Scratch That SDR!

When you think of a software defined radio, what language might you consider reaching for to create the software part of the equation? C? C++, maybe?

How about Scratch?

“What, Scratch as in the visual programming language aimed at young people?”, we hear you cry incredulously. It’s not exactly the answer you’d expect for an SDR, but thanks to [Andrew Back]’s work there is now ScratchRadio, a set of Scratch extensions for software defined radio. Why on earth do this? The aim is to lower the barrier to entry for software defined radio as far as possible, and to place it in a learning environment such as Scratch seems an ideal way to achieve that.

Of course, Scratch itself isn’t powerful enough for the heaviest of heavy lifting, so in reality this is a Scratch wrapper for a LuaRadio backend. It was created with the LimeSDR Mini in mind, but given that LuaRadio is not specific to that hardware we’d expect it to work with other SDRs such as the ever-popular RTL chipset TV sticks. It gives an owner of a Raspberry Pi 3 the ability to experiment with SDR coding without the need for a huge level of experience, and that to our mind can only be a good thing.

If you fancy trying ScratchRadio, you can find the code in its GitHub repository, and take it from there. Meanwhile we covered LuaRadio last year, so if Scratch is a little basic for you and GNU Radio too advanced, give it a try.

Radio icon: [Sakurambo], (CC BY-SA 3.0).

Scratch cat logo: MIT Media Lab.

Water Slide + Ferris Wheel = SlideWheel

This might be German engineering at its funnest. [Wiegand Maelzer GmbH] have created a new type of amusement park ride that combines the thrill of a water slide with the gentle revolutions of a Ferris wheel.

Inspired by the wish of a young Swiss boy in 2012, the whimsical feat of engineering known as the SlideWheel was realized this year. This is isn’t quite the giant sloshing drowning machine it appears to be on first blush, though. It begins and ends at the same shallow pool, where three- and four-person rafts are lifted into the ride by conveyor belt. What happens next is difficult to describe. It’s easier just to watch the first-person video below that demonstrates the pendulum-like motion that comes from floating while rotating.

SlideWheel moves at a modest 3 RPM, though this can be adjusted. Travel speed through the tube maxes out at 40 KPH/ 25 MPH, but will vary depending on the raft’s location, the position of the wheel, and gravity. The ride can handle up to three rafts at a time and delight 720 people per hour. A trip through the tube lasts a mere two minutes, but all those who’ve tried it say the experience seems much longer.¬†[Wiegand Maelzer] have already received a few orders and are working on a dry version for malls and indoor amusement parks.

Not enough of an engineering feat, you say? Here’s a car-juggling robot.

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Hackaday Links: ūüĎĽ ūüéÉ Spooky Edition, 2017

A few links posts ago, we wrote something about a company selling huge LED panels on eBay, ten panels for $50. Those panels are gone now, but a few lucky hackers got their hands on some cool hardware. Now there’s a project to reverse engineer these Barco NX-4 LED panels. Who’s going to be the first to figure out how to drive these things? Doesn’t matter — it’s a group project and we’re all made richer by the contributions of others.

Prague is getting a new hackerspace.

A year and a half ago, a $79 3D printer popped up on Kickstarter. I said I¬†would eat a hat if it shipped by next year. Seeing as how it’s basically November, and they’re not selling a $79 printer anymore — it’s $99 — this might go down as one of my rare defeats, with an asterisk, of course. I’m going to go source some very large fruit roll-ups and do this at Supercon. Thanks, [Larry].

Speaking of bets, this week Amazon introduced the most idiotic thing ever invented. It’s called Amazon Key. It’s an electronic lock (dumb), connected to the Internet (dumber), so you let strangers into your house to deliver packages (dumbest). CCC is in a few months, so I don’t know if Amazon Key will be hacked by then, but I’m pretty confident this will be broken by March.

The Lulzbot Taz is one of the best printers on the market, and it is exceptionally Open Source. The Taz is also a great printer for low-volume production. It was only a matter of time until someone built this. The Twoolhead is a parallel extruder for the Taz 6. Instead of one extruder and nozzle, it’s two, and instead of printing one object at a time, it prints two. Of course it limits the build volume of the printer, but if you need smaller parts faster, this is the way to go.

Hey, did you hear? Hackaday is having a conference the weekend after next. This year, we’re opening up the doors a day early and having a party at the Evil Overlord’s offices. Tickets are free for Supercon attendees, so register here.

At CES this year, we caught wind of one of the coolest advances in backyard astronomy in decades. The eVscope¬†is ‘astrophotography in the eyepiece’, and it’s basically a CCD, a ton of magic image processing, and a small display, all mounted inside a telescope. Point the scope at a nebula, and instead of seeing a blurry smudge, you’ll see tendrils¬†and filaments of interstellar gas in almost real-time. Now the eVscope¬†is on Kickstarter. It’s a 4.5 inch almost-Newtonian (the eyepiece is decoupled from the light path, so I don’t even know how telescope nomenclature works in this case), an OLED display, and a 10-hour battery life.

Is the fidget spinner fad over? Oh, we hope not. A technology is only perfected after it has been made obsolete. Case in point? We can play phonographs with lasers. The internal combustion engine will be obsolete in automobiles in twenty years, but track times will continue going down for forty. Fidget spinners may be dead, but now you can program them with JavaScript. What a time to be alive!

Audio tomphoolery¬†even an idiot tech blogger can see through! I received¬†a press kit for a USB DAC this week that included the line, “…low drop out voltage regulators running at 3.3 V, meaning the 5 V USB limit is well preserved.” Yes, because you’re running your system at 3.3 V, you won’t draw too much current from a USB port. That’s how it works, right?

