Let The Wookie Win With This DIY Holochess Table

May 8, 2025 by 9 Comments

If you have seen Star Wars, you know what is being referenced here. Holochess appeared as a diversion built into the Millennium Falcon in the very first movie, way back in 1977. While not quite as iconic a use of simulated holograms as tiny Princess Leia begging for hope, it evidently struck a chord with [Maker Mac70], given the impressive effort he’s evidently gone through to re-create the game table from the film.

The key component of this unit is a plate from Japanese firm ASKA3D that scatters light from displays inside the table in just such a way that the diverging rays are focused at a point above its surface, creating the illusion of an image hovering in space. Or in this case, hovering at the surface of a acrylic chessboard. Granted, this technique only works from one viewing angle, and so is not a perfect recreation of a sci-fi holoprojector. But from the right angle, it looks really good, as you can see in the video below.

There are actually six SPI displays, driven by an Arduino GIGA, positioned and angled to project each character in the game. Placing two of the displays on 3D printed gantries allows them to move, allowing two creatures to battle in the center of the table. As [Maker Mac70] admits, this is quite a bit simpler than the Holochess game seen in the film, but it’s quite impressive for real world hardware.

If this all seems a little bit familiar, we covered an earlier floating display by [Maker Mac70] last year. This works on similar principles, but uses more common components which makes the technique more accessible. If chess isn’t your forte, why not a volumetric display that plays DOOM? If you’re interested in real holograms, not Sci-Fi, our own [Maya Posch] did a deep dive you may find interesting. Continue reading “Let The Wookie Win With This DIY Holochess Table” →

The Owon HDS160 Reviewed

May 8, 2025 by 11 Comments

These days, if you are in the market for a capable digital voltmeter, you might as well consider getting one with an oscilloscope built-in. One choice is the Owon HDS160, which [Kerry Wong] covers in the video below. The model is very similar to the HDS120, but the multimeter in the HDS160 has more counts–60,000 vs 20,000 as you might expect from the model number.

The internal chip is an HY3131, which is rated at 50,000 counts which is odd since the meter is 60,000 counts, but presumably the meter uses some capability of the chip, possibly putting it out of spec. The oscilloscope is the same between the two models. Almost everything else works the same, other than the capacitance measuring feature, as the video shows.

The difference in cost between the two units isn’t much, so if you are shopping, the small extra cost is probably worth it. Not that a 20,000 count meter isn’t perfectly fine for most normal uses.

[Kerry] really likes scopemeters. He gets excited about bench scopes, too.

Continue reading “The Owon HDS160 Reviewed” →

Flow Visualization With Schlieren Photography

May 8, 2025 by 9 Comments

The word “Schlieren” is German, and translates roughly to “streaks”. What is streaky photography, and why might you want to use it in a project? And where did this funny term come from?

Think of the heat shimmer you can see on a hot day. From the ideal gas law, we know that hot air is less dense than cold air. Because of that density difference, it has a slightly lower refractive index. A light ray passing through a density gradient faces a gradient of refractive index, so is bent, hence the shimmer. Continue reading “Flow Visualization With Schlieren Photography” →

An oscilloscope display is shown, showing two plots. A blue plot is shown at one level, and over multiple exposures at different places, it jumps to a higher level. Another yellow trace is shown which, at some point after the blue trace has jumped to a higher level, also jumps cleanly to a higher level. The yellow line is labeled "CFD output," while the blue line is labeled "leading edge discriminator."

A Constant-Fraction Discriminator For Sub-Nanosecond Timing

May 8, 2025 by 3 Comments

Detecting a signal pulse is usually basic electronics, but you start to find more complications when you need to time the signal’s arrival in the picoseconds domain. These include the time-walk effect: if your circuit compares the input with a set threshold, a stronger signal will cross the threshold faster than a weaker signal arriving at the same time, so stronger signals seem to arrive faster. A constant-fraction discriminator solves this by triggering at a constant fraction of the signal pulse, and [Michael Wiebusch] recently presented a hacker-friendly implementation of the design (open-access paper).

