Hacking Transmitters, 1920s Style

November 28, 2019 by Sharon Lin 9 Comments

The origin of the term “breadboard” comes from an amusing past when wooden bread boards were swiped from kitchens and used as a canvas for radio hobbyists to roll homemade capacitors, inductors, and switches. At a period when commercial electronic components were limited, anything within reach was fair game.

[Andy Flowers], call sign K0SM, recently recreated some early transmitters using the same resources and techniques from the 1920s for the Bruce Kelley 1929 QSO Party. The style of the transmitters are based on [Ralph Hartley]’s oscillator circuit built for Bell Telephone in 1915. Most of the components he uses are from the time period, and one of the tubes he uses is even one of four tubes from the first Transatlantic contact in 1923.

Apart from vacuum tubes (which could be purchased) and meters (which could be scrounged from automobiles) [Flowers] recreated his own ferrite plate and outlet condensers for tuning the antennas. The spiderweb coils may not be as common today, but can be found in older Crosley receivers and use less wire than comparable cylindrical coils.

A number of others features of the transmitters also evoke period nostalgia. The coupling to the antenna can be changed using movable glass rods, although without shielding there are quite a number of factors to account for. A vertical panel in the 1920s style also shows measurements from the filament, plate current, and antenna coupling.

While amature radio has become increasingly high-tech over the last few years, it’s always good to see dedicated individuals keeping the old ways alive; no matter what kind of technology they’re interested in.

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A Python Serial Terminal To Get You Out Of A Jam

November 28, 2019 by Tom Nardi 21 Comments

When fiddling around with old computers, you can occasionally find yourself in a sticky situation. What may be a simple task with today’s hardware and software can be nearly impossible given the limited resources available to machines with 20 or 30 years on the clock. That’s where [bison] recently found himself when he needed to configure a device over serial, but didn’t have any way of installing the appropriate terminal emulator on his Fujitsu Lifebook C34S.

His solution, since he had Python 2.6 installed on the Debian 6 machine, was to write his own minimal serial terminal emulator. He intended for the code to be as terse as possible so it could be quickly typed in, should anyone else ever find themselves in need of talking to a serial device on Linux but can’t get screen or minicom installed.

The code is very simple, and even if you never find yourself needing to fire up an impromptu terminal, it offers an interesting example of how straightforward serial communications really are. The code opens up the /dev/ttyS0 device for reading, and after appending the appropriate return character, pushes the user’s keyboard input into it. Keep looping around, and you’ve got yourself an interactive terminal.

With this program written, [bison] was able to connect the 266 MHz C34S to his Retro WiFi SI, a modem adapter that bridges the gap between a vintage computer and modern wireless network. Gadgets like these allow you to browse BBSes as the creator intended, and can be fashioned with nothing more exotic than an ESP8266 running some open source code.

Progressive Or Thrash? How Metal Detectors Discriminate

November 26, 2019 by Kristina Panos 37 Comments

Metal detecting is a fun pastime, even when all you can find is a little bit of peace and a whole lot of pop tabs. [Huygens Optics] has a VLF-based metal detector that offers much more feedback than just a beep or no beep. This thing is fancy enough to discriminate between types of metal and report back a numerical ID value from a corresponding range of conductivity.

Most pop tabs rated an ID of 76 or 77, so [Huygens Optics] started ignoring these until the day he found a platinum wedding band without looking at the ID readout. Turns out, the ring registered in the throwaway range. Now thoroughly intrigued by the detector’s ID system, [Huygens Optics] set up a test rig with an oscilloscope to see for himself how the thing was telling different metals apart. His valuable and sweeping video walk-through is hiding after the break.

A Very Low-Frequency (VLF) detector uses two coils, one to emit and one to receive. They are overlapped just enough so that the reception coil can’t see the emission coil’s magnetic field. This frees up the reception coil’s magnetic field to be interrupted only by third-party metal, i.e. hidden treasures in the ground.

Once [Huygens Optics] determined which coil was which, he started passing metal objects near the reception coil to see what happened on the ‘scope. Depending on the material type and the size and shape of the object, the waveform it produced showed a shift in phase from the emission coil’s waveform. This is pretty much directly translated to the ID readout — the higher the phase shift value, the higher the ID value.

We’ve picked up DIY metal detectors of all sizes over the years, but this one is the ATtiny-ist.

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Cardboard Computer Replica Is Cheap And Easy To Make

November 22, 2019 by Lewin Day 10 Comments

Replicating 1960s-era computer hardware can be a daunting task. Components can be hard to find, schematics thin on the ground, and software near-unobtainable. Of course, not every computer from the decade consisted of expensive high-end electronics – CARDIAC was built out of common cardboard, and making your own is a cinch!

