Wiremold is great stuff — it’s relatively cheap, easy to work with, and offers all sorts of adapters and angle pieces which take the hassle out of running (and hiding) wires. But [Dr. Gerg] found a shortcoming of this otherwise very flexible product: since each run is intended to start and end in a surface mounted box, he couldn’t find an end cap that would let him close off a section.

The solution? A desktop 3D printer and a chunk of OpenSCAD code telling it what to extrude. When you break it down, the Wiremold profile is fairly straightforward, and can be easily described with geometric primitives. A handful of cylinders, a cube or two, tie it all together with the hull() function, and you’re there.

We’d say this would be a fantastic project to cut your OpenSCAD teeth on, but since [Dr. Gerg] was kind enough to share the source code, you don’t have to figure it out on your own. Though there’s still benefit in reading over it if you’re looking for some practical examples of how the “Programmers Solid 3D CAD Modeller” gets things done.

So why would you want a Wiremold endcap? In the case of [Dr. Gerg], it sounds like he was trying to cover up a short run of wire that was running vertically. But we could imagine other applications for this basic design now that it’s out in the wild. For example, a short length of Wiremold outfitted with a pair of printed caps could make for a nice little enclosure if you’ve got a small project that needs protecting.

Sometimes it’s the most straightforward of hacks which are also the most satisfying, and so it is that we’d like to draw your attention to [mikeandmertle]’s PVC thumb nuts. They provide a cheap an easy to make way to create thumb-tightenable nuts for your projects.

Starting with a PVC sheet, a series of discs can be cut from it with a hole saw. The hole in the centre of the disc is chosen such that it’s a bit smaller than the required nut, so that it can be pressed into the space with a bolt and a washer. Then a second PVC disc is glued over one side of the first before being sanded to a regular shape, resulting in a captive nut at the centre of a finger-sized and easily turnable handle.

We like this project, and we think that quite a few of you will too. We wonder how much torque it will take, but we’re guessing that a threaded insert could easily be substituted for the nut in more demanding applications. And of course, for more demanding applications you could always try knurling.

If you follow the world of microcontrollers, then you’ll probably be familiar with the most recent crop of ten cent parts. They bring power and features previously the preserve of much more expensive chips into the super-budget arena, and they’re appearing in plenty of projects on these pages.

If you’re not familiar with them it can seem daunting to decide which one to use, so to help you [Zach of All Trades] is comparing two of the more common ones. The CH32V003 with a RISC-V core and the PY32F002 with an ARM Cortex M0+ core are both pretty similar on paper, but which should you use?

The video below gives a run-down of each part along with some demonstrations before making its conclusions. The ARM-based part isn’t as quick as the RISC-V one but has a slight edge on peripherals, while the support is where a potential winner emerges in the shape of the CH32. That should be the last word, but for that the PY32 has the distance advantage over its rival of ready availability.

So this look at two families of cheap microcontrollers reveals the pros and cons of each, but in reality it provides an introduction to two sets of powerful chips for pennies.

As we’ve observed before, there are more chips to be found in this market.

The triboelectric effect is familiar to anyone who has rubbed wool on a PVC pipe, or a balloon on a childs’ hair and then stuck it on the wall. Rubbing transfers some electrons from one material to the other, and they become oppositely charged. We usually think of this as “static” electricity because we don’t connect the two sides up with electrodes and wires. But what if you did? You’d have a triboelectric generator.

In this video, [Cayrex] demonstrates just how easy making a triboelectric generator can be. He takes pieces of aluminum tape, sticks them to paper, and covers them in either Kapton or what looks like normal polypropylene packing tape. And that’s it. You just have to push the two sheets together and apart, transferring a few electrons with each cycle, and you’ve got a tiny generator.

As [Cayrex] demonstrates, you can get spikes in the 4 V – 6 V range with two credit-card sized electrodes and fairly vigorous poking. But bear in mind that current is in the microamps. Given that, we were suprised to see that he was actually able to blink an LED, even if super faintly. We’re not sure if this is a testament to the generator or the incredible efficiency of the LED, but we’re nonetheless impressed.

