Safety Systems for Stopping An Uncontrolled Drone Crash

We spend a lot of time here at Hackaday talking about drone incidents and today we’re looking into the hazard of operating in areas where people are present. Accidents happen, and a whether it’s a catastrophic failure or just a dead battery pack, the chance of a multi-rotor aircraft crashing down onto people below is a real and persistent hazard. For amateur fliers, operating over crowds of people is simply banned, but there are cases where professionally-piloted dones are flying near crowds of people and other safety measures need to be considered.

We saw a skier narrowly missed by a falling camera drone in 2015, and a couple weeks back there was news of a postal drone trial in Switzerland being halted after a parachute system failed. When a multirotor somehow fails while in flight it represents a multi-kilogram flying weapon equipped with spinning blades, how does it make it to the ground in as safe a manner as possible? Does it fall in uncontrolled flight, or does it activate a failsafe technology and retain some form of control as it descends?

Is One In Three Thousand An Acceptable Crash Rate?

With customers demanding faster delivery and low or no-cost delivery the industry is scrambling to develop delivery systems that undercut competitors. The Swiss postal service — appropriately named Swiss Post — are testing autonomous multirotors operated by the drone delivery startup Matternet. The design includes a parachute that can be deployed to slow an uncontrolled fall. But spinning rotors and string-like items don’t mix well. In their testing, a failure occurred almost immediately following deployment when the line securing the parachute to the machine caught in a rotor and broke/

In 3000 flights they had experienced only one other failure, when a machine deployed its parachute successfully and descended into Lake Zurich. Swiss Post are now insisting on some upgrades to the system including two lines to tether the parachute instead of just one, and metal reinforcement for the parachute lines. It’s unclear whether Matternet have developed their own parachute system or whether they used one off-the-shelf, but the incident provides a rare public examination of the technology.

Save the Drone: Parachutes and Lost Propeller Operation

There are multiple manufacturers offering parachute systems for existing multirotors, either triggered through the machine’s firmware or through their own on-board sensors. Just one example is SkyCat, whose spring-loaded parachute canon is demonstrated in this video. It’s interesting to browse their various sites and observe the different marketing tacks for the different communities, for professional systems the emphasis is on safety when flying over crowds while for the enthusiast flier the emphasis is on protecting the valuable machine from damage.

Of course, a parachute is not the only game in town when it comes to multirotor safety. There are systems that can keep a multirotor flying without a propeller. Clever algorithms in the flight controller can detect when a motor fails or a propeller is lost, and use the remaining motors to induce a spin and bring the craft to ground with some stability.

Normally, multirotor aircraft rely on the force from one rotor to keep that side of the aircraft level. Losing one propeller upsets a delicate balance between all rotors, but equilibrium can be regained in an emergency situation by using extreme yaw so that the force of the remaining propellers is be averaged over all sides of the aircraft. A team at ETH Zurich pioneered this technique. It has been used to great effect by the drone show provider Verity Studios who have produced a series of videos showing it in action. Even when the machine is assaulted in flight with a piece of timber and loses a rotor it regains level flight under some control and is able to descend safely.

We Have To Take This Technology Seriously

At the professional level, these technologies are essential for craft flying in proximity to an audience. Unfortunately these systems are absent from the hobby side of things. We are unaware of any open source or otherwise free drone firmwares that contain something like the ETZ algorithms, and we can’t find any parachute failsafe systems that we might have featured in the past.

Perhaps this doesn’t matter for a casual user with a small drone and an eye to safe flying rules, but should it be something that we think about? Those serious in the hobby are operating thousands of dollars worth of equipment worth protecting from a sudden and unexpected meeting with the cold hard earth. And we exist as never before in a hostile environment where the drone is the subject of a questionable moral panic, and anything to make flight safer and mitigate fear can only be a good thing. As always the comments are open.

Posted in algorithm, Current Events, drone, drone hacks, ETH Zurich, failsafe, Featured, Matternet, multirotor, parachute, Swiss Post, Verity Studios | Leave a comment

DIY PC Test Bench Puts Hardware Troubleshooting Out in the Open

If you’ve built a few PCs, you know how frustrating troubleshooting can be. Finding a faulty component inside the cramped confines of a case can be painful — whether its literal when sharp edges draw blood, or just figurative when you have to open that cramped case multiple times to make adjustments.

