Hackaday Prize Entry: Ears On The Back Of Your Head

From context clues, we can tell that [TVMiller] has been in and around NYC for some time now. He has observed a crucial weakness in the common metropolitan. Namely, they deafen themselves with earphones, leaving them senseless in a hostile environment.

To fix this problem, he came up with a simple hack, the metrophone. An ultrasonic sensor is hung from a backpack. The user’s noise making device of choice is plugged into one end, and the transducer into the other. When the metropolitan is approached from the rear by a stalking tiger or taxi cab, the metrophone will reduce the volume and allow the user to hear and respond to their impending doom. Augmentation successful.

The device itself consists of an off-the-shelf ultrasonic sensor, an Arduino, and a digital potentiometer. It all fits in a custom 3D printed enclosure and runs of two rechargeable coin cells. A simple bit of code scales the volume to the current distance being measured by the ultrasonic sensor once a threshold has been met.

In the video after the break, you can observe [TVMiller]’s recommended method for tranquilizing and equipping a metropolitan in its natural habitat without disturbing its patterns or stressing it unduly.

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Fixing the Terrible Range of your Cheap NRF24L01+ PA/LNA Module

nRF24L01+ PA/LNA module specs look great on paper. Wireless communication up to 1000m in a small package readily available from a variety of cheap sources in China? The hard work of software connectivity already done by a variety of open source projects? Sounds great! But if you mashed BUY and are getting maybe 1% of that range, don’t worry because thanks to these clear directions, they can be fixed.

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Exoskeleton Boots Put a Spring in your Step

Human ancestors have been walking around on two legs for a few million years. We’d imagine that by now we’ve figured out a pretty efficient mechanism for getting around. Unconvinced, however, researchers at Carnegie Mellon University have developed an “exo”-boot that reduces the metabolic rate of walking by seven percent. Best of all, the mechanism requires no additional source of active power input besides the human legs that are wearing them.

Upon close inspection, the boots reduce the overall applied torque at the angle joint at a critical point where the heel begins to lift off the ground. Energy in, energy out. The spring ratchets to a loaded position as the user plants their foot. This ratchet releases, re-engaging the stored spring force as the user brings their heel back off the ground. A seven percent reduction in metabolic rate may not sound like much, but, according to the paper, it’s the equivalent of about four kilograms less weight in your backpack on that next hiking trip.

As for what specific costs are being reduced to lower the body’s metabolic rate, the researchers still aren’t completely sure. An off-the-cuff look at the joints and moments from a mechanics perspective won’t give us a sure-fire answer since the energy consumption processes of muscles are, well, complicated. In fact, by varying spring stiffness in their design, they discovered that springs that were either too stiff or too loose had no effect on the metabolic rate. Yes, they’ve certainly stumbled on a sweet spot in terms of well-mixed circumstances, but the answer behind why the new robot-legs work so smoothly will be a study for the future.

If you haven’t jumped into the world of exo-skeleton building, let [James Hobson] be your guide into pushing our bounds with homebrew mechanical advantages. Now let’s keep our fingers crossed for some long-fall boots.

via [The Washington Post]

Leg Mounted Beer Bottles for Underwater Propulsion

Sitting on the beach, finishing off a beer one day, [Rulof] realized that if he put a motor in the beer bottle with a propeller at the bottle’s mouth, he could attach the result to his leg and use it to propel himself through the water. Even without the added bonus of the beautiful Mediterranean waters through which he propels himself, this is one hack we all wish we’d thought of.

These particular beer bottles were aluminum, making cutting them open to put the motor inside easy to do using his angle grinder. And [Rulof] made good use of that grinder because not only did he use it to round out parts of the motor mounting bracket and to cut a piston housing, he also used the grinder to cut up some old sneakers on which he mounted the bottles.

You might wonder where the pistons come into play. He didn’t actually use the whole pistons but just a part of their housing and the shaft that extends out of them. That’s because where the shaft emerges from the housing has a water tight seal. And as you can see from the video below, the seal works well in the shallow waters in which he swims.

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Exquisite LED Handbag in the Wild

There is a lot of spectacle on display at Maker Faire. But to be honest, what I love seeing the most are well-executed builds pulled off by passionate hackers. Such is the case with [Debra Ansell]. She wasn’t exhibiting, just taking in all the sights like I was. But her bag was much better than my drab grey camera-equipment filled backpack; she build a handbag with an LED matrix and did it so well you will scratch your head trying to figure out if she bought it that way or not.

Gerrit and I walked right up and asked if she’d show it to us. We weren’t the only ones either. [Debra’s] bag started drawing a crowd as she pulled out her cellphone and sent “Hackaday” to the 10×15 matrix over Bluetooth. Check out our video interview below.

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How to Fail at Laser Cutting

Laser cutters are CNC power tools, which means an operator uploads a job digitally and then pushes START to let the machine do all the work while they lie back in a hammock sipping a margarita, occasionally leaping out in a panic because the sound coming from the machine changed slightly.

Like other power tools, laser cutters are built around doing one thing very well, but they require an operator’s full attention and support. The operator needs to handle all the other things that go on before, during, and after the job. It’s not too hard to get adequate results, but to get truly professional and repeatable ones takes work and experience and an attention to detail.

People often focus on success stories, but learning from failures is much more educational. In the spirit of exploring that idea, here are my favorite ways to fail at laser cutting and engraving. Not all of these are my own personal experience, but they are all someone’s personal experience.

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Kerbal Space Program for the Apple II

[Vince Weaver] tried to use his time machine to jump a few years in the future to get a less buggy version of Kerbal Space Program, but as usual with time travel, nothing went right and he ended up heading to 1987. Finding himself in an alternate timeline where KSP had been released for the Apple II, he brought back a copy.

Well, that’s the narrative proposed by [Vince Weaver] on his YouTube channel. The real story, and hack, being that he wrote a version of KSP for the Apple II in Applesoft Basic. He has used the language for the ridiculous before. You can build a rocket, select a pilot, launch, and if you’re lucky (or skilled), reach orbit.

We loaded up his disk image on an Apple II emulator and gave it a try. We managed to murde—lose a few pilots, but that was about it.  It was hard not to get distracted by the graphics and remember to point the rocket the right direction. Either way, it was a neat bit of fun in retro computing. Video after the break.

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