Tech In Plain Sight: Glucose Meters

October 20, 2021 by Al Williams 27 Comments

If you or someone you know is diabetic, it is a good bet that a glucose meter is a regular fixture in your life. They are cheap and plentiful, but they are actually reasonably high tech — well, at least parts of them are.

The meters themselves don’t seem like much, but that’s misleading. A battery, a few parts, a display, and enough of a controller to do things like remember readings appears to cover it all. You wouldn’t be surprised, of course, that you can get the whole affair “on a chip.” But it turns out, the real magic is in the test strip and getting a good reading from a strip requires more metrology than you would think. A common meter requires a precise current measurement down to 10nA. The reading has to be adjusted for temperature, too. The device is surprisingly complex for something that looks like a near-disposable piece of consumer gear.

Of course, there are announcements all the time about new technology that won’t require a needle stick. So far, none of those have really caught on for one reason or another, but that, of course, could change. GlucoWatch G2, for example, was a watch that could read blood glucose, but — apparently — was unable to cope with perspiration.

Even the meters that continuously monitor still work in more or less the same way as the cheap meters. As Hackaday’s Dan Maloney detailed a few years back, continuous glucose monitors leave a tiny sensor under your skin and measure fluid in your body, not necessarily blood. But the way the sensor works is usually the same.

For the purposes of this article, I’m only going to talk about the traditional meter: you insert a test strip, prick your finger, and let the test strip soak up a little bit of blood.

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Refining The Greatest Joystick Of The 1980s

October 20, 2021 by Tom Nardi 24 Comments

The Competition Pro joystick is often considered to be the pinnacle of input devices, at least as far as the 1980s gaming goes. But the design isn’t perfect, and time hasn’t been kind to certain aspects of its mechanism. For example, the large rubber disc used to keep the stick centered on early generations of the hardware will invariably be hardened up on any surviving specimens. Looking to return these classic controllers to their former glory, and then some, [mageb] has released a number of 3D printed modifications for the Competition Pro that should be of great interest to the vintage gamer.

First and foremost is the deletion of the original rubber disc for a new spring mechanism. Even if this is the only modification you do, [mageb] says you’ll already have a better and longer-lasting joystick to show for it. But if you want to continue with the full rebuild, be aware that there’s no going back to stock. Once you start cutting the original parts, you’re committed to taking it all the way.

Assuming you’re not afraid to get your hands dirty, the next step is cutting the metal contacts from the bottom of the face buttons so they’ll work with the new microswitch array he’s designed. Each button gets its switch, and four handle movement of the joystick. You can try out different switches to adjust the feel of the joystick, but [mageb] assures us that he’s already done the research and put the best quality switches in the bill of materials.

The end result is a Competition Pro joystick that looks more or less the same from the outside, but is considerably improved internally. That’s always a win in our books, though we’re sure somebody out there is going to get mad that the brittle old rubber disc wasn’t sent to the Smithsonian.

Know Audio: It All Depends On The DAC

October 20, 2021 by Jenny List 29 Comments

Our trip through the world of audio technology has taken us step-by step from your ears into a typical home Hi-Fi system. We’ve seen the speakers and the amplifier, now it’s time to take a look at what feeds that amplifier.

Here, we encounter the first digital component in our journey outwards from the ear, the Digital to Analogue Converter, or DAC. This circuit, which you’ll find as an integrated circuit, takes the digital information and turns it into the analogue voltage required by the amplifier.

There are many standards for digital audio, but in this context that used by the CD is most common. CDs sample audio at 44.1 kHz 16 bit, which is to say they express the level as a 16-bit number 44100 times per second for each of the stereo channels. There’s an electrical standard called i2s for communicating this data, consisting of a serial data line, a clock line, and an LRclock line that indicates whether the current data is for the left or the right channel. We covered i2s in detail back in 2019, and should you peer into almost any consumer digital audio product you’ll find it somewhere. Continue reading “Know Audio: It All Depends On The DAC” →

KiCad Team Releases Warning Regarding Domain Name

October 20, 2021 by Jim Heaney 23 Comments

On October 19th, [Seth_h] from the KiCad Project posted on the KiCad forums that the project’s original domain name kicad-pcb.org has been unexpectedly sold to a third party, and urged members of the community to avoid any links to this old website.

KiCad has used the domain kicad-pcb.org since 2012 as the official source for information on and downloads of their popular open-source electronics design software. Unfortunately, the original domain name was purchased before KiCad was formalized as an organization, so it was not directly under their control. This all came to head when the old domain name was unexpectedly sold to an unnamed third party that was not affiliated with the project. Currently, the old domain is just a website covered in ads, but the KiCad team fears that it may be used maliciously in the future.

With KiCad’s popularity, thousands of tutorials, articles, and project guides over the years have included links to the old KiCad domain. A Google search in October 2021 found more than 19,000 instances of the old domain spread across the internet. [Seth_h] has called upon the community to make every effort possible to update old links, reducing the chance that people stumble across the wrong website.

