Evolving RC Circuits

October 18, 2026 by 3 Comments

We are surrounded by evolving algorithms and AI models, and it feels like we have to evolve to them as well. Of course, the world itself is always evolving, and when we have to implement filtering circuits based on current environments it might not last all that long. [Saikarthik Ramakrishnan] realized that this phenomenon can easily apply to simple RC circuits, so why not make them adapt to the changing world itself? This is exactly what the Darwin Board is meant to do: act like an evolving simple RC circuit for whatever environment or signal you want gone.

RC circuits are normally considered to be relatively simple in the world of circuits; however, the real world isn’t always all that simple. This simple evolutionary algorithm implemented by [Saikarthik Ramakrishnan] attempts to apply similar principles used in other evolving models to the humble RC circuit. Based on an ESP32, the Darwin Board is a fairly simple model of 2040 possible combinations of genomes. Yes, each possible RC circuit is its own genome, which allows simple evolution from one to another based on current requirements.

You should certainly consider checking out the project’s GitHub repository here to try out the mutating circuit itself. While this project might complicate what is normally fairly simple, there is sometimes beauty in simplicity. So why not use a comically simple circuit for a smart home feature?

A waterfall display is shown, with a prominent yellow block in the upper right corner of the display.

Turning A Wi-Fi Adapter Into An SDR

October 18, 2026 by 1 Comment

Since the discovery of an undocumented I/Q sampling feature in ESP32 chips about two weeks ago, there’s been a flood of similar features being found in other wireless chips, including LoRa and Wi-Fi chipsets. The latest chip to join their ranks is the MediaTek MT7921AU, often used in Wi-Fi adapters, with two different projects developing independent SDR drivers for it in the last few days.

The first was BirriaSDR, which discovered that the chip exposes raw I/Q samples for debugging and calibration; BirriaSDR instead streams these to the host at 40 Msps in 14-bit resolution, with the option to tune from 2156 to 2610 MHz. BirriaSDR uses libusb to directly communicate with the Wi-Fi adapter and access its registers; it doesn’t make any permanent firmware changes, so the Wi-Fi adapter goes back to its original state after being used as an SDR. BirriaSDR implements an API similar to the RTL-SDR’s.

Mtk79ICAP, by contrast, exposes the MT7921AU’s sampling features over a standard SoapySDR interface. Unlike BirriaSDR, it applies some firmware changes to the chip, and it requires a modified driver to work. However, it can reach a maximum bandwidth of 80 MHz and tune to the 5 GHz bands. The Wi-Fi adapter in use can also simultaneously work in monitor mode and stream SDR data, though this only works when automatic gain control is enabled.

This is the second MediaTek chip we’ve seen repurposed for SDR work, after the earlier MT7996. Conveniently, Wi-Fi adapters often have external antennas, which should make it easier to connect a frequency mixer circuit. These adapters aren’t quite there yet, but some hackers have already used the ESP32 to transmit arbitrary signals.

Making A New Mechanism For A Reciprocating Pencil Sharpener

October 17, 2026 by No comments

An engineer’s greatest tool is the writing utensil. Be it pen or pencil, we use them for everything from making diagrams to marking out cuts. But as with any practitioner of an art, we can tend to become rather particular about the details. [Choronva Engineering] is not different, and to that end set out to re-invent the pencil sharpener. 

In this case, [Chronova]’s ideal pencil tip shape is a concave cone. This is a shape quite trivial to make by using a knife, but rather impossible with a traditional twisting motion. But what if one automatized the knife whittling motion? This is actually a very old idea, with examples dating back to at least 1910. In this example, the blade is guided along two tracks with a particular curvature to enable the concave cone. This is driven by a cam shaft connected to a little cranking mechanism. Initial tests showed the mechanism works quite well at producing a cutoff of the desired shape, but lacks a pencil rotation mechanism.

CAD mockup of the lantern-pinion mechanism.

Inspired by the Geneva wheel, [Chronova] developed a fresh intermittent mechanism for improved satisfaction in the sharpener’s operation. Instead of two gear-like mechanisms on a flat plane, the input and output can sit at a 90 degree offset from each other giving room for the blade’s motion. Rotation is input on a part called the indexing pinion which outputs on a lantern pinion.

At every full rotation of the indexing pinion, it interfaces with the lantern pinion moving it two teeth. Because of this quirk, by making the lantern with an odd number of teeth, twice the number of indexing positions are available in the output. At all other points in the pinion’s rotation the lantern is locked in place.

The pencil is held in place with a collect chuck and mounted on a screw coupled to the lantern pinion’s rotational output. This enables the pencil to move forward slightly with every turn of the crank. The project is topped of neatly with a shavings catcher and handle.

It works rather well, but a practical pencil sharpener that does not make. It takes a rather long time, and is fairly laborious to use. But over-engineering machines to do simple tasks is still quite fun!

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Busting The Myth That Plastics Are Chemically Inert In Water

October 17, 2026 by 2 Comments

One of the often made claims about plastics is that they are chemically inert under most conditions, such as when exposed to water. This long-held belief has also challenged the notion that micro- and nanoplastics (MNPs) are dangerous to organisms such as us human animals. A hitherto unknown mechanism between common plastics as investigated by [Naixin Qian] et al. and published in Nature serves to generate highly reactive hydroxyl radicals when exposed to water.

