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Learn About Blockchains By Building One

23 November, by Jenny List[ —]

What do we curious Hackaday scribes do when we want to learn about something? First port of call: search the web.

When that something is blockchain technology and we’re looking for an explanation that expands our cursory overview into a more fundamental understanding of the basic principles, there is a problem. It seems that to most people blockchains equate to one thing: cryptocurrencies, and since cryptocurrencies mean MONEY, they then descend into a cultish frenzy surrounded by a little cloud of flying dollar signs. Finding [Daniel van Flymen]’s explanation of the fundamentals of a blockchain in terms of the creation of a simple example chain using Python was thus a breath of fresh air, and provided the required education. Even if he does start the piece by assuming that the reader is yet another cryptocurrency wonk.

We start by creating a simple class to hold all the Python functions, then we are shown a single block. In his example it’s a JSON object, and it contains the payload in the form of a transaction record along with the required proof-of-work and hash. We’re then taken through a very simple proof-of-work algorithm, before being shown how the whole can be implemented as very simple endpoints.

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You are not going to launch a cryptocurrency using this code, and indeed that wasn’t our purpose in seeking it out. But if you are curious about the mechanics of a blockchain and are equally tired of evangelists of The Blockchain who claim it will cure all ills but can’t explain it in layman’s terms, then this relatively simple example is for you.

The wrong way to build a blockchain image: Jenny List. #FarmLife.

Filed under: Software Hacks

Functioning Technic SLJ900 Bridge Builder

23 November, by John Baichtal[ —]

There is definitely a passion for detail and accuracy among LEGO builders who re-create recognizable real-world elements such as specific car models and famous buildings. However, Technic builders take it to a level the regular AFOLs cannot: Not only must their model look like the original, it has to function the same way. Case in point, [Wolf Zipp]’s version of a massive bridge-building rig. The Chinese-built SLJ900 rolls along the tops of bridges and adds ginormous concrete spans with the aplomb found only in sped-up YouTube videos. It is nevertheless a badass robot and a worthy target for Technicization.

[Wolf]’s model is 2 meters long and weighs 10.5kg, consisting of 13 LEGO motors and a pneumatic rig, all run by a handheld control box. The rig inserts LEGO connectors to a simulated bridge span, lifts it up, moves it over the next pier, then drops it down into place. The span weighs 2.5kg by itself — that ain’t no styrofoam! There are a lot of cool details in the project. For instance, the mechanism that turns the wheels for lateral movement consists of a LEGO-built pneumatic compressor that trips pneumatic actuators that lift the wheels off the ground and allows them to turn 90 degrees.

Sometimes it blows the mind what can be built with Technic. Check out this rope-braiding machine and this 7-segment display we’ve posted.

Filed under: Toy Hacks

Teardown Of A Cheap Glue Gun

23 November, by Jenny List[ —]

A hot glue gun is one of those standard tools of the hardware hacker’s bench, called upon to provide adhesion between an astonishing range of materials, and to provide a handy filler and strain relief in the form of blobs of polymer glue. We’ve all got one, but how many of us have taken a look inside it?

[Andrew Lorimer] bought a super-cheap eBay glue gun, and subjected it to a teardown. As you might expect, he found it to be a pretty simple device with only a trigger mechanism and a dumb heating element, but his write-up is of passing interest because he’s characterised its heating element. It has a positive temperature coefficient, which means that its resistance increases from around 2.5 kΩ at room temperature to about 7 kΩ at its 150 ºC operating temperature. This limits the current, and provides a very simple thermostat action.

The build quality is surprisingly good for such a cheap appliance, and he notes a surfeit of screws holding its shell together. But the quality of the insulation and strain relief leaves a lot to be desired, and he wonders whether it truly qualifies for its double-insulated logo. The LED pilot light is simply fed from the 240 V mains supply through a 250 kΩ resistor which he replaces with a 12 kΩ component for a brighter result.

We cover plenty of teardowns here at Hackaday. Often they are of extremely expensive and complex devices, but sometimes they are of much simpler subjects.

Filed under: Teardown

Digital Panel Meter Tear Down

23 November, by Al Williams[ —]

[Big Clive] had some 22mm digital AC voltmeters, made to put in a panel. There was a time when this would have been a significant pain, since it required you to make a large square hole. Of course, in a world of CNC and 3D printers that isn’t as big a deal as it used to be, but the ones [Clive] has are nice because having a round footprint you can drill a hole for them with a hole saw or a stepped bit. Of course, he wasn’t satisfied to just use these inexpensive meters. He had to tear one apart to look inside. You can see his review and teardown in the video below. The meters are available in a range of AC voltages, although [Clive] didn’t think the ones he had would safely handle their rated maximum.