[Colonel Camp] decided to make life a bit easier by building this PC test bench which makes component troubleshooting much easier and can be built with old parts you probably have lying around. [Camp] was inspired by an old Linus PC Tech Tips video on the same topic. The key to the build is an old PC case. These cases are often riveted together, s a drill makes quick work of disassembling the chassis to easily get to all of the components. The motherboard pan and rear panel/card cage become the top shelf of the test bench, while the outer shell of the case becomes the base and a storage area. Two pieces of lumber support the upper shelf. The build was primed and painted with several coats of grey.

[Camp] built up his testbench with a modest motherboard, cooler and a 970 video card. He loaded up Manjaro Linux to verify everything worked. The basic hardware has already been replaced with a new system including a ridiculously huge cooler. But that’s all in a day’s work for a test bench PC.

We’ve seen some wild workbenches over the years, and this one fits right in for all your PC projects. Check out the video after the break!

Posted in hardware, pc, Test bed, test bench, tool hacks | Leave a comment

Millenium Falcon HID: Get Unity to Talk to Teensy

Here’s one that proves a hardware project can go beyond blinking LEDs and dumping massive chunks of data onto a serial console. Those practices are fine for some, but [dimtass] has found a more elegant hack for a more civilized age. His 3D Millennium Falcon model gets orientation data from his IMU as an an HID device.

The hardware involved is an MPU6050 6-axis sensor that is interfaced with a Teensy 3.2 board. [dimtass] documents his approach to calibrating the IMU going a bit further by using a Python script to generate offsets. We’ve advocated using Jupyter notebooks in the past and this is a good example of Jupyter plotting the data and visualizing the effect of the offsets in a second pass.

When in action, the Teensy reads IMU data and sends it over a USB RAW HID interface. For the uninitiated, HID transfers are more reliable than USB CDC transfers (virtual serial port) because they use smaller data chunks per event/transaction and usually don’t require special drivers On the computer side, [dimtass] has written a small application that gets the IMU values over the RAW HID and then provides it to the visualization application.

A 3D Millennium Falcon model is rendered in Unity, the popular open source game development engine. Even though Unity has an API, this particular approach is more OS specific using a shared-memory technique. The HID application writes to a file (/tmp/hid-shared-buffer) which is then read by Unity to make orientation changes to the rendered model.

[dimtass] provides lots of details on the tools used to bring his project to life and it can be a great starting point for more projects that need interfacing sensors with a visualization system. We have seen ways to turn a person’s head into a joystick and if you need a deeper dive into Unity, look no further.

Posted in IMU, Microcontrollers, millenium falcon, mpu6050, peripherals hacks, Teensy, Teensy 3.2, unity, usb, USB CDC, USB RAW HID | Leave a comment

Overclocking In An SNES Emulator

The bsnes emulator has a new overclocking mode to eliminate slowdowns in SNES games while keeping the gameplay speed accurate. We’re emulating old SNES hardware on modern machines that are vastly more powerful. Eliminating slowdowns should be trivial, right? For an emulator such as bsnes, which is written to achieve essentially pixel-perfect accuracy when emulating, the problem is decidedly non-trivial. Stick around to learn why.

The Super Nintendo was an impressive system, for its time — mostly. The SNES framerate is locked to 60 FPS, which is a bit surprising considering the NTSC standard was only 30 FPS. NTSC calls for 30 frames per second, but those are interlaced frames. 30 times a second the even scanlines are updated, and 30 times a second the odd scanlines are updated. So 60 times a second, half of the screen is updated, alternating between the even and odd lines.

At the top of each frame the equivalent of half a scanline marks whether the rest of the frame is even or odd scanlines. In order to produce a clean 60 FPS, the SNES didn’t interlace, and just always wrote to the same 240 scanlines. This is also why retro consoles can look so terrible on modern monitors. The blank scanlines were hidden by the analog fuzziness of CRT TVs.

The SNES primary processor runs all the game logic and updates the graphics 60 times per second, finishing each frame’s calculations before the TV began writing that frame to the screen. Games were generally carefully written to make sure each frame’s processing would finish within that 16 millisecond window.

Most games have a few scenarios where lots of things are happening at once, and the processor just can’t keep up with the framerate. In this case, the game begins to lag. Since the framerate is hard synced to 60fps, the previous frame is simply shown again, and the game is paused for that frame while processing finishes.

The bsnes solution is a clever one. Virtual scanlines are added, but the audio and video emulation is paused. This allows the whole process to happen very rapidly, and yet continue to sync with the normal 60 FPS. Below is the Gradius III demo, showing off the results.

