Kritik sah

If you spend any time near a gym, you may be familiar with Bluetooth heart rate monitors — a small pack of electronics mounted on a strap round the chest which can relay heart rate data to an external logger or display. We’re pleased to see [Milos Rasic]’s project then, an open-source version of one of those monitors . The heart rate capture is done by an AD8232, while the Bluetooth part is handled by a Seeed Studio XAIO ESP32 board. Power is provided by a single 3.7 V cell, with a boost converter to push that up to 5 V. The design omits a charge controller to keep things simple, so figuring out how to top off the cell is left as an exercise — no pun intended — for the user. Software is loaded through the Arduino IDE, which raises the possibility that other ESP32 CPUs could be supported with a bit of modification. All in all it’s a surprisingly simple project, and while the manufactured version is cheap enough it’s still very much worth having ...

[Bas BotBerg] wanted to use a portable Bluetooth thermal printer to run off reports on sensor data collected by an ESP32-C3 microcontroller. But as is so often the case these days, the only official way to interface with the printer was through a proprietary smartphone application provided by the manufacturer. With no documentation on how the thing works, he set out to reverse engineer the printer’s communications protocol so he could control it from the MCU — but the route he took to get there was a bit different than what we usually see, and is an excellent case study for those who might have similar projects in mind. The standard procedure for something like this, if it can be called that, is to use Android’s built-in debugging capability to log Bluetooth communications while running the manufacturer’s application. The resulting file can be fed into Wireshark, and with patience and some educated guesses, you can usually work out the various commands and val...

Being able to monitor voltages and currents is essential for many applications, with the national electrical grid being no exception. The obvious complication here is that the voltages and currents are massively higher than for those other applications, making safely monitoring these somewhat of an engineering challenge. The used systems for current monitoring are detailed by [Jordan Taylor], also known as [The Electric Brit], in an explainer of grid-level current transformers (CTs) and associated elements that help to provide galvanic isolation for safe current measurements. Even if the basic principles remain the same, when you’re dealing with currents of 5 kA and more, the associated clearances and penalties for getting a detail wrong increasingly correspondingly. The CTs help to implement over-current protection (OCP), over-voltage protection (OVP) as well as differential protection, which is useful to detect leakage and shorts, which could also happen inside the CT if the w...

There are many uninterruptible power supply (UPS) solutions for the Raspberry Pi that take the form of HATs with a battery on board, but they’re not suitable for every situation. Web3-Pi are using the Pi 5 as an Ethereum node, and found the need for a UPS that didn’t sit on top of the Pi. Their solution is the Web3 Pi UPS , a device that sits in the USB power chain. It’s a box that takes three power inputs, USB-C PD, a barrel jack, or a hot-swappable Sony camera battery, and puts out the constant 5 V at 5 A the Pi requires. The USB output isn’t just for power, it can communicate with the Pi to deliver telemetry and ask the OS to shut itself down if power reserves are failing. Inside are a CH32 RISC-V microcontroller that handles the power circuitry, and an RP2040 that handles control and an OLED screen for a UI. The project’s web site also mentions provision for an LTE add-on for remote monitoring, however this doesn’t at the time of writing appear ...

As any science YouTuber or first-year physics student is quick to point out, the universe is mostly empty space. Not just space itself, but the amount of “empty” space between nuclei and their electrons is also huge. Getting rid of this empty space results in all kinds of interesting phenomena like degenerate matter and black holes. But the concept can be extrapolated into our daily lives as well; many things are so filled with air that we can get a lot more usable storage space by compressing them down a little bit. [Super Valid Designs] took this concept to a coat closet, building one that can hold an impressive number of coats . He started by looking at an existing closet, which could hold around 21 coats but only if someone used two hands to cram the coats into the space. After a trip to a store which sells rugs, he saw a much better design that lets all the rugs pivot like the pages on a book, and took this idea to his closet using a similar mechanism designed for stor...

