Hackaday Editors Mike Szczys and Elliot Williams discuss the highlights of the great hacks from the past week. On this episode we discuss wireless charging from scratch, Etch-A-Sketch selfies, the robot arm you really should build yourself, bicycle tires and steel nuts for anti-slip footwear, and bending the piezo-electric effect to act as a VLF antenna. Plus we delve into articles you can’t miss about 5G and robot firefighting.
Take a look at the links below if you want to follow along, and as always, tell us what you think about this episode in the comments!
[Ignacio]’s VIRK I is a robot arm of SCARA design with a very memorable wooden body, and its new gripper allows it to do a simple pick and place demo. Designing a robot arm is a daunting task, and the fundamental mechanical design is only part of the whole. Even if the basic framework for a SCARA arm is a solved problem, the challenge of building it and the never-ending implementation details make it a long-term project.
When we first saw VIRK I in all its shining, Australian Blackwood glory, it lacked any end effector and [Ignacio] wasn’t sure of the best way to control it. Since then, [Ignacio] has experimented with Marlin and Wangsamas support for SCARA arms, and designed a gripper based around a hobby servo. It’s as beautiful to see this project moving forward as it is to see the arm moving ping-pong balls around, embedded below.
The robot arm in question comes from Owi, and it is by every measure not a good robot arm. It is, however, an excellent toy filled with motors and plastic linkages that serves as a good stand-in for a proper robotic arm.
Control of this toy robot arm is done through a Leap Motion controller. While the Leap Motion is a few years old at this point, it is a very effective way to ‘measure’ the position and rotation of a hand in 3D space. The only thing that’s required is the Leap Motion controller itself and a tabletop.
The end result is a robot that can be controlled by a hand. While this robot arm is really just a toy, it was fun to assemble and a little bit of hardware hacking with an Arduino turned this into a working robot arm controlled by a human. Scale this up, establish an island lair, and you’re on your way to taking over the world.
[igarrido] has shared a project that’s been in the works for a long time now; a wooden desktop robotic arm, named Virk I. The wood is Australian Blackwood and looks gorgeous. [igarrido] is clear that it is a side project, but has decided to try producing a small run of eight units to try to gauge interest in the design. He has been busy cutting the parts and assembling in his spare time.
Besides the beautifully finished wood, some of the interesting elements include hollow rotary joints, which mean less cable clutter and a much tidier assembly. 3D printer drivers are a common go-to for CNC designs, and the Virk I is no different. The prototype is driven by a RAMPS 1.4 board, but [igarrido] explains that while this does the job for moving the joints, it’s not ideal. To be truly useful, a driver would need to have SCARA kinematic support, which he says that to his knowledge is something no open source 3D printer driver offers. Without such a driver, the software has no concept of how the joints physically relate to one another, which is needed to make unified and coherent movements. As a result, users must control motors and joints individually, instead of being able to direct the arm as a whole to move to specific coordinates. Still, Virk I might be what’s needed to get that development going. A video of some test movements is embedded below, showing how everything works so far.
Cycloidal drives are fascinating pieces of hardware, and we’ve seen them showing up in part due to their suitability for 3D printing. The open source robot arm makers [Haddington Dynamics] are among those playing with a cycloidal drive concept, and tucked away in their August 2018 newsletter was a link they shared to a short but mesmerizing video of a prototype, which we’ve embedded below.
A cycloidal drive has some similarities to both planetary gearing and strain-wave gears. In the image shown, the green shaft is the input and its rotation causes an eccentric motion in the yellow cycloidal disk. The cycloidal disk is geared to a stationary outer ring, represented in the animation by the outer ring of grey segments. Its motion is transferred to the purple output shaft via rollers or pins that interface to the holes in the disk. Like planetary gearing, the output shaft rotates in the opposite direction to the input shaft. Because the individual parts are well-suited to 3D printing, this opens the door to easily prototyping custom designs and gearing ratios.
[Haddington Dynamics] are the folks responsible for the open source robot arm Dexter (which will be competing in the Hackaday Prize finals this year), and their interest in a cycloidal drive design sounds extremely forward-thinking. Their prototype consists of 3D printed parts plus some added hardware, but the real magic is in the manufacturing concept of the design. The idea is for the whole assembly to be 3D printed, stopping the printer at five different times to insert hardware. With a robot working in tandem with the printer, coordinating the print pauses with automated insertion of the appropriate hardware, the result will be a finished transmission unit right off the print bed. It’s a lofty goal, and really interesting advancement for small-scale fabrication.
Robotic arms – they’re useful, a key part of our modern manufacturing economy, and can also be charming under the right circumstances. But above all, they are prized for being able to undertake complex tasks repeatedly and in a highly precise manner. Delivering on all counts is DEXTER, an open-source 5-axis robotic arm with incredible precision.
DEXTER is built out of 3D printed parts, combined with off-the-shelf carbon fiber sections to add strength. Control is through five NEMA 17 stepper motors which are connected to harmonic drives to step the output down at a ratio of 52:1. Each motor is fitted with an optical encoder which provides feedback to control the end effector position.
Unlike many simpler projects, DEXTER doesn’t play in the paddling pool with 8-bit micros or even an ARM chip – an FPGA lends the brainpower to DEXTER’s operations. This gives DEXTER broad capabilities for configuration and expansion. Additionally, it allows plenty of horsepower for the development of features like training modes, where the robot is stepped manually through movements and they are recorded for performance later.
It’s a project that is both high performing and open-source, which is always nice to see. We look forward to seeing how this one develops further!
Somehow, walking robots at our level never really seem to deliver on the promise that should be delivered by all those legs. Articulation using hobby servos is simple enough to achieve, but cumbersome, slow, and not very powerful. [Paul Gould] has a plan to make a better, 3D-printed articulated robot actuator.
His solution is both novel and elegant, a fairly conventional arm geometry that has at its joints a set of brushless motors similar to but a little larger than the kind you might be more familiar with on multirotors, paired with 3D-printed cycloidal gearboxes. Magnetic encoders provide the necessary positional feedback, and the result is a unit that is both compact and powerful.
With such a range of small brushless motor controllers on the market, it’s at first sight unexpected that he’s designed his own controller board. But this gives him complete control over his software, plus the CAN bus that ties everything together. He’s given us a video which we’ve placed below the break, showing the build process, the impressive capabilities of his system, and a selection of builds including a robot dog complete with tail. This is definitely a project to watch.