555 Makes A Useful Beat Frequency Oscillator

August 22, 2026 by Zoe Skyforest 6 Comments

If you’ve got a cheap ham rig, it might not be very practical for you to receive certain transmissions out of the box. However, if you were to hack in a convenient little beat frequency oscillator (BFO) to your rig, then you’d be up and running. Here’s a simple way to do just that with a venerable old part everybody knows and loves.

The build in question concerns the use of a 555 timer IC. It’s seasoned with the right smattering of resistors and capacitors to taste, producing a 455 kHz beat frequency oscillator. This can be injected into the intermediate frequency chain of a receiver, making up for the lack of a steady carrier wave when receiving continuous-wave and single side-band suppressed carrier transmissions. Thanks to a potentiometer in the circuit, it’s tunable, too, from 455 kHz, plus or minus twenty percent or so. Thanks to the versatility of the 555, it’s possible to run the chip on a wide voltage range, anywhere from 4.5 volts to 16 volts, which makes it easy to install in just about any old radio set without requiring adding a specialized power supply. There’s also an alternative design that EDN covered in greater detail some time ago.

If you’re eager to dive into a wider range of transmissions than your radio can currently receive, this old-school ham hack could be just what the shack ordered. We feature plenty of good ham hacks around these parts, and don’t forget—we always want to hear about the freshest ones on the tipsline.

Building An Analog Geiger Counter

August 22, 2026 by Zoe Skyforest 14 Comments

These days, it’s plenty easy to build a Geiger counter with a microcontroller that has a nice fancy display and a simple digital readout for how many radiations you’re likely sucking up into your delicate fleshy body. But you can still do things the old fashioned way, as [ludens] demonstrates with this analog Geiger counter project.

With a goal of measuring low-level radiation sources and the normal background levels on Earth, [ludens] selected a large Geiger tube for its sensitivity—a Chinese J306β in particular. It’s rated to output 88 counts per minute at the average background level, or 8 counts per second when exposed to 1µSv/h. It’s quite a large device, measuring 200 mm long and 18 mm in diameter, and it sticks out on top of the device like a big fat antenna.

Since the large tube puts out plenty of counts at even low levels, [ludens] decided it would be easy to average the output with a simple analog low-pass circuit. Everything runs off a single AA battery, with a power supply built to step that up to 5 V for the ICs and 400 V for the tube itself. CMOS Schmitt triggers are responsible for running the show, with an old-school analog dial showing the reading.

There are two ranges to use, depending on the magnitude of the radiation source—1 uSv/h, and 10 uSv/h. The high range isn’t particularly high, but as [ludens] notes—”If anything I find pegs that scale, I prefer to run, instead of measuring exactly how much radiation there is! So I don’t need a higher scale than 10µSv/h.”

If you’ve ever wanted to build a Geiger counter that has that classic Cold War feel, this is a great way to go about it. Alternatively, you can always go the more modern route and build something digital and networkable for logging purposes.

Samsung Printer Is The Next Frontier Of Minecraft Servers

August 20, 2026 by Tyler August 6 Comments

While DOOM remains the undisputed champion of ‘game you play on every piece of hardware’ it seems that the role of ‘game you play on everything just because you can’ is slowly being shifted to Minecraft, as we have yet another Minecraft server somewhere Minecraft has no business being served– in this case, a Samsung Printer.

The hack actually requires opening up the printer to get at the debug ports to bang your way in via serial, but as any security expert will tell you, once the black hats have physical access to a machine, they own it. That isn’t to say it’s easy– [vimpo] had to dump the firmware and find an exploit. Since it’s 2026 [vimpo] tried to get an LLM to do all that hard work for him, and while it helped with identifying functions in the dump, ultimately the hacking still fell upon [vimpo]’s human intelligence, though not before burning through millions of tokens. Having found a good old fashioned UDP overflow exploit, he’s gets control of the printer and puts an improved version of his lightweight Minecraft server, UCraft, on it. Like the server, the exploit is also on GitHub but you’ll very likely need the exact same printer to get it to work: a Samsung C410W with firmware V3.00.02.20, DEC-15-2015. One important caveat is that while you can still use the printer as intended after this hack, you cannot do so while playing Minecraft: it crashes the server if you try. Good to know.

In case you’re wondering, yes, this is the same guy who got a Minecraft server running on a light-bulb, which arguably more impressive. Where he might mine and/or craft next is anybody’s guess. Somebody else already did the ESP32-C3, and while we suspect nothing will ever beat the 1960s Univac implementation for sheer impracticality, we’re willing to be surprised.

Continue reading “Samsung Printer Is The Next Frontier Of Minecraft Servers” →

A small, 3D-printed banjo frame that uses a party balloon for the resonating chamber.

May This Balloon Banjo Resonate With You

August 17, 2026 by Kristina Panos 8 Comments

Most instruments, with maybe the exception of pianos, have consumable parts. Guitars need string changes, bows need rosin, saxophones need reeds. [Co:Creation Lab]’s balloon banjo requires both fishing line and a party balloon, lest it be semi-silent.