Since around 2012, research into triboelectric nanogenerators has heated up, as our devices use less and less power and the structures to harvest these tiny amounts of power get more and more sophisticated. One of the coolest such electron harvesters is 3D printable, but in terms of simplicity, it’s absolutely hard to beat some pieces of metal and plastic tape shoved into your shoe.

You have an old radio — in the case of [The Radio Mechanic], a Stromberg Carlson — and it needs new knobs. What do you do? You can’t very well pop down to the local store and find any knobs anymore. Even if you are lucky enough to be around an electronics store, they aren’t going to have knobs to do justice to an antique radio. You could 3D print them, of course, but there are a number of issues with transferring the old knob to a CAD file for printing. So [The Radio Mechanic] decided to cast them instead.

He printed some fixtures to help with the molding using two-part molding silicone. He mounted the knob on a shaft in a jig, filled the jig with silicone, and lowered the knob into the mix. The next day, he had a good-looking mold.

The next step, of course, is to cast with resin. Admittedly 3D printing would have been faster, but would not have as nice a surface finish. The epoxy resin is clear, but he was hopeful that some caramel pigment would match the original knob color. Spoiler alert: it didn’t. The resulting knob looked translucent, like a root beer barrel candy, rather than the brown sugar color of the original knob.

The knob needed a spring insert to hold the shaft, so he repurposed some from a different kind of radio. Overall, this is the kind of thing we always think we are going to do when we need something and then we rarely follow through. Then again, we rarely have the patience to wait as long as these two knobs took to make.

Of course, a casting guerrilla doesn’t have to make just knobs. You can even add metal powders to do cold metal casting.

This ultra-cute tiny LiDAR rangefinder project by [gokux] can be thought of as a love letter to the incredible resources and components hobbyists and hackers of all types have access to nowadays. In fact, it all stemmed from coming across a miniscule half-inch 64×32 OLED display module that was simply too slick to pass up.

To use it, one simply powers it on and the display will read out the distance in millimeters. The VL53L0X time-of-flight sensor inside works by sending out a laser pulse and measuring how long it takes for the pulse to bounce back. We hope you’re curious about what such a sensor looks like on the inside, because here’s a nifty teardown of these fantastic devices. The device can technically measure distances of up to 2 m, but [gokux] says accuracy drops off after 1 m.

The main components besides the OLED display and VL53L0X sensor are an ESP32-C3 board (which handily integrates battery charging circuitry), 3D-printed enclosure, tiny rechargeable battery, and power switch. The whole thing is under one cubic inch. Not bad, and it even makes a passable keychain. Parts list, code, and 3D model files, including STEP format, are all available if you’d like to spend an afternoon making your own.

Even among ThinkPads, which are nearly universally loved by hardware hackers and Linux tinkerers alike, the 701c is a particularly rare and desirable machine. Best known for it’s “butterfly” slide out keyboard, the IBM-designed subnotebook from the mid-1990s has gained a following all its own, with active efforts to repair and restore any surviving specimens still out in the wild.

[polymatt] has already taken on a number of 701c restoration projects, but the recent release of a 3D printable case for the vintage laptop is arguably the most impressive to date. After spending an untold number of hours with an original case and a pair of calipers, the final design has been released under the Creative Commons Attribution-NonCommercial license — in other words, you’re free to print one to spruce up your 701c, but don’t run off a stack of them and start trying to move them on Etsy.

Originally, [polymatt] just wanted to 3D print a replacement for the laptop’s display bezel. But as often happens with these sort of projects, things just sort of started rolling and pretty soon the whole case was modeled. As you might imagine, the printed case has some slight differences between the original. For example, the printed version is designed to use heat set inserts. There’s also certain components, such as the hinges, which need to be sourced from an original case.

The most obvious use of these files is to perform repairs — if a piece of your 701c case has broken, you might be able to use one of these files to create a replacement. But it also offers some fascinating possibilities for future modifications. If you were planning on replacing the internals of the 701c with something more modern, these files would make an excellent starting point to create a customized case to better fit more modern components.

