Apple’s AirPods can pair with their competitors’ devices and work as basic Bluetooth earbuds, but to no one’s surprise most of their really interesting features are reserved for Apple devices. What is surprising, though, is that simple Bluetooth device ID spoofing unlocks these features, a fact which [Kavish Devar] took advantage of to write LibrePods, an AirPods controller app for Android and Linux.

In particular, LibrePods lets you control noise reduction modes, use ear detection to pause and unpause audio, detect head gestures, reduce volume when the AirPods detect you’re speaking, work as configurable hearing aids, connect to two devices simultaneously, and configure a few other settings. The app needs an audiogram to let them work as hearing aids, and you’ll need an existing audiogram – creating an audiogram requires too much precision. Of particular interest to hackers, the app has a debug mode to send raw Bluetooth packets to the AirPods. Unfortunately, a bug in the Android Bluetooth stack means that LibrePods requires root on most devices.

This isn’t the first time we’ve seen a hack enable hearing aid functionality without official Apple approval. However, while we have some people alter the hardware, AirPorts can’t really be called hacker- or repair-friendly.

Thanks to [spiralbrain] for the tip!

Cycloidal drives have an entrancing motion, as well as a few other advantages – high torque and efficiency, low backlash, and compactness among them. However, much as [Sergei Mishin] likes them, it can be difficult to 3D-print high-torque drives, and it’s sometimes inconvenient to have the input and output shafts in-line. When, therefore, he came across a video of an industrial three-ring reducing drive, which works on a similar principle, he naturally designed his own 3D-printable drive.

The main issue with 3D-printing a normal cycloidal drive is with the eccentrically-mounted cycloidal plate, since the pins which run through its holes need bearings to keep them from quickly wearing out the plastic plate at high torque. This puts some unfortunate constraints on the size of the drive. A three-ring drive also uses an eccentric drive shaft to cause cycloidal plates to oscillate around a set of pins, but the input and output shafts are offset so that the plates encompass both the pins and the eccentric driveshaft. This simplifies construction significantly, and also makes it possible to add more than one input or output shaft.

As the name indicates, these drives use three plates 120 degrees out of phase with each other; [Sergei] tried a design with only two plates 180 degrees out of phase, but since there was a point at which the plates could rotate just as easily in either direction, it jammed easily. Unlike standard cycloidal gears, these plates use epicycloidal rather than hypocycloidal profiles, since they move around the outside of the pins. [Sergei] helpfully wrote a Python script that can generate profiles, animate them, and export to DXF. The final performance of these drives will depend on their design parameters and printing material, but [Sergei] tested a 20:1 drive and reached a respectable 9.8 Newton-meters before it started skipping.

Even without this design’s advantages, it’s still possible to 3D-print a cycloidal drive, its cousin the harmonic drive, or even more exotic drive configurations.

Like many classic board games, Ludo offers its players numerous opportunities to inflict frustration on other players. Despite this, [Viktor Takacs] apparently enjoys it, which motivated him to build a thoroughly modernized, LED-based, WiFi-enabled game board for it (GitHub repository).

The new game board is built inside a stylish 3D-printed enclosure with a thin white front face, under which the 115 LEDs sit. Seven LEDs in the center represent a die, and the rest mark out the track around the board and each user’s home row. Up to six people can play on the board, and different colors of the LEDs along the track represent their tokens’ positions. To prevent light leaks, a black plastic barrier surrounds each LED. Each player has one button to control their pieces, with a combination of long and short presses serving to select one of the possible actions.

The electronics themselves are mounted on seven circuit boards, which were divided into sections to reduce their size and therefore their manufacturing cost. For component placement reasons, [Viktor] used a barrel connector instead of USB, but for more general compatibility also created an adapter from USB-C to a barrel plug. The board is controlled by an ESP32-S3, which hosts a server that can be used to set game rules, configure player colors, save and load games, and view statistics for the game (who rolled the most sixes, who sent other players home most often, etc.).

If you prefer your games a bit more complex, we’ve also seen electronics added to Settlers of Catan. On a rather larger scale, there is also this LED-based board game which invites humans onto the board itself.

Thanks to [Victoria Bei] for the tip!

It’s relatively easy to understand how optical microscopes work at low magnifications: one lens magnifies an image, the next magnifies the already-magnified image, and so on until it reaches the eye or sensor. At high magnifications, however, that model starts to fail when the feature size of the specimen nears the optical system’s diffraction limit. In a recent video, [xoreaxeax] built a simple microscope, then designed another microscope to overcome the diffraction limit without lenses or mirrors (the video is in German, but with automatic English subtitles).

The first part of the video goes over how lenses work and how they can be combined to magnify images. The first microscope was made out of camera lenses, and could resolve onion cells. The shorter the focal length of the objective lens, the stronger the magnification is, and a spherical lens gives the shortest focal length. [xoreaxeax] therefore made one by melting a bit of soda-lime glass with a torch. The picture it gave was indistinct, but highly magnified.

Besides the dodgy lens quality given by melting a shard of glass, at such high magnification some of the indistinctness was caused by the specimen acting as a diffraction grating and directing some light away from the objective lens. [xoreaxeax] visualized this by taking a series of pictures of a laser shining through a pinhole at different focal lengths, thus getting cross sections of the light field emanating from the pinhole. When repeating the procedure with a section of onion skin, it became apparent that diffraction was strongly scattering the light, which meant that some light was being diffracted out of the lens’s field of view, causing detail to be lost.

To recover the lost details, [xoreaxeax] eliminated the lenses and simply captured the interference pattern produced by passing light through the sample, then wrote a ptychography algorithm to reconstruct the original structure from the interference pattern. This required many images of the subject under different lighting conditions, which a rotating illumination stage provided. The algorithm was eventually able to recover a sort of image of the onion cells, but it was less than distinct. The fact that the lens-free setup was able to produce any image at all is nonetheless impressive.

To see another approach to ptychography, check out [Ben Krasnow’s] approach to increasing microscope resolution. With an electron microscope, ptychography can even image individual atoms.

We’ve probably all had a few conversations with people who hold eccentric scientific ideas, and most of the time they yield nothing more than frustration and perhaps a headache. In [Bertrand Selva]’s case, however, a conversation with a flat-earth believer yielded a device that uses a pair of gyroscopes to detect earth’s rotation, demonstrating that rotation exists without the bulkiness of a Foucalt pendulum.

[Bertrand] built his apparatus around a pair of BMI160 MEMS gyroscopes, which have a least significant bit for angular velocity corresponding to 0.0038 degrees per second, while the earth rotates at 0.00416 degrees per second. To extract such a small signal from all the noise in the measurements, the device makes measurements with the sensors in four different positions to detect and eliminate the bias of the sensors and the influence of the gravitational field. Before running a test, [Bertrand] oriented the sensors toward true north, then had a stepper motor cycle the sensors through the four positions, while a Raspberry Pi Pico records 128 measurements at each position. It might run the cycle as many as 200 times, with error tending to decrease as the number of cycles increases.

A Kalman filter processes the raw data and extracts the signal, which came within two percent of the true rotational velocity. [Bertrand] found that the accuracy was strongly dependent on how well the system was aligned to true north. Indeed, the alignment effect was so strong that he could use it as a compass.

In the end, the system didn’t convince [Bertrand]’s neighbor, but it’s an impressive demonstration nonetheless. This system is a bit simpler, but it’s also possible to measure the earth’s rotation using a PlayStation. For higher precision, check out how the standards organizations manage these measurements.