Mysterious Files PH

Poorly designed PCBs and enclosures that slowly cook the electrolytic capacitors within are a common failure scenario in general, but they seem especially prevalent in so-called Internet-of-Things devices. The SwitchBot Plug Mini that [Denki Otaku] took a look at after many reports of them failing is one such example.

These Mini Plugs are ‘smart’ plugs that fit into a regular outlet and then allow you to control them remotely, albeit not integrated into a wall or such like the Shelly 2.5 smart relay that also began dying in droves. Yet whereas with the Shelly relays this always seemed to take a few years to show up, generally in the form of WiFi connectivity issues, these SwitchBot plugs sometimes failed within weeks or start constantly switching the relay on and off.

After SwitchBot started an exchange program for these plugs, [Denki Otaku] decided to examine these failed devices from affected users. Inside a dead unit the secondary side’s 680 µF capacitor was clearly bulging and had cooked off its electrolyte as a teardown of a dead capacitor confirmed. After replacing this one capacitor a formerly unresponsive plug sprung back to life.

This failed capacitor is important as it serves as the buffer for the 3.3 V rail, which otherwise sags below the operational range of the microcontroller during power-hungry WiFi operations, causing it to reset. As for the question of why this failure happened, there are two possibilities: one involves the B- or C-tier capacitor – for which no datasheet could be found – being unsuitable for dealing with the ripple current it was exposed to, the other being the high temperatures in that section of the PCB.

As a thermal image of the working PCB shows, the voltage regulator and switching circuitry present on the PCB – right below where the failed capacitor is located – reach a temperature of up to about 50°C, without taking into account the sealed enclosure that the PCB is located in.

The WiFi module that is located next to the capacitor and sticking up vertically from the PCB also reached a similar high temperature, making sure to bake the affected capacitor from below and the side. Even in open air the capacitor reached a temperature of about 43°C.

While a higher-quality capacitor will very likely cope with ripple current better, ultimately it’s pretty much just an unnecessarily stressful environment for electrolytic capacitors. While investigating two newer batches of these Plug Minis that are not subject to recall, the older unit still had the same flawed capacitor, while the new unit had replaced it with what looks like a polymer capacitor with the same ratings.

Interestingly, one of the failed plugs that [Denki Otaku] got sent did use one of these polymer capacitors, but appears to have another fault that wasn’t further investigated. Either way, the use of a polymer capacitor seems to help with the longevity to get it at least past the warranty period, but without a redesign these units seem doomed to fail due to rapid capacitor aging.

Fidget toys are everywhere these days. A particularly popular type simply puts some keyboard switches on a plate to provide a certain type of clicky satisfaction. [wjddnjsdnd] took that concept a step further, building a keychain-sized fidget toy that actually has games on it.

The build is based around six key switches in a 2 x 3 array. The key switches are notable in this case for being magnetic shaft keys. Rather than using a mechanical switch to indicate a keypress, the keycap instead merely moves a magnet which triggers a signal in a hall effect sensor beneath the key. In this case, the build uses A3144 hall effect sensors, which are read by the Arduino Nano running the show. The Nano is also hooked up to a small SSD1306 OLED display over I2c, which it uses for displaying the game state. There’s also a TP4056 module to handle charging the attached 380 mAh lithium-ion battery which powers the pocket-sized device.

The Arduino Nano is not a powerful platform for gaming, but it can handle the basics. The Gamebox Clicker, as it’s called, features a Pong clone, a stairs game, and a recreation of Snake. Think early mobile phone games, and you’d be on the money.

It’s an interesting build, and one that would be a great way to get used to using magnetic key switches as well as small embedded displays. We’ve seen Arduino boards turned into microconsoles many times before, too. If you’d like to sound off about magnetic vs. mechanical key switches, jump into the comments, or otherwise let us know about your best electronic fidget projects on the tipsline. Happy hacking.

This week, Hackaday’s Elliot Williams and Kristina Panos met up over coffee to bring you the latest news, mystery sound results show, and of course, a big bunch of hacks from the previous seven days or so.

We found no news to speak of, except that Kristina has ditched Windows after roughly 38 years. What is she running now? What does she miss about Windows? Tune in to find out.

On What’s That Sound, Kristina thought it was a jackhammer, but [Statistically Unlikely] knew it was ground-tamper thingy, and won a Hackaday Podcast t-shirt! Congratulations!

After that, it’s on to the hacks and such, beginning with 3D printing on the nano scale, and a couple of typewriter-based hacks.  Then we take a look at the beauty of the math behind graph theory, especially when it comes to circuit sculptures and neckties.

