For many years now a source for some of the smallest and cheapest home made CNC mechanisms has been the seemingly never-ending supply of surplus CD and DVD-ROM drives. The linear actuator that moves the laser may not be the longest or the strongest, but it’s free, and we’ve seen plenty of little X-Y tables using CD drives. It’s these mechanisms that [Nemo404] has taken a little further, freeing the lead screw and motor from the drive chassis and placing them in a 3D-printed enclosure for a complete linear actuator that can be used in other projects. (Video, embedded below.)
There seems to be no positional feedback, not even the limit switch that would grace a typical CD drive, but aside from that it makes for a compact unit. There are two versions, one for a linear bearing and the other for the brass bushes found in CD drives. It’s unclear how strong the result is, but it appears to be strong enough to demonstrate lifting a small container of screws.
It should be said that, at least technically, the Husqvarna TS 348XD in question was still working. It’s just that [xxbiohazrdxx] noticed the locking differential, which is key to maintaining traction on hilly terrain, didn’t seem to be doing anything when the switch was pressed. Since manually moving the engagement lever on the transmission locked up the differential as expected, the culprit was likely in the electronics.
Testing the dead actuator.
As [xxbiohazrdxx] explains, the switch on the dash is connected to a linear actuator that moves the lever on the transmission. The wiring and switch tested fine with a multimeter, but when the actuator was hooked up to a bench power supply, it didn’t move. Even more telling, it wasn’t drawing any power. Definitely not a good sign. Installing a new actuator would have solved the problem, but it was an expensive part that would take time to arrive.
Repairing the dead actuator seemed worth a shot at least, so [xxbiohazrdxx] cracked it open. The PCB looked good, and there were no obviously toasted components. But when one of the internal microswitches used to limit the travel of the actuator was found to be jammed in, everything started to make sense. With the switch locked in the closed position, the actuator believed it was already fully extended and wouldn’t move. After opening the switch itself and bending the contacts back into their appropriate position, everything worked as expected.
A tiny piece of bent metal kept this $4,000 machine from operating correctly.
As interesting as this step-by-step repair process was, what struck us the most is [xxbiohazrdxx]’s determination to fix rather than replace. At several points it would have been much easier to just swap out a broken part for a new one, but instead, the suspect part was carefully examined and coaxed back to life with the tools and materials on-hand.
The device, trademarked as the Kataka but generically referred to as a Segmented Spindle, is a compact form of linear actuator that uses a novel belt arrangement to create a device that can reduce to a very small thickness, while crowing to seemingly impossible dimensions when fully extended. This is the key advantage over conventional actuators, which usually retract into a housing of at least the length of the piston.
It’s somewhat magical to watch the device in action, seeing the piston appear “out of nowhere”. Kataka’s youtube channel is now sadly inactive, but contains many videos of the device used in various scenarios, such as lifting chairs and cupboards. We’re impressed with the amount of load the device can support. When used in scissor lifts, it also offers the unique advantage of a flat force/torque curve.
Most records of the device online are roughly a decade old. Though numerous prototypes were made, and a patent was issued, it seems the mechanism never took off or saw mainstream use. We wonder if, with more recognition and the advent of 3D printing, we might see the design crop up in the odd maker project.
Dishwashers are great at washing dishes and even rinsing them, most of the time. Where they tend to fail is in the drying part. Somehow these things dry hot enough to warp stoneware dishes, but not so well that things are actually dry when you open the door. Blame it on the lack of air movement.
[Ivan Stepaniuk] is listening for the dishwasher’s frequencies with a microphone, amplifying them with a trusty LM386, and using an STM32 blue pill to crunch the audio. [Ivan] has plans to incorporate an ESP8266 board for IoT, presumably to get a notification when the door has been opened successfully. Check out the demo after the break.
Most experiments in flexible robot actuators are based around pneumatics, but [Ayato Kanada] and [Tomoaki Mashimo] has been working on using a coiled spring as the moving component of a linear actuator. Named the flexible ultrasonic motor (FUSM), [Yunosuke Sato] built on top of their work and assembled a pair of FUSM into a closed-loop actuator with motion control in two dimensions.