[Peter Sripol] is building an ultralight in his basement. The last few weeks of his YouTube channel have been the must-watch videos of the season. He’s glassed the wings, installed all the hardware (correctly), and now he has the motors and props mounted. This is an electric ultralight, so he’s using a pair of ‘150 cc’ motors from HobbyKing. No, that’s not displacement, it’s just a replacement for a 150 cc gas engine. On a few YouTube Live streams, [Peter] did what was effectively a high-speed taxi test that got out of hand. It flew. Doing that at night was probably not the best idea, but we’re looking forward to the videos of the flight tests.

Magnetic Tape Storage May Not be Retro

Magnetic storage is quickly becoming an antiquated technology but IBM may have given it a few more years. Currently, magnetic storage is still manufactured as hard disk drives (HDDs) but you won’t find a tape drive in a modern consumer computer. That’s not likely to change but IBM is pushing the envelope to make a tape drive that will be smaller and more economical than other massive storage options. In many ways, they’re the antithesis of solid state drives (SSDs) because tape drives are slow to retrieve data but capable of holding a lot inexpensively.

Three advances are responsible for this surge in capacity. Firstly, the tape ‚Äúgrains,‚ÄĚ where each bit is recorded, have been shrunk by sputtering metal to a film instead of painting it on. Secondly, better servo control allows the reading mechanisms to read those tiny grains with the necessary accuracy. Lastly, stronger computation is used to read the data by using error detection and correction because when your tape is traveling four meters per second, it takes a long time to go back and double-check something.

IBM’s tape drive won’t replace your hard drive but it could back it up daily, many times over.

Check this out if your wetware needs a memory boost or this if your breakfast needs a memory boost.

Immersive VR with a 200-Degree Stereoscopic Camera

VR is in vogue, but getting on board requires a steep upfront cost. Hackaday.io user [Colin Pate] felt that $800 was a bit much for even the cheapest commercial 360-degree 3D camera, so he thought: ‘why not make my own for half that price?’

[Pate] knew he’d need a lot of bandwidth and many GPIO ports for the camera array, so he searched out the Altera Cyclone V SOC FPGA and a Terasic DE10-Nano development board to host it. At present, he has four Uctronics OV5642 cameras on his rig, chosen for their extensive documentation and support. The camera mount itself is a 3D-printed octagon so eight of the OC5642 can capture a full 360-degree photo.

Next: producing an image!

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Hi-Res, Body-Sized Pressure Sensor Mat

Hackers often find uses for pressure sensitive materials, detecting footfalls during walking or keypresses in a synthesizer being two examples. [Marco Reps] decided he’d make a hi-res, body-sized pressure sensitive mat mainly for computer-guided physiotherapy, though he wouldn’t rule out using it for gaming (twister anyone?). That meant making the equivalent of a body-sized matrix circuit of around 7000 sensors, as well as a circuit board with a multitude of shift registers. The result has a surprisingly good resolution, capable of making clearly distinguishable the heel, arch and front part of a foot.

His choice of pressure sensitive material was¬†Velostat, a polymeric foam available as large sheets. The foam is impregnated with carbon black to make it electrically conductive, but being a foam, its resistance changes when pressure is applied. The first layer of the mat is made up of one centimeter wide strips of copper tape laid out lengthwise and spaced one centimeter apart. That’s followed by the Velostat and then another layer of copper tape oriented horizontally this time. The pressure sensors are the sandwiches formed by where the tapes overlap. In the first video below he shows how he measured and graphed the Velostat’s dynamic range to help decide to use one centimeter squares. He also puts together a smaller prototype, with good results.

Testing the mat
Testing the mat

For the body-sized mat, we count around 50 by 140 overlapping areas for a total of around 7000 one square centimeter sensors. And of course to measure each sensor in that large matrix, as you can imagine, he made up a custom circuit board with shift registers. The board works by applying positive voltage to the columns one-by-one, while each time going through all the rows and reading their voltages. Making the board was in itself was an adventure, taking a chance on a Chinese manufacturer asking only $2. But watch the second video below where he evaluates the result, including trying unsuccessfully to delaminate a board. Sadly he forgot to include places on the board for diodes, one for each column, and fixing that is another adventure he walks us through. Patience was definitely a prerequisite here, not only for making the mat, and fixing the diode problem, but also for connecting up 96-pin ribbon cables. We applaud his efforts, and his results. Check out the second video below for the making of the large mat and the circuit board.

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Junkbox Freezer Alarm Keeps Steaks Safe

A fully stocked freezer can be a blessing, but it’s also a disaster waiting to happen. Depending on your tastes, there could be hundreds of dollars worth of food in there, and the only thing between it and the landfill is an uninterrupted supply of electricity. Keep the freezer in an out-of-the-way spot and your food is at even greater risk.

Mitigating that risk is the job of this junkbox¬†power failure alarm.¬†[Derek]’s freezer is in the garage, where GFCI outlets are mandated by code. We’ve covered circuit protection before, including GFCIs, and while they can save a life, they can also trip accidentally and cost you your steaks. [Derek] whipped up a simple alarm based on current flow to the freezer. A home-brew current transformer made from a split ferrite core and some magnet wire is the sensor, and a couple of op-amps and a 555 timer make up the detection and alarm part. And it’s all junk bin stuff — get a load of that Mallory Sonalert from 1983!

Granted, loss of power on a branch circuit is probably one of the less likely failure modes for a freezer, but the principles are generally applicable and worth knowing. And hats off to [Derek] for eschewing the microcontroller and rolling this old school. Not that there’s anything wrong with IoT fridge and freezer alarms.

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