The Vibrating Reed Inverter: Possibly The Simplest Inverter You Can Make

March 29, 2021 by Jenny List 27 Comments

Those of us who work on the road have a constant dread of being stuck somewhere without power, facing a race between a publication deadline and a fast-failing laptop battery. We’re extremely fortunate then to live in an age in which a cheap, lightweight, and efficient solid-state switch-mode inverter can give us mains power from a car cigarette lighter socket and save the day. Before these inverters came much heavier devices whose transistors switched at the 50Hz line speed, and before them came electromechanical devices such as the rotary converter or the vibrating reed inverter. It’s this last type that [Robert Murray-Smith] has taken a look at, making what he positions as the simplest inverter that it’s possible.

If you’ve ever played with relays, you’ll probably be aware that a relay can be wired as a buzzer, and it’s this property that a vibrating reed inverter harnesses. He takes an octal relay and wires it up with a small mains transformer for an immediate and very cheap inverter. It’s not perfect, as he points out the frequency isn’t right. The relay will eventually wear out unless the arcing problem is improved with the addition of a capacitor. But it does make a rough and ready inverter if you find yourself in a MacGyver-style tight spot with only your junk box for salvation.

If inverters pique your interest, it might benefit you to know how they work.

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A Deep Dive Into E-Ink Tag Hacking

March 28, 2021 by Stephen Ogier 7 Comments

Over the last decade or so, e-ink price tags have become more and more ubiquitous, and they’ve now reached the point where surplus devices can be found inexpensively on various websites. [Dmitry Grinberg] found a few of these at bargain-basement prices and decided to reverse engineer and hack them into monochrome digital picture frames.

Often, the most difficult thing about repurposing surplus hardware is the potential lack of documentation. In the two tags [Dmitry] hacked, not only are the labels not documented at all, one even has an almost-undocumented SoC controlling it. After some poking around and some guesswork, he was able to find connections for both a UART and an SWD debugging interface. Fortunately, the manufacturers left the firmware unprotected, so dumping it was trivial.

Even with the firmware dumped, code for controlling peripherals (especially wireless devices) is often inscrutable. [Dmitry] overcomes this with a technique he calls “Librarification” in which he turns the manufacturer’s firmware into libraries for his custom code. Once he was able to implement his custom firmware, [Dmitry] developed his own code to wirelessly download and display both gray-scale and two-color images.

Even if you’re not interested in hacking e-ink tags, this is an incredible walk-through of how to approach reverse-engineering an embedded or IoT device. By hacking two different tags with completely different designs, [Dmitry] shows how to get into these systems with intuition, guesswork, and some sheer persistence.

If you’d like to see some more of [Dmitry]’s excellent reverse-engineering work, take a look at his reverse-engineering and ROM dump of the PokeWalker. If you’re interested in seeing what else e-ink tags can be made to do, take a look at this weather station made from the same 7.4″ e-ink tag.

Archery Release Becomes Reusable Balloon Cutdown Mechanism

March 27, 2021 by Donald Papp 11 Comments

A cutdown in high-altitude balloon (HAB) parlance refers to detaching a payload, and can refer to the act of severing a line or to the mechanism itself. How is this done? The most common way is the “hot wire” method: a segment of wire is heated rapidly with a high current, causing it to melt through something like a nylon line.

But there’s more than one way to solve a problem, and while documenting different cutdown methods, [KI4MCW] found that a caliper-style archery release plus hobby servo could be used as a high strength cutdown mechanism. An archery release (or bow release) is a tool to assist in holding the string of a bow in the drawn position, and cleanly release it at the touch of a lever or button. It occurred to [KI4MCW] that these features might be made to serve as a payload release as well, and you can see here the crude but successful prototype for a reusable cutdown.

The archery release [KI4MCW] obtained opens its jaws when a trigger-style lever on the side is pulled. The force required to trigger this is remarkably low, and a low-torque economical hobby servo easily does the job. In fact, the force needed to trip the release is so low that [KI4MCW] added a short rubber band to provide some opposing tension on the lever, just to be sure no spontaneous triggers occurred. The device hasn’t flown yet, but the prototype looks promising. Maybe a mechanism like this would be appropriate for a payload like dropping a high-altitude RC glider from a balloon.

A Handy Reference For Display Drivers And LCD Controllers

March 20, 2021 by Chris Lott 3 Comments

Ever tried to find the data on a mysterious LCD controller that’s kicking around in your parts bin? Well check out this list of various LCD controllers that [Achim] has put together. He summarizes the basic specifications for each controller and includes data sheet links if available (note — the website is in German, although most of the data itself is in English). All in all, he has collected 72 controllers from five different manufacturers, and 46 of them have data sheets. For each controller, he tabulates maximum resolution, color depth, type of interface, and the targeted display technology. For example, here is the entry for the Ilitech ILI9341 TFT controller commonly found in embedded projects:

Furthermore, many of the controllers also have a short video clip showing them in operation posted over on [Achim]’s YouTube channel, where he also has a bunch of quick (less than one minute) videos of all sorts of embedded goodies. We do find this table of controllers to be a little dated — for example, another popular controller used on small color OLED displays, the Solomon Systech SDS1351, is not included. But it is certainly a good resource to bookmark.

