The Questionable Benefits Of Paying More For Air Quality Monitors

September 28, 2023 by 12 Comments

Does paying more for air quality monitors (AQMs) make sense? This was the question which [Achim Haug] at the Air Gradient project sought to answer, with the answer being a rather revealing ‘not at all’. Using data from the independent South Coast Air Quality Management District agency (South Coast AQMD), a plot was created of a range of commercially available AQMs for PM2.5 pollutants and their performance against a reference monitor. Here a value of 1.00 would mean performance equal to the (expensive, calibrated) reference.

R2 vs Price. Data Source: South Coast AQMD Data
R2 vs Price. Data Source: South Coast AQMD Data

This plot shows clearly that paying more for an AQM does not get you better performance, with the reason for this explored in a follow-up article by [Achim], where a range of AQMs are checked for which PM2.5 sensors they actually use. Perhaps unsurprisingly, most AQMs use the same PM2.5 sensors, with the sensor module not really affecting the cost of the AQM as they all cost about $10-20 in bulk.

Rather it seems that the other sensors (for CO2, NO2 and other measurements) along with features such as WiFi, LoRa determine much of the price tag. For getting good measurements, properties such as airflow over the sensors, the implemented compensation algorithms are probably the main things you want to look at when purchasing (or building)  an AQM.

(Heading image: particulate matter sizes, relative to a human hair. Credit: California ARB)

The Oldest Living Torrent Is 20 Years Old

September 28, 2023 by 41 Comments

Twenty years ago, in a world dominated by dial-up connections and a fledgling World Wide Web, a group of New Zealand friends embarked on a journey. Their mission? To bring to life a Matrix fan film shot on a shoestring budget. The result was The Fanimatrix, a 16-minute amateur film just popular enough to have its own Wikipedia page.

As reported by TorrentFreak, the humble film would unknowingly become a crucial part of torrent history. It now stands as the world’s oldest active torrent, with an uptime now spanning a full 20 years. It has become a symbol of how peer-to-peer technology democratized distribution in a fast-changing world.

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Looking Inside A 3D Printer Nozzle With Computed Tomography

September 28, 2023 by 16 Comments

Have you ever wondered what’s actually going on inside the hotend of your 3D printer? It doesn’t seem like much of a mystery — the filament gets melty, it gets squeezed out by the pressure of the incoming unmelty filament, and lather, rinse, repeat. Or is there perhaps more to the story?

To find out, a team from the University of Stuttgart led by [Marc Kreutzbruck] took the unusual step of putting the business end of a 3D printer into a CT scanner, to get a detailed look at what’s actually going on in there. The test setup consisted of a Bondtech LGX extruder and an E3D V6 hot end mounted to a static frame. There was no need for X-Y-Z motion control during these experiments, but a load cell was added to measure extrusion force. The filament was a bit specialized — high-impact polystyrene (HIPS) mixed with a little bit of tungsten powder added (1% by volume) for better contrast to X-ray. The test system was small enough to be placed inside a micro CT scanner, which generated both 360-degree computed tomography images and 2D radiographs.

The observations made with this experimental setup were pretty eye-opening. The main take-home message is that higher filament speed translates to less contact area between the nozzle wall and the melt, thanks to an air gap between the solid filament and the metal of the nozzle. They also saw an increased tendency for the incoming filament to buckle at high extruder speeds, which matches up with practical experience. Also, filament speed is more determinative of print quality (as measured by extrusion force) than heater temperature is. Although both obviously play a role, they recommend that if higher print speed is needed, the best thing to optimize is hot end geometry, specifically an extended barrel to allow for sufficient melting time.

Earth-shattering stuff? Probably not, but it’s nice to see someone doing a systematic study on this, rather than relying on seat-of-the-pants observations. And the images are pretty cool too.

The Robot That Lends The Deaf-Blind Community A Hand

September 28, 2023 by 1 Comment

The loss of one’s sense of hearing or vision is likely to be devastating in the way that it impacts daily life. Fortunately many workarounds exist using one’s remaining senses — such as sign language — but what if not only your sense of hearing is gone, but you are also blind? Fortunately here, too, a workaround exists in the form of tactile signing, which is akin to visual sign language, except that it uses one’s sense of touch. This generally requires someone who knows tactile sign language to translate from spoken or written forms to tactile signaling. Yet what if you’re deaf-blind and without human assistance? This is where a new robotic system could conceivably fill in.