Header image: Sandos (CC BY-SA 3.0).

Posted in computer hacks, emulation, nintendo hacks, overclocking, snes | Leave a comment

[Jessica] Is Soft On Robot Grippers

It is an old movie trope: a robot grips something and accidentally crushes it with its super robot strength. A little feedback goes a long way, of course, but futuristic robots may also want to employ soft grippers. [Jessica] shows how to build soft grippers made of several cast fingers. The fingers are cast from Ecoflex 00-50, and use air pressure.

A 3D-printed mold is used to cast the Ecoflex fingers, which are only workable for 18 minutes after mixing, so it’s necessary to work fast and have everything ready before you start.

Once cast the Ecoflex is fairly easy to puncture, a paper clip can be enough to punch an air hole through the wall. There may be some leaks that are easier to detect if the part is submerged in water, in which case any holes can be patched with fresh Ecoflex. If an air channel is clogged it may be necessary to recast the whole part, but the mold is reusable.

Speaking of reusing the mold, it’s also possible to create three more fingers and use a 3D printed hub to make an entire gripper hand. As a practical matter, you should probably have force control. Soft grippers can be very — pardon the pun — flexible.

Posted in 3d Printer hacks, ecoflex, gripper, robot, robot arm, robot hand, robots hacks, soft robotics | Leave a comment

Cheap Electric Scooter Gets a Big Brake Upgrade; Unlocks Proper Drift Mode

The last few years have seen a huge rise in the prominence of electric scooters. Brushless motors, lithium batteries, and scooter sharing companies have brought them to the mainstream. However, electric scooters of a variety of designs have been around for a long time, spawning a dedicated subculture of hackers intent on getting the best out of them.

One such hacker is yours truly, having started by modifying basic kick scooters with a variety of propulsion systems way back in 2009. After growing frustrated with the limitations of creating high-speed rotating assemblies without machine tools, I turned my eye to what was commercially available. With my first engineering paycheck under my belt, I bought myself a Razor E300, and was promptly disappointed by the performance. Naturally, hacking ensued as the lead-acid batteries were jettisoned for lithium replacements.

Over the years, batteries, controllers and even the big old heavy brushed motor were replaced. The basic mechanical layout was sound, making it easy to make changes with simple hand tools. As acceleration became violent and top speeds inched closer to 40 km/h, I began to grow increasingly frustrated with the scooter’s one glaring major flaw. It was time to fix the brakes.

Stop Me If You’ve Heard This One Before

A typical band brake, similar to the type fitted to the Razor E300. Note the drum, top right, which is mounted to the wheel to be braked.

The Razor E300 comes stock with a band-brake, akin to an inside out drum brake. When the brake lever is pulled, the brake cable pulls on a lever which tightens the band around a drum attached to the driven wheel at the rear of the scooter.

Band brakes are cheap to make and can be effective in some applications. Unfortunately, the cheap stamped metal shell used on the E300’s brake is prone to deformation, causing misalignment between the band and drum. Simply riding carelessly up and down bumpy footpaths is enough to cause problems. Typically the brake ends up either scraping continuously on the drum, wasting power, or is unable to effect enough friction to slow the scooter down. Either way, it usually can’t lock the rear wheel for doing awesome skids and that’s a shame. With electric scooters having a somewhat uncool vibe akin to the Segway, the impact of not being able to do the aforementioned awesome skids cannot be understated.

Stepping Up to Disc Brakes

Like all variants of drum-type brakes, the band brake pales in comparison to the superior disc technology. For automotive and large-scale applications, this is primarily due to improved heat dissipation and easier maintenance. In our case, other factors are more important — bicycle disc brakes are cheap and readily available on eBay, and with the right installation, shouldn’t suffer the same issues with rubbing or lack of stopping power. A series of discs in various sizes, along with calipers and mounting brackets were sourced for under $50 AUD. The calipers can be mounted out of the way of obstacles,  and the right sized disc should also be safe from impacts.

Despite going through years of formal engineering training, I’ve never been one to enjoy drawing up a design before getting down to work. Instead, after letting the parts marinate in their shipping boxes for 18 months, I finally took them out on a sunny winter’s day and began staring at the back of the scooter until a plan came together.

The drum was cut back to leave a plate suitable for mounting the brake disc.

