Walnut Case Sets This Custom Arduino-Powered RPN Calculator Apart From The Crowd

How many of us have an everyday tool that’s truly unique? Likely not many of us; take a look around your desk and turn out your pockets, but more often than not, what you’ll find is that everything you have is something that pretty much everyone else on the planet could have bought too. But not so if you’ve got this beautiful custom RPN calculator in a wooden case.

This one comes to us from [Shinsaku Hiura], who generally dazzles us with unique mechanical clocks and displays. This calculator solves a more practical problem — the dearth of RPN calculators on the market with the correct keyboard feel, specifically with the large keys and light touch he desired. Appropriately, the build started with a numeric keypad, which once liberated of its USB interface was reverse-engineered to figure out how the matrix was wired. Next up, a custom PCB to connect the keypad to an Arduino and a 20×4 LCD display was milled up, while a test case was designed and printed to check fitment. The final case was milled from a block of solid walnut and fitted with an acrylic window, for a sharp look with clean lines and pleasing colors.

As for the calculator itself, the demo below shows it going through its paces. The code is clever because it leverages the minimal number of keys available by hiding all the scientific and engineering functions behind a “secret silver key” that was once the equals key and obviously not needed in RPN. Hats off to [Shinsaku] for a handsome and unique addition to his desk.

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PSU charging an externally connected supercapacitor bank that's powering the phone. There's a current clamp on one of the wires to measure charging current, and a multimeter measuring the charging voltage.

Just How Fast Could You Charge An IPhone?

An iPhone 8, now a relatively cheap model, can charge its battery fully in two hours’ time. There’s hardly ever a need for faster charging, but it’s fair to ask – how much faster could it really go? [Scotty Allen] from [Strange Parts], back after a hiatus, is back to stretching the limits of what a regular iPhone can do, and decides to start off with an exploration of battery technologies.

What people commonly encounter is that charging speed depends on the charger involved, but even one hundred chargers in parallel won’t speed up this iPhone’s charging rate, so what’s up? First off, the phone’s charger chip and the battery’s BMS will both limit charging current, so for experiment purposes, those had to be bypassed. First attempt was using a hefty DC power supply with the original cell, and, unsatisfied with the lack of fire and still relatively slow charging, [Scotty] decides to up the ante.
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A personal computer drive bay with a glowing LED display

Turbo Button Pays Charming Homage To Early Personal Computers

The PC turbo button and LED clock speed display were common features on early personal computers. Wanting to add a little retro chic to his modern battle-station, [Matthew Frost] assembled a charming and functional homage to the turbo button control panel.

In days past, this automotive nomenclature implied a performance boost when activated. Instead, ‘turbo mode’ would clock your x86 processor at its rated speed. Disabling ‘turbo’ would throttle the CPU, often all the way down to 4.77MHz. Inherited from the original IBM PC, some early computer programs relied on this specific clock speed, and would otherwise run too fast (or not at all) on faster hardware. PC marketing teams and engineers alike stopped including the turbo button and glowing clock speed numbers around the Pentium era.

This modern re-imagining of the turbo button uses an Arduino microcontroller, seven-segment display and tactile switches to emulate the look and feel of the original hardware. Instead of directly adjusting the CPU clock speed, hitting turbo switches between balanced and high-performance Windows power plans. The seven-segment display measures this clock speed in GHz to two decimal places. We’ll admit that it’s pretty satisfying to see those numbers inch higher when switching to turbo.

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Screenshot from the video showing comparisons between diffused light pictures at different brightnesses and diffusers applied

LED Diffusers Confusing? Organize A Practical Contest

We all want a nice and shiny LED strip that doesn’t actually look like it consists of individual LEDs – a bar of uniform light is just that much more attractive. There’s all kinds of diffusion options available out there, but they can be confusing – sometimes you’d just like to know, which one is better? If there’s one thing that could easily settle this, it’s a practical test, and that’s what [The Hook Up] has devised for us to learn from.

First off, he talks about LED strips available – between 30, 60 and 144 LED per meter variations, the latter is going to be easier to diffuse than the former. From there, there’s a few different kinds of diffuser covers and aluminum profiles you can get, and [The Hook Up] pairs them in combinations, filming them from a distance and giving us concise visuals of how each combination works at different duty cycles, as well as making brightness measurements every now and then to evaluate losses of different diffuser layers. He proposes a simple rule – when picking a diffuser, distance between the LEDs and the diffuser has to be larger than the between-LED distance, and experiments confirm that. In the end, one of the takeaways is that the differences between 60LED/m and 144LED/m strips are not significant enough that they can’t be compensated for with a decent diffuser.

