Mysterious Files PH

Recently the Practical Engineering YouTube channel featured a functional recreation of a pump design that is presumed by some to have been used to pump water up to the medieval Alhambra palace and its fortress, located in what is today Spain. This so-called pulser pump design is notable for not featuring any moving parts, but the water pump was just one of many fascinating engineering achievements that made the Alhambra a truly unique place before the ravages of time had their way with it.

Although the engineering works were said to still have been functional in the 18th century, this pumping system and many other elements that existed at the peak of its existence had already vanished by the 19th century for a number of reasons. During this century a Spanish engineering professor, Cáceres, tried to reconstruct the mechanism as best as he could based on the left-over descriptions, but sadly we’ll likely never know for certain that it is what existed there.

Similarly, the speculated time-based fountain in the Court of the Lions and other elements are now forever lost to time, but we have plenty of theories on how all of this worked in a pre-industrial era.

Alhambra

A UNESCO World Heritage Site since 1984, the Alhambra saw its first construction in 1238 CE by Muhammad I, the first Nasrid emir. The Nasrid dynasty would last from 1238 to 1491 CE when the Muslim state of al-Andalus fell during the Christian Reconquista.

Even after the end of the Nasrid dynasty would the Alhambra see further construction by Charles V in the 16th century. This made the Alhambra a rather unique amalgamation of Islamic and Renaissance-era architecture and engineering. Sadly by the 18th century the structure had been abandoned for centuries, invaded by squatters, and partially destroyed by the troops of Napoleon in 1812.

Only after these troubled times did an appreciation for such cultural heritage begin to flourish, with European and American tourists alike frequenting the area. One of them – US author Washington Irving – was so inspired by his visit in 1828 that he’d end up writing Tales of the Alhambra, containing many myths, stories, sketches, and essays pertaining to the site. This book in particular was instrumental in making an international audience aware of this site and its legacy.

This renewed attention resulted in the site becoming recognized first as a Spanish Cultural Heritage monument in 1870 and subsequently by UNESCO more than a century later.

Water Features

Most fortresses of the era relied primarily on water cisterns that collected rainwater, as well as access to local rivers in some form, usually requiring human or animal labor to transport the latter. This was also how the Alhambra started in its initial fortress form, called the Alcazaba, meaning ‘citadel’ in Spanish, from Arabic al-qaṣabah. The water from this cistern didn’t just supply drinking water, but also for the bathhouse (hammam) and water elements like a pool or fountain for houses in the interior urban area. These houses additionally featured latrines that were flushed using this cistern water.

As the Alhambra expanded, with many palaces and related structures added, its water requirements increased correspondingly. Rather than some small decorative water features for a dozen houses and a communal bath, there were now reflective pools, fountains and a much larger population. This necessitated finding more efficient ways to get more water up the hill on which the Alhambra was constructed.

In addition to the aforementioned pump, there was also an aqueduct (the Acequia Real) that carried water from the Darro River. At a distance of 6.1 km from the fortress the river is at a sufficiently high elevation to provide water using just gravity. This aqueduct additionally provided water via additional branches to gardens and settlements beyond the Alhambra’s walls.

Many details can be found in this 2019 summary of applied hydraulic techniques at al-Andalus fortresses by Luis José García-Pulido and Sara Peñalver Martín.

As noted in that overview article, the reason for the Alhambra being significantly more advanced than other fortresses in the al-Andalus region was that it was the seat of the Nasrid dynasty, ergo it was only natural that it’d not only get all the palaces and comforts, but also the most advanced technologies for supplying water.

Unfortunately the unique pumping device that was used to supply the Alcazaba with water from the aqueduct was replaced in the 18th century with a more basic syphon system and the original device was removed. Up till that point the previous device had continued to work, despite the new owners of the Alhambra not understanding its operating principles. This left 19th century researchers like Cáceres to essentially fully rely on notes made during the previous century.

That said, there are also hints that the Alcazaba of the Antequera fortress used a similar device to pump water uphill, featuring ceramic pipes and other features that are described in by Sancho de Toledo in 1545. Unfortunately these accounts were all written by people who lacked the engineering know-how of the original Nasrid engineers – or any engineering knowledge at all – and thus had no understanding of the workings of these pumps.

This means that we will unfortunately never know exactly what this device looked like or how it worked, but we can still look at some mechanisms which we are familiar with today that could have been used. The concept of the hydraulic ram or pulser pump would seem to come closest compared to what little we do know.

Self-Powered Pumps

Unlike a water pump that uses e.g. an impeller to impart kinetic energy and thus move the liquid, a self-powered pump uses physical phenomena like the water hammer effect or the fact that gas in a liquid will rise in order to effect a pumping effect. The hydraulic ram, for example, uses the water hammer effect and relies only on the kinetic energy of the incoming water.

