Cassette Lamp Is A Throwback To The Pencil-Winding Glory Days

March 17, 2021 by 18 Comments

The audio cassette was the first music format that truly championed portability. It was robust, compact, and let people take music on the go to soundtrack their very lives. It was later supplanted by the higher-quality CD and then further digital technologies, but the format remains a nostalgic highlight for many. It also inspired this excellent lamp build from [Fab].

The lamp consists of 8 clear cassettes assembled into a rough cube-like shape on a 3D printed frame. The cassettes are edge-lit from below by a set of WS2812B LEDs, letting them glow in full-color splendour. The real magic of the lamp is the interface, however. A pencil can be inserted to turn the tape reels, just like rewinding a real cassette. However, in this case, they’re attached to a pair of rotary encoders, which are used to vary the color of the LEDs. As a bonus, the entire lamp runs off a Wemos D1, making it possible to update the lamp remotely over the Internet.

It’s a stylish build that would make an excellent conversation piece in any hip maker’s loungeroom. It’s a great nod to the creator of the compact cassette, [Lou Ottens], who passed away earlier this month. Video after the break.

Continue reading “Cassette Lamp Is A Throwback To The Pencil-Winding Glory Days” →

Running 57 Threads At Once On The Arduino Uno

March 17, 2021 by 44 Comments

When one thinks of the Arduino Uno, one thinks of a capable 8-bit microcontroller platform that nonetheless doesn’t set the world alight with its performance. Unlike more modern parts like the ESP32, it has just a single core and no real multitasking abilities. But what if one wanted to run many threads on an Uno all at once? [Adam] whipped up some code to do just that.

Threads are useful for when you have multiple jobs that need to be done at the same time without interfering with each other. The magic of [Adam]’s ThreadHandler library is that it’s designed to run many threads and do so in real time, with priority management as well. On the Arduino Uno, certainly no speed demon, it can run up to 57 threads concurrently at 6ms intervals with a minumum timing error of 556 µs and a maximum of 952 µs. With a more reasonable number of 7 threads, the minimum error drops to just 120 µs.  Each thread comes with an estimated overhead of 1.3% CPU load and 26 bytes of RAM usage.

While we struggle to think of what we could do with more than a handful of threads on an Arduino Uno, we’re sure you might have some ideas – sound off in the comments. ThreadHandler is available for your perusal here, and runs on SAMD21 boards as well as any AVR-based boards that are compatible with TimerOne. We’ve seen other work in the same space before, such as ChibiOS for the Arduino platform. Video after the break.

Continue reading “Running 57 Threads At Once On The Arduino Uno” →

Science Officer…Scan For Elephants!

March 17, 2021 by 29 Comments

If you watch many espionage or terrorism movies set in the present day, there’s usually a scene where some government employee enhances a satellite image to show a clear picture of the main villain’s face. Do modern spy satellites have that kind of resolution? We don’t know, and if we did we couldn’t tell you anyway. But we do know that even with unclassified resolution, scientists are using satellite imagery and machine learning to count things like elephant populations.

When you think about it, it is a hard problem to count wildlife populations in their habitat. First, if you go in person you disturb the target animals. Even a drone is probably going to upset timid wildlife. Then there is the problem with trying to cover a large area and figuring out if the elephant you see today is the same one as one you saw yesterday. If you guess wrong you will either undercount or overcount.

The Oxford scientists counting elephants used the Worldview-3 satellite. It collects up to 680,000 square kilometers every day. You aren’t disturbing any of the observed creatures, and since each shot covers a huge swath of territory, your problem of double counting all but vanishes.

Continue reading “Science Officer…Scan For Elephants!” →

The Devil Is In The Details For This Open Air Laser

March 17, 2021 by 23 Comments

Normally, we think of lasers as pretty complex and fairly intimidating devices: big glass tubes filled with gas, carefully aligned mirrors, cooling water to keep the whole thing from melting itself, that sort of thing. Let’s not even get started on the black magic happening inside of a solid state laser. But as [Jay Bowles] shows in his latest Plasma Channel video, building a laser from scratch isn’t actually as difficult as you might think. Though it’s certainly not easy, either.

The transversely excited atmospheric (TEA) laser in question uses high voltage passed across a a pair of parallel electrodes to excite the nitrogen in the air at standard atmospheric pressure, so there’s no need for a tube and you don’t have to pull a vacuum. The setup shakes so many UV photons out of the nitrogen that it doesn’t even need any mirrors. In fact, you should be able to get almost all the parts for a TEA laser from the hardware store. For example, the hexagonal electrodes [Jay] ends up using are actually 8 mm hex keys with the ends cut off.