We also talk display hacking, macro pads with haptic feedback knobs, and writing code in Welsh. Finally, we discuss the Virtual Boy, and ponder whether vibe coding is killing open source.

Check out the links below if you want to follow along, and as always, tell us what you think about this episode in the comments!

Download in DRM-free MP3 and savor at your leisure.

Episode 356 Show Notes:

News:

• No news is good news, except that Kristina ditched Windows after ~38 years!

What’s that Sound?

• Congrats to [Statistically Unlikely] who knew this was an Earth-stomping machine!

Interesting Hacks of the Week:

• The Latest From RepRapMicron – Nail Gel, First Objects, And More
• Lego Typewriter Writes Plastic Letters
• Comprehensive Power Management For The Raspberry Pi
• Crouching Typewriter, Hidden PC
• The Graph Theory Of Circuit Sculptures
  • The 85 Ways to Tie a Tie
  • The Mathematics of Tie Knots
• DIY Macropad Rocks A Haptic Feedback Wheel
  • Simplifying The SmartKnob

Quick Hacks:

• Elliot’s Picks:
  • 5K IMac Turned Into 5K Display
  • CPU Scheduler Divines The Will Of The Heavens
  • An Event Badge Re-Imagined As A Cyberdeck
  • Ysgrifennu Côd Yn Gymraeg (Writing Code In Welsh)
• Kristina’s Picks:
  • Ordering Pizza On Your Sega Dreamcast Is Very Clunky Indeed
  • Need A Curved Plastic Mesh? Print Flat, Curve Later
  • Running DOOM And Super Mario 64 Inside A PDF File

Can’t-Miss Articles:

• After 30 Years, Virtual Boy Gets Its Chance To Shine
• How Vibe Coding Is Killing Open Source

The joy of camera hacking lies for many at the low end of the market. Not working with many-thousand-dollar Leicas, but in cheap snapshot cameras that can be had for next to nothing at a thrift store. [Marek Sokal] has a perfect example, in a 3D printed 35mm camera body using the lens and shutter assembly from a vintage Soviet Lomo Smena 8M.

The build is a work in progress, a printed assembly that holds the 35mm film cartridge, provides the focal plane for the film, and houses the take-up reel. It fits together with M2 screws, as per the Lomo lens.

We like this build, because we can see beyond the Lomo. In a box above the desk where this is being written there is a pile of old plastic snapshot cameras from the 1960s through 1980s, none of which is worth anything much, but all of which have a similar shutter and lens assembly. In many cases it’s not a huge task to do with them what [Marek] has with the Lomo and mount them to a back like this. The LEGO film camera may not have gained approval, but this prove that making cameras of your own is still pretty easy.

When it comes to seaborne propulsion, one simple layout has largely dominated over all others. You pair some kind of engine with some kind of basic propeller at the back of the ship, and then you throw on a rudder to handle the steering. This lets you push the ship forward, left, and right, and stopping is just a matter of turning the engine off and waiting… or reversing thrust if you’re really eager to slow down.

This basic system works for a grand majority of vessels out on the water. However, there is a more advanced design that offers not only forward propulsion, but also steering, all in the one package. It may look strange, but the Voith Schneider propeller offers some interesting benefits to watercraft looking for an edge in maneuverability.

Spinning Underwater Wings

The Voith Schneider propeller design looks rather unlike any propeller you might have seen before. Perhaps the most obvious reason is because of its axis of operation. Traditional propellers tend to operate in an axis parallel with the waterline, or at least within a few degrees or so. However, the Voith Schneider design spins about the vertical axis instead. This is because it uses vertically-oriented blades mounted on a rotating plate. Each blade has a hydrofoil profile, which enables it to generate thrust when moving through the water. By spinning these blades at speed and varying their angle of attack, it’s possible to create a thrust vector in any direction on the horizontal plane. A special gear system is used to vary the angle of each blade as the plate rotates, such that the overall net thrust generated by all the blades is in the desired direction of travel.

This design has certain key advantages over a traditional maritime propulsion setup. Namely, by fitting a vessel with Voith-Schneider propellers, it’s possible to add a great deal of maneuverability, to the point where a traditional rudder becomes entirely unnecessary. Instead of having to thrust the ship forwards and then turn, it’s possible to directly push the vessel with each individual thruster in the direction that is desired. This can be particularly useful for low-speed operations like docking, and provides a much more instantaneous change of direction than is possible with a regular propeller and rudder setup.