The basic hydraulic ram functional sequence involves the water current pushing the normally open waste valve close, at which point the water hammer effect from the sudden current cessation forces the delivery valve open and pushing water into the delivery pipe.

This process will reverse again after a short while,  sending a pressure wave upstream and eventually leading to the waste valve reopening. The downstream flow will then resume again, restarting the whole process.

In terms of technological complexity this is a very straightforward design, with the most complex parts being the valves and the pressure vessel that cushions the system against pressure shocks. This is however a design that would have been technologically quite feasible to manufacture and operate.

Another, similar type of pump is the gas lift pump. A very small variant of this is commonly used in devices like coffee percolators, with the pulser pump being in effect a very large implementation of the same general principle. Rather than applying heat to the water reservoir in order to create gas (i.e. steam), the pulser pump uses an air compressing effect that’s also used with water-powered trompe air compressors.

As water falls down a pipe it drags air bubbles along with it, which eventually arrive at the bottom where said air is trapped in a cavity while the water flows on to a lower elevation.

The thinner pipe through which water ultimately is pumped is inserted into this air chamber in such a way that it’ll alternately ingest water and air as the level of the latter varies over time. This way pockets of water become trapped between pockets of air, with a resulting pulsing output of water at the end of this pipe.

Whether the original device at the Alhambra or Antequera exactly matches either pump design will likely remain forever a mystery, but neither were beyond the technological means of the time, with the pulser pump arguably even more straightforward due to a lack of need for any valves and pressure vessels.

Time Or Reflective Fountain

Although the Practical Engineering video focuses on this pump design, its author – Grady – was inspired by a Primal Space video that’s basically just history slop content, not citing any proper sources and propagating myths and misinformation as fact. The worst offender is probably the myth that the fountain that is found in the Court of the Lions was time-activated, with the only evidence for it being a clock being that there are twelve lion statues and there are two times twelve hours in a day.

When we consider the archaeological evidence that exists so far, as well as the findings during the recent restorations, it seems clear that the marble block with its many holes through which the water entered the bowl was intended to diffuse the flow. Around the bowl we can see a corresponding poem of twelve verses by the vizier and poet Ibn Zamrak.

In verses 3 through 7 it specifically refers to “[..] which runs to that which is still, that we know not which of them is flowing”. This quite strongly suggests that the theme was similar to that of the many reflective pools that were so popular around the Alhambra and elsewhere. The idea of it being a time-controlled mechanism would thus seem to be a purely Western interpretation, barring some hitherto unknown evidence appearing.

Lossy History

Perhaps the most cruel aspect of history is that, much like time itself, it has no concern for those of us who live in the present. Throughout the eons as empires rise and crumble back into dust, wondrous inventions are made and soon again forgotten, leaving behind only echoes of deeds and wonder.

If we’re lucky some of it is recorded in a form as durable as Sumerian clay tablets buried underneath desert sands, but if not then what once was shall never be again. This impermanence is the eternal curse of the past, and also the reason why it’s always so important to make multiple copies of your important data.

Due to the passage of time history is mostly just ruins, pot shards and bones buried in mud and sand. Some will try to spruce things up with one’s imagination resulting in faux romanticism, but this naturally bears little connection to the past. That today the Alhambra has been largely restored is testament to how much more respectful we now approach the past, but the parts that were erased after the demise of the Nasrid dynasty are sadly likely to be lost forever.

Featured image: Reflective pool of the Court of the Myrtles, looking north towards the Comares Tower. (Credit: Tuxyso, Wikimedia)

One of the great things about building electronics today is how affordable SMT components have become — sometimes just fractions of a cent each. That low price often means ordering far more than you need so you’ll have spares on hand the next time a project calls for them. Keeping track of exactly how many of each part you actually have, though, is rarely easy. To solve that problem, [John] built the Dotterboard, an open-source SMT tape counter.

While working on some of his other projects, [John] found himself managing thousands of tiny SMT parts and decided it was time to automate the counting. The Dotterboard takes inspiration from the BeanCounter — a compact, portable SMT tape counter — but expands the design to handle larger components beyond the 8 mm tapes the BeanCounter targets.

The Dotterboard is mostly 3D-printed and uses just a few common hardware parts such as springs and ball bearings. An OLED displays the current count, which comes from an encoder tracking movement and multiplying by the number of components per hole. At the heart sits an RP2040 Zero that needs nothing more than a single USB-C cable for power, unlike the bulky industrial SMT counters that demand AC outlets and desk space.

Be sure to check out all the details of the build on [John]’s website, and grab the files from his GitHub if you want to make your own. Let us know what are some projects you’ve done to save you the headache of doing the same task by hand for hours on end.

