Many of us will have broken a laptop at one point or another, destroying the screen or smashing the case. It can be frustrating, as there’s a perfectly usable computer in there, trapped inside a broken husk of a body. [Matthew] saw this not as a problem, but an opportunity – and built a beautiful all-in-one desktop PC. (Video, embedded below.)
With a badly damaged Thinkpad laptop to hand, an ASUS monitor was sourced with a thin body and flat back, perfect for mounting hardware. An MDF base was created, on to which the laptop motherboard was mounted. A USB hub and audio amplifier were then added, along with a USB power isolator and soundcard to avoid problems with groundloops from the onboard headphone output. Speakers were Harman Kardon units salvaged from an old television, providing great quality sound for the build.
There’s plenty of great ideas in the video, from using epoxy for a strong permanent assembly, to a nifty hack to make the power button work. It has us contemplating a build for our own broken laptops in the junkpile. We’ve seen other creative all-in-one builds too, like this one inside a printer.
For most people, a software defined radio is a device. An RTL-SDR dongle perhaps, or the HackRF that a popular multi-tool for working in the radio frequency realm. But as they explain, the SDR hardware can be considered merely as the analogue front end, being just the minimal analogue circuitry coupled with a digitiser. The real software-defined part comes — as you might expect — in the software
Kate and Mike introduce GNU Radio Companion — the graphical UI for GNU Radio — as their tool of choice and praise it’s use as a general purpose digital signal processing system whether or not that includes radio. Taking their own Great Scott Gadgets GreatFET One USB hackers toolkit peripheral as an input device they demonstrate this by analysing the output from a light sensor. Instantly they can analyse the mains frequency in a frequency-domain plot, and the pulse frequency of the LEDs. But their bag of tricks goes much deeper, exploring multiple “atypical use cases” that unlock a whole new world through creative digital signal processing (DSP).
Most countries have dropped the requirement for learning Morse code to become a ham radio operator. Because of that, you might think Morse code is dead. But it isn’t. Some people like the nostalgia. Some like that you can build simple equipment to send and receive Morse code. Others like that Morse code is much more reliable than voice and some older digital modes. Regardless of the reason, many people want to learn Morse code and it is still a part of the ham radio scene. The code has a reputation of being hard to learn, but it turns out that is mostly because people haven’t been taught code in smart ways.
I don’t know if they still do, but some youth organizations used to promote some particularly bad ways to learn the code. The second worse way is to learn “dots and dashes” and many people did learn that way. The very worst way was using an image like the adjacent one to try to map the dots and dashes into letter shapes. This chart dates back to at least 1918 when a Girl Guides handbook printed it.
Even if you are a visual learner, this is a bad idea. The problem is, it is nearly impossible to hear sounds at 20 or 30 words per minute and map them to this visual representation. Another visual method is to use a binary tree where left branches are dots and right branches are dashes.
If you only need to master 5 words per minute to get a merit badge, you might get away with this. But for real use, 5 words a minute is very slow. For example, this sentence would take about 3 minutes to send at that speed. Just that one sentence.
Have you heard the exciting news about Betelgeuse? It’s been hard to miss these days, with reports of the red supergiant star suddenly dimming, and speculation growing that the star will go supernova sometime in the next 10,000 years. But the exciting part is that astronomers have gotten together and scheduled the Betelgeuse supernova for February 21, 2020. Or at least that’s how at least a half-dozen poorly written articles make it sound. We thought that seemed odd, so we dug a bit and the real story is more complicated and more interesting. Betelgeuse is normally a variable star that goes through complex cycles of brightening and dimming. Its current dimming is unprecedented in magnitude, but the timing coincides with its normal cycle. If this dimming is just a deepening of its normal cycle, the star should start brightening again on February 21. If it doesn’t, it could mean the star is entering the next phase in its evolution. We’d love to see a star so bright it’s visible in daylight and casts shadows at night, but we’ll just have to see what happens on Friday.
One of the last two factories in the world that makes the lacquer master discs needed to make vinyl records burned to the ground last week. Luckily nobody was hurt, but it took 82 firefighters hours to get the blaze under control. It remains to be seen how this loss will impact the vinyl record market, but since the appearance of a new star in the sky has long been seen as a bad omen and a portent of doom, if Betelgeuse does go boom next week, expect to hear the hipsters gnash their teeth and rend their man-buns. In the meantime, enjoy perhaps your last look at the fascinating vinyl manufacturing process.