If you want to change the resonance, just increase or decrease the amount of air inside the balloon. Neither the balloon nor the strings need tools to adjust, but we might argue that tuning pegs are tools.

The balloon banjo was the result of a design constraint: a parent should be able to build it with their child. To that end, there are no metal screws, no recurring snap-fits in the assembly, and a single, internal, one-time-use snap fit for the adult’s tactile satisfaction. Instead, the balloon banjo uses 3D-printed screws. A six-year-old can turn them with their fingers, and it’s difficult to over-tighten them and strip the plastic threads.

Be sure to check it out in action after the break. If you would rather use extant plastic to make music, the Bottlephone 2.0 is calling.

Continue reading “May This Balloon Banjo Resonate With You” →

Holograms, From Your Plotter

August 13, 2026 by Jenny List 17 Comments

When mass-printed holograms appeared on magazines in the 1980s they were a huge novelty, before degrading to the level of kids’ stickers in the years since. At the time they were seen as not for ordinary people to make, but the truth is they can be created without lasers or an optics lab. [Jordan Matelsky] is here to show us how they can be made using as humble a device as a pen plotter.

The effect of an interference pattern from a set of fine lines in a thin film can be demonstrated at its simplest with an oily finger and a mobile phone screen, and once he’s demonstrated that he takes us through some of the theory involved in shifting the light to make an image. There are some false starts with different materials, but eventually he shows us some finished holograms scribed on the polycarbonate of a CD case. It seems you really can make a hologram with a pen plotter. If these images interest you, we’ve looked deeper into the subject in the past. Meanwhile, one of the plotter-scribed holograms can be seen below. Continue reading “Holograms, From Your Plotter” →

A man's hand is shown adjusting a black Bakelite dial on the front panel of an instrument. The instrument is contained in a wooden box, and to the left of the box, a thermocouple is inserted into the flame of an alcohol burner.

Reading A Thermocouple With Mercury And A Potentiometer

August 5, 2026 by Aaron Beckendorf 2 Comments

If you’ve ever thought about the nomenclature of electrical components, potentiometer stands out as a strange name, etymologically suggesting something like a voltmeter. In fact, the component took its name from a voltage-measuring instrument also named the potentiometer. [Alnwlsn] recently took a look at one such device, which was integrated into a thermometer, and the Weston cell used to calibrate it.

The potentiometer (instrument) has a galvanometer at its heart. One side of the galvanometer is connected to the center lead of a potentiometer (component) which spans a voltage source; the other side is connected to a reference voltage. The potentiometer can be adjusted until no current flows through the galvanometer, at which point both sides match the reference voltage. The reference voltage source can then be replaced with some other source, which can then be measured relative to the reference by adjusting the potentiometer until both the voltages match. The reference voltage source is a Weston cell, which uses two mercury electrodes, one amalgamated with cadmium, to produce a stable 1.018 volt reference; despite being 74 years old, this particular cell still measured at 1.017 volts.

In this case, the potentiometer was made to measure the voltage produced by a thermocouple. After calibrating the potentiometer and connecting an iron-constantan thermocouple, [Alnwlsn] tested it with ice and boiling water, and in each case it proved accurate. In a more extreme test, it captured the temperature difference between the base and the tip of an alcohol flame.

For a bit more on the history of similar devices, check out the history of Weston Electrical Instruments.

Continue reading “Reading A Thermocouple With Mercury And A Potentiometer” →

Sharkfin Bites Attack Shark

July 28, 2026 by Elliot Williams 12 Comments

The Attack Shark is a modern keyboard with fancy magnetic keyswitches, macros, configurable blinky LEDs, and more. The problem is that the configuration software only works on Windows, so [JR Lanteigne] set out to fix that. Along the way, he completely worked out the configuration protocol that this keyboard needs, and wrote the comfortable sharkfin web-app so that you can flash yours too.

Don’t have an Attack Shark? Well, you might have one of the 522 other boards that are made on the same ROYUAN hardware, but are re-branded under 100 different names. Want to find out if yours is supported? Look it up in the list here, or just plug it in and find out.

[RJ]’s path to reverse engineering the config protocol wasn’t entirely straightforward, but since the “Windows only” application was actually an Electron app under the hood, he patched it to run on Linux and logged a few configuration sessions. Of course there are gotchas like two different firmware generations and the fact that writing to flash too fast put the keyboard into a boot loop, but after these problems were surmounted, it just remained to map all of the bytes out, and wrap it all up in a user-friendly application.

We don’t have one of these fancy-schmancy keyboards, but if we did, we’d certainly be glad to have the configuration protocol documented. Nothing is worse than finding out that the company that made your keyboard has gone belly-up, and you’re left with a backlight setup that doesn’t match your new deskpad. If you’re a keyboard-head and you don’t already follow [Kristina]’s series, well you should.