Building An Oxygen Concentrator: It Isn’t Rocket Science

May 10, 2021 by Jenny List 41 Comments

Back at the start of the pandemic, a variety of hacker designs for life-saving machinery may have pushed the boundaries of patient safety. There are good reasons that a ventilator must pass extensive safety testing and certification before it can be attached to a patient, because were it to in some way fail, the patient would die. A year later, we have many much safer and more realistic ways to use our skills as part of the effort.

Probably one of the most ambitious projects comes from a coalition of Indian hackerspaces who are adapting a proven oxygen concentrator for local manufacture. Among them is Hackaday’s own [Anool Mahidharia], who hosts a Maker’s Asylum video (embedded below) explaining how the oxygen concentrator works and how they can be made safely.

The team have proven their ability in manufacturing over the past year, here showing off the M19 motorised air purifying respirator.

An oxygen concentrator is both surprisingly simple and imbued with a touch of magic. At its center are two columns of zeolite, a highly porous aluminosilicate mineral that performs the task of a molecular sieve. When air is pumped into the column, the zeolite traps nitrogen, leaving the oxygen-enriched remnant to be supplied onwards. There are two such columns to allow each to be on an alternate cycle of enrichment or purging to remove the accumulated nitrogen.

The point of the video is to show that such a device can be constructed from readily available parts and with common tools; as the title says it isn’t rocket science. Concentrators produced by the hackerspace coalition won’t save the world on their own, but as a part of the combined effort they can provide a useful and reliable source of oxygen that will make a significant difference in a country whose oxygen distribution network is under severe strain.

We previously covered the Indian oxygen concentrator effort when they launched the project. Their website can be found on the Maker’s Asylum website, and their crowdfunding campaign can be found on the Indian crowdfunding platform, Ketto. They have already proved their ability to coordinate large-scale manufacturing with their previous PPE and respirator projects, so please consider supporting them if you can. Meanwhile, we can’t help a twinge of space envy, from the fleeting glimpse of Maker’s Asylum in the video.

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Ello Is A Tiny Computer With A C — Interpreter?

May 9, 2021 by Jenny List 32 Comments

When we talk about a retrocomputer, it’s our normal practice to start with the hardware. But with [KnivD]’s ELLO 1A while the hardware is interesting enough it’s not the stand-out feature. We are all used to microcomputers with a BASIC interpreter, but how many have we seen with a C interpreter? The way C works simply doesn’t lend itself to anything but a compiler and linker, so even with a pared-down version of the language it still represents a significant feat to create a working interpreter.

The hardware centres around a PIC32MX, and has onboard SD card, VGA, sound, and a PS/2 keyboard port. The PCB is a clever design allowing construction with either through-hole or surface-mount components to allow maximum accessibility for less advanced solderers. Full information can be found on the project’s website, but sadly for those wanting an easy life only the PCB is as yet available for purchase.

We’re privileged to see a huge array of retrocomputing projects here at Hackaday, but while they’re all impressive pieces of work it’s rare for one to produce something truly unexpected. This C interpreter certainly isn’t something we’ve seen before, so we’re intrigued to see what projects develop around it.

Polyphony On A Tiny Scale

May 9, 2021 by Jenny List 4 Comments

Older readers may remember the Stylophone, a small battery powered electric organ using conductive PCB pads and a stylus to create notes. The simple multivibrators in those instruments made them monophonic, but here in 2021 we can do better than that! [Sjm4306] has gone the extra mile with a PCB organ, by making a capacitive-touch instrument that boasts four-note polyphony.

At its heart is an ATmega328p whose software sports four tone generators that each emerge on a different pin. These are summed using a set of 100 Ω resistors and fed to a tiny speaker. Power comes from a CR2032 lithium cell, and he notes that a higher voltage delivers more volume.

The full story is detailed in the video below the break, along with a bit of four-note polyphonic action. We’re guessing that this instrument would sound sensational when hooked up to a reverb unit.

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Fix Your Nokia’s White Screen Of Death

May 9, 2021 by Jenny List 17 Comments

Today the Nokia brand can be found on a range of well-screwed-together Androind phones and a few feature phones, but as older readers will remember that before their descent into corporate chaos and the Windows Phone wilderness, there was once a time when the Finnish manufacturer dominated the mobile phone landscape and produced some of the most innovative and creative handset designs ever created. It’s for some of these that [Michael Fitzmayer] has done some work providing tools revive the devices from an unfortunate bricking.