A single FUSM is pretty interesting by itself, its coiled spring is the only mechanical moving part. An earlier paper published by [Kanada] and [Mashimo] laid out how to push the spring through a hole in a metal block acting as the stator of this motor. Piezoelectric devices attached to that block minutely distorts it in a controlled manner resulting in linear motion of the spring.
For closed-loop feedback, electrical resistance from the free end of the spring to the stator block can be measured and converted to linear distance to within a few millimeters. However, the acting end of the spring might be deformed via stretching or bending, which made calculating its actual position difficult. Accounting for such deformation is a future topic for this group of researchers.
This work was presented at IROS2020 which like many other conferences this year, moved online and became IROS On-Demand. After a no-cost online registration we can watch the 12-minute recorded presentation on this project or any other at the conference. The video includes gems such as an exaggerated animation of stator block deformation to illustrate how a FUSM works, and an example of the position calculation challenge where the intended circular motion actually resulted in an oval.
Speaking of conferences that have moved online, we have our own Hackaday Remoticon coming up soon!
Building and maintaining a garden takes a lot of work. And unless you have a greenhouse, you’re forced to leave your hard work outside to fend for itself against the double-edged sword of the elements. Rain and sun are necessary, but hard, pelting hail is never welcome. Just ask [Nick Rogness]. He didn’t go through all the trouble of building a 12’x12′ garden and planting tasty vegetables just to have Mother Nature spew her impurity-filled ice balls on it every other night during the summertime.
[Nick] did what any of us would do: fight back with technology. His solution was to build a retractable roof that covers the garden with a heavy duty tarp. A Raspberry Pi Zero W controls pair of linear actuators via motor controllers, and [Nick] put a limit switch in each of the four corners to report on the roof status. He can run the roof manually, or control it with his phone using MQTT. The whole thing runs on a 12V marine battery that gets charged up by a solar panel, so part of the interface is dedicated to reporting the battery stats.
[Nick] ran out of time to implement all the features he wanted before the season started, but there’s always next year. He has big plans that include soil moisture sensors, rain detection sensors, and an automatic watering system that collects and uses rain water. We planted the bite-size demo video for you after the break — just wash the dirt off and you’re good to go.
Maybe someday [Nick] will create a system that can automate the entire garden, like the FarmBot. Hey, we’re just trying to plant seeds of ideas.
[Tristan Shone], aka Author & Punisher, found a way to make industrial music even heavier. This former mechanical engineer from Boston crafted his one-man band in the university fab labs of Southern California while pursing an art degree. He started machining robust custom MIDI controllers that allow him to get physical while performing, instead of hunching over tiny buttons and trying to finesse microscopic touch pad-style pitch sliders.
Our favorite is probably Grid Iron, because it looks like the most fun. Grid Iron is a rhythm controller that works by running back and forth and side-to-side over a grid of machined textures that act like speed bumps. A spring-loaded stylus picks up the textures, and an encoder translates them to sound. Eight buttons along the 3D-printed pistol grip let [Tristan] make changes on the fly.
Tired of twiddling tiny knobs, [Tristan] made Big Knobs, a set of three solid aluminum knobs that look to be 3-4″ in diameter. These are assigned jobs like delay and filter, and their weight combined with ball bearings allows them to spin almost indefinitely while [Tristan] injects other sounds into the mix.
[Tristan] has made a few custom microphones to make the most of his voice. One is a trachea mic made from four piezos strapped to his throat that picks up every possible vocal utterance and other guttural sounds quite nicely. The other is an 8-pack of mics built into a curved metal box. He can assign a different effect to each one and do things like turn a breathy scream into the sounds of swelling cymbals.
There are more machines not covered in the video, and you can read about those on [Tristan]’s site. In a bonus video after the break, [Tristan] discusses a trio of pneumatically-driven mask controllers he made.