Whatever you end up doing with these files, don’t be shy — let us know.

The ULN2003 IC is an extremely versatile part, and with the help of [Hulk]’s deep dive, you might just get some new ideas about how to use this part in your own projects.

Inside the ULN2003 you’ll find seven high-voltage and high-current NPN Darlington pairs capable of switching inductive loads. But like most such devices there are a variety of roles it can fill. The part can be used to drive relays or motors (either brushed or stepper), it can drive LED lighting, or simply act as a signal buffer. [Hulk] provides some great examples, so be sure to check it out if you’re curious.

Each of the Darlington pairs (which act as single NPN transistors) is configured as open collector, and the usual way this is used is to switch some kind of load to ground. Since the inputs can be driven directly from 5 V digital logic, this part allows something like a microcontroller to drive a high current (or high voltage, or both) device it wouldn’t normally be able to interface with.

While the circuitry to implement each of the transistor arrays isn’t particularly complex and can be easily built by hand, a part like this is a real space saver due to how it packs everything needed in a handy package. Each output can handle 500 mA, but this can be increased by connecting in parallel.

There’s a video (embedded below) which steps through everything you’d like to know about the ULN2003. Should you find yourself wanting a much, much closer look at the inner secrets of this chip, how about a gander at the decapped die?

Metal-oxide semiconductor field-effect transistors (MOSFETs) see common use in applications ranging from the very small (like CPU transistors) to very large (power) switching applications. Although its main advantage is its high power efficiency, MOSFETs are not ideal switches with a perfect on or off state. Understanding the three main sources of switching losses is crucial when designing with MOSFETs, with a recent All About Circuits article by [Robert Keim] providing a primer on the subject.

As it’s a primer, the subthreshold mode of MOSFET modes of operation is omitted, leaving the focus on the linear (ohmic) mode where the MOSFET’s drain-source is conducting, but with a resistance that’s determined by the gate voltage. In the saturated mode the drain-source resistance is relatively minor (though still relevant), but the turn-on time (R_DS(on)) before this mode is reached is where major switching losses occur. Simply switching faster is not a solution, as driving the gate incurs its own losses, leaving the circuit designer to carefully balance the properties of the MOSFET.

For those interested in a more in-depth study of MOSFETs in e.g. power supplies, there are many articles on the subject, such as this article (PDF) from Texas Instruments.

If you need to make polyurethane belts in custom lengths, it’s not too hard. You just need to take lengths of flexible polyurethane filament, heat the ends, and join them together. In practice, it’s difficult to get it right by hand. That’s why [JBVCreative] built a 3D printed jig to make it easy. 

The jig consists of two printed sliders that mount on a pair of steel rods. Each slider has a screw-down clamp on top. The clamps are used to hold down each end of the polyurethane filament to be joined. Once installed in the jig, the ends of the filament can be heated with a soldering iron or other element. and then gently pushed together. The steel rods simply enable the filament to be constrained linearly so the ends don’t shift during the joining process.

The jig doesn’t produce perfect belts. There’s still a small seam at the join that is larger than the filament’s base diameter. A second jig for trimming the belt to size could be helpful in this regard. Still, it’s a super useful technique for making custom belts. This could be super useful to anyone needing to restore old cassette decks or similar mechanical hardware.

[Thanks to Keith Olson for the tip!]

As [Electronoobs] points out, everything has resistance. So, how hard can it be to make a high-power resistor? In the video below, he examines a commercial power resistor and how to make your own using nichrome wire.

Sure, in theory, you can use a long piece of wire, but normally, you want to minimize the amount of space occupied. This leads to winding the wire around some substrate. If you just wind the wire, though, you get an inductor. This can cause nasty voltage spikes when there is a change in current through the resistor. You can get “noninductive” wire wound resistors that use either two opposing windings or alternate the turn direction on each turn. This causes the magnetic fields to tend to cancel out, reducing the overall inductance.