The N-Gage was the phone giant’s attempt to produce a handset that doubled as a handheld game console, and though it was a commercial failure at the time it has retained a following among enthusiasts. The flaw comes as its Symbian operating system fills its user partition, at which point the infamous “White Screen Of Death” occurs as the device can no longer reboot. Rewriting the flash chip used to be handled by Nokia service tools, but these can no longer be found. His fix substitutes a “Blue pill” STMF103-based dev board that connects to the Nokia FBus serial port and does its job. It’s possible that it could be used on other Symbian devices, but for now it’s only been tested on the N-Gages.

It’s easy to forget when a smartphone is defined by iOS and Android, that Symbian gave us a smartphone experience for the previous decade. For those of us who still pine for their miniaturised Carl Zeiss Tessar cameras and candybar form factors, it’s good to see them receiving some love.

Thanks [Razvan] for the tip.

A MIDI Controller — From A Twister Mat?

May 9, 2021 by Jenny List 3 Comments

Twister, the mildly embarrassing but strangely enjoyable floor contortion game that most of us have vague youthful memories of from Christmas parties. Could a Twister mat be used as an input device? [Guy Dupont] took those 24 coloured dots and made just that, after a conversation with a friend.

Wiring up a floor-sized plastic mat isn’t as easy as it might seem, and early experiments with copper foil and capacitive touch sensor chips proved to be a failure. The replacement came in the form of force sensitive resistors, read by a brace of MCP3008 multiplexed analogue-to-digital converters. These are then read by an ESP32 that does all the MIDI magic. We’re treated in the video below the break to full details including the entertaining sight of him playing Twister to a beat, prompted by a robotic-voiced random move generator, and we can see that this devices has some potential.

We’ve not seen another Twister mat before, but force sensitive resistors have made an appearance in a much higher-resolution array. It’s the LED floor game controller that has us going though.

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Calibrating A VNA The Proper Way

May 8, 2021 by Jenny List 16 Comments

Those of us who have bought cheap TinyVNA devices for our RF experimentation will be used to the calibration procedure involving short-circuit, 50 Ω, and open terminations, followed by a direct connection between ports. We do this with a kit of parts supplied with the device, and it makes it ready for our measurements. What we may not fully appreciate at the level of owning such a basic instrument though, is that the calibration process for much higher-quality instruments requires parts made to a much higher specification than the cheap ones from our TinyVNA. Building a set of these high-quality parts is a path that [James Wilson] has taken, and in doing so he presents a fascinating discussion of VNA calibration and the construction of standard RF transmission line components.

We particularly like the way that after constructing his short, load and open circuit terminations using high-quality SMA sockets, he put a custom brass fitting 3D printed by Shapeways on the end of each to make them easier to handle while preserving their RF integrity. If we’d bought a set of terminations looking like these ones as commercial products we would be happy with their quality, but the real test lay in their performance. Thanks to a friend he was able to get them tested on instruments with much heftier price tags, and found them to be not far short of the simulation and certainly acceptable within his 3 GHz range.

Curious about VNAs at the affordable end of the spectrum? We took a look at the TinyVNA, which while it is something of a toy is still good enough for lower frequency measurements.

Finally An Inexpensive Route To Digital Radio Listening

May 8, 2021 by Jenny List 30 Comments

An inexorable trend over the last decade or more has been the exodus of AM radio stations from the low frequency and HF broadcast bands. The bandwidth and thus audio quality at these frequencies puts them at a disadvantage against FM and internet streamed services, and the long-distance advantage of HF has been reduced by easy online access to overseas content. The world has largely moved on from these early-20th-century technologies, leaving them ever more a niche service.

Happily for medium- and long-wave enthusiasts there is a solution to their decline, in the form of DRM, or Digital Radio Mondiale, a digital scheme that delivers cleaner audio and a range of other services in the same space as a standard-sized AM channel. DRM receivers are somewhat rare and usually not cheap though, so news of an Android app DRM receiver from Starwaves is very interesting indeed.

DRM uses a licensed encoding scheme from the Fraunhofer Institute, and this product follows on from a line of hardware DRM receivers that Starwave have developed using their technology. It uses the Android device as a front-end for any of a number of SDR receivers, including the popular RTL-SDR series. It supports the VHF variant of DRM, though we’re guessing that since the best chance of finding a DRM channel for experimentation is on HF that an RTL-SDR with the HF modification will be required. We think it’s an interesting development because the growth of DRM is a chicken-and-egg situation where there must be enough receivers in the wild for broadcasters to consider it viable.