After the Orion capsule of the Artemis I lunar mission returned to Earth, it was found that massive chunks of its heatshield had been ripped off, posing a serious risk to any future missions. In a recent video in which [polymatt] takes a break from repairing old laptop shells and the like, he tries to recreate the Orion’s heatshield using a variety of methods and materials. For this test a number of samples were created, each using the same kind of segmented structure as the larger Orion heatshield. The filler was created from the published materials for the heat shield by NASA, requiring just serious mixing. The resulting samples were then cured with thermocouples inserted, before they got blasted with the heat from a propane torch, trying to simulate the various re-entry patterns. Perhaps unsurprisingly, the results matched the findings by NASA for why the Orion’s heat shield had failed, being the build-up of gases due to the sustained pyrolysis processes that eventual...

We try to steer clear of politics and societal issues here at Hackaday, so a protest is not usually the sort of thing we’d cover. But we figure it’s safe enough to bend the rules a bit when the ones doing the protesting happen to be robots . About 30 bots gathered — or at least were commanded to gather by the event organizers — in Warsaw to spur discussion about the impact AI and robots will have on the labor market. Beyond getting public and media attention, the demonstration was also designed to raise awareness of what modern humanoid robots can do. While we appreciate the idea of showing robots taking the “jobs” of the protesters, it does seem somewhat ironic that marching around and chanting for hours is exactly the sort of repetitive work that most people would be happy to see taken over by machines. Although we hope these protests remain peaceful, there’s always a chance things can turn violent when tensions are high. Should things go so...

It is a classic Hackaday situation. You have an Egret GT E-scooter. It has a screen that shows the usual dash stats, but that led to an annoyance. You could accidentally enter firmware update mode and, from there, enter operational mode without the security PIN. [Ben] couldn’t let that stand, so he reverse-engineered the protocol and rewrote the firmware in Rust . As he put it, “… because I have to break… everything I own…” We get it. The mobile app was useful for some basic info, since sniffing Bluetooth is fairly easy and analyzing mobile code is, more or less, straightforward. Analysis revealed some data that doesn’t show on the display and that several things are sent back to home base tagged with the scooter’s unique ID — another reason to gut the existing firmware. Internally, the scooter uses the CAN Bus, so out came the oscilloscope and a homebrew CAN decoder.  Surprisingly, the CAN bus is accessible on the USB-C port...

If you’ve never heard of the Spin Semiconductors FP-1 digital signal processor chip, don’t worry– that just means you haven’t been deep into guitar petals and audio effects hardware lately. [adamjvr], a.k.a. [avr] has, and he’s gone to the point of creating a PC-based emulator of this sound chip to simplify development. If you don’t see the utility, stop and think about the development cycle without a simulation like this: you program, you flash to a board, and you test there. Not only does the ‘flash to the board’ step add time and friction, you do also have a limited number of flashes on the board’s memory. With an emulator on your PC, the workflow tightens to ‘code, test’ and you don’t flash the board until the simulated DSP is doing the sounds you want it to. As for the FV-1 itself, it’s an interesting little chip in that it’s quite a full-featured DSP– rather, it’s small instruction s...

You want Retro? We did, when we started our retrocomputing challenge. [Peter] decided that transistors weren’t retro enough, and sent us this lovely homebrew relay computer , complete with 16- bit CPU, which is rather more bits than one normally associates with clicky clacky contacts. The architecture is very simple– it just uses an accumulator register, ACCU, and goes from there. All mathematics and save/load operations go through ACCU. There whole instruction set is only 19 commands, and he’s used that set to program such lovely things as calculating 3 digits of Pi– which only took 8 minutes of glorious clicking. There’s a demo video of that embedded below. [Peter] has even implemented a display by hooking his computer to a 32×32 LED matrix, but don’t expect it to relay updates really quickly. If this computer looks familiar, it’s because its earlier incarnation was one of the more “extra” entries in last year’s one-...