Nichrome wire has more resistance per millimeter and can dissipate more power. Modern digital meters can measure the resistance of a wire if you account for the test leads. To make a substrate, [Electronoobs] got creative since he anticipated generating a lot of heat. The final product even uses water cooling.

Why do you want a big resistor? Maybe you need a dummy load, or you want to drain some batteries. If you want to recycle nichrome wire, it is much more common than you might expect.

As curious people, we’re all incredibly fortunate to live in an age where information can so easily be obtained. If you want to learn how something works, from a cotton gin to an RBMK reactor, you’re just a few keystrokes away from articles, diagrams, and videos on the subject. But as helpful as all of that information can be, we also know that there’s no substitute for hands-on experience.

While we can’t recommend you try building a miniature graphite-moderated nuclear reactor, there’s plenty of other devices that you can study by constructing your own functioning model. For example, when [Jorisclayton] wanted to really know what was going on inside a computer, they decided to go back to basics and build their own Z80 machine. To maximize the experience, they skipped any of the existing kit designs and instead wired the whole thing up by hand across a few perfboards.

The main board contains a 4 MHz Z80 processor, paired with 32K ROM and 64K RAM. Here you’ll also find the clock generator, I/O decoder, serial port, voltage regulator, and a trio of expansion slots that use a long strip of 2.54 mm pin headers as the interface. In the first expansion slot you’ve got a primordial “graphics card” based around the TMS9918 video display controller (VDC) and 16K of additional RAM. The second expansion card has a CompactFlash reader and an LED array mapped to I/O address 0x00h so it can be used for various notifications.

[Jorisclayton] says the final expansion board is still being worked on, but the idea is for it to handle user input through a PS/2 keyboard connector, as well as provide ports for a pair of Super Nintendo (or compatible) controllers. Everything is held together with a minimalist 3D printed frame to show off all that careful soldering.

Obviously there’s no PCB design files to share for this one, but [Jorisclayton] has posted a schematic for wiring everything up if you’re looking for resources to build your own Z80 computer. Sure the chips themselves might no longer be in production, but that doesn’t mean this venerable CPU is going anywhere just yet.

Fidget toys all have a satisfying mechanical action to engage with, and [uhltimate]’s OTF (out the front) “fidget knife” model provides that in spades. The model snaps open and closed thanks to a clever arrangement of springs and latches contained in only three printed pieces.

Here’s how it works: at rest, the mock blade (orange in the image above) is latched in the closed position. As one presses the slider forward, the bottom spring begins to pull up against the blade until it moves far enough to release the latch. When the latch is released, the tension built up in the spring propels the blade outward where it again latches in the open position. Retraction is the same essential process, just in the opposite direction (and using a latch on the opposite side of the blade, which faces the other direction.)

As you may imagine, effective operation depends on the material. The model is designed to be printed in PLA, but [uhltimate] also provides a part variation with a stiffer spring for those who find that basic model isn’t quite up to the task for whatever reason. Smooth surfaces are also helpful for hitch-free operation, but lubrication shouldn’t be necessary.

If this sort of thing is up your alley, don’t miss the satisfying snap action of this 3D printed toggle mechanism, either!

Here’s a CH552G-based USB Blaster project from [nickchen] in case you needed more CH552G in your life, which you absolutely do. It gives you the expected IDC-10 header ready for JTAG, AS, and PS modes. What’s cool, it fits into the plastic shell of a typical USB Blaster, too!

The PCB is flexible enough, and has all the features you’d expect – a fully-featured side-mounted IDC-10 header, two LEDs, a button for CH552 programming mode, and even a UART header inside the case. There’s an option to add level shifter buffers, too – but you don’t have to populate them if you don’t want to do that for whatever reason! The Hackaday.io page outlines all the features you are getting, though you might have to ask your browser to translate from Chinese.