Although generative language models have found little widespread, profitable adoption outside of putting artists out of work and giving tech companies an easy scapegoat for cutting staff, their their underlying technology remains a fascinating area of study. Stepping back to the more innocent time of the late 2010s, before the cultural backlash, we could examine these models in their early stages. Or, we could see how even older technology processes these types of machine learning algorithms in order to understand more about their fundamentals. [Damien] has put a 60s-era IBM as well as a PDP-11 to work training a transformer algorithm in order to take a closer look at it.

For such old hardware, the task [Damien] is training his transformer to do is to reverse a list of digits. This is a trivial problem for something like a Python program but much more difficult for a transformer. The model relies solely on self-attention and a residual connection. To fit within the 32KB memory limit of the PDP-11, it employs fixed-point arithmetic and lookup tables to replace computationally expensive functions. Training is optimized with hand-tuned learning rates and stochastic gradient descent, achieving 100% accuracy in 350 steps. In the real world, this means that he was able to get the training time down from hours or days to around five minutes.

Not only does a project like this help understand these tools, but it also goes a long way towards demonstrating that not every task needs a gigawatt datacenter to be useful. In fact, we’ve seen plenty of large language models and other generative AI running on computers no more powerful than an ESP32 or, if you need slightly more computing power, on consumer-grade PCs with or without GPUs.

Whether it’s a new couch or a rare piece of hardware picked up on eBay, we all know what it feels like to eagerly await a delivery truck. But the CERN researchers involved in a delivery earlier this week weren’t transporting anyone’s Amazon Prime packages, they were hauling antimatter.

Moving antimatter, specifically antiprotons, via trucks might seem a bit ridiculous. But ultimately CERN wants to transfer samples between various European laboratories, and that means they need a practical and reliable way of getting the temperamental stuff from point A to B. To demonstrate this capability, the researchers loaded a truck with 92 antiprotons and drove it around for 30 minutes. Of course, you can’t just put antiprotons in a cardboard box, the experiment utilized a cryogenically cooled magnetic containment unit that they hope will eventually be able to keep antimatter from rudely annihilating itself on trips lasting as long as 8 hours.

Speaking of deliveries, anyone building a new computer should be careful when ordering components. Shady companies are looking to capitalize on the currently sky high prices of solid-state drives by counterfeiting popular models, and according to the Japanese site AKIBA PC Hotline, there are some examples in the wild that would fool  all but the most advanced users. They examine a bootleg drive that’s a nearly identical replica of the Samsung 990 PRO —  the unit and its packaging are basically a mirror image of the real deal, the stated capacity appears valid, and it even exhibits similar performance when put through a basic benchmark test.

But while the drive’s sequential read and write speeds are within striking distance of the official numbers from Samsung, things start to fall apart when doing random speed tests or performing real-world operations. It took the fake drive over 25 minutes to write a 370 GB file, while the authentic one ripped through the same file in less than 4: giving a true write speed of 261 MB/s and 1,861 MB/s, respectively.

Luckily you don’t have to time how long it takes to dump 100+ GB of data on the drive just to see if it’s legitimate, Samsung offers a tool that can communicate with the drive and determine if it’s an original or not. If they don’t already, we imagine other manufacturers will roll out similar capabilities in an effort to combat these sophisticated clones.

Of course, computers aren’t the only things in our modern world that are impacted by the rising prices of memory and flash storage. On Friday, Sony announced that they would be implementing higher prices across their PlayStation line starting this week to compensate for what they call “pressures in the global economic landscape.”

Starting April 2nd (presumably they didn’t want consumers to think this was a joke), the base model PS5 will be bumped up to $649.99 in the US and €649.99 in Europe, while the PS5 Pro will be set at an eye-watering 899.99 in both currencies. Admittedly we’ve done absolutely no research to support this, but surely that must make the latter system the most expensive home game console in history by a considerable margin. In comparison, Microsoft’s top of the line Xbox Series X is currently priced at $799, though the model with the smaller 1 TB drive is still available for $649.

One might think that the skyrocketing cost of memory would force developers to take a lesson from the early days of computing, and usher in a new era of highly optimized code that manages to do more with less. That would be nice. Instead, we have now have DOOM rendered in the browser using CSS.

As Niels Leenheer explains in the write-up, the original goal was to have the entire game running in CSS. But he quickly ran into issues trying to implement the game logic. So he settled for letting Claude port the open source C code for the base game over to JavaScript, which freed him up to work on doing the graphics in CSS.

If you’re interested in web development it’s a fascinating look at how far the modern browser can be pushed, and even if you don’t, it’s a surprisingly smooth way to play the classic shooter without having to install anything.

