2025-12-15 05:00:09
If you live in a major city, you’ve probably seen a street performer with some variety of slapophone. It’s a simple musical instrument that typically uses different lengths of PVC pipe to act as resonant cavities. When struck with an implement like a flip-flop, they release a dull but pleasant tone. [Ivan Miranda] decided to build such an instrument himself and went even further by giving it MIDI capability. Check it out in the video below.
[Ivan’s] design uses a simple trick to provide a wide range of notes without needing a lot of individual pipes. He built four telescoping pipe assemblies, each of which can change length with the aid of a stepper motor and a toothed belt drive. Lengthening the cavity produces a lower note, while shortening it produces a higher note. The four pipe assemblies are electronically controlled to produce notes sent from a MIDI keyboard, all under the command of an Arduino. The pipes are struck by specially constructed paddles made of yoga mats, again controlled by large stepper motors.
The final result is large, power-hungry, and vaguely playable. It’s a little unconventional, though, because moving the pipes takes time. Thus, keypresses on a MIDI keyboard set the pipes to a given note, but don’t actually play it. The slapping of the pipe is then triggered with a drum pad.
We love weird instruments around these parts.
2025-12-15 02:00:54
One part wants 3.3V logic. Another wants 5V. What do you do? Over on the [Playduino] YouTube channel, there’s a recent video running us through a not-so-recent concern: various approaches to level-shifting.
In the video, the specific voltage domains of 3.3 volts and 5 volts are given, but you can apply the same principles to other voltage domains, such as 1.8 volts, 2.5 volts, or nearly any two levels. Various approaches are discussed depending on whether you are interfacing 5 V to 3.3 V or 3.3 V to 5 V.
The first way to convert 5 V into 3.3 V is to use a voltage divider, made from two resistors. This is a balancing act: if the resistors are too small, the circuit wastes power; if they are too large, they inhibit fast signals.
The second approach to converting 5 V into 3.3 V is to use a bare resistor of at least 10K. This is a controversial approach, but it may work in your situation. The trick is to rely on the voltage drop across the series resistor to either drop enough voltage or limit the current flowing through input protection diodes, which will clamp the voltage but also burn out with too much current flow.
The third approach to converting 5 V into 3.3 V is to use chips from the 74AHC series or 74LVC series, such as inverting or non-inverting buffers. These chips can do the level shifting for you.
The easiest approach for going in the other direction is to simply connect them directly and hope you get lucky! Needless to say, this approach is fraught with peril.
The second approach for converting 3.3 V into 5 V is to make your own inverting or non-inverting buffer using, in this case, an N-channel Enhancement-mode MOSFET. Use one MOSFET for an inverting buffer and two MOSFETs for a non-inverting buffer. Just make sure you pick N-MOSFETs with 3.3 V or 5 V gate drive voltage VGS. Alternatively, you can use a buffer from the 74HCT series.
The video provides a myriad of approaches to level shifting, but you still have to decide. Do you have a favorite approach that wasn’t listed? Have you had good or bad luck with any of the approaches? Let us know in the comments! For more info on level shifting, including things to watch out for, check out When Your Level Shifter Is Too Smart To Function.
2025-12-14 23:00:00
PLA (polylactic acid) has become the lowest common denominator in FDM 3D printing, offering decent performance while being not very demanding on the printer. That said, it’s often noted that the supposed biodegradability of PLA turned out to be somewhat dishonest, as it requires an industrial composting setup to break it down. Meanwhile, a potential alternative has been waiting in the wings for a while, in the form of PHA. Recently, [JanTec Engineering] took a shot at this filament type to see how it prints and tests its basic resistance to various forms of abuse.
PHA (polyhydroxyalkanoates) are polyesters that are produced by microorganisms, often through bacterial fermentation. Among their advantages are biodegradability without requiring hydrolysis as the first step, as well as UV-stability. There are also PLA-PHA blends that exhibit higher toughness, among other improvements, such as greater thermal stability. So far, PHA seems to have found many uses in medicine, especially for surgical applications where it’s helpful to have a support that dissolves over time.
As can be seen in the video, PHA by itself isn’t a slam-dunk replacement for PLA, if only due to the price. Finding a PHA preset in slicers is, at least today, uncommon. A comment by the CTO of EcoGenesis on the video further points out that PHA has a post-printing ‘curing time’, so that mechanical tests directly after printing aren’t quite representative. Either you can let the PHA fully crystallize by letting the part sit for ~48 hours, or you can speed up the process by putting it in an oven at 70 – 80°C for 6-8 hours.