Sadly, there’s no firmware or PCB sources – just schematics, .hex, BOM, and Gerber .zip, so you can’t fix firmware bugs, or add the missing USB-C pulldowns. Nevertheless, it’s a cool project and having the PCB for it is lovely, because you never know when you might want to poke at a FPGA on a short notice. Which is to say, it’s yet another CH552 PCB you ought to put in your PCB fab’s shopping cart! This is not the only CH552G-based programming dongle that we’ve covered – here’s a recent Arduino programmer that does debugWire, and here’s like a dozen more different CH552G boards, programmers and otherwise.

It’s with a tinge of sadness that we and many others reported on the recent move by Zilog to end-of-life the original Z80 8-bit microprocessor. This was the part that gave so many engineers and programmers their first introduction to a computer of their own. Even though now outdated its presence has been a constant over the decades. Zilog will continue to sell a Z80 derivative in the form of their eZ80, but that’s not the only place the core can be found on silicon. [Rejunity] is bringing us an open-source z80 core on real hardware, thanks of course to the TinyTapeout ASIC project. The classic core will occupy two tiles on the upcoming TinyTapeout 7. While perhaps it’s not quite the same as a real 40-pin DIP in your hands, like all of the open-source custom silicon world, it’s as yet early days.

The core in question is derived from the TV80 open-source core, which we would be very interested to compare when fabricated at TinyTapeout’s 130nm process with an original chip from a much larger 1970s process. While It’s true that this project is more of an interesting demonstration of TinyTapeout than a practical everyday Z80, it does at least serve as a reminder that there may be a future point in which a run of open-source real Z80s or other chips might become possible.

This isn’t the first time we’ve featured a TinyTapeout project.

Let’s face it — electronics are hard. Difficult concepts, tiny parts, inscrutable datasheets, and a hundred other factors make it easy to screw up in new and exciting ways. Sometimes the Magic Smoke is released, but more often things just don’t work even though they absolutely should, and no amount of banging your head on the bench seems to change things.

It’s at times like this that one questions their sanity, as [Gili Yankovitch] probably did when he discovered that not all CH32V003s are created equal. In an attempt to recreate the Linux-on-a-microcontroller project, [Gili] decided to go with the A4M6 variant of the dirt-cheap RISC-V microcontroller. This variant lives in a SOP16 package, which makes soldering a bit easier than either of the 20-pin versions, which come in either QFN or TSSOP packages.

Wisely checking the datasheet before proceeding, [Gili] was surprised and alarmed that the clock line for the SPI interface didn’t appear to be bonded out to a pin. Not believing his eyes, he turned to the ultimate source of truth and knowledge, where pretty much everyone came to the same conclusion: the vendor done screwed up.

Now, is this a bug, or is this a feature? Opinions will vary, of course. We assume that the company will claim it’s intentional to provide only two of the three pins needed to support a critical interface, while every end user who gets tripped up by this will certainly consider it a mistake. But forewarned is forearmed, as they say, and hats off to [Gili] for taking one for the team and letting the community know.

As DDR SDRAM increases in density and speed, so too do new challenges and opportunities appear. In the recent DDR5 update by JEDEC – as reported by Anandtech – we see not only a big speed increase from the previous maximum of 6800 Mbps to 8800 Mbps, but also the deprecation of Partial Array Self Refresh (PASR) due to security concerns, and the introduction of Per-Row Activation Counting (PRAC), which should help with row hammer-related (security) implications.

Increasing transfer speeds is primarily a matter of timings within the limits set by the overall design of DDR5, while the changes to features like PASR and PRAC are more fundamental. PASR is mostly a power-saving feature, but can apparently be abused for nefarious means, which is why it’s now gone. As for PRAC, this directly addresses the issue of row hammer attacks. Back in the 2014-era of DDR3, row hammer was mostly regarded as a way to corrupt data in RAM, but later it was found to be also a way to compromise security and effect exploits like privilege escalation.

The way PRAC seeks to prevent this is by keeping track of how often a row is being accessed, with a certain limit after which neighboring memory cells get a chance to recover from the bleed-over that is at the core of row hammer attacks. All of which means that theoretically new DDR5 RAM and memory controllers should be even faster and more secure, which is good news all around.