Lastly, the public is finally getting some information about the health scare aboard the International Space Station that triggered the first-ever medical evacuation from the orbiting laboratory back in January. As we predicted in our previous coverage, NASA was unwilling to put personal information about one of their astronauts on the public record, and have remained tight-lipped about the situation. So it was Crew-11 Pilot Mike Fincke himself that decided to not only come forward as the individual who experienced the issue, but to detail what he went through in an interview with the Associated Press.

So what happened? Well, nobody is quite sure yet. Fincke says he was eating dinner the night before he was scheduled to go on a spacewalk outside the Station, and suddenly realized he couldn’t speak. His crewmates realized he was in distress, and contacted medical personnel at Mission Control on his behalf. Testing performed both on the Station and back on Earth has yet to provide any explanation for the episode. It lasted approximately 20 minutes, and he’s experienced no issues since. Space is kinda crazy like that sometimes.

See something interesting that you think would be a good fit for our weekly Links column? Drop us a line, we’d love to hear about it.

Although GNSS systems like GPS have made pin-pointing locations on Earth’s sphere-approximating surface significantly easier and more precise, it’s always possible to go a bit further. The latest innovation involves strapping laser retroreflector arrays (LRAs) to newly launched GPS satellites, enabling ground-based lasers to accurately determine the distance to these satellites.

Similar to the retroreflector array that was left on the Moon during the Apollo missions, these LRAs will be most helpful with scientific pursuits, such as geodesy. This is the science of studying Earth’s shape, gravity and rotation over time, which is information that is also incredibly useful for Earth-observing satellites.

Laser ranging is also essential for determining the geocentric orbit of a satellite, which enables precise calibration of altimeters and increasing the accuracy of long-term measurements. Now that the newly launched GPS III SV-09 satellite is operational this means more information for NASA’s geodesy project, and increased accuracy for GPS measurements as more of its still to be launched satellites are equipped with LRAs.

Unless you’re into circuit sculptures, generally speaking, a working circuit isn’t the end-point of a lot of electronics projects. To protect your new creation from grabby hands, curious paws, and the ravages of nature, you’ll probably want some kind of enclosure. These days a lot of us would probably run it off on the 3D printer, but some people would rather stay electronics hobbiests without getting into the 3D printing hobby. For those people, [mircemk] shares how he creates professonal-looking enclosures with handtools.

The name [mircemk] will seem familiar to longtime readers– we’ve featured many of his projects, and they’ve always stood out for the simple but elegant enclosures he uses. The secret, it turns out, is thin PVC sheeting from a sign shop. At thicknesses upto and including 5 mm, the material can be bent by hand and cut with hobby knives. It’s obviously also amenable to drilling and cutting with woodworking tools as well. Drilling is especially useful to make holes for indicator LEDs. [mircemk] recommends cyanoacrylate ‘crazy’ glue to hold pieces together. For holding down the PCB, the suggestion of double-sided tape will work for components that won’t get too hot.

Rather than paint, the bold contrasting colours we’ve become used to are applied using peel-and-stick wallpaper, which is a great idea. It’s quick, zero mess, and the colour is guaranteed to be evenly applied. It might even help hold the PVC enclosure together ever so slightly. You can watch him do it in the video embedded below.

We hate to say it, but for a one-off project, this technique probably does beat a 3D printed box for professional looks, assuming you have [mircemk]’s motorskills. If you don’t have said motor skills, check out this parametric project box generator. If you’d rather avoid PVC while making a square box to hold a PCB, have you considered using PCBs?

Thanks to [mircemk] for the tip! If you have a tip or technique you want to share, please box it up and send it to the tipsline

It’s one thing to learn about transmission lines in theory, and quite another to watch a voltage pulse bounce off an open connector. [Alpha Phoenix] bridges the gap between knowledge and understanding in the excellent videos after the break. With a simple circuit, he uses an oscilloscope to visualize the propagation of electricity, showing us exactly how signals travel, reflect, and interfere.

The experiment relies on a twisted-pair Y-harness, where one leg is left open and the other is terminated by a resistor. By stitching together oscilloscope traces captured at regular intervals along the wire, [Alpha Phoenix] constructs a visualization of the voltage pulse propagating. To make this intuitive, [Alpha Phoenix] built a water model of the same circuit with acrylic channels, and the visual result is almost identical to the electrical traces.

For those who dabble in the dark art of RF and radio, the real payoff is the demonstration of impedance matching in the second video. He swaps resistors on the terminated leg to show how energy “sloshes” back when the resistance is too high or too low. However, when the resistor matches the line’s characteristic impedance, the reflection vanishes entirely—the energy is perfectly dissipated. It really makes it click how a well-matched, low SWR antenna is crucial for performance and protecting your radio.

[Alpha Phoenix] is a genius at making physics visible. He even managed “film” a laser beam traveling at light speed.