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Hackaday Links: September 5, 2021

Good news from Jezero crater as the Mars rover Perseverance manages to accomplish for the first time what it was sent to do: collect and cache core samples from rocks. Space buffs will no doubt recall that Perseverance’s first attempt at core sampling didn’t go as planned — the rock that planetary scientists selected ended up being too soft, and the percussive coring bit just turned the core sample into powder. The latest attempt went exactly as planned: the cylindrical coring bit made a perfect cut, the core slipped into the sample tube nested inside the coring bit, and the core broke off cleanly inside the sample tube when it was cammed off-axis. Operators were able to provide visible proof that the core sample was retained this time using the Mastcam-Z instrument, which clearly shows the core in the sample tube. What’s neat is that they then performed a “percuss to ingest” maneuver, where the coring bit and sample tube are vibrated briefly, so that the core sample and any dust grains left around the sealing rim slide down into the sample tube. The next step is to transfer the sample tube to the belly of the rover where it’ll be hermetically sealed after some basic analysis.

Did any Android users perhaps oversleep this week? If you did, you’re not alone — lots of users of the Google Clock app reported that their preset alarms didn’t go off. Whether it was an actual issue caused by an update or some kind of glitch is unclear, but it clearly didn’t affect everyone; my phone mercilessly reminded me when 6:00 AM came around every day last week. But it apparently tripped up some users, to the point where one reported losing his job because of being late for work. Not to be judgmental, but it seems to me that if your job is so sensitive to you being late, it might make sense to have a backup alarm clock of some sort. We all seem to be a little too trusting that our phones are going to “just work,” and when they don’t, we’re surprised and appalled.

There seem to be two kinds of people in the world — those who hate roller coasters, and those who love them. I’m firmly in the latter camp, and will gladly give any coaster, no matter how extreme, a try. There have been a few that I later regretted, of course, but by and large, the feeling of being right on the edge of bodily harm is pretty cool. Crossing over the edge, though, is far less enjoyable, as the owners of an extreme coaster in Japan are learning. The Dodon-pa coaster at the Fuji-Q Highland amusement park is capable of hitting 112 miles (180 km) per hour and has racked up a sizable collection of injuries over the last ten months, including cervical and thoracic spine fractures. The ride is currently closed for a safety overhaul; one has to wonder what they’re doing to assess what the problem areas of the ride are. Perhaps they’re sending crash test dummies on endless rides to gather data, a sight we’d like to see.

And finally, you may have thought that phone phreaking was a thing of the past; in a lot of ways, you’d be right. But there’s still a lot to be learned about how POTS networks were put together, and this phone switch identification guide should be a big help to any phone geeks out there. Be ready to roll old school here — nothing but a plain text file that describes how to probe the switch that a phone is connected just by listening to things like dial tones and ring sounds. What’s nice is that it describes why the switches sound the way they do, so you get a lot of juicy technical insights into how switches work.

ESP32 Video Input Using I2S

Computer engineering student [sherwin-dc] had a rover project which required streaming video through an ESP32 to be accessed by a web server. He couldn’t find documentation for the standard camera interface of the ESP32, but even if he had it, that approach used too many I/O pins. Instead, [sherwin-dc] decided to shoe-horn a video into an I2S stream. It helped that he had access to an Altera MAX 10 FPGA to process the video signal from the camera. He did succeed, but it took a lot of experimenting to work around the limited resources of the ESP32. Ultimately [sherwin-dc] decided on QVGA resolution of 320×240 pixels, with 8 bits per pixel. This meant each frame uses just 77 KB of precious ESP32 RAM.

His design uses a 2.5 MHz SCK, which equates to about four frames per second. But he notes that with higher SCK rates in the tens of MHz, the frame rate could be significantly higher — in theory. But considering other system processing, the ESP32 can’t even keep up with four FPS. In the end, he was lucky to get 0.5 FPS throughput, but that was adequate for purposes of controlling the rover (see animated GIF below the break). That said, if you had a more powerful processor in your design, this technique might be of interest. [Sherwin-dc] notes that the standard camera drivers for the ESP32 use I2S under the hood, so the concept isn’t crazy.

