LMR is possibly the most popular DIY robotics website around and was started up by a fun-loving Dane, [Frits Lyneborg]. It grew a large community around building up minimal robots that nonetheless had a lot of personality or pushed a new technical idea into the DIY robotics scene. [Frits] says that he hasn’t had time for DIY robotics for a while now, and doesn’t have the resources to run a gigantic web forum either, so he worked out a deal to let the Canadian hobbyist supply company Robot Shop take it over.
LMR has always been a little bit Wild-West, and many of the members quite opinionated, and that’s been part of its charm. So when the new corporate overlords came in, set up “Rules” (which have seemingly been downgraded to “suggestions”) and clarified the ownership of the content, some feathers were ruffled.
A few weeks later, everything looks to be settling back down again. (Edit: Or has it?!? See the comments below.) We wish LMR all the best — everyone loves robots, and LMR is a tremendous resource for the newbie interested in getting into DIY robotics on the cheap. More than a few LMR posts have been featured here at Hackaday over the years. Among our favorites are this drumming rover, a clever 3D printed gripper, and this wicked bicycle-style balancer.
We love interrupts in our microcontroller projects. If you aren’t already convinced, go read the first installment in this series where we covered the best aspects of interrupts.
But everything is not sunshine and daffodils. Interrupts take place outside of the normal program flow, and indeed preempt it. The microcontroller will put down whatever code it’s running and go off to run your ISR every time the triggering event happens. That power is great when you need it, but recall with Spider-Man’s mantra: With great power comes great responsibility. It’s your responsibility to design for the implicit high priority of ISRs, and to make sure that your main code can still get its work done in between interrupt calls.
Put another way, adding interrupts in your microcontroller code introduces issues of scheduling and prioritization that you didn’t have to deal with before. Let’s have a look at that aspect now, and we’ll put off the truly gruesome side-effects of using interrupts until next time.
Regular Hackaday readers are used to seeing the hacks that use a cheap USB TV dongle as a software defined radio (SDR). There’s plenty of software that will work with them including the excellent GNU Radio software. However, the hardware is pretty bare-bones. Without modifications, the USB dongle won’t get lower frequencies.
There’s been plenty of other SDR radios available but they’ve had a much heftier price tag. But we recently noticed the SDRPlay RSP, and they now have US distribution. The manufacturer says it will receive signals with 12-bits of resolution over the range of 100 kHz to 2 GHz with an 8MHz bandwidth. The USB cable supplies power and a connection to the PC. The best part? An open API that supports Windows, Linux, Mac, Android, and will even work on a Raspberry Pi (and has GNU Radio support, too).
For most of us, hacking is a hobby, a pleasant diversion from reality. Yes, a lot of us work on projects which have the potential to change the world – witness the 2015 Hackaday Prize semifinalist list. But in general, almost any of us could walk away from the shop at any time without dire consequences. Indeed, that’s the reason a lot of our work benches are littered with projects started with the best of intentions but left unfinished for lack of funds, lack of interest, or lack of time. We’re free to more or less willingly shelve a project and come back to it whenever we please, or not at all.
But not everyone has that luxury. For some people, hacking is much more than a hobby – it’s a means of survival. Sometimes people are thrown into situations where they have to cobble together a solution to an immediate problem with whatever is at hand, when the penalty for failure is much higher than a cluttered bench and a bruised ego. I’ve already covered one such case, where biohacked insulin saved hundreds of lives in occupied Shanghai in WWII.
In this occasional series I’ll explore historical cases where hacking really counted; cases where lives were saved or improved by a hack performed under desperate conditions.
A Bustle in the Hedgerow
Unsurprisingly, war offers a lot of opportunities for field expedient solutions under dire circumstances, and battlefield conditions might be the most extreme example of hacking when it counts.
In the early days of the Invasion of Normandy during WWII, Allied forces were having a difficult time dealing with the bocage terrain of northern France. A mixture of pasture and woodland, the Normandy bocage was a natural killing field for Allied tanks because the woodlands took the form of hedgerows – earthen dikes topped with thick tangles of brush. Hedgerows separated pastures and kept livestock controlled, but also made things tough on infantry and mechanized cavalry alike. Climbing the steep hedgerows exposed the vulnerable bottom hull of the tanks to enemy fire, and waiting for engineers to demolish the hedgerows with explosive made them sitting ducks for German artillery. The Allied advance was seriously hampered by the hedgerows, and both men and materiel were being winnowed down from fixed German positions chosen specifically to take advantage of the bocage terrain.
Enter Sgt. Curtis Grubb Culin III. Sgt. Culin, a tanker himself, was acutely aware of how vulnerable he was in his Sherman M4. The hedgerows were the problem, one apparently known to Allied command prior to the invasion for which no provision had been made. In the tradition of soldiers at the front of every battle throughout history, Sgt. Culin and his fellow tankers had to improvise a solution.
