[Jeri] Builds a Magnetic Loop Antenna

Most new hams quickly learn that the high-frequency bands are where the action is, and getting on the air somewhere between 40- and 160-meters is the way to make those coveted globe-hopping contacts. Trouble is, the easiest antennas to build — horizontal center-fed dipoles — start to claim a lot of real estate at these wavelengths.

So hacker of note and dedicated amateur radio operator [Jeri Ellsworth (AI6TK)] has started a video series devoted to building a magnetic loop antenna for the 160- and 80-meter bands. The first video, included after the break, is an overview of the rationale behind a magnetic loop. It’s not just the length of the dipole that makes them difficult to deploy for these bands; as [Jeri] explains, propagation has a lot to do with dipole height too. [Jeri] covers most of the mechanical aspects of the antenna in the first installment; consuming a 50-foot coil of 3/4″ copper tubing means it won’t be a cheap build, but we’re really looking forward to seeing how it turns out.

We were sorry to hear that castAR, the augmented reality company that [Jeri] co-founded, shut its doors back in June. But if that means we get more great projects like this and guided tours of cool museums to boot, maybe [Jeri]’s loss is our gain?

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Listening for Hand Gestures

[B. Aswinth Raj] wanted to control a VLC player with hand gestures. He turned to two common ultrasonic sensors and Python to do the job. There is also, of course, an Arduino. You can see a video of the results, below.

The Arduino code reads the distance from both sensors — one for the left hand and the other for the right. This allows the device to react to single hand gestures that get closer or further away from one sensor as well as gestures involving both hands. For example, raising your left hand and moving it closer or further away will adjust the volume. The right hand controls rewind and fast forward. Raising both hands will start or stop playback.

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The Internet of Jack-O’-Lanterns

As the candy rush fades, the Halloween hacks continue pouring in. [Jeremy S Cook] has taken a few fundamental concepts and dressed them up inside the smartest pumpkin on the block.

This pumpkin has a WEMOS D1 Mini ESP8266 brain, LED eyes in place of a candle for illumination, and a small USB power bank for power. The code [Cook] is using is a modified sketch by YouTuber [Innovative Tom], which creates a server on your network — don’t forget to insert your network credentials! — that enable control of the LEDs from your computer or smart phone.

[Cook] has wired the LEDs to the relevant pins on the D1 Mini, zip-tied the battery and board together and stuff them in a plastic bag to keep them dry. Stick that into the pumpkin, hot glue the LEDs in place, and test it out!

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Add Intuitiveness to OpenSCAD With Encoders

The first time I saw 3D modeling and 3D printing used practically was at a hack day event. We printed simple plastic struts to hold a couple of spring-loaded wires apart. Nothing revolutionary as far as parts go but it was the moment I realized the value of a printer.

Since then, I have used OpenSCAD because that is what I saw the first time but the intuitiveness of other programs led me to develop the OpenVectorKB which allowed the ubiquitous vectors in OpenSCAD to be changed at will while keeping the parametric qualities of the program, and even leveraging them.

All three values in a vector, X, Y, and Z, are modified by twisting encoder knobs. The device acts as a keyboard to

  1. select the relevant value
  2. replace it with an updated value
  3. refresh the display
  4. move the cursor back to the starting point

There is no software to install and it runs off a Teensy-LC so reprogramming it for other programs is possible in any program where rotary encoders may be useful. Additional modes include a mouse, arrow keys, Audacity editing controls, and VLC time searching.

Here’s an article in favor of OpenSCAD and here’s one against it. This article does a good job of explaining OpenSCAD.

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Hackaday Prize Entry: Volturnus ROV Rules the River

Water is kind of like information: both are a vital part of life and are found all around us. But not all water or information is healthy. Much of it may look harmless, but is actually polluted. A staggering number of people in the world have no access to fresh, clean water. ROVs can collect samples and detect pollution, but commercial types are way too expensive for the legions of people who need them.

UV light reveals the presence of optical brightening agents in a sample of lake water.

[allai5] wants to be the catalyst for change. She’s the president of Rogue Robotics, a group of high school students throughout central New Jersey who have pooled their talents to design and build a simple, open-source ROV that’s affordable, repeatable, and environmentally friendly. The team uses Volturnus ROV to collect water samples and UV light to determine the presence of a general type of pollutant known as optical brightening agents (OBAs). This is the stuff they add to laundry detergents and copy paper to whiten the fibers’ appearance. By design, OBAs fluoresce brightly under UV light. After soaking a cotton pad in water sample, it’s easy to see if OBAs are present.

