Skin-Mounted Wearable Bend Sensor Gets Close And Personal

July 10, 2021 by Donald Papp 1 Comment

[Mikst] has been working on wearable electronics and sensors for a long time, and shared the results of a different kind of bend sensor that fits directly onto the skin. It’s true that this kind of sensor design isn’t re-usable, but it is also very simple and inexpensive. It’s just a proof of concept right now, but we could see it or some of the other ideas [Mikst] tries, used in niche wearable applications where space is critical, like cosplay.

At its heart the sensor is made from two strands of conductive thread and a small strip of stretchy, conductive fabric common in wearable e-textiles. It is stuck directly to the skin using a transparent, non-woven medical adhesive dressing that is particularly good at conforming to contoured areas of the body. In this case, it is used to stick the stretchy piece of conductive fabric directly onto [Mikst]’s knuckle, where it responds to even small movements. You can watch a multimeter measuring the resistance changes in the video, embedded below.

We’ve seen [Mikst]’s work before in finding unusual solutions to e-textile problems, such as a three-conductor pivoting connection used to mount a wearable hall effect sensor.

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Building A Big Ol’ Powerful Wheelbarrow

July 10, 2021 by Lewin Day 16 Comments

Sometimes you’ve gotta haul big heavy loads around a wide area. Regular wheelbarrows are fine, but it can quickly grow tiring when one has to make multiple trips. [Workshop from Scratch] instead elected to build a powered wheelbarrow, with plenty of grunt to shift loads about.

The build is absolutely from the ground up, welded up from sections of steel RHS, and given rear steering for plenty of maneuverability. The actual job of steering is handled by a rack repurposed from automotive use, set up with a single-sided attachment to the rear wheel assembly. It’s quite a neat and tidy way of doing the job, and seems to work well. Drive is sent to the front wheels through a hydrostatic lawnmower transmission. A 17-horsepower engine provides plenty of grunt for the job at hand, even coming with electric start already fitted for the ultimate in ease-of-use.

It’s impressive to see just how much of the rig was put together from raw materials; even the fuel tank was fabricated in steel. We’ve seen similar builds from [Workshop from Scratch] before, like this tidy bandsaw. Video after the break.

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You Can’t Fix What You Can’t Measure

July 10, 2021 by Elliot Williams 13 Comments

Last year, as my Corona Hobby™, I took up RC plane flying. I started out with discus-launched gliders, and honestly that’s still my main love, but there’s only so much room for hackery in planes that are designed to be absolutely minimum weight and maximum performance; these are the kind of planes that notice an extra half gram in the tail. So I’ve also built a few crude workhorse planes — the kind of things that you could slap a 60 g decade-old GoPro on and it won’t even really notice. Some have ended their lives in trees, but most have been disassembled and reincarnated — the electronics live on in the next body.

The journey has been really fun. I’ve learned about aerodynamics, gotten an excuse to put together a 4-axis hot-wire CNC styrofoam cutter, and covered everything in sight with carbon fiber tow, which is cheaper than you might think but makes the plane space-age. My current workhorse has bolted on an IMU, GPS, and a minimal Ardupilot setup, though I have yet to really put it through its paces. What’s holding me back is the video link — it just won’t work reliably further than a few hundred meters, and I certainly don’t trust it to get out of line-of-sight.

My suspicion is that the crappy antennas I have are holding me back, which of course is an encouragement to DIY, but measuring antennas in the 5.8 GHz band is tricky. I’d love to just be able to buy one of the cheap vector analyzers that we’ve covered in the past — anyone can make an antenna when they can see what they’re doing — but they top out at 2.4 GHz or lower. No dice. I’m blind in 5.8 GHz.

Of course, I do have one way in, and that’s tapping into the received signal strength indicator (RSSI) of a dedicated 5.8 GHz receiver, and just testing antennas out in practice, but that only gives a sort of loose better-worse indication. More capacitance or more inductance? Plates closer together or further apart? Try it out and see, I guess, but it’s time-consuming.

Moral of the story: don’t take measurement equipment for granted. Imagine trying to build an analog circuit without a voltmeter, or to debug something digital without a logic probe. Sometimes the most important tool is the one that lets you see the problem in the first place.