A constant-fraction discriminator splits the input signal into two components, inverts one component and attenuates it, and delays the other component by a predetermined amount. The sum of these components always crosses zero at a fixed fraction of the original pulse. Instead of checking for a voltage threshold, the processing circuitry detects this zero-crossing. Unfortunately, these circuits tend to require very fast (read “expensive”) operational amplifiers.

This is where [Michael]’s design shines: it uses only a few cheap integrated circuits and transistors, some resistors and capacitors, a length of coaxial line as a delay, and absolutely no op-amps. This circuit has remarkable precision, with a timing standard deviation of 60 picoseconds. The only downside is that the circuit has to be designed to work with a particular signal pulse length, but the basic design should be widely adaptable for different pulses.

[Michael] designed this circuit for a gamma-ray spectrometer, of which we’ve seen a few examples before. In a spectrometer, the discriminator would process signals from photomultiplier tubes or scintillators, such as we’ve covered before.

3D Printed TPU Bellows With PLA Interface Layers

May 8, 2025 by 22 Comments

Of all FDM filament types, flexible ones such as TPU invite a whole new way of thinking, as well as applications. Case in point the TPU-based bellows that the [Functional Part Friday] channel on YouTube recently demonstrated.

The idea is quite straightforward: you print TPU and PLA in alternating layers, making sure that the TPU is connected to its previous layer in an alternating fashion. After printing, you peel the PLA and TPU apart, remove the PLA layers and presto, you got yourself bellows.

There were some issues along the way, of course. Case in point the differences between TPU from different brands (Sainsmart, Sunlu) that caused some headaches, and most of all the incompatibility between the Bambu Lab AMS and TPU that led to incredibly brittle TPU prints. This required bypassing the feed mechanism in the AMS, which subsequently went down a rabbit hole of preventing the PTFE tube from getting sucked into the AMS. Being able to print TPU & PLA at the same time also requires a printer with two independent extruders like the Bambu Lab H2D used here, as both materials do not mix in any way. Great news for H2D and IDEX printer owners, of course.

As for practical applications for bellows, beyond printing your own 1900s-era camera, accordion or hand air bellows, you can also create lathe way covers and so on.

Continue reading “3D Printed TPU Bellows With PLA Interface Layers” →

Jellybean Mac Hides Modern PC

May 7, 2025 by 19 Comments

The iMac G3 is an absolute icon of industrial design, as (or perhaps more) era-defining than the Mac Classic before it. In the modern day, if your old iMac even boots, well, you can’t do much with it. [Rick Norcross] got a hold of a dead (hopefully irreparable) specimen, and stuffed a modern PC inside of it.

From the outside, it’s suprizingly hard to tell. Of course the CRT had to go, replaced with a 15″ ELO panel that fits well after being de-bezeled. (If its resolution is only 1024 x 768, well, it’s also only 15″, and that pixel density matches the case.) An M-ATX motherboard squeezes right in, above a modular PSU. Cooling comes from a 140 mm case fan placed under the original handle. Of course you can’t have an old Mac without a startup chime, and [Rick] obliges by including an Adafruit FX board wired to the internal speakers, set to chime on power-up while the PC components are booting.

These sorts of mods have proven controversial in the past– certainly there’s good reason to want to preserve aging hardware–but perhaps with this generation of iMac it won’t raise the same ire as when someone guts a Mac Classic. We’ve seen the same treatment given to a G4 iMac, but somehow the lamp doesn’t quite have the same place in our hearts as the redoubtable jellybean.

Superconductivity News: What Makes Floquet Majorana Fermions Special For Quantum Computing?

May 7, 2025 by 13 Comments

Researchers from the USA and India have proposed that Floquet Majorana fermions may improve quantum computing by controlling superconducting currents, potentially reducing errors and increasing stability.

In a study published in Physical Review Letters that was co-authored by [Babak Seradjeh], a Professor of Physics at Indiana University Bloomington, and theoretical physicists [Rekha Kumari] and [Arijit Kundu], from the Indian Institute of Technology Kanpur, the scientists validate their theory using numerical simulations.

Continue reading “Superconductivity News: What Makes Floquet Majorana Fermions Special For Quantum Computing?” →