We’ve covered several articles about generating video over I2S before, including this piece¬†from back in 2019. Have you ever commandeered a protocol for “off-label” use?

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No Hole In One: Perseverance Strikes Out On First Mars Core Attempt

There’s a military adage that no plan survives first contact with the enemy. While we haven’t gone to war with Mars, at least not yet, it does seem to be a place where the best-laid scientific plans are tested in the extreme. And the apparent failure of Perseverance to retrieve its first Martian core sample is yet another example of just how hard it is to perform geotechnical operations on another planet.

To be sure, a lot about the first sampling operation went right, an especially notable feat in that the entire process is autonomous. And as we’ve previously detailed, the process is not simple, involving three separate robotic elements that have to coordinate their operations perfectly. Telemetry indicates that the percussive drill on the end of the 2.1 m robotic arm was able to use its hollow coring bit to drill into the rock of Jezero crater, and that the sample tube inside the coring bit was successfully twisted to break off the core sample.

But what was supposed to happen next — jamming of the small core sample inside the sample tube — appears not to have happened. This was assessed by handing the sample tube off to the Sample Handling Arm in the belly of Perseverance, where a small probe is used to see how much material was recovered — none, in this case. NASA/JPL engineers then began a search for the problem. Engineering cameras didn’t reveal the core sample on the Martian surface, meaning the sample handling robots didn’t drop it. The core sample wasn’t in the borehole either, which would have meant the camming mechanism designed to retain the core didn’t work. The borehole, though, looked suspicious — it appears not to be deep enough, as if the core sample crumbled to dust and packed into the bottom of the hole.

If this proves to be the cause of the failure, it will be yet another example of Martian regolith not behaving as expected. For InSight, this discovery was a death knell to a large part of its science program. Thankfully, Perseverance can pick up and move to better rock, which is exactly what it will be doing in September. They still have 42 unused sample tubes to go, so here’s to better luck next time.

[Featured images: NASA/JPL-Caltech]

3D Printed Mecanum Wheels For Hoverboard Motors

At this point, somebody taking the motors out of a cheap “hoverboard” and using them to power a scooter or remote controlled vehicle isn’t exactly a new idea. But in the case of the FPV rover [Proto G] has been working on, his choice of motors is only part of the story. The real interesting bit is the 3D printed omnidirectional Mecanum wheels he’s designed to fit the motors, which he thinks could have far reaching applications beyond his own project.

Now, that isn’t to say that the rover itself isn’t impressive. All of the laser cutting and sheet metal bending was done personally by [Proto G], and we love the elevated GoPro “turret” in the front that lets him look around while remotely driving the vehicle. Powered by a pair of Makita cordless tool batteries and utilizing hobby-grade RC parts, the rover looks like it would be a fantastic robotic platform to base further development on.

The Mecanum wheels themselves are two pieces, and make use of rollers pulled from far smaller commercially available wheels. This is perhaps not the most cost effective approach, but compared to the alternative of trying to print all the rollers, we see the advantage of using something off-the-shelf. If you’re not sure how to make these weird wheels work for you, [Proto G] has also released a video explaining how he mixes the RC channels to get the desired omnidirectional movement from the vehicle.

If you’re content with more traditional wheeled locomotion, we’ve previously seen how quickly a couple of second-hand hoverboards can be turned into a impressively powerful mobile platform for whatever diabolical plans you may have.

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Scratch Built Tracked Robot Reporting For Duty

Inspired by battle-hardened military robots, [Engineering Juice] wanted to build his own remote controlled rover that could deliver live video from the front lines. But rather than use an off-the-shelf tracked robot chassis, he decided to design and 3D print the whole thing from scratch. While the final product might not be bullet proof, it certainly doesn’t seem to have any trouble traveling through sand and other rough terrain.

Certainly the most impressive aspect of this project is the roller chain track and suspension system, which consists of more than 200 individual printed parts, fasteners, bearings, and linkages. Initially, [Engineering Juice] came up with a less complex suspension system for the robot, but unfortunately it had a tendency to bind up during testing. However the new and improved design, which uses four articulated wheels on each side, provides an impressive balance between speed and off-road capability.