Hydroxyl radicals (HO•) are the neutral form of the hydroxide ion (OH–). It’s a free radical that tends to be extremely short-lived due to its reactivity, much like the singular oxygen molecule that is freed at the plastic-water interface. The energy provided for this reactivity comes from the electrostatic effect, itself highly correlated with many plastics, with the six types of microplastics used in the experiment showing varying levels of free radicals, particularly for the more hydrophobic types.

This high reactivity of free radicals is a well-known problem in cellular biology, with evolution having developed many tools over the years to deal with capturing these radicals as well as repair the (DNA) damage that they can cause. The effect of these microplastics and their generated free radicals was thus studied as well.

Of note here is that the electrostatic effect itself already serves to draw charged biomolecules to it, before the impact of free radicals is considered. By using mouse red blood cells and exposing them to polystyrene (PS) microplastics fatal damage was observed to the red blood cells.

This indicates that there are at least three possible ways in which MNPs can be harmful to organisms. It also provides another clue to how this may affect the ageing of plastics, among other implications.

Currently there is still ongoing debate on whether MNPs are truly harmful and just how prevalent they may be in e.g. our bodies. Reliably detecting them in e.g. biological tissues remains a challenge, which this new study may also be helpful with, since one of our biggest blind spots is that we lack solid knowledge of how MNPs may behave inside an organism.

2026 Retrocomputing Challenge: Dollhouse Arcade Cabinet Runs Remote DOS Games

October 17, 2026 by 1 Comment

Classic DOS games never ran from within stand-up arcade cabinets in dollhouses, but [Juha Lilja] imagines a world in which they did. His Micro DOS arcade cabinet is described as a device that “runs nothing” because the tiny unit is actually streaming the games over Wi-Fi from a nearby PC. That doesn’t mean it’s just a glorified movie player, though — the cabinet is playable, if a bit awkward to do so.

An economical development board and a 3D-printed enclosure is all it takes to put classic DOS games into dollhouse-sized arcade cabinet.

The core of the micro arcade cabinet is a M5Stack AtomS3R running as an embedded remote terminal. One tilts the whole cabinet as if it were a virtual joystick to send up, down, left, and right. Button presses are done by pushing on the physical screen; it supports single, double, and long-clicks. While in theory one could install a micro joystick and buttons instead, [Juha] aimed to keep everything self-contained and use only what was already built into the AtomS3R. In this case, that’s a motion sensor and the single button which is activated by pressing the screen.

The games themselves run on a PC, with screen contents being streamed wirelessly to the little display and inputs being sent back. The firmware on the AtomS3R doesn’t know or care what game is being played; all it does is display what it’s told, and send back input events. The back end does the rest. This makes it pretty flexible, and a tiny arcade cabinet is a handy way to demonstrate the whole system. It’s a pretty slick addition to his daughter’s dollhouse, too.

If streaming DOS games (or whatever else) to economical endpoints is giving you some ideas, the GitHub repository holds code and a fuller explanation of how it works. There’s a deeper discussion on some of the finer technical points, as well. Watch it in action in the video embedded just below the page break.

2026 Hackaday Retrocomputing Contest

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Building A Flying Drone With A Single Propeller

October 17, 2026 by 4 Comments

Technically all that you need in order to make a drone fly is a single motor and single propeller, but realistically it becomes basically impossible to fly it at that point. In the case of helicopters you therefore need a second rotor somewhere to provide counterbalance to the first and to be able to steer.

There are of course a number of ways to make a drone fly with a single helicopter, but the compromise usually is to use very large propellers, as well as other mechanisms that make for a very large drone. This wasn’t good enough for [Joshua Bird] who wanted to have a very small, single propeller drone.

Key to making it work is not only a very high RPM, but also a hinged propeller hub that manipulates the  angle of the blades in such a way that both pitch and roll can be controlled if you react quickly enough. This turned out to be impossible using standard motor ESCs that do not directly measure the motor’s speed and position but rely on back EMF.

In the final prototype of the drone such details had to be measured directly, with super-fast adjustments to the motor’s speed only possible with custom controller code and a lot of trial and error. Even then the drone would often lose track of its position and crash once more. The solution there was to add an infrared beacon in the room and a sensor on the drone, to give it a fixed reference point.

You can find the project files so far on the GitHub project page, with upcoming changes to the drone design involving improvements like adding a scanner to the drone so that it can autonomously use features in its environment as fixed reference points. That way it might conceivably be able to fly outside as well, which would be quite exciting to see.

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2026 Retrocomputing Challenge: Oldputer Gives Old Eyes Relief With E-ink Display

October 17, 2026 by 2 Comments

Modern computers are towers of glass and metal with very few large deviations from one to another. Monitor A will go against B, except you can’t tell them apart unless they’re on. At least, that is, compared to how different the old bulky monitors look compared to the new. [Andrzej Górski] seems to agree with this sentiment with his Oldputer, a blast from the past.

[Andrzej Górski]’s inspiration came from one component, and the main component of the project, an old e-ink display. When life gives you one of the slowest versions of a display, there really isn’t too much else to do other than pair it with slow old computers of the past. From that inspiration, there isn’t entirely a whole lot to do other than throw in an ESP32 and some LEDs for indicator lights. Put all this into a fun case, and you get one pretty desk ornament for whatever information you wanna display.

If you want to replicate the past again, you might want to look for the project GitHub here. If you’re looking for something even older, check out the replica of the MCM/70!

2026 Hackaday Retrocomputing Contest