We suspect that [Achim] made this table as a result of developing µGUI, a small (only three files) C-language graphics library (see the GitHub repository) he released back in 2015. Do you have any good resources for tracking down unknown LCD controllers? If so, share in the comments below. And thanks to [Dmitry] for sending in this tip.

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Injecting Bugs With An Electric Flyswatter

March 15, 2021 by Stephen Ogier 9 Comments

Hardware fault injection uses electrical manipulation of a digital circuit to intentionally introduce errors, which can be used to cause processors to behave in unpredictable ways. This unintentional behavior can be used to test for reliability, or it can be used for more nefarious purposes such as accessing code and data that was intended to be inaccessible. There are a few ways to accomplish this, and electromagnetic fault injection uses a localized electromagnetic pulse to flip bits inside a processor. The pulse induces a voltage in the processor’s circuits, causing bits to flip and often leading to unintentional behavior. The hardware to do this is very specialized, but [Pedro Javier] managed to hack a $4 electric flyswatter into an electromagnetic fault injection tool. (Page may be dead, try the Internet Archive version.)

[Pedro] accomplishes this by turning an electric flyswatter into a spark-gap triggered EMP generator. He removes the business end of the flyswatter and replaces it with a hand-wound inductor in series with a small spark gap. Pressing the power button on the modified flyswatter charges up the output capacitor until the developed voltage is enough to ionize the air in the spark gap, at which point the capacitor discharges through the inductor. The size of the spark gap determines the charge that is built up—a larger gap results in a larger charge, which produces a larger pulse, which induces a larger voltage in the chip.

[Pedro] demonstrates how this can be used to produce arithmetic glitches and even induce an Arduino to dump its memory. Others have used electromagnetic fault injection to corrupt SRAM, and intentionally glitching the power supply pins can also be used to access otherwise protected data.

Reverse Engineering The Weather Channel’s Magic

March 14, 2021 by Tom Nardi 32 Comments

For American readers of a certain age, Local on the 8s likely holds a special spot in your heart. The program, once a staple of The Weather Channel, would provide viewers with a text and eventually graphical depiction of their local forecast set to some of the greatest smooth jazz ever heard outside of an elevator. In the days before smartphones, or even regular Internet access for that matter, these broadcasts were a critical part of planning your day in the 1980s through to the early 2000s.

Up until recently the technical details behind these iconic weather reports were largely unknown, but thanks to the Herculean efforts of [techknight], the fascinating engineering that went into the WeatherSTAR 4000 machines that pumped out current conditions and Shakin’ The Shack from CATV distribution centers all over the US for decades is now being documented and preserved. The process of reversing the hardware and software has actually been going on for the last couple of years, but all those juicy details are now finally going to be available on the project’s Hackaday.IO page.

It all started around Christmas of 2018, when an eBay alert [techknight] had configured for the WeatherSTAR 4000 finally fired off. His offer was accepted, and soon he had the physical manifestation of Local on the 8s in his own hands. He’d reasoned that getting the Motorola MC68010 machine working would be like poking around in a retrocomputer, but it didn’t take long for him to realize he’d gotten himself into a much larger project than he could ever have imagined.

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Keep Cool With This Open Source AVR Fan Controller

March 12, 2021 by Tom Nardi 12 Comments

We’ve all got projects kicking around that we haven’t had time to document for our own purposes, let alone expose to the blinding light of the Internet. There are only so many hours in a day, and let’s face it, building the thing is a lot more fun than taking pictures of it. It took [Matthew Millman] the better part of a decade to combine everything he’s learned over the years to finally document the definitive version of his open source intelligent fan controller, but looking at the final result, we’re glad he did.

At the heart of this board is an ATmega328P, but don’t call it an Arduino. [Matthew] makes it very clear that if you want to hack around with the code for this project, you’re going to need to not only have a programmer for said chip, but know your way around AVR-GCC. He’s provided pre-built binaries for those content to run with the default settings, but you’ve still got to get it flashed onto the chip yourself. The project is designed to use the common DS18B20 temperature sensor, and as an added bonus, the firmware can even check if yours is a bootleg (spoilers: there’s an excellent chance it is).

Arguably the most interesting feature of this fan controller is its command line interface. Just plug into the serial port on the board, open your terminal emulator, and you’ll have access to a concise set of functions for querying the sensors as well as setting temperature thresholds and RPM ranges for the fans. There’s even a built-in “help” function should you forget a command or the appropriate syntax.

Originally [Matthew] developed this project as a way to control multiple fans inside of a PC case, but naturally, things have changed quite a bit since those early days. While today there’s no shortage of fancy controllers that can handle throttling an array of fans based on the internal temperature of your rig, there’s still something to be said for rolling your own solution. More importantly, there’s certainly other potential uses for a fully open source programmable fan controller.