018. A sturdy frame secures motor and propeller combination to the strain gauge assembly. An ATMEGA328 handles sending commands to the motor controller, reading the strain gauge results, and spitting out data to the LCD.

It’s a cheap and effective build that solves a tricky problem and would be a useful addition to the workshop for any serious modeler. We’ve seen other approaches in this area too, for those eager to graph their motor performance data. Video after the break.

[Thanks to Baldpower for the tip!]

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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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