Internally there’s a Raspberry Pi 4 paired with an L298 dual H-bridge controller board to drive the heavy duty gear motors. While the Pi is running off of a standard USB power bank, the drive motors are supplied by a custom 18650 battery pack utilizing a 3D printed frame to protect and secure the cells. A commercial night vision camera solution that connects to the Pi’s CSI header is mounted in the front, with live video being broadcast back to the operator over WiFi.

To actually control the bot, [Engineering Juice] has come up with a Node-RED GUI that’s well suited to a smartphone’s touch screen. Of course with all the power and flexibility of the Raspberry Pi, you could come up with whatever sort of control scheme you wanted. Or perhaps even go all in and make it autonomous. It looks like there’s still plenty of space inside the robot for additional hardware and sensors, so we’re interested to see where things go from here.

Got a rover project in mind that doesn’t need the all-terrain capability offered by tracks? A couple of used “hoverboards” can easily be commandeered to create a surprisingly powerful wheeled platform to use as a base.

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3D-Printed Scale Model Of Perseverance Rover Seems As Complicated As The Real One

Sometimes the best way to figure out how something works is to make a model of it. 3D-modeling software makes it possible to do the job in silico, and sometimes that’s enough. But to really get inside the designer’s head, executing a physical model, like this quarter-scale RC-controlled Perseverance rover, is a great way to go.

If you’re looking for cutting-edge tech or groundbreaking design, this build will probably not light your fire. But a closer look will show not only great details about how JPL designs robots that can operate on Mars, but some great design and 3D-printing tips too.¬†[Dejan]’s modeling process started with the 3D renderings of Perseverance available on the NASA website, which went into SolidWorks via Blender. [Dejan] was intent on capturing all the details of the rover, even those that ended up just for looks. But there’s plenty of functionality, too — the running gear looks and functions just like the six-wheel double-bogie design used on Perseverance, as well as Curiosity before it. This revealed an interesting fact that we didn’t previously realize — that the hull is suspended from a single pivot point on each side, while a linkage across the deck both prevents the body from pivoting and provides differential control of the drive bogies on either side of the rover.

The video below shows both the impressive amount of 3D printing needed to make all the model’s parts as well as the involved assembly process. It also shows the Arduino-controlled model being piloted around via radio control. There’s a lot to learn from this model, and [Dejan]’s craftsmanship here is top-notch too. We’ve seen such builds before from him, like this 3D-printed SCARA arm, a CNC hot-wire foam cutter, and an automated wire bender.

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Hoverboard Turned Heavy Duty Remote Control Rover

They might not be the hoverboards we were promised in Back to the Future II, but the popular electric scooters that have commandeered the name are exciting pieces of tech in their own way. Not because we’re looking to make a fool of ourselves by actually riding one, but because they’re packed full of useful hardware that’s available for dirt cheap thanks to the economies of scale and the second-hand market.

In his latest video, the ever resourceful [MakerMan] turns a pair of hoverboards into a capable remote controlled mobile platform perfect for…well, whatever you want to move around. Its welded steel construction is certainly up for some heavy duty tasks, and while we can’t say we’d ever tow a SUV with it as shown in the video below, it’s nice to know we’d have the option.

The project starts by liberating the four wheel motors from the scooters and carefully cutting down the frame to preserve the mounting hardware. These mounts are ultimately welded to the frame of the rover, with a piece of diamond plate screwed down on top. On the bottom, [MakerMan] mounts the two control boards and a custom fabricated 36 V battery pack.

He doesn’t go into any detail on how he’s interfacing the RC hardware with the motor controllers, but as we’ve seen with past hacks, there’s open source firmware replacements for these boards that allow them to be controlled by external inputs. Presumably something similar is being used here, but we’d be interested to hear otherwise. Of course you could swap the RC hardware out for a microcontroller or Raspberry Pi if you were looking to make some kind of autonomous rover.

Don’t have a welder or convenient collection of scrap steel laying around? No worries. Prolific tinkerer [Aaron Christophel] put something very similar together using bolted aluminum extrusion.

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