RC HalfTrack Is Lasercut Masterpiece

The half-track is a vehicle design that has gradually fallen out of favour in the decades since World War II. Combining the benefits of easy driving and handling of wheeled vehicles with the strong mud and snow performance of a tracked vehicle, they served a niche before largely being phased out with the rise of the armoured personnel carrier. [JackCarter] wished to build his own, so whipped up a lasercut RC version of the SdKfz 251 22.

The work is impressive, with [JackCarter] creating the design in Solidworks from photos and illustrations of the vehicle. The moving parts are lasercut, including the tracks themselves, assembled from many tiny lasercut MDF parts. The benefit of using lasercutting to make the model is that it was easy for [Jack Carter] to create simple jigs to ease the process of putting the tracks together. A NodeMCU with a motor shield controls the gear motors used to drive the tracks, and drives a servo for steering. Control is via a smartphone, thanks to the Blynk framework which makes building apps for custom projects easy.

The finished product really shows off [JackCarter]’s 3D design skills, and looks like great fun to build and drive. We’d love to see it with a lick of paint and some period decals to really complete the look. Hackers love a good tracked vehicle, and we’ve seen some impressive builds before. Video after the break.

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SDR Transmitting Gets The Power

Most hobby-grade software defined radio setups don’t transmit. Of the few that do, most of them put out anemic levels around one milliwatt or so. If you want to do something outside of the lab, you’ll need an amplifier and that’s what [Tech Minds] shows how to do in a recent video. (Embedded below.)

The video covers LimeSDR, HackRF, and the Pluto SDR, although the amplifiers should work with any transmitter. The SPF5189Z module is quite cheap and covers 50 MHz to 4 GHz, amplifying everything you throw at it. The downside is that it will amplify everything you throw at it, even parts of the signal you don’t want, such as spurs and harmonics.

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A Tiny Jacob’s Ladder You Can Build At Home

Big fizzing electrical arcs are fun, and handled properly, not too dangerous either. The Jacob’s Ladder is one such piece of arc-generating equipment, one that featured heavily in vintage sci-fi films. It remains a charming demonstration of high-voltage electrical principles, and you can easily build your own mini version at home.

The build starts with a basic high-voltage step-up kit that turns 4V DC into 15 kV at the output. At this voltage level, it’s possible to generate an arc in air. To create the Jacob’s ladder, the kit is wired up to a pair of closely-spaced electrodes that slowly get farther apart as they go up vertically. When an arc jumps from one electrode to the other, it ionises the air, and the voltage sags due to the current flow. The flowing current heats up the air, which begins to rise, taking the current path with it, causing the familiar climbing arc we all know and love. As the distance between the electrodes increases towards the top, the arc can eventually no longer be sustained. With no current flowing, the voltage rises again, and a new arc forms at the bottom of the device, repeating the process.

It’s a fun build that would make an excellent desk toy, albeit best shown under glass to avoid accidental electric shocks. You can even build a larger one out of microwave parts if you’re so inclined. Video after the break.

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WaterAid Finds Potable Water And Stops Polluters

Millions of people all over the world don’t have access to clean drinking water, and it’s largely because of pollution by corporations and individuals. Solving this problem requires an affordable, scalable way to quickly judge water quality, package the data, and present it to an authority that can crack down on the polluters before the evidence dissipates. Ideally, the solution would be open source and easy to replicate. The more citizen scientists, the better.

[Andrei Florian]’s WaterAid flows directly from this line of thinking. Dip this small handheld device below the surface, and it quickly takes a bunch of water quality and atmospheric readings, averages them, and sends the data to a web dashboard using an Arduino MKR GSM.

WaterAid judges quality by testing the pH and the turbidity of the water, which gauges the amount of impurities. Commercial turbidity sensors work by measuring the amount of light scattered by the solids present in a liquid, so [Andrei] made a DIY version with an LED pointed at a photocell. WaterAid also reads the air temperature and humidity, and reports its location along with a timestamp.