The all-LEGO version barely cuts paper. (Credit: Jamie’s Brick Jams, YouTube) Although building a table saw out of LEGO is probably not the first thing that comes to mind when you look at those colorful bits of plastic, [Jamie] has been on a bit of a search for more applications of his LEGO-based air-powered motors. Naturally this led to the idea of doing something useful with it, like making a table saw you can actually use for real wood . Starting off with a basic prototype using only regular LEGO pieces to get the mechanism figured out, [Jamie] then builds this up into said air-powered table saw featuring an actual metal blade. Suffice it to say that this isn’t something that you want your children to do with their LEGO while unsupervised. The star of the show is of course the air-powered turbine that spins the blade. This is something that [Jamie] has been working on for a while , going through a number of prototypes to figure out a 3D printed geometry for the turbine...

[Andy Huot] has a fantastic-looking infinity mirror digital clock that really raises the bar. It uses high quality components, smart use of RGB LED animations, and a clever “stacked diffuser” vertical design to the 7-segment display elements that really enhances the infinity mirror effect. It needs to be seen in action, so check it out. The end result is expressly portal-like, with the smooth animations of the LEDs really playing into the effect. The size helps, too. It’s 24 inches in diameter, giving it considerable presence. The stacked diffuser design for each display element really enhances the effect. A basic infinity mirror design consists of lit elements sandwiched between a reflective back surface and a partially-reflective, partially-transmissive top cover. That same basic principle is used here, but with great care given to ensure nothing so much as a fingerprint spoils the illusion. For example, the top cover is a disk of acrylic with a 90% reflective f...

Folding a sheet of metal in a straight line is one thing, but how does one fold multiple curved lines into a sheet of aluminum without fancy machines? [John] demonstrates how to do exactly that with little more than hand tools and a fair bit of patience. The secret is drilling a lot of small holes along each fold line . Complex shapes are possible with planning, hand tools, and patience. First, a bit of background. [John] wanted to fabricate a curved piece of aluminum as cover that would match the sleek aerodynamic lines of a Belly Tank Lakester . The trick is that there isn’t a single straight line to be found, and the fold lines are all curves. How can one do such folding with only hand tools? [John] found that fabrication was possible by drilling small holes all along each fold line, then carefully bending as needed. The line of holes weakens the metal, acting like a score line, and allow the required curves to be made cleanly. There’s some finishing work and straight...

When you see a listing for an Ethernet switch whose specification list is in effect ‘yes’, with a four-digit price tag when new, and with the seller asking for less than 10% of said $3,000 asking price in an ‘untested’ condition, the only rational thing to do is of course to mash that ‘buy’ button. This is what [This Does Not Compute] did, and created a video about to show what a great investment decision this was. Naturally this Juniper EX4100-F-12P switch came without power supply brick for its 48VDC input. Figuring out its pin-out and probing said input showed that the voltage rails had been shorted, giving a first clue as to why this switch had been on sale for so very cheap. Bravely hoping that it would be a straightforward fix, the unit was disassembled. With a 280 Watt power brick, it’s little wonder that the top of the unit is a one massive aluminium heatsink, including a large heatpipe. Also visible on the lid near the power input w...

For a little while vacuum tubes and semiconductors were fighting a heated battle for dominance, with bipolar junction transistors and 1959’s RCA Nuvistor both allowing you to build a compact circuit with relatively low power usage and no high voltages. Although we now know that semiconductor technology won out overwhelmingly, that doesn’t mean that you cannot build a brand new Nuvistor board in 2026, as [Eric Schlaepfer] AKA [TubeTimeUS] recently did . Nuvistors saw their most use in small-signal radio frequency applications, like VHF and UHF, with excellent low-noise characteristics that saw them used until the early 1970s in television sets, radios and oscilloscopes, as well as in space probes like the 1960s US Ranger Moon missions, so by that metric they had a good run. Nothing so exciting is built in this video, sadly, but alongside a breakdown on how nuvistors work, we do see a discrete 555-style timer built using a gaggle of tetrode nuvistors, giving a pretty good i...