Rather elegantly, the drum for the band brake serves nicely as a mounting surface for the brake disc. By removing the friction surface with an angle grinder, I was left with a nice flat plate attached to the axle, to which I would bolt on the brake disc. With a slight modification to the disc’s mounting lugs to clear the centre of the axle, it slid on to the hub and was attached with three M4 bolts.

A ruler was used to check that the disc was perpendicular to the axle and aligned properly. Spacers were required to be added to the rear assembly to make up for the missing width of the original band brake assembly; in this case, a series of three half-inch washers did the trick.

The caliper was more difficult, requiring the fabrication of a custom bracket to marry the caliper mounting hardware with the frame of the E300. A piece of steel L-angle was massaged into the right shape to bolt to the rear frame upright. Plate steel would probably have sufficed, but a hacker often uses what falls first to hand. Getting the mount right was crucial to ensure the brakes worked effectively, as misaligning the caliper to the disc would cause the pads to wear prematurely and slow the scooter down. Thankfully, the mounting hardware that ships with the calipers allows some adjustment of the final position, meaning the bracket doesn’t have to be made to a particularly high level of accuracy.

With everything bolted up, all that was left to do was replace the original brake cable with one long enough to reach the rear caliper, which was mounted further aft than the original band brake. The original brake lever was also of cheap construction and was replaced with a nicer all-metal unit also sourced from eBay.

How Does It Perform?

Skids in mud make for a fun, albeit messy, afternoon.

After some initial headaches with the original plastic brake lever falling to pieces, the new disc brake setup performed brilliantly. Thick, fat, high speed skids are now easy to perform even on grippy asphalt surfaces. There is little to no noise from the brake when not in use, which is a huge improvement over the continually screeching band brake. This has the side effect of greatly improving the scooter’s stealth capabilities. Dynamically, it’s a much better experience, though the lack of a front brake is still felt when descending slippery muddy hills.

The scooter is now a joy to ride, and it’s an upgrade I wish I’d completed much sooner. Anyone handy with a power drill and grinder should be able to complete the switch in a weekend. Hopefully this hack inspires you to mod your own vehicles for ever greater performance, and to those that get stuck in, I look forward to seeing you on the trails!

Posted in band brake, brake, brakes, disc brake, disc brakes, electric scooter, Featured, razor scooter, scooter, Skills, transportation hacks | Leave a comment

Remote ADS-B Install Listens in on All the Aircraft Transmissions with RTL-SDR Trio, Phones Home on Cellular

When installing almost any kind of radio gear, the three factors that matter most are the same as in real estate: location, location, location. An unobstructed location at the highest possible elevation gives the antenna the furthest radio horizon as well as the biggest bang for the installation buck. But remote installations create problems, too, particularly with maintenance, which can be a chore.

So when [tsimota] got a chance to relocate one of his Automatic Dependent Surveillance-Broadcast (ADS-B) receivers to a remote site, he made sure the remote gear was as bulletproof as possible. In a detailed write up with a ton of pictures, [tsimota] shows the impressive amount of effort he put into the build.

The system has a Raspberry Pi 3 with solid-state drive running the ADS-B software, a powered USB hub for three separate RTL-SDR dongles for various aircraft monitoring channels, a remote FlightAware dongle to monitor ADS-B, and both internal and external temperature sensors. Everything is snuggled into a weatherproof case that has filtered ventilation fans to keep things cool, and even sports a magnetic reed tamper switch to let him know if the box is opened. An LTE modem pipes the data back to the Inter, a GSM-controlled outlet allows remote reboots, and a UPS keeps the whole thing running if the power blips atop the 15-m building the system now lives on.

Nobody appreciates a quality remote installation as much as we do, and this is a great example of doing it right. Our only quibble would be the use of a breadboard for the sensors, but in a low-vibration location, it should work fine. If you’ve got the itch to build an ADS-B ground station but don’t want to jump in with both feet quite yet, this beginner’s guide from a few years back is a great place to start.

Posted in ACARS, ads-b, co-linear, coaxial, dongle, FlightAware, misc hacks, Raspberry Pi 3, RTL-SDR, wireless hacks | Leave a comment

Print Your Own Heat Shrink Labels for Factory-Chic Wire Naming

Heat shrink tubing is great for insulating wires. Labeling wires in a bundle is always useful, too. [Voltlog] has a cheap Brother label printer and discovered he can buy knock off label cassettes for a lot less from China. However, he also found something else: cassettes with heat shrink tubing in them made for the same kind of printer. Could he use the heat shrink cassettes to make neat wire labels? In his first video the answer was sort of, but not really. However, he later had a breakthrough and made a second video explaining how to do it. You can see both videos, below.

