servo

Robot Arms Nudge the Hands of Time in the Strangest Clock

May 9, 2019 by 8 Comments

We see a lot of clocks here at Hackaday. Digital clocks, retro clocks, lots of Nixie clocks, binary clocks, and clocks that appear to be designed specifically to be unreadable. But this dual-servo kinematic clock is something we haven’t seen yet, and it’s certainly worth a mention.

[mircemk]’s idea is simple and hearkens back to grammar school days when [Teacher] put a large cardboard clock dial on the blackboard and went through the “big hand, little hand” drill. In this case, the static cardboard clock has been replaced by a 3D-printed dial and hands, while a pair of servos linked together by two arms takes the place of the teacher. The video below shows it in action; the joint in the linkage between the two servos has a screw sticking out that can be maneuvered across the clock face to reposition the hands. It’s a little jittery, though; [mircemk] might want to tune the servo loops up a bit or tighten the linkage joints to make things a little smoother.

Even with the shakes, we find it wonderfully weird and hard to stop watching. It reminds us a bit of this luminous plotting clock from a while back – same linkage, different display.

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New Part Day: Lynxmotion Smart Servos

May 3, 2019 by 28 Comments

Anyone who shops for robotics kits would have come across a few designed by Lynxmotion. They’ve been helping people build robots since 1995, from robot arm kits to hexapod chassis and everything in between. We would expect these people know their motors, so when they launched their own line of servo motors called Lynxmotion Smart Servos (LSS), it is worth spending a bit of time to look over what they offer.

While these new devices have a PWM mode compatible with classic remote control servos, unleashing their full power requires bidirectional communication over a serial bus. We’ve previously given an overview of three serial bus servos already on the market for comparison. A quick look at the $68-$100 price tags listed on Lynxmotion’s parent company RobotShop made it clear they do not intend to compete on price, so what interesting features do these new kids on the block have?

Digging into product documentation found some great details. Acceleration and deceleration rates are adjustable, which can help with smoother robot movement. There’s also an adjustable level of “stiffness” that adds some “give” (compliance) so a robot won’t have to be as stiff as… well, a robot!

Mechanically, the most interesting internal component is the magnetic position sensor. They are far more precise than potentiometers, but more importantly, they allow positioning anywhere within full 360 degrees. Many other serial bus servos are constrained to positions within an arc less than 360 degrees leaving a blind spot.

An interesting quirk of the LSS offerings is that the serial communication protocol uses human-readable text characters, so sending a number 255 means transmitting a three byte string ‘2’, ‘5’, and ‘5’ instead of single byte 0xFF. This would make debugging our custom robot code far easier, at the cost of reduced bandwidth efficiency and loss of checksum for detecting communication errors. It’s a trade-off that some robot builders would be happy to make, but others might not.

Externally, these servos have bountiful mounting options including some we didn’t know to ask for. Historically Lynxmotion kits have used a wide variety of servo mounting brackets, so they are motivated to make mechanical integration easy. The most novel offering is the ability to bolt external gears to the servo body. A set of 1:3 gears allow for gearing the servo up or down, or you can use a set of 1:1 gears for a compact gripper.

As you’d expect of servos in this price range, they all have metal gears, but they also have the ability to power the motor directly from a battery pack (a 3 cell lithium polymer is recommended). There are additional features, like an RGB LED for visual feedback, which we didn’t cover here so dig into the documentation for more. We look forward to seeing how these interesting little actuators perform in future robotics projects.

A Word Clock, The Hard Way

April 2, 2019 by 19 Comments

We’ve all seen word clocks, and they’re great, but there are only so many ways to show the time in words. This word clock with 114 servos is the hard way to do it.

We’re not sure what [Moritz v. Sivers] was aiming for with this projection clock, but he certainly got it right. The basic idea is to project the characters needed to compose the time messages onto a translucent PVC screen, which could certainly have been accomplished with just a simple character mask and some LEDs. But for extra effect, [Moritz] mounted each character to a letterbox mounted over a Neopixel. The letterboxes are attached to a rack and pinion driven by a micro servo. The closer they get to the screen, the sharper the focus and the smaller the size of the character. Add in a little color changing and the time appears to float out from a jumbled, unfocused background. It’s quite eye-catching, and worth the 200+ hours of printing time it took to make all the parts. Complete build instructions are available, and a demo video is after the break.

We like pretty much any word clock – big, small, or even widescreen. This one really pushes all our buttons, though.

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Printed Perching Pals Proliferate

March 30, 2019 by 4 Comments

Anansi in African folktale is a trickster and god of stories, usually taking physical form of a spider. Anansi’s adventures through oral tradition have adapted to the situation of people telling those stories, everything ranging from unseasonable weather to living a life in slavery. How might Anansi adapt to the twenty-first century? [odd_jayy] imagined the form of a cyborg spider, and created Asi the robot companion to perch on his shoulder. Anyone who desire their own are invited to visit Asi’s project page.

Asi was inspired by [Alex Glow]’s Archimedes, who also has a project page for anyone to build their own. According to [Alex] at Superconference 2018, she knew of several who have done so, some with their own individual customization. [odd_jayy] loved the idea of a robot companion perched on his shoulder but decided to draw from a different pool of cultural folklore for Asi. Accompanying him to various events like Sparklecon 2019, Asi is always a crowd pleaser wherever they go.

Like every project ever undertaken, there is no shortage of ideas for Asi’s future and [odd_jayy] listed some of them in an interview with [Alex]. (Video after the break.) Adding sound localization components will let Asi face whoever’s speaking nearby. Mechanical articulation for legs would allow more dynamic behaviors while perched, but if the motors are powerful enough, Asi can walk on a surface when not perched. It’s always great to see open source projects inspire even more projects, and watch them as they all evolve in skill and capability. If they all become independently mobile, we’ll need clarification when discussing the average velocity of an unladen folklore robot companion: African or European folklore?