Overall, it would seem that if your goal is to have truly biodegradable parts, PHA is hard to beat. Hopefully, once manufacturing capacity increases, prices will also come down. Looking for strange and wonderful printing filament? Here you go.
2025-12-14 20:00:04
The best part about BEV and hybrid cars is probably the bit where their electronics are taken out for a good teardown and comparison with previous generations and competing designs. Case in point: This [Denki Otaku] teardown of a fifth-generation Prius inverter and motor controller, which you can see in the video below. First released in 2022, this remains the current platform used in modern Prius hybrid cars.
Compared to the fourth-generation design from 2015, the fifth generation saw about half of its design changed or updated, including the stack-up and liquid cooling layout. Once [Otaku] popped open the big aluminium box containing the dual motor controller and inverters, we could see the controller card, which connects to the power cards that handle the heavy power conversion. These are directly coupled to a serious aluminium liquid-cooled heatsink.
At the bottom of the Prius sandwich is the 12VDC inverter board, which does pretty much what it says on the tin. With less severe cooling requirements, it couples its heat-producing parts into the aluminium enclosure from where the liquid cooling loop can pick up that bit of thermal waste. Overall, it looks like a very clean and modular design, which, as noted in the video, still leaves plenty of room inside the housing.
Regardless of what you think of the Prius on the road, you have to admit it’s fun to hack.
2025-12-14 17:00:33
When driving around in video games, whether racing games like Mario Kart or open-world games like GTA, the game often displays a mini map in the corner of the screen that shows where the vehicle is in relation to the rest of the playable area. This idea goes back well before the first in-vehicle GPS systems, and although these real-world mini maps are commonplace now, they don’t have the same feel as the mini maps from retro video games. [Garage Tinkering] set out to solve this problem, and do it on minimal hardware.
Before getting to the hardware, though, the map itself needed to be created. [Garage Tinkering] is modeling his mini map on Need For Speed: Underground 2, including layers and waypoints. Through a combination of various open information sources he was able to put together an entire map of the UK and code it for main roads, side roads, waterways, and woodlands, as well as adding in waypoints like car parks, gas/petrol stations, and train stations, and coding their colors and gradients to match that of his favorite retro racing game.
To get this huge and detailed map onto small hardware isn’t an easy task, though. He’s using an ESP32 with a built-in circular screen, which means it can’t store the whole map at once. Instead, the map is split into a grid, each associated with a latitude and longitude, and only the grids that are needed are loaded at any one time. The major concession made for the sake of the hardware was to forgo rotating the grid squares to keep the car icon pointed “up”. Rotating the grids took too much processing power and made the map updates jittery, so instead, the map stays pointed north, and the car icon rotates. This isn’t completely faithful to the game, but it looks much better on this hardware.
The last step was to actually wire it all up, get real GPS data from a receiver, and fit it into the car for real-world use. [Garage Tinkering] has a 350Z that this is going into, which is also period-correct to recreate the aesthetics of this video game. Everything works as expected and loads smoothly, which probably shouldn’t be a surprise given how much time he spent working on the programming. If you’d rather take real-world data into a video game instead of video game data into the real world, we have also seen builds that do things like take Open Street Map data into Minecraft.
Thanks to [Keith] for the tip!
2025-12-14 14:00:15
Most humans like games. But what are games, exactly? Not in a philosophical sense, but in the sense of “what exactly are their worky bits, so we know how to make them?” [Raph Koster] aims to answer that in a thoughtful blog post that talks all about game design from the perspective of what, exactly, makes them tick. And we are right into that, because we like to see things pulled apart to learn how they work.
On the one hand, it’s really not that complicated. What’s a game? It’s fun to play, and we generally feel we know a good one when we see it. But as with many apparently simple things, it starts to get tricky to nail down specifics. That’s what [Raph]’s article focuses on; it’s a twelve-step framework for how games work, and why they do (or don’t) succeed at what they set out to do.
[Raph] says the essentials of an engaging game boil down to giving players interesting problems to solve, providing meaningful and timely feedback, and understanding player motivation. The tricky part is that these aren’t really separate elements. Everything ties together in a complex interplay, and [Raph] provides insights into how to design and manage it.
It’s interesting food for thought on a subject that is, at the very least, hacker-adjacent. After all, many engaging convention activities boil down to being games of some kind, and folks wouldn’t be implementing DOOM on something like KiCAD’s PCB editor or creating first-person 3D games for the Commodore PET without being in possession of a healthy sense of playfulness.