Inside, the modules reminded us of cordwood construction in a way. Most of the electronics are on a small round board. But several components connect to the board and the bottom cap in a vertical orientation. The meters are available in several colors, but [Clive] likes the red ones as they appear brighter than the others. The voltage reading compared favorably to a Fluke meter.

The verdict is that for the price (under $2 from China; a little more in the US) they are handy, but you might not want to consider running significant voltage through them. You could use these instead of pilot lights and get the voltage reading for free. We were surprised that someone doesn’t make a DC version in the same form factor, at least if they do, we couldn’t find it. If you don’t mind drilling the square hole and letting a bezel cover your sins, you could use a universal meter with an Arduino instead for many applications.

Filed under: Teardown

Trinket Chills Your Drinks

22 November, by Rich Hawkes[ —]

Who wants warm drinks? Well, coffee drinkers, we guess. Other than them, who wants warm drinks? Tea drinkers, sure. How about room temperature drinks? No one, that’s who. It’s silly to buy a refrigerator to cool down a single drink, so what option are you left with? Ice cubes? They’ll dilute your drink. Ice packs and a cooler? Sure, they’ll keep your drinks cold, but they’re hardly cool are they? No, if you want a cold drink the cool way, you build a thermoelectric cooler. And if you want to build one, you’re in luck, because [John Park] has a tutorial to do just that up on AdaFruit.

The parts list includes an AdaFruit Trinket M0, a more powerful version of AdaFruit’s Trinket line. The Trinket is used to control the main part in this build, a Peltier thermoelectric cooler, as well as the temperature display and switches. The other part controlled by the microcontroller is a peristaltic pump, which is used to do the dispensing of the liquid. The code to control everything is written in Python as the Trinket M0 comes with AdaFruit’s CircuitPython by default. Also included in the tutorial are the files for the stand, should you want to 3D print it or cut it with a CNC or laser cutter.

After the break, you can watch as [John] goes over the project and builds it, or go to the AdaFruit website and follow the instructions to build your own. As [John] says, there might be better ways to chill your drinks, but this is “definitely one of the more science-y and interesting ones.” For more projects using the Peltier Effect, try this one that uses the effect in sous-vide cooking, or this one, a Peltier cooled micro-fridge!

Filed under: hardware

A Passion for the Best is in Mechanical Keyboards

22 November, by Brian Benchoff[ —]

There is an entire subculture of people fascinated by computer keyboards. While the majority of the population is content with whatever keyboard came with their computer or is supplied by their employer — usually the bottom basement squishy membrane keyboards — there are a small group of keyboard enthusiasts diving into custom keycaps, switch mods, diode matrices, and full-blown ground-up creations.

Ariane Nazemi is one of these mechanical keyboard enthusiasts. At the 2017 Hackaday Superconference, he quite literally lugged out a Compaq with its beautiful brominated keycaps, and brought out the IBM Model M buckling spring keyboard.

Inspired by these beautiful tools of wordcraft, [Ariane] set out to build his own mechanical keyboard and came up with something amazing. It’s the Dark Matter keyboard, a custom, split, ergonomic, staggered-columnar, RGB backlit mechanical keyboard, and at the 2017 Hackaday Superconference, he told everyone how and why he made it.

A rubber dome keyboard. The only spring pressure comes from a sheet of rubber

Ninety-nine percent of the keyboards you’ll ever see are crappy rubber dome keyboards. This is a specific type of switch, made with two contacts on a PCB, a sheet of rubber with a bunch of little bubbles in it, and a conductive foam pad mounted to the bottom of a key. The keys get their springiness from these rubber domes, and when a key is pressed it smashes into the PCB contacts, closing a circuit.

It’s certainly an inexpensive way to build a keyboard, but compared to a true mechanical switch it feels like crap. The key doesn’t activate until it hits bottom, and the lifetime of each of these switches is measured in the tens of thousands of cycles instead of the millions of cycles a mechanical keyswitch can handle.

The Cherry MX Blue keyswitch

On the other end of the spectrum is a mechanical keyswitch, best represented by the Cherry MX switch; a make and model of switch, with clones also built by Gateron and Kailh. These switches use actual springs and bits of brass to close a switch and they provide tactile feedback to the typist. There are even different varieties of MX-style switch; the ones with red stems are almost linear in their feedback, while browns, clears, and blues have a little bit of resistance in the middle of the key’s travel. The blues are clicky and are somehow even louder than the buckling springs found in the IBM Model M. They sound like a machine gun, and it’s awesome.

An entire community has grown up around putting these MX-style switches into custom designed enclosures for the perfect typing experience. There are innovations in ergonomics like columnar spacing, where the Q, A, and Z keys are in a straight line. There are split keyboards, where the left and right side of the keyboard are attached by a cable. Ariane decided he wanted the ultimate keyboard. It would be a split keyboard, and it should have a columnar layout. Because he’s part of the Hackaday crowd, this keyboard must have a ton of blinkies. This led to the creation of the Dark Matter keyboard, one of the most technologically impressive keyboards we’ve seen in a long time.