At 12″ x 12″ x 18″, Volturnus ROV is compact enough to explore most of the nooks and crannies of any body of water. It moves under the power of three thrusters—500 GPH bilge pump motors driven by a pair of L298N controllers—and is controlled by an Arduino Mega using a wireless joystick. The driver of the ROV navigates the drink through the eyes of a waterproof car back-up camera whose feed is flipped with a Python script.

Volturnus ROV is not a one-stop solution for dealing with marine pollution. The team would like to add filtration in the future and move the electronics to the bottom so it can go faster. Rogue Robotics’ aim has always been to make an ROV that does a few things well. Right now, it’s an excellent jumping-off point for awareness and blueprint for action. Find your inspiration after the break.

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Teardown With A Twist: 1975 Sinclair Scientific Calculator

When writing a recent piece about Reverse Polish Notation, or RPN, as a hook for my writing I retrieved my Sinclair Scientific calculator from storage. This was an important model in the genesis of the scientific calculator, not for being either a trailblazer or even for being especially good, but for the interesting manner of its operation and that it was one of the first scientific calculators at an affordable price.

I bought the calculator in a 1980s rummage sale, bodged its broken battery clip to bring it to life, and had it on my bench for a few years. Even in the early 1990s (and even if you didn’t use it), having a retro calculator on your bench gave you a bit of street cred. But then as life moved around me it went into that storage box, and until the RPN article that’s where it stayed. Finding it was a significant task, to locate something about the size of a candy bar in the storage box it had inhabited for two decades, among a slightly chaotic brace of shelves full of similar boxes.

The Sinclair's clean design still looks good four decades later.
The Sinclair’s clean design still looks good four decades later.

Looking at it though as an adult, it becomes obvious that this is an interesting machine in its own right, and one that deserves a closer examination. What follows will not be the only teardown of a Sinclair Scientific on the web, after all nobody could match [Ken Shirriff]’s examination of the internals of its chip, but it should provide an insight into the calculator’s construction, and plenty of satisfying pictures for lovers of 1970s consumer electronics.

The Sinclair is protected by a rigid black plastic case, meaning that it has survived the decades well. On the inside of the case is a crib sheet for its RPN syntax and scientific functions, an invaluable aid when it comes to performing any calculations.

It shares the same external design as the earlier Sinclair Cambridge, a more humble arithmetic calculator, but where the Cambridge’s plastic is black, on the Scientific it is white. The LED display sits behind a purple-tinted window, and the blue-and-black keyboard occupies the lower two-thirds of the front panel. At 50 x 111 x 16 mm it is a true pocket calculator, with an elegance many of its contemporaries failed to achieve and which is certainly not matched by most recent calculators. Good industrial design does not age, and while the Sinclair’s design makes it visibly a product of the early 1970s space-age aesthetic it is nevertheless an attractive item in its own right.

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Friday Hack Chat: Fundamentals Of RF

Designing a system for communication over RF is a dark art. It’s an obscure domain filled with photonmancy, wires going every which way, and imaginary numbers. RF is reserved entirely for wizards. The guy who simplified Maxwell’s equations into the form we now use went literally insane and replaced all the furniture in his house with granite blocks. This is weird stuff, man.

For this week’s Hack Chat, we’re talking about RF. Everything from the capabilities of different bands, how bandwidth is incorporated into designs, different modulation schemes, RF concepts, I/Q, Nyquist, and other deep-dive topics that elucidate the mysteries of the universe and include all the math.

If you’ve ever wondered how bits get turned into radio waves, what all the PSKs and SSBs are all about, and how bandwidth and range of a radio system play into what frequencies are used, this is the Hack Chat for you.

Our guest for this week’s Hack Chat is [Nick Kartsioukas]. He’s an infosec engineer, an amateur radio operator with an Extra license, hardware hacker, plays around with radio and antenna projects, SDR, and he’s an RC pilot. There’s a lot of RF swimming around [Nick], and he’s got the skills to pay the bills.

This is a community Hack Chat, and we’re taking questions from the community. If you have a question or something you’d like to discuss, add it to the sheet.

join-hack-chatOur Hack Chats are live community events on the Hackaday.io Hack Chat group messaging. This Hack Chat is going down noon, PDT, Friday, November 3rd. Do you wish every time zone was UTC? Yeah, it’s a great idea, but when you really think about it, it would be terrible. Here’s a time zone converter!

Click that speech bubble to the left, and you’ll be taken directly to the Hack Chat group on Hackaday.io.

You don’t have to wait until Friday; join whenever you want and you can see what the community is talking about.

We’re also looking for new Hack Chat hosts! If you’ve built something cool, you’re working on an interesting project, or you’re about to introduce a really cool product, hit us up! Email our wonderful community managers, and we’ll see if we can slot you in.