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3-DOF Robot Arm Wrist Without The Motor Weight

A major challenge of robotic arms is the weight of the actuators, especially closer to the end of the arm. The long lever arm means more torque is required from the other actuators, and everything flexes a bit more. To get around this, [RoTechnic] moved the wrist stepper motors off the arms entirely.

He built a push-pull mechanism that uses braided fishing line to transfer motion to the robot arm’s wrist using Bowden tubes. The motors are mounted on the arm’s base, with a drum and two lengths of fishing line on the shafts. The lines pass through an adjustable tensioner before entering the Bowden tubes. This drum mechanism is also present on each of the three rotating axes of the wrist.

[RoTechnic] used an Arduino-powered RAMPS board as a controller, which is programmed to accept over the serial interface. He created a simple GUI and scripting interface in Jupyter Labs to generate and send command, which seems like an excellent solution for testing.

We can see this mechanism being a useful for a variety of motion applications, and definitely something to add to the idea toolbox. It is somewhat similar to some other cable-operated joints we’ve seen in humanoid robots and other 3D printed arms.

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M.2 For Hackers – Connectors

In the first M.2 article, I’ve described real-world types and usecases of M.2 devices, so that you don’t get confused when dealing with various cards and ports available out there. I’ve also designed quite a few M.2 cards and card-accepting adapters myself. And today, I’d like to tell you everything you need to know in order to build M.2 tech on your own.

There’s two sides to building with M.2 – adding M.2 sockets onto your PCBs, and building the PCBs that are M.2 cards. I’ll cover both of these, starting with the former, and knowing how to deal with M.2 sockets might be the only thing you ever need. Apart from what I’ll be describing, there’s some decent guides you can learn bits and pieces from, like the Sparkfun MicroMod design guide, most of which is MicroMod-specific but includes quite a few M.2 tips and tricks too.

First, Let’s Talk About The Y-Key

What could you do with a M.2 socket on your PCB? For a start, many tasty hobbyist-friendly SoMs and CPUs now have a PCIe interface accessible, and if you’re building a development board or a simple breakout, an M.2 socket will let you connect an NVMe SSD for all your high-speed low-power storage needs – many Raspberry Pi Compute Module mainboards have M.2 M-key sockets specifically for that, and there’s NVMe support in the RPi firmware to boot. Plus, you can always plug a full-sized PCIe adapter or an extender into such a socket and connect a PCIe network card or other much-needed device – even perhaps, an external GPU! However, as much as PCIe-equipped SoMs are tasty, they’re far from the only reason to use M.2 sockets.

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Infrastructure diagram of [Stefan]'s network at the end of his fiber optics journey

Say No To Obsolescence, Wire Up Your House With Fiber

These days, if you wire your house with anything less than gigabit, you might end up throttling your Internet connection. If you wired things up using two pairs per device back in 100BASE-T days, however, you’ll want to redo your cabling before you buy new switches. Now, some of us are already starting to equip ourselves with 2.5G hardware — which may require new cabling once again. Would you like to opt out of the Ethernet cabling upgrade rat race, at least for a while? Do like [Stefan Schüller] did, and use fiber optics for your home networking needs!

[Stefan] walks you through everything you’d need to know if you ever choose to look into fiber for your networking needs, and explains the design decisions he’s made — from splicing fiber optics himself, to building a PC to do routing instead of getting a hardware Small Form-factor Pluggable (SFP) equipped router. He also describes pitfalls, like SFP modules requiring reconfiguration to work with different router brands, and having to buy a fiber splicer with an eye-watering pricetag.

In the end, he shows a cost breakdown, and says he’s quite happy with the upgrade. While the costs might seem prohibitive compared to running Ethernet, upgrading to fiber will have your equipment function at top speed whenever you need it – who knows, perhaps in a few years time, 2.5G will no longer suffice for new advancements in home technology needs, and we’ll see more SFP modules in hackers’ hands. After all, modern TVs already use fiber optics for video data transfer.

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