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A 3D Printed Blooming Rose For (Next) Valentines Day

March 17, 2019 by 5 Comments

Inspiration runs on its own schedule: great ideas don’t always arrive in a timely manner. Such was the case with [Daren Schwenke]’s notion for creating a 3D-printed blooming rose for his valentine, a plan which came about on February 13. Inspired by [Jiří Praus]’s animated wireframe tulip, [Daren] figured he could make a rose from clear printed petals colored by RGB LEDs. 24 hours seemed tight but sufficient, so he diligently set to work, but – after a valiant effort – finally had to extend the schedule. It’s now more than a month later, and tweaks to the design continue, but the result is nothing short of spectacular.

We first saw a discussion of the idea over on Hack Chat, and followed as it evolved into a project on hackaday.io. There, you can read the full details of the trials and tribulations that had to be endured to make this project happen. From a printer that wouldn’t boot, through testing PLA, TPU, and nylon filament, trying a number of different approaches for springs and hinges to operate the petals, and wiring the delicate DotStar LEDs with magnet wire, you can get a really good sense of the amount of experimentation it takes to complete a project like this. If you know anyone who still thinks 3D printing is as easy as clicking a button, send them over to read the logs on this project.

An early try at forming PLA petals

What finally materialized is a terrific combination of common hacker technologies. The petals are printed flat in nylon, then formed over a hot incandescent chandelier bulb. The stem and leaves are also printed, but the side stem has a piece of magnet wire embedded in the print as a capacitive touch sensor; when the leaf is touched, the rose blossom opens or closes. Magnet wire for the LEDs and a connecting rod for the mechanics run through the main stem to the base, where a 9g servo is responsible for controlling the bloom. The whole thing is controlled, naturally, with an Arduino. To move the project along a little more quickly, [Daren] enlisted the help of another Hack Chat denizen, [Morning.Star], who did an amazing job on the software without any access to the actual hardware.

Be sure to check out the video of the rose in action, after the break.

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Reverse Engineering Keeps Keck Telescopes on Track

February 26, 2019 by 12 Comments

Perched atop a dormant volcano far above the roiling tropical air of the Big Island of Hawai’i sit two of the largest optical telescopes in the world. Each 10-meter main mirror is but a single part of a magnificent machine weighing in at some 400 tons that needs to be positioned with incredible precision. Keeping Keck 1 and Keck 2 in peak operating condition is the job of a team of engineers and scientists, so when the servo amplifiers running the twelve motors that move each scope started to show their age, [Andrew] bit the bullet and rebuilt the obsolete boards from scratch.

The Keck telescopes were built over three decades ago, and many of the parts, including the problematic servo amps, are no longer made. Accumulated wear and tear from constant use and repeated repairs had taken their toll on the boards, from overheated components to lifted solder pads. With only some barely legible schematics of the original amplifiers to go by, [Andrew] reverse engineered new amps. Some substitutions for obsolete components were needed, the PCB design was updated to support SMD parts, and higher-quality components were specified, but the end result is essentially new amplifiers that are plug-in replacements for the original units. This should keep the telescopes on track for decades to come.

Not to sound jealous, but it seems like [Andrew] has a great gig. He’s shared a couple of his Keck adventures before, like the time a failed LED blinded the telescope. He’s also had a few more down-to-earth hacks, like fixing a dodgy LCD monitor and making spooky blinkeneyes for Halloween.

Building a Semiautomatic Swag Launcher

February 15, 2019 by 4 Comments

Regular readers of Hackaday have certainly seen the work of [Jeremy Cook] at this point. Whether you remember him from his time as a writer for this fine online publication, or recognize the name from one of his impressive builds over the last few years, he’s a bona fide celebrity around these parts. In fact, he’s so mobbed with fans at events that he’s been forced to employ a robotic companion to handle distributing his personalized buttons for his own safety.

Alright, that might be something of a stretch. But [Jeremy] figured it couldn’t hurt to have an interesting piece of hardware handing out his swag at the recent Palm Bay Mini Maker Faire. Anyone can just put some stickers and buttons in a bowl on a table, but that’s hardly the hacker way. In the video after the break, he walks viewers through the design and construction of this fun gadget, which takes a couple unexpected turns and has contains more than a few useful tips which are worth the cost of admission alone.

Outwardly the 3D printed design is simple enough, and reminds us of those track kits for Matchbox cars. As you might expect, getting the buttons to slide down a printed track was easy enough. Especially when [Jeremy] filed the inside smooth to really get them moving. But the goal was to have a single button get dispensed each time the device was triggered, but that ended up being easier said than done.

The first attempt used magnets actuated by two servos, one to drop the button and the other to hold up the ones queued above it. This worked fine…at first. But [Jeremy] eventually found that as he stacked more buttons up in the track, the magnets weren’t strong enough to hold them back and they started “leaking”. This is an excellent example of how a system can work perfectly during initial testing, but break down once it hits the real world.

In this case, the solution ended up being relatively simple. [Jeremy] kept the two servos controlled by an Arduino and a capacitive sensor, but replaced the magnets with physical levers. The principle is the same, but now the system is strong enough to hold back the combined weight of the buttons in the chute. It did require him to cut into the track after it had already been assembled, but we can’t blame him for not wanting to start over.

Just like the arcade inspired candy dispenser, coming up with a unique way of handing out objects to passerby is an excellent way to turn the ordinary into a memorable event. Maybe for the next iteration he can make it so getting a button requires you to pass a hacker trivia test. Really make them work for it.

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