Nintendo has made many game consoles in its long history — one that famously overlaps that of the Ottoman Empire — but only one of them was ever Super . It’s that console, the Super Nintendo Entertainment System, that [Inkbox] has decided to delve deeply into as he crafts a game in assembly using all the hardware tricks he can . Hardware tricks he’ll need, given he’s limited to the two 64 kB RAM banks and 3.58 MHz Ricoh 6502-based CPU. Even the 4 MB limit he sets for a historically-accurate homemade cartridge seems positively claustrophobic by modern standards. The game he’s after making is a top-down adventure game a la Zelda , and [Inkbox] gets right into the weeds explaining how the SNES works as he shows his work in this nearly hour long video. If you’re looking for a deep dive into the architecture, along with how it is meant to be used, you could certainly find worse sources. Everything from the different graphics modes to what registers ...

A fun part of modifying something like a motorbike is that you sometimes have to come up with creative solutions to basic questions, like how you can still access the fuel tank’s cap after extending it forward. In the case of [KRTframework] this meant that the fuel cap was now underneath the bodywork, requiring a suitable way to access it. Of course, this meant making a hidden access panel with a custom hinge , to not break the bike’s clean lines. To make the process as easy as possible, a 3D scanner was used to get detailed measurements on what the new bodywork would look like. Using these the new bodywork was created, including what would be the hidden access panel, yet finding a suitable hinge mechanism wasn’t easy. This is where this custom design was created, with detailed assembly covered in the video. To bridge the gap between the opening and the fuel tank a part was 3D-printed that also contains the simple push-to-open latch mechanism. Of course, in the comme...

Remember those tiny little droids skittering around the pristine corridors of the Death Star in  Star Wars ? [heychaostheory] has put together something vaguely along the lines of those charming little mobile toasters. It’s an autonomous mouse droid with party mode! The build is interesting in that it’s based on an off-the-shelf metal robot chassis—which provides mounting points for the gearmotors and wheels that make up the drivetrain. The mouse droid body sits atop this, being a 3D printed part that is afixed with heat set inserts and nylon standoffs. It’s 3D printed and expertly decorated with a fun vibe. Inside the body lives an Arduino Uno, hooked up to an L298 motor driver board and ultrasound sensors used for obstacle avoidance. It’s also got a smattering of LEDs to flash, because blinkenlights matter. The best bit, though, is the party mode button, which fires off music via a DFPlayer Mini module. The mouse droid may not be as flashy and imposing as the...

There are plenty of ways to capture 3D images or simulations of such if you know what you’re doing with camera hardware and fancy mathematics. However, a little more unusual is the idea of capturing a 3D image while using no lens at all — and yet, [okooptics] has achieved just that! The basic concept builds on an older project from [okooptics], wherein images were captured from a Raspberry Pi camera with no regular lens element installed. In its place was a thin layer of Scotch tape over the sensor, acting as a diffuser. With the right deconvolution math, it’s possible to actually recover a real image out of the blurry mess this setup initially captures. [okooptics] was then able to push this into three dimensions by weighting the point spread function used to deconvolute the image. Adding directional bias to the process creates a similar effect to slightly shifting the cameras position, actually revealing a view from a slightly different angle of objects in front of...

You can 3D print all kinds of things, from Yoda heads to little models of Pikachu. Eventually, though, most of us get to a point where we want to print something a little more interesting. The lenticular prints developed by MIT CSAIL are very much that. (h/t Core77 ). The ShiftLens concept is simple enough—there’s a lens layer printed in transparent material. Beneath that, lives a patterned layer in alternating colors, corresponding with the linear lenses of the layer above. Then, there’s an actuation mechanism that can shift the lens layer relative to the pattern layer. This creates a changing color effect as the mechanism is shifted. The actuation mechanism can be a knob, switch, or roller—anything that moves the layers relative to each other. On its own, it’s a bit of a curio—but there are some fun demos. In particular, using the lenticular printing on a bottle to form an indicator for when the container is closed properly. There isn’t a publicly available de...