RepRapMicron Uses Fibre Optics To Print Tiny Benchy In Resin

October 23, 2026 by Maya Posch 8 Comments

The 0.5 mm Benchy made with the MicroRepRap UV head.

The RepRapMicron (also µRepRap) is pretty much the microscopic take on what RepRap did for more macroscale manufacturing, with the most recent innovation being a UV print head, called the PIKA UV Head. What this does is use off-the-shelf optical fiber and UV LED modules to create 3D structures in-situ in a UV resin, allowing for pretty small structures to be printed, down to a resolution of about 9 µm.

More photos of prints can be found on the blog page with links to YouTube videos. It’s naturally somewhat tricky to get clean photographs of a 3D print that’s small enough to lose forever if you so much as sneeze or breathe too loudly.

For the UV head assembly a single mode fiber optical cable was used in the form of a regular patch cord that got trimmed a bit with a hacksaw. This was used in combination with a “3W” UV LED module, which may or may not be its true rating, but it was definitely able to cure the SLA resin. The used resin was regular eSun Standard Resin.

Afterwards you have to do the typical SLA post-processing, including cleaning off of liquid resin – both the part and fiber – and curing the part. So far results are pretty decent, with overhangs still being a weak spot that will be addressed in future revisions.

Reconstructing The Ancient Chinese Storm Of Crows Weapon

October 23, 2026 by Maya Posch 17 Comments

The Chinese had been using large crossbows – akin to Greek and Roman ballistae – for warfare for many of the same reasons that European armies loved them. Their single, large arrow was effectively unstoppable, though this also was rather useless against large groups of infantry unless they were so kind to neatly line up. Old Chinese records mention a special kind of ammunition, called a cup arrow, or ‘storm of crows’, which involves launching many smaller arrows instead of a single large one, a feat that [Tod] really wanted to try and recreate.

In itself this doesn’t sound too complex: just grab some arrows, loosely tie them together in a bundle and slap them on the crossbow. Yet with the immense forces applied on this bundle it clearly turns out that the engineering challenge isn’t quite that straightforward, as the arrows love to scatter wildly in all directions or otherwise be rather unpredictable.

Although we can find historical references to multiple bolt siege crossbows being used, details are sparse on how the Chinese engineers addressed these aforementioned issues, so [Tod] tries a range of approaches to try and make it work on his own siege crossbow. Unfortunately he wasn’t able to make it work reliably, but he says he’ll be back with a range of improvements, with the community invited to pitch in their own ideas.

These type of weapons were very commonly used in China and surrounding nations from hundreds of years BCE to around the 16th century CE, when black powder was used to launch projectiles like fire arrows from a Huo Che or the Korean equivalent of the Hwacha, effectively multiple rocket launchers, not unlike the MLRS units seen in militaries today.

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Restoring A Soviet ES-4001 Mainframe Control Panel

October 22, 2026 by Maya Posch 19 Comments

Recently the [Chornobyl Family] got their hands on an ES-4001 control panel for a 1970s-era Soviet mainframe, with the intention to restore it to full working order. Not just because they’re really into cool old Soviet technology, but also because of the connection that this control panel holds to the Chernobyl nuclear accident that was so instrumental to the area in modern times.

The Duga-1 computer room with what's left of the ES-1060 mainframe. (Credit: Chornobyl Family, YouTube) — The Duga-1 computer room with what’s left of the ES-1060 mainframe. (Credit: Chornobyl Family, YouTube)

During the 1970s the USSR felt that it could not be left behind in the race to create better digital computers. This led them to not only create a few original designs, but also effectively clone the IBM System/360 and System/370. This resulted in the ES EVM-series of mainframes, with an ES-1060 finding itself installed at the Duga-1 early warning radar system near what is now the Chornobyl nuclear power plant in Ukraine.

Although the radar arrays are the most well-known feature of the Duga-1, below it is the computer center where the ES-1060 was installed. It was never put into service following the ChNPP Unit-4 accident — all that remains of a once pinnacle of Soviet engineering are the picked-over carcass of the mainframe and its control panel.

The control panel in question was obtained was from the early 1980s, serving a more gentle service life in a datacenter and looks to be in a mostly good condition. That said, there was still enough to be done to make it work and undo the damage of its violent removal from the mainframe. Along the way we also learn how the system was used and how the control panel works.

Although similar in some ways to the System/370, it’s still very different, and with only about 300 of these mainframes produced, it’s worth saving whatever elements still remain today, along with the surviving documentation.

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Floating-Point Addition And Subtraction On Intel’s 8087

October 22, 2026 by Maya Posch No comments

Although you can do basic floating point format operations like addition and subtraction just fine on any CPU, having specialized hardware for it can provide a significant speed boost. Here Intel’s 8087 was the first mainstream floating-point coprocessor to provide this option to a wide audience, with [Ken Shirriff] recently reverse-engineering using an 8087 die how these basic operations were implemented.