While kicking around ideas, one of the men suggested setting saw teeth on the front of a tank to cut through the hedgerows. He later attributed the comment to “A Tennessee hillbilly named Roberts”, and it was met with general laughter from the group as a crackpot scheme. But Sgt. Culin saw the potential in the idea, and began to develop it into a prototype.
Raw materials for his prototype were not hard to come by. Czech hedgehogs, giant anti-tank barriers made of crossed steel beams, still littered the Normandy beaches. The failed German defenses were harvested with a cutting torch and welded to the underside of a tank to form a series of “tusks” across the hull between the tracks. Equipped with these tusks, the tank could now blast through the tangled roots of the brush-covered earth of the hedgerow dykes.
When demonstrated for General Omar Bradley, he was impressed enough to order them built in quantity for the tanks. Eventually the prototype became an engineered product (dubbed the “Culin Rhino Device”) that was fitted to many tanks before being shipped over from England. Rhino-equipped tanks ripped across Normandy and shredded the German battle plan, which assumed the hedgerows would funnel Allied forces through heavily defended chokepoints.
Without Sgt. Culin’s battlefield hack, and his inspiration by a hillbilly named Roberts whom history otherwise forgets, the invasion of Europe might have taken a very different course. The fact that he did the hack while under fire makes it all the more impressive, and is a perfect example of hacking when it counts.
Know of any more examples of hacking when it counts? Send us a tip for use in a future Hacking When it Counts article.
Last week, Parallax released an open hackable electronic badge that will eventually be used at dozens of conferences. It’s a great idea that allows badge hacks developed during one conference to be used at a later conference.
[Mark] was at the Hackable Electronics Badge premier at the 2015 Open Hardware Summit last weekend, and he just finished up the first interactive hack for this badge. It’s the zombie apocalypse in badge form, pitting humans and zombies against each other at your next con.
The zombie survival game works with the IR transmitter and receiver on the badge normally used to exchange contact information. Upon receiving the badge, the user chooses to be either a zombie or survivor. Pressing the resistive buttons attacks, heals, or infects others over IR. The game is your standard zombie apocalypse affair: zombies infect survivors, survivors attack zombies and heal the infected, and the infected turn into zombies.
Yes, a zombie apocalypse is a simple game for a wearable with IR communications, but for the Hackable Electronics Badge, it’s a great development. There will eventually be tens of thousands of these badges floating around at cons, and having this game available on day-one of a conference will make for a lot of fun.
Signals Intelligence (SigInt) isn’t something that you normally associate with home hackers, but the Deep Sweep project is looking to change that: it is a balloon platform that captures radio signals in the stratosphere, particularly conversations between drones and satellites. Created by three students at the Frank Ratchye Studio for Creative Inquiry at Carnegie-Mellon, Deep Sweep is a platform that is attached to a balloon and which captures signals over a wide range of frequencies, logging them for later analysis. The current version captures data on three frequency bands: LF/HF (10KHz-30KHz), UHF (650 – 1650MHz) and SHF (10-20GHz). The latter are often the bands used for satellite links between drones and satellites. They are difficult to intercept from the ground, as the signals are directed upwards towards the satellite. By creating a platform that can fly several kilometers above the earth, they are hoping to be able to capture some of this elusive traffic.
So far, the team has made two flights in Europe, both of which encountered technical issues. The first had a battery fault and only captured 10 minutes of data, and the second flew further than expected and ended up in Belarus, a country that isn’t likely to welcome this kind of thing. Fortunately, they were able to recover the balloon and are working on future launches in Europe and the USA. It will be interesting to see how the Department of Homeland Security feels about this.
Robots of the future will be in the home, and ready to do whatever job we tell them to do. But they’ll need to know where they are within the house. Dead reckoning with accelerometers and gyroscopes are just a sufficient solution; what we really need is an indoor location service. For his Hackaday Prize entry, [Göran] is doing just that. He’s building a small device that will find its position with 10 cm precision, indoors.
[Göran]’s LPS Mini is built around a very interesting part – the Decawave DWM100. It’s a module that uses an 802.15 radio to trilaterate the distance from several ‘anchors’ to a tag. This, by itself, gives the LPS Mini a navigation system with 10 cm precision. Even higher precision can be accomplished with an IMU gathering accelerometer, gyro, and compass data, and even further with a tiny altimeter. The result is a tiny board that knows exactly where it is.
As far as practical uses go, these LPS Mini boards were used to move beds around an art exhibit at Hayward Gallery in London. While moving beds around an art gallery doesn’t sound like a game-changing invention, think about the uses for GPS in the 1980s – no one could have imagined a chip that would tell you where you are or that could keep a quadcopter on the right heading.
You can check out [Göran]’s video for the LPS Mini below.