At first, the printer didn’t even want to recognize the cassette. It seems like Brother doesn’t want you using exotic tapes with cheap printers. No worry, this isn’t sophisticated DRM, just a sense hole that you need to cover with tape. This discovery was made using the extremely scientific trick of covering all the holes that were not on a regular cassette.

With the holes covered up, the printer worked, but the print came out mirrored. To understand why, you have to understand how the normal labels work. In the cassette, the label material has no paper backing which is separate in a different part of the cartridge. The printer marks the backside of the see-through label and then bonds the paper backing to it as it exits the printer. This makes sense because it puts the markings under the tape where they are relatively safe from moisture or physical abrasion.

However, with heat shrink, it isn’t transparent and there’s no backing material. So the reverse print doesn’t really help you. It turns out the cheap printer can do non-mirrored printing, but to make that work, one of the holes in the special cassette needed to stay open. Once the proper holes were covered and uncovered, everything worked great.

Heat shrink is probably more high tech than you’d think. Did you know you can get it with adhesive inside it, too?

Posted in heat shrink, heatshrink, label, label printer, tool hacks | Leave a comment

Simple Bluetooth Car Audio From A Pi Zero

When [Sami Pietikäinen] realized that the Bluetooth built into his car didn’t support audio, he didn’t junk it and buy a Tesla. Instead, he decided to remedy the problem by building a small Bluetooth device that plugged into the Aux socket. To do this, he used a Raspberry Pi Zero with a pHAT DAC (Digital to Audio Converter). That’s perhaps using a sledgehammer to crack a walnut, but sometimes you work with what you have. The interesting part is to be found in what he did next: he used Yocto to optimize the device down to make it as simple and straightforward as possible.

That’s because the Raspbian OS he used for the first version does way more than was needed: The device just has to handle Bluetooth and the audio output, and really didn’t need all of the other stuff that Raspbian tries to install and run.

So for the second version, he dispensed with Raspbian and used Yocto, a project that allows you to create a customized Linux distribution. By stripping out the stuff the project does not need, he made the project much faster and more streamlined. He used Meta-raspberrypi, a Board Support Package (BSP) that provides the basis for running Yocto on a Pi, then tweaked a pre-built Yocto image to disable all of the features that he did not need.

The result is a device that is much simpler and which boots up and is ready to play music in about five seconds. That’s a considerable improvement over the thirty to sixty-second boot time of the standard Raspbian image (assuming it boots at all), and is a nice example of how simpler is sometimes better.

Posted in audio, bluetooth, Raspberry Pi, Yocto | Leave a comment

1940s Portable Radio Is A Suitcase

The meaning of the word portable has changed a bit over the years. These days something has to be pretty tiny to be considered truly portable, but in the 1940s, anything with a handle on it that you could lift with one hand might be counted as portable electronics. Zenith made a line of portable radios that were similar to their famous Transoceanic line but smaller, lighter, and only receiving AM to reduce their size and weight compared to their big brothers. If you want to see what passed for portable in those days, have a look at [Jeff Tranter’s] video (below) of a 6G601 — or maybe it is a GG601 as it says on the video page. But we think it is really a 6G601 which is a proper Zenith model number.

According to [Jeff], 225,350 of these radios were made, and you can see that it closes up like a suitcase. The initial 6 in the model number indicates there are 6 tubes and the G tells you that it can run with AC or batteries.

We love the name and appearance of the built-in antenna: wavemagnet. Marketing types existed back in the 1940s, too. You can remove the antenna and use built-in suction cups to affix it to a window. This is a great idea and one we wish more portable radios had.

The radio does have some asbestos in it, so that’s a concern if you want to rebuild one of these. [Jeff] says if it isn’t flaking apart you should be ok, but he wore a mask while dusting the case out, anyway.

The tube used modern (for the time) loctal tubes that used 1.5V filaments that were easy on batteries. No printed circuit board here, hand wiring was the order of the day. The radio sounds great, and the back part of the video talks about what he had to do to restore the radio to its current glory.

There’s not much good on AM anymore unless, of course, you put it there. We’ve also written about restoring old radios if you want more on that topic.

Posted in am radio, radio, teardown, vintage radio, wireless hacks, zenith | Leave a comment