The real-world speed-up of even simple operations like adding two floating point numbers compared to the 8086 CPU was on the order of a hundred times, which is very relevant the moment you start doing interesting things with spreadsheets, not to mention rendering 3D scenes in CAD software or even games.

As always, the devil is in the details, with sneaky infinities and edge cases also providing the biggest potential for speed-ups in dedicated silicon, along with the large circuitry spent on the shifter. With floating point values being very much about aligning values with shifting by a number of bits, this circuitry along with the detecting of over- and underflows is the key element why the 8087 and its successors were so crucial in making floating-point operations at all feasible in PC applications.

How this shifting works in theory is detailed in the article by [Ken], along with how the 8087 implements this in its circuits. Naturally, a large part of this is implemented in microcode, the listing for which is also provided. From this it’s quite clear how what seems like a simple set of operations is actually quite complex, making even the now much maligned x87 ISA an improvement over doing it all in integer-based software.

Making A Five-Segment Display With Platinum-Titanium Cathodes

October 21, 2026 by Maya Posch 16 Comments

Before the advent of effective semiconductor LEDs many display types existed to display things like numbers and other characters. The Nixie tube is a well-known one, along with VFDs and there are also lesser known ones such as Burrough’s Panaplex, which all saw plentiful use in everything from calculators to audio equipment. The design that [Witchcraft and Alchemy] made appears to lean heavily on this Panaplex design.

Rather than neon, this uses argon as the gas. The anode is formed by the indium-tin oxide layer on a piece of glass, with the cathode sputtered onto the other side in the form of first a titanium layer followed by platinum. This combination helps to prevent the latter from flaking off due to incompatibilities between the molecular matrices of the glass and platinum.

Since this is an early prototype, only five segments were sputtered onto the glass and driven with a 74141 Nixie driver IC, creating the expected purple glow in a vacuum chamber. Following this a self-contained prototype was created, but this proved to be less successful, with the prototype quickly failing to light up as expected.

For a next attempt no tape or epoxy for sealing the device will be used, but rather a gasket instead of gluing the front glass onto the device. The use of conductive vias should make the device’s vacuum more permanent, and enable those last two segments to make it a seven-segment display. The final change should be to use a Penning mixture instead of pure argon.

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Every Type Of Current Sensor Explained

October 21, 2026 by Maya Posch 7 Comments

Measuring electric currents is an essential element of many electrical systems, but doing so in a way that is as nonintrusive as possible is not an easy problem to solve. Due to this we got a wide variety of current sensors to choose from for any given application, with [ElectrArc240] running us through these variants in a recent video.

The fairly low-tech, cheap and quite reliable method of using a shunt resistor is first demonstrated. This sees a lot of use in fairly low-voltage and low-current applications, with for example videocards using it to limit the amount of power the GPU can use, a feature that modders will happily bypass. Here simply the voltage drop across a known resistance value is measured, from which the current can be derived.

Of course, you got higher voltage and higher current applications too, as well as direct- and alternating current, with the latter especially allowing for easy current measurements simply from the electromagnetic field, or flux. Anyone who has used a clamp meter can attest to that such contact-free current sensing works, even for DC applications.

Beyond the basic transformer type you got many variants including Hall-Effect, TMR and fluxgate sensors, as well as the fiber-optic current sensor that uses an interferometer to measure the phase-change induced by the magnetic field – the Faraday effect – to the transmitted electromagnetic radiation. These more exotic types will improve resolution, at the cost of a rapidly increasing void in your project budget.

These various sensor types and their construction are demonstrated and discussed in the video, including when you’d want to use a specific type, and what the potential gotchas are with each type. Even if for many applications a simple shunt resistor suffices, it’s a good idea to know these different types, as well as their underlying theory of operation.

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Using Ultrasound And Microbubbles To Make Tiny Devices

October 20, 2026 by Maya Posch 9 Comments

Although we generally do not look at bubbles in fluids as more than a curiosity – if not an outright annoyance – in certain contexts they can be very useful. If you can namely control their formation and position, you can use them in small systems to control actuators and dynamically affect acoustic systems. The main issues here are that controlling their formation, lifetime and controllability remain hard to solve. This is what [Zhiyuan Zhang] et al. sought to address, with a recent study published in Science Advances covering their approach using ultrasound-driven, electronically programmable microbubbles.

There’s also a Cornell press release article about their findings, which uses a new device that produces hydrogen bubbles along a grid of electrodes, before using ultrasound to steer them around. Using this chip-like device they claim to be able to control the 10-100 micron sized bubbles, with the ultrasound matching the resonant frequency of the target bubble. With each bubble size having its own resonant frequency, this allows for individual control by varying the induced oscillations.

Although in the demonstrated 2D setup this microbubble approach works well, it still requires a fairly bulky bench top setup around it which would need to be scaled down to be more practical. There is also the issue that the chamber geometry affects the movement of a bubble, which becomes especially important to further research when using complex (3D) chambers with this technology.