[Editor’s Note: We think we got ’em all, let us know if we missed any.]

Luckily, Digikey has swooped in to help save the day. They purchased a new domain, kicad.org, from squatters and donated it to the KiCad Project. (Update: Digi-key donated the KiCad.org domain back in October of 2020 after noticing fishy squatters going back to at least 2016) [Seth_h] explains in his post that a number of safeguards have been put in place to prevent this from happening in the future, including not having the domain name owned by a single person, and having all KiCad trademarks registered to the Linux Foundation.

There’s a good reason why KiCad has gotten so popular, it is packed full of great features for PCB design. Check out our coverage of some of the new features we are most excited for in KiCad 6.0 here.

Spinning Threads Put The Bite On Filament In This Novel Extruder Design

October 20, 2021 by Dan Maloney 29 Comments

When it comes to innovation in FDM 3D printing, there doesn’t seem to be much room left to move the needle. Pretty much everything about filament printing has been reduced to practice, with more or less every assembly available off the shelf. Even the business end — the extruder — is so optimized that there’s not much room left for innovation.

Or is there? The way [David Leitner] sees it, there is, which is why he built this rolling-screw extruder (if you can get to the Thingiverse link, [David] cross-posted on reddit, too). Standard extruders work on the pinch-roller principle, where the relatively soft filament is fed past a spring-loaded gear attached to a stepper motor. The stepper rotates the gear, which either advances the filament into or retracts it from the hot end. [David]’s design instead uses a trio of threaded rods mounted between two rings. The rods are at an angle relative to the central axis of the rings, forming a passage that’s just the right size for the filament to fit in. When the rings spin, the threads on the rods engage with the filament, gripping it around its whole circumference and advancing or retracting it depending on which way it’s spinning. The video below shows it working; we have to admit it’s pretty mesmerizing to watch.

[David] himself admits there’s not much advantage to it, perhaps other than a lower tendency to skip since the force is spread over the entire surface of the filament rather than just a small pinch point. Regardless, we like the kind of thinking that leads to something like this, and we’ll bet there are probably unseen benefits to it. And maybe the extruder actually is a place for innovation after all; witness this modular nozzle swapping system.

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An Arduino Nano connected to a portable tape recorder

Audio Tape Interface Revives Microcassettes As Storage Medium

October 20, 2021 by Robin Kearey 37 Comments

In the early 1980s cassette tapes were the standard storage medium for home computer users; readers of a certain age will remember fiddling with audio jacks, tape counters and signal levels, then waiting for several minutes while a program (hopefully) loaded correctly. While most people happily upgraded to much more reliable floppy disks, [Zack Nelson] decided to go back in time and add a suitably classic storage medium to a retrocomputing project, in the form of a cassette interface. The cassette player he had available was a Pearlcorder L400, which uses the smaller microcassette instead of the familiar audio tapes used in your Walkman or boombox.

[Zack] designed the entire thing from the ground up: first he decided to use differential Manchester encoding, which provides immunity against common disturbances like speed variations (which cause wow and flutter). The data is encoded in the frequency range from 1 kHz to 2 kHz, which suits the bandwidth of the cassette player. Next, he designed the interface between the computer and the tape recorder; built from an op-amp and a comparator with a handful of discrete components, it filters the incoming signal and clips it to provide a clean digital signal to be read out directly by the computer.

The system is demonstrated by hooking it up to an Arduino Nano, which reads out the data stream at about 3000 baud. The noise it makes should bring back memories to anyone brought up with the “PRESS PLAY ON TAPE” message; if it inspires you to make your own, we’re happy to report that full schematics and source code are available. [Zack] is not the first one to make his own cassette interface; we’ve seen a somewhat more complicated analog design before, as well as one based on an FPGA.

Flickering Jack O’ Lantern Is An Easy Beginner Build

October 19, 2021 by Lewin Day 8 Comments

The Jack o’ Lantern is a fun Halloween tradition, though one that does come with a few risks. It’s pretty easy to slice off a bit of finger when carving a stiff pumpkin, and candles draw more enmity from fire crews than most household items. For the electronics beginner looking for a learning project, [Oyvind’s] build might be a nice safe bet.

The build starts with a 3D-printed pumpkin figurine with a suitably spooky face, though [Oyvind] notes there’s nothing stopping this project from being executed with a real orange gourd instead. Inside, an Arduino is hooked up to a trio of orange LEDs. They’re attached to PWM pins and each is given a random brightness value at regular intervals to create a pleasant flickering effect.

It’s a very simple project, but it’s also the kind of thing that’s perfect for introducing new people into the world of electronics. There’s little to get wrong, and mistakes aren’t costly, making it an ideal project for beginners. From there, the sky really is the limit! Video after the break.

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