Voith Schneider thrusters are particularly useful for ships like tugs where precision maneuverability is a huge aid to operations. Numerous thrusters are often to a given vessel, providing greater total thrust and additional control. It’s also typical to fit Voith Schneider propellers with a guard underneath, which prevents grounding damage and can act as a sort of nozzle that improves low-speed performance. These propellers are perhaps not the ideal choice for watercraft aiming for outright speed, but for lower-speed work, they can offer great benefits in control.

The design looks somewhat unintuitive and even futuristic, but it actually goes back a long way. The first prototype was actually designed as a water turbine for generating electricity. However, it proved unexceptional in this role. It was only when the device was tested as a pump that engineers realized it could be repurposed as a combined thruster to replace a traditional propeller and rudder. A patent was issued in Germany in 1972, and the first prototype was tested on the water all the way back in 1928, on a small 60-horsepower vessel known as the Torqueo. The design soon found use on a number of German vessels in the interwar period, including minesweepers. The Voith Schneider design can be operated quite slowly while still providing thrust, minimizing cavitation and thus sound signature, which is considered advantageous for this role. In some German designs, such as the failed Graf Zeppelin aircraft carrier, the thrusters were even installed alongside regular propulsion systems, and made retractable so they wouldn’t present additional drag when not in use. Some decades later, the US Navy itself would later field similarly-equipped minesweepers in the 1990s, though all examples were dismantled and sold off by the early 2000s. Beyond military uses, the thruster has found application in a number of ferries and tugs around the world, and remain in production today.

Despite their unique abilities, Voith Schneider propellers remain a curio rather than a fixture in the shipping world. In the past century of their existence, just 4,500 examples have been built, near exclusively by Voith AG, and thus they are equipping a relatively small amount of the global maritime fleet. They compete with more familiar designs, such as azimuth thrusters, which are widely popular and more intuitive to understand. Given their oddball nature, and moderate level of mechanical complexity, they’re perhaps never going to supplant the tried-and-true prop and rudder that propels most conventional vessels. Still, if you’re looking to build a ship that can elegantly strafe in any direction you want to go, it’s hard to go past the Voith Schneider concept for all the benefits it brings.

When you think of a toy tractor, what probably comes to mind is something with fairly simple lines, maybe the iconic yellow and green, big rear tires, small front ones. Well, that’s exactly what [James] built, with simple, clean lines and a sturdy build that will hold up to driving around off-road in the garden. This Tractor is a great build, combining CAD, metal and wood work, some 3D printing, and electronics.

Starting at the power plant for the build, [James] went with a 350W DC motor powered by a 36V Li-ion battery from an e-bike. The motor turns a solid rear axle he made on a mini-lathe, connected to a set of riding lawn mower wheels. The mini-lathe spindle bore was too small to accommodate the shaft, and the lathe was not long enough to use the tailstock, so [James] had to get creative, using a vice and a piece of wood to make a stand–in tailstock, allowing him to turn this custom rear axle. The signature smoothly curved bonnet was made possible with plywood and body filler, rather than the sheet metal found on full-sized tractors. In fact, most of the build’s frame used plywood, giving it plenty of strength and, once painted, helping give it the appearance of a toy pulled out of a toybox.

This build had a bit of many domains in it, and all combined into a fantastic final result that no doubt will bring a smile to any face that gets to take the Tractor for a ride. Thanks [James] for documenting your build process, the hacks needed to pull off the tough bits along the way in making this fun toy. If you found this fun, be sure to check out another tractor related project.

Macropads can be as simple as a few buttons hooked up to a microcontroller to do the USB HID dance and talk to a PC. However, you can go a lot further, too. [CNCDan] demonstrates this well with his sleek macropad build, which throws haptic feedback into the mix.

The build features six programmable macro buttons, which are situated either on side of a 128×64 OLED display. This setup allows the OLED screen to show icons that explain the functionality of each button. There’s also a nice large rotary knob, surrounded by 20 addressable WS2811 LEDs for visual feedback. Underneath the knob lives an an encoder, as well as a brushless motor typically used in gimbal builds, which is driven by a TMC6300 motor driver board. Everything is laced up to a Waveshare RP2040 Plus devboard which runs the show. It’s responsible for controlling the motors, reading the knob and switches, and speaking USB to the PC that it’s plugged into.

It’s a compact device that nonetheless should prove to be a good productivity booster on the bench. We’ve featured [CNCDan’s] work before, too, such as this nifty DIY VR headset.