Continue reading “The Devil Is In The Details For This Open Air Laser” →

Unicode: On Building The One Character Set To Rule Them All

March 17, 2021 by 75 Comments

Most readers will have at least some passing familiarity with the terms ‘Unicode’ and ‘UTF-8’, but what is really behind them? At their core they refer to character encoding schemes, also known as character sets. This is a concept which dates back to far beyond the era of electronic computers, to the dawn of the optical telegraph and its predecessors. As far back as the 18th century there was a need to transmit information rapidly across large distances, which was accomplished using so-called telegraph codes. These encoded information using optical, electrical and other means.

During the hundreds of years since the invention of the first telegraph code, there was no real effort to establish international standardization of such encoding schemes, with even the first decades of the era of teleprinters and home computers bringing little change there. Even as EBCDIC (IBM’s 8-bit character encoding demonstrated in the punch card above) and finally ASCII made some headway, the need to encode a growing collection of different characters without having to spend ridiculous amounts of storage on this was held back by elegant solutions.

Development of Unicode began during the late 1980s, when the increasing exchange of digital information across the world made the need for a singular encoding system more urgent than before. These days Unicode allows us to not only use a single encoding scheme for everything from basic English text to Traditional Chinese, Vietnamese, and even Mayan, but also small pictographs called ‘emoji‘, from Japanese ‘e’ (絵) and ‘moji’ (文字), literally ‘picture word’.

Continue reading “Unicode: On Building The One Character Set To Rule Them All” →

Experimenting With 3D Printed Rocket Nozzles

March 17, 2021 by 7 Comments

Rocketry is an exacting science, involving a wide variety of disciplines, encompassing everything from fluid mechanics to thermodynamics and materials engineering. As complex as it sounds, that doesn’t mean it’s beyond the purview of the average maker. [Sciencish] demonstrates this with a series of experiments on rocket nozzles in the home lab. (Video, embedded below.)

The video starts with an amusing analogy about nozzle design based on people fleeing a bad pizza. From there, [Sciencish] 3D prints a wide variety of nozzle designs for testing. The traditional bell nozzle is there, of course, along with the familiar toroidal and linear aerospikes and an expansion deflection design. Of course, 3D printing makes it easy to try out fun, oddball geometries, so there’s also a cowbell nozzle , along with the fancy looking square and triangular aerospikes too. Testing involves running the nozzles on a test stand instrumented with a load cell. A soda bottle is filled with rubbing alcohol vapour, and the mixture is ignited, with each nozzle graded on its thrust output. The rockets are later flown outside, reaching heights over 40 feet.

[Sciencish] notes that the results are a rough guide only, as the fuel/air mixture was poorly controlled. Despite this, it’s a great look at nozzle design and all the science involved. It also wouldn’t be too hard to introduce a little more rigour and get more accurate data, either. However, if solid fuels are more your jam, consider brewing up some rocket candy instead.

Continue reading “Experimenting With 3D Printed Rocket Nozzles” →

Hacking A Digital Microscope Camera For Fun And Automated PCB Inspection

March 17, 2021 by 5 Comments

A desire for automated PCB inspection has led [charliex] down some deep rabbit holes. He’s written his own inspection software, he’s mounted his PCB vise on a stepper-controlled table, and now he’s hacked his digital microscope camera to allow remote and automated control.

Eakins cameras have become a relatively popular, relatively inexpensive choice for electronics hobbyists to inspect their small-scale work. The cameras have a USB port for a mouse and overlay a GUI on the HDMI output for controlling the camera’s various settings and capturing images to the SD card. Using the mouse-based GUI can feel clunky, though, so users have already endeavored to streamline the process to fit better in their workflow. [charliex] decided to take streamlining a few steps further.

One issue in microscope photography is that microscopes have an extremely tight focus plane. So, even at the minuscule scales of an SMD circuit board, the components are simply too tall. Only a sub-millimeter-thick layer can be in focus at a time. If you take just a single image, much of what you want to see will be lost in the blurry distance. Focus stacking solves this problem by taking multiple pictures with the focus set at different depths then combining their focused bits into a single sharp image.

This takes care of the focus issue, but even the most streamlined and intuitive manual controls become tedious given the multitude of pictures required. So [charliex] searched for a way to remotely control his camera, automating focus stacking and possibly even full PCB scans.

Continue reading “Hacking A Digital Microscope Camera For Fun And Automated PCB Inspection” →