CARDIAC stood for Cardboard Illustrative Aid To Computation. Consisting of a series of sliding cardboard parts, it acted as a basic guide to the principles of computation. Through the use of a pencil and the associated guidebook, students could run simple programs to learn how to program computers at the barebones level.

Finding the paper-based computational learning tool highly valuable in their youth, [megardi] wanted to bring it back for a new audience. Thankfully, there are plenty of resources on the web that made it easy to whip up art files to reprint the device. [megardi] then also wrote up the instructions on how to accurately reproduce a CARDIAC, with helpful tips on how to best put it together. For a quick test, any old paper will do, while using 110 g cardstock and a laminator makes a sturdier build that can be used with dry-erase markers.

CARDIAC remains an excellent tool for teaching the basics of Von Neumann architecture computing. We’ve discussed similar teaching tools before, too – from the days when “real” computers were too expensive to let students anywhere near them. How times change!

Time Sync Through Your VGA Connector

November 10, 2019 by Jenny List 16 Comments

While it might be in its twilight years, the venerable VGA video connector conceals a versatile interface that can still provide the experimenter with the opportunity for a variety of hacks. We’ve not seen anything quite like [flok]’s one, in which he uses the VGA interface to insert timing information from which an NTPd instance gets its reference.

If this seems counter-intuitive because a VGA interface is an analogue output rather than a digital input, then you are correct to smell a rat. And he comes clean in his first sentence, as he’s not using the VGA lines themselves but the I²C interface that is a feature of all but the most basic of VGA cards. This is the means by which a plug-and-play operating system can identify a monitor’s capabilities, but there’s little to stop it being used for other purposes. In this case an Arduino fed by a 1-pulse-per-second timing signal from a temperature compensated crystal oscillator provides the I²C peripheral which is polled by NTPd.

This project should be of interest to any tinkerer because of its invaluable information on identifying and using the I²C interface on a VGA socket. So if you’ve used your VGA card as an SDR you might find it interesting, but hurry or you could have missed the boat entirely.

VGA plug image: Swift.Hg [CC BY-SA 3.0]

Projector And NES Mini Hide Out Inside The Real Thing

November 5, 2019 by Tom Nardi 5 Comments

Taking a page out of the Xzibit Engineering Handbook, [Geeksmithing] recently decided that the gutted carcass of an original Nintendo Entertainment System would make a perfect home for…a smaller NES. Well, that and two wireless controllers. Plus a projector. Oh, and batteries so it can be used on the go. Because really, at that point, why not?

The video after the break starts with a cleverly edited version of a legitimate NES commercial from the gaming glory days of the 1980s, and segues into an rundown of all the modern hardware [Geeksmithing] crammed into the case of this legendary console. It helps that the official NES Classic used for the project is so much smaller than its more than thirty year old predecessor, leaving plenty of room inside to get creative. We particularly like the dual wireless controllers which are conveniently hiding inside the original cartridge slot.

Frankly, that alone would have made this project worthwhile in our book, but [Geeksmithing] didn’t stop there. He also added in a pico projector that’s normally covered up by the black facia on the rear of the console, complete with a “kickstand” to tip the system up to the appropriate angle. Continuing with the theme of enabling ad-hoc NES play sessions, he also packed in enough batteries to keep the system running for a respectable amount of time. There’s even put an inductive charging coil in the bottom of the system so he can top off the batteries just by dropping the system on a modified SNES mousepad.

Last time [Geeksmithing] checked in, he was embedding a Raspberry Pi into a Super Mario Thwomp that was made from real concrete. We can’t wait to see what he comes up with next.

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Brachiograph: A Simple And Cheap Pen-Plotter

October 30, 2019 by Maya Posch 7 Comments

The BrachiGraph project consists out of two parts, the hardware design for a servo-driven drawing arm (pen plotter) and software utilities (written in Python) that allow the drawing arm’s servos to be controlled in order to convert a bitmap image into a collection of lines that can be used to draw an image resembling the original, in a variety of styles. All of the software and designs needed to make your own version can be found on the Github page for the project.

Considering an estimated €14 worth of materials for the project, the produced results are nothing short of amazing, even if the principles behind the project go back to the Ancient Greek , of course. The basic hardware is that of a pantograph, which provides the basic clues for how the servos on the plotter arm are being driven.

The main achievement here is definitely that of minimalism, with three dirt-cheap SG-90 microservos along with some bits of wood, a clothes-peg or equivalent, and of course a pen providing a functional plotter that anyone can assemble on a slow Sunday afternoon from random bits lying around the workshop.