The Tatum T1 in use, with a more human-like skin covering the robot. (Credit: Tatum Robotics)
The Tatum T1 in use, with a more human-like skin covering the robot. (Credit: Tatum Robotics)

Developed by Tatum Robotics, the Tatum T1 is a a robotic hand and associated software that’s intended to provide this translation function, by taking in natural language information, whether spoken, written or in some digital format, and using a number of translation steps to create tactile sign language as output, whether it’s the ASL format, the BANZSL alphabet or another. These tactile signs are then expressed using the robotic hand, and a connected arm as needed, ideally using ASL gloss to convey as much information as quickly as possible, not unlike with visual ASL.

This also answers the question of why one would not just use a simple braille cell on a hand, as the signing speed is essential to keep up with real-time communications, unlike when, say, reading a book or email. A robotic companion like this could provide deaf-blind individuals with a critical bridge to the world around them. Currently the Tatum T1 is still in the testing phase, but hopefully before long it may be another tool for the tens of thousands of deaf-blind people in the US today.

Proper Video, From An ESP32

September 27, 2023 by 19 Comments

Back in the day a miniature television, probably on a wristwatch, was the stuff of science fiction. Now, it’s something which can be done with a commodity microcontroller, as [Atomic14] shows us with the ESP32-TV that plays both video and sound. Even with modern silicon it’s still somewhat pushing the envelope.

As he explains in the video below the break, not all formats are simple enough to be decoded on the fly by a microcontroller. But he finds an AVI file to be within its capabilities which can be created with a bit of ffmpeg wizardry. The board is a fairly standard ESP32 device with an I2C bus, and the video stream isn’t too fast for this meager interface. You’ll maybe recognize the Muppets clip, but it’s possible that the early-80s BBC comedy staple The Young Ones might have passed you by if you’re not British.

We think this code is likely to be of use in quite a few projects, and it would be great to see it further refined. Small video players for not a lot of money can never be a bad thing.

Previous ESP32 video projects which have appeared on these pages have been more likely to involve driving a display directly.

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Investigating The Fourth Passive Component

September 27, 2023 by 45 Comments

When first learning about and building electronic circuits, the first things all of us come across are passive components such as resistors, capacitors, and inductors. These have easily-understandable properties and are used in nearly all circuits in some way or another. Eventually we’ll move on to learning about active components like transistors, but there’s a fourth passive circuit component that’s almost never encountered. Known as the memristor, this mysterious device is not quite as intuitive as the other three, so [Andrew] created an Arduino shield to investigate their properties.

Memristors relate electric charge and magnetic flux linkage, which means that their resistance changes based on the current that passes through them. As their name implies, this means they have memory, and retain their properties even after power is removed. [Andrew] is testing three different memristors, composed of tungsten, carbon, and chromium, using this specialized test set. The rig is based on an Arduino Uno and has a few circuit components that can be used as references and generates data on the behavior of the memristors under various situations.

The memristors used here do exhibit expected behavior when driven with positive voltage signals, but did exhibit a large amount of variability when voltage was applied in a negative direction. [Andrew] speculates that using these devices for storage would be difficult and would likely require fairly bespoke applications for each type. But as the applications for these seemingly bizarre circuit components increase, we expect them to improve much like any other passive component.

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Explore Linux Space Time

September 27, 2023 by 7 Comments

If you’ve ever wondered how much memory a process uses, you’ve probably used a form of task manager or system monitor. System monitors can be useful to identify resource hogs, but are often less versatile if you want more details about just one process. If you’ve ever faced this problem, then [Fabien Sanglard]’s Space-Time explorer is for you!

The wonderfully punny Space-Time tool records physical memory usage, time spent in user space vs. kernel space and even threads and subprocesses created. These words may not mean much to some readers, so let’s quickly go over them: Physical memory usage is the actual amount of RAM given (not always the same as requested). The kernel (which lives in kernel space) is the supervisor to all processes on a computer. In contrast, every process lives in it’s own “user space”, a way of protecting the kernel. Finally, a subprocess (or “child process”) is simply a process started by another process (the “parent”). Continue reading “Explore Linux Space Time” →