This device can run in one of two modes, depending on the application. The enterprise mode is designed for a fleet of devices placed strategically about a body of water. In this mode, the devices sample continuously, taking readings every 15 minutes, and can send notifications that trigger on predefined thresholds. There’s also a one-and-done individual mode for hikers and campers who need to find potable water. Once WaterAid takes the readings, the NeoPixel ring provides instant color-coded judgment. Check out the demo after the break.

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Easy-To-Use Music Player Relies On RFID

Microwaves used to be simple to use. Set the dial for the desired time, and hit start. Then, everything went digital and the average microwave now takes between four and six button presses in precise order just to start heating. Music players have gone down a similar path, and those that grew up in the era of vinyl records can find modern digital media simply too hard to work with. To solve this problem, [ananords] whipped up Juuke, a music player focused on ease of use.

The Juuke has a simplistic interface intended to be as easy to use as possible. Songs are selected using printed cards with embedded RFID tags – placing them on the Juuke triggers playback. Volume is controlled with a simple knob, and the only two buttons are for play/pause and shuffle mode.

Underneath, an Arduino Uno runs the show, hooked up to a RC522 RFID interface board. Music is handled by the DFPlayer mini, which loads tracks off a microSD card. The DFPlayer can be hooked up to a speaker directly, but there’s also a 3.5mm jack output if the device is to be used with an external amplifier.

It’s a tidy project, and one that actually looks pretty fun to use. Obviously, there’s some time investment required to prepare the SD card and produce the RFID cards, but the final product could be fun to use at a party, too. We’ve seen similar builds before, as well. Video after the break.

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Impossibilities And 3D Printing

This week our own [Donald Papp] wrote a thought-provoking piece on buying and selling 3D-printer models. His basic point: if you don’t know what you’re getting until you’ve purchased it, and there’s no refund policy, how can you tell if your money is being well spent? It’s a serious problem for these nascent markets, because when customers aren’t satisfied they won’t come back.

It got me thinking about my own experience, albeit with all of the free 3D models out there. They are a supremely mixed bag, and even though you’re not paying for the model, you’re paying in printing time, filament, and effort. It pays to be choosy, and all of [Donald]’s suggestions hold in the “free” market as well.

Failenium Falcon. Image by Johannes

Only download models that have been printed at least once, have decent documentation about things like layer height, filament type, and support, and to the best of your abilities, be critical about the ability to fabricate the part at all. Fused-deposition printers can only print on top of previous layers, and have a distinct grain, so you need to watch out for overhangs and print orientation. With resin printers, you need to be careful about trapped volumes of uncured resin. You want to be sure that the modeler at least took these considerations into account.

But when your parts have strength requirements, fits, and tolerances, it gets even worse. There’s almost no way a designer can know if you’re overextruding on your first layers or not. Different slicers handle corners differently, making inner surfaces shrink to varying degrees. How can the designer work around your particular situation?

My personal answer is open-source. Whenever possible, I prefer models in OpenSCAD. If you download an STL with ten M8 bolt holes, you could widen them all in a modeling program, but if you’ve got the source code, it’s as easy as changing a single variable. Using the source plays to the customizability of 3D printing, which is perhaps its strongest suit, in my mind. Nobody knows exactly how thick your desk is but you, after all. Making a headphone hook that’s customizable is key.

So even if the markets for 3D prints can solve the reliability problems, through customer reviews or requirements of extensive documentation, they’ll never be able to solve the one-size-fits-nobody issue. Open source fixes this easily. Sell me the source, not the STL!

Two Days Left To Enter The Hackaday Prize!

Your entry for the 2020 Hackaday Prize needs to be in by Monday morning, August 31st!

This is the deadline for initial entries, if you’re one of the one hundred lucky projects that advance to the finals you’ll still have another month to polish up your project. Why not make this weekend your own personal hackathon?

Entries focus on four challenges outlined by our non-profit partners this year. From improving modular dome housing and developing manufacturing techniques in disaster zones, to designing interfaces for people with physical challenges and protecting natural ocean landscapes, there’s plenty of room to be creative here. In addition to the $50,000 grand prize there are still nine other top prizes up for grabs.

You can do this. Tell your story, show a proof of concept, and document it to convince the judges your project is viable. It’ll be tight, but hackers work best when deadlines are looming. We can’t wait to see what you come up with between now and Monday!