Fractal Vise Holds Odd-Shaped Objects Tight

July 10, 2021 by Lewin Day 29 Comments

A regular vice is great if you want to clamp rectangular objects, but it can fall down a little with more complex shapes. Inspired by an ancient vise [Chris Borge] whipped up his own 3D-printed fractal clamping tool.

The inspiration for this one comes from the [Hand Tool Rescue] video that shows of the clever mechanism. The vice uses a series of interlocking parts that can freely articulate to grip the object of interest via several protruding fingers. In reproducing the design, [Chris] had some issues initially with the joints, but settling on a dovetail similar to that of the original metal vice which got things working nicely.

[Chris] notes that while the design works, it could still use some refinement. Silicone or rubber tips on the fingers could give the vice better grip, and there remain some flexural issues that could be improved. Overall, however, it’s a useful table vice for small jobs on weird shaped things. We’ve seen 3D-printed vices before, particularly in the PCB vice space, but the grip scheme user here is totally unique.

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Up Close And Personal With Some Busted Avionics

July 10, 2021 by Tom Nardi 1 Comment

When he found this broken Narco DME 890 that was headed for the trash, [Yeo Kheng Meng] did what any self-respecting hardware hacker would do: he took it back to his workbench so he could crack it open. After all, it’s not often you get to look at a piece of tech built to the exacting standards required by even outdated avionics.

DME stands for “Distance Measuring Equipment”, and as you might expect from the name, it indicates how far the aircraft is from a given target. [Yeo Kheng Meng] actually goes pretty deep into the theory behind how it works in his write-up if you’re interested in the nuts and bolts of it all, but the short version is that the pilot selects the frequency of a known station on the ground, and the distance to the target is displayed on the screen.

Inside the device, [Yeo Kheng Meng] found several densely packed boards, each isolated to minimize interference. The main PCB plays host to the Mostek MK3870 microcontroller, an 8-bit chip that screams along at 4 MHz and offers a spacious 128 bytes of RAM. It doesn’t sound like much to the modern AVR wrangler, but for 1977, it was cutting edge stuff.

Digging further, [Yeo Kheng Meng] opens up the metal cans that hold the transmitter and receiver. Thanks to the excellent documentation available for the device, which contains extensive schematics and block diagrams, he was able to ascertain the function of many of the components. Even if you’re unlikely to ever go hands on with this type of technology, it’s fascinating to see the thought and attention to detail that goes into even seemingly mundane aspects of the hardware.

Hungry for more airworthy engineering? We’ve taken a close look at some hardware pulled from a civilian airliner, as well as some battle-hardened electronics that once graced the cockpit of an AH-64 Apache attack helicopter.

Home Automation For Fans Of Quick-and-Dirty Solutions

July 9, 2021 by Dan Maloney 25 Comments

At Hackaday, we celebrate all kinds of projects, but we’ll have to admit that the polished and professional-looking builds tend to catch our eye a lot more than perhaps they should. There’s plenty of love to be had for the rougher builds, though, of which this quick-and-dirty home automation system is a perfect example.

Before anyone rushes to state the obvious with, “Should have used some relays,” consider that [MAKE_IT_WITH_ME]’s stated goal was to get the basics of a home automation system built with pretty much nothing but what can be found in one of those Arduino starter kits. And further, consider that landlords might not look kindly on tenants who wire a bunch of SSRs or Sonoff switches into the walls of their building. So this minimalist build is perfect for certain use cases. Its interface to the building’s electrical system is 100% mechanical, via a servo that travels along the bank of switches on a stepper-driven leadscrew. The servo has a modified horn to properly flick the rocker-style switches, and although changing from switch to switch is a bit slow, it works surprisingly well. The video below shows it in action.

While we can see it possibly working as-is for Decora-style switches that are seen in some markets, we’d think some mods would be in order for the more standard toggle-style switch — perhaps a finger extending out from the horn, along with a second servo to tilt the whole assembly away from the wall to allow it to clear the switch bats.

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3D Printed Copper Rocket Nozzle Costs Under Two Grand

July 9, 2021 by Al Williams 19 Comments

You don’t think of hobby-grade 3D printing as a good method for creating rocket nozzles. But [Mister Highball] managed to create a copper nozzle using a common printer, a kiln, and some special copper-bearing filament.

The copper filament is about 90% metal. Virtual Foundry recommends preheating it before printing and you have to sinter it in an oven to remove the plastic and leave a solid metal piece which will, of course, shrink.

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