Like a lot of mechanical keyboard projects, Ariane is using a Teensy as the controller for each half of his keyboard. Unlike most mechanical keyboard projects, Ariane is using the Teensy LC, the cost-reduced version of this family of dev boards. Until very recently, the most popular firmwares for keyboards haven’t been brought over to the Teensy LC. Ariane did just that, and added support for driving WS2812 RGB LEDs. Combine this with an MX-compatible keyswitch with a clear housing and some polycarbonate keycaps, and Ariane made the blinkiest keyboard you’ve ever seen that doesn’t have individual OLED displays embedded in each keycap.

Ariane’s talk is a wealth of information on how to manufacture keyboards, from firmware and software development to how to build an enclosure. Keyboards are a surprisingly popular side topic in our little niche here on Hackaday, and we’re pleased Ariane could give this talk and extol the virtues of mechanical keyboards.

Filed under: cons, Hackaday Columns

Radio Apocalypse: The GWEN System

22 November, by Dan Maloney[ —]

Recent developments on the world political stage have brought the destructive potential of electromagnetic pulses (EMP) to the fore, and people seem to have internalized the threat posed by a single thermonuclear weapon. It’s common knowledge that one bomb deployed at a high enough altitude can cause a rapid and powerful pulse of electrical and magnetic fields capable of destroying everything electrical on the ground below, sending civilization back to the 1800s in the blink of an eye.

Things are rarely as simple as the media portray, of course, and this is especially true when a phenomenon with complex physics is involved. But even in the early days of the Atomic Age, the destructive potential of EMP was understood, and allowances for it were made in designing strategic systems. Nowhere else was EMP more of a threat than to the complex web of communication systems linking far-flung strategic assets with central command and control apparatus. In the United States, one of the many hardened communications networks was dubbed the Groundwave Emergency Network, or GWEN, and the story of its fairly rapid rise and fall is an interesting case study in how nations mount technical responses to threats, both real and perceived.

Reliability Through Physics

GWEN began as a patch for a perceived gap in the communications network connecting the country’s strategic nuclear assets — primarily the launch control centers (LCC) of the ballistic missile launch facilities — to the National Command Authority, which is basically the president. Like all strategic communications systems, GWEN was designed to incorporate best practices for surviving the electromagnetic effects of an EMP. But GWEN had another mission.

Ground wave propagation. Source: Electronics Notes

Groundwave propagation is the tendency of certain radio waves to hug the surface and follow the curvature of the earth and is an exception to the general rule that radio waves only travel in straight lines. The earth acts as a conductor below 5 MHz, so radio waves traveling along the surface of the earth induce currents. The induced currents slow down propagation near the surface, curving the wavefront down as it spreads out. There is considerable attenuation of the signal, of course, and careful consideration has to be given to antenna design and construction. But when properly engineered, ground wave propagation systems can be very effective at over-the-horizon communications that do not rely on the ionosphere.

Groundwave propagation requires long wavelengths to work, so GWEN operated in the low frequency (LF) band from 150 to 175 kHz, well below the commercial AM radio medium frequency (MF) band from 530 to 1700 kHz.

GWEN Nodes

A GWEN relay node. Source: Wikipedia, public domain.

GWEN was envisioned as a wide area network of LF relay nodes about 150 to 200 miles apart. Each GWEN relay node communicated to input-output nodes, which were generally located at Air Force bases and other such facilities. The relay nodes were to take command and control messages from the IO nodes and propagate them over the entire network until they reached receive-only nodes, typically the LCC bases. GWEN encoded messages on the LF signals using minimum-shift keying at a data rate of 1200 bps. Messages were encrypted, of course.

Only about 58 of the planned 240 GWEN stations were built between 1982 and the early 1990s, when the program was shut down. GWEN was mostly a victim of Congress, who were unwilling to fund what they perceived to be a Cold War relic after the fall of the Soviet Union. There was also a certain amount of NIMBY-ism with regard to future GWEN sites; with the increasingly popular perception that everything from power lines to cell towers were capable of causing profound biological effects, the prospects of having a powerful radio transmitter that would also be a possible war target in the neighborhood was more than enough reason to mothball the program.

By that time, GWEN’s technology was certainly looking a little long in the tooth anyway, with the rise of the Internet and the proliferation of satellite communications. This may prove shortsighted, though; while there’s certainly a lot of redundancy built into today’s strategic communication systems, there’s something to be said for a simple and robust system that uses basic physical principle like GWEN did.

Filed under: Featured, History, Original Art, Wireless Hacks

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