Rent it once, rent it for life? Apparently, at least if you rent a Ford vehicle from Enterprise and install the FordPass app on your phone. That was the experience of one Masamba Sinclair when he rented a Ford Expedition in October and found that even five months later, the app – which he never unpaired from the rental vehicle – allowed him to start and stop the car’s engine, unlock the doors, and even track its location. The same thing even happened again this month when he rented a Mustang. Ford and Enterprise might both want to rethink the security model here; leaving it up to the customer to unlink the car from the app is a recipe for disaster.
Don’t forget that we have a really interesting contest going on right now: the Train All The Things machine learning contest. With so many different machine learning platforms and frameworks available today, you can surely find a way to build something that really shines. The early entries are interesting, with everything from an intelligent bat detector to sunglasses that give you control of the world. The contest is sponsored by Digi-Key and runs through April 7, so get started on your AI masterpiece and send it in.
Speaking of Digi-Key, they’ve put together a handy list of vendors from their line card who are reporting impacts from the Covid-19 outbreak in China. We wondered about supply chain effects from the outbreak recently, and this is confirmation that we’re starting to see a pinch. As of this writing, there are 62 vendors listed, with the majority reporting impacts from the extension of the Chinese New Year holiday. We’ll stay on top of this story, and of course we continue to wish our friends in China well.
There are a variety of ways to enjoy your audio, of which headphones are one. Making a set of headphones is a straightforward enough project, but [madaeon] has taken the art to a new level by building the headphone drivers from scratch rather than using an off-the-shelf pair.
The result is a set of moving coil drivers with a construction technique involving using the semi-opaque thin window from an envelope as a diaphragm and as a former for the coil. Cyanoacrylate adhesive holds everything in place. The diaphragm is suspended across the mouth of a cardboard tube with the coil positioned above a magnet, resulting in the minimum moving mass necessary for as good a sound reproduction as possible. Judge for yourself, there’s a video that we’ve placed below the break.
The drivers are placed in a set of 3D-printed on-ear holders, and while they probably won’t match an expensive set of commercial headphones, we’d hazard a guess that they won’t have too bad quality. At the very least, it’s an interesting design to base further experimentation on.
Microcontrollers tend to consume other kinds of electronics. A project you might once have done with a 555 now probably has a cheap microcontroller in it. Music synthesizers? RC controllers? Most likely, all microcontroller-based now. We always thought RF electronics would be immune to that, but the last decade or two has proven us wrong. Software-defined radio or SDR means you get the RF signal to digital as soon as possible and do everything else in software. If you want an introduction to SDR, Elektor now has an inexpensive RF shield for the Arduino. The Si5351-based board uses that oscillator IC to shift RF signals down to audio frequencies and then makes it available to the PC to do more processing.
The board is available alone or as part of a kit that includes a book. There’s also a series of Elektor articles about it. There’s also a review video from Elektor about the board in the video, below.
If you’ve ever worked with vacuum tubes, you’ll probably have a healthy appreciation for high voltage power supplies. These components require higher potentials to get those electrons moving, or so we’re told. It’s not the whole truth though, as [Albert van Dalen] demonstrates with his tube preamplifier running from only 3.3 V. If your first thought is that he must have made a flyback converter to step that voltage up to something more useful then you’re in for a surprise, because the single 6J6 pentode really does run from just 3.3 volts. Even its heater, normally supplied with 6.3 V, takes the lower voltage.
The circuit appears at first sight to be a conventional single-ended design, but closer examination reveals a grid bias circuit more reminiscent of a bipolar transistor. This results in a positive grid voltage rather than the more usual negative, and an unusually high 0.3 mA grid current. The cathode current is only 0.15 mA, but the preamplifier delivers a 3.5x gain. There is more detail on his website.
It would be interesting to subject this circuit to a full audio analysis and comparison with a more conventional design. As with so much in the world of audio there’s some smoke and mirrors around what constitutes the so-called “valve sound”, and it’s a question whether the satisfaction comes through the sound itself or the bragging rights of having a unit with a vacuum tube on show. Still, this is a simple enough design which takes few resources to build, so we look forward to seeing further experimentation. Careful though – down the vacuum audio route can lie folly.
