Gas-Tight FDM 3D Printing Is Within Your Grasp

June 8, 2024 by Jenny List 65 Comments

The widespread availability of inexpensive 3D printers has brought about a revolution in what can be easily made at home. However these creations aren’t perfect, particularly when it comes to the adhesion between their layers. Aside from structural failures along the layer lines there is also the question of those joins being permeable, limiting the possibility for waterproof or gas proof prints. It’s something [German Engineer] has tackled in a new video, in which he’s looking at the design and preparation of small propane tanks.

A blurry image of a red 3d-printed part exploding — This is the frame at which the 3D printed tank explodes

The attraction of propane as a fuel is that it liquefies easily on compression, so a propane cylinder or tank will be an equilibrium of liquid propane with pressurized gas above it, whose pressure depends on the ambient temperature. This means that any tank must be expected to have a working pressure somewhere between 150 and 200 PSI, with of course a design pressure far exceeding that for safety reasons.

Filling a 3D printed tank immediately results in the propane escaping, as he demonstrates by putting one of his prints under water. He solves this with a sealant, Diamant Dichtol, which is intended to polymerize in the gaps between layers and create a gas-tight tank. A range of three tanks of different thicknesses are treated this way, and while the 1 mm thick variety bursts, the thicker ones survive.

It’s clear that this technique successfully creates gas-tight prints, and we can see the attraction of a small and lightweight fuel tank. But we can’t help worrying slightly about the safety, for even when the material is a lightweight 3D print, high pressure equipment is not to be trifled with. Tanks do burst, and when that happens anyone unfortunate enough to be close by sustains nasty, even life-threatening injuries. Use the technique, but maybe don’t hit it with high pressures.

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Turning An ATX PSU Into A Variable Bench Supply

May 23, 2024 by Lewin Day 84 Comments

Bench power supplies can sometimes be frustratingly expensive and also kind of limited. If you’re enterprising and creative, though, you can create your own bench supply with tons of features, and it doesn’t have to break the bank either. Do what [Maker Y] did—grab an ATX supply and get building!

ATX power supplies work as a great basis for a bench power supply. They have 12 volt, 3.3 volt, and 5 volt rails, and they can supply a ton of current for whatever you might need. [Maker Y] decided to break out these rails on banana plugs for ease of access, and fused them for safety, too. But the build doesn’t stop there. [Maker Y] also added a buck-boost converter to provide a variable voltage output from 1 to 30 volts for added flexibility. As a nice final touch, the rig also features a pair of USB A ports compatible with Quick Charge 3.0, for keeping smart devices charged while working in the lab.

[Caelestis Workshop] also designed a fully enclosed version if you prefer that style. Check it out on Instructables.

No matter which way you go, it’s a pretty simple build, with a bunch of off-the-shelf parts tossed together in a 3D printed housing. Ultimately, though, it’s got more functionality than a lot of cheap off-the-shelf bench supplies. You can build it just about anywhere on Earth where you can get cheap eBay parts via post. Continue reading “Turning An ATX PSU Into A Variable Bench Supply” →

Software Bug Results In Insulin Pump Injuries, Spurs Recall

May 11, 2024 by Dan Maloney 24 Comments

Managing Type 1 diabetes is a high-stakes balancing act — too much or too little insulin is a bad thing, resulting in blood glucose levels that deviate from a narrow range with potentially dire consequences on either side. Many diabetics choose to use an insulin pump to make managing all this easier, but as a recent recall of insulin pump software by the US Food and Drug Administration shows, technology isn’t foolproof.

Thankfully, the recall is very narrow in scope. It’s targeted at users of the Tandem t:slim X2 insulin pump, and specifically the companion application running on iOS devices. The mobile app is intended to run on the user’s phone to monitor and control the pump. The pump itself is a small, rechargeable device that users often keep on their belt or tucked into a pocket that delivers a slow, steady infusion of insulin during the day, plus larger bolus doses to compensate for meals.

But version 2.7 of the t:connect mobile app can crash unexpectedly, and on iOS devices, that can lead to the OS continually relaunching it. Each time it does this, the app tries to reconnect with the pump via Bluetooth, which eventually runs down the battery in the pump. Once the battery is dead, no more insulin can be delivered, potentially leading to a condition called hyperglycemia (“hyper” meaning an excess, “gly” referring to sugar, and “emia” meaning presence in blood — excess sugar in the blood.)

Untreated hyperglycemia can progress to a much more serious state called diabetic ketoacidosis, which can lead to coma and death. Thankfully, nobody has suffered that fate from this bug, but the FDA has received over 200 reports of injuries, hence the recall. Tandem sent out a notice to all affected customers back in March to update their apps, but it’s still possible that some users didn’t get the message.

Apart from the human cost of this bug, there’s a lesson here about software design and unintended consequences. While it intuitively seems like a great idea to automatically relaunch a crashed app, especially one with a critical life-safety function, in hindsight, the better course might have been to just go into a safe mode and alert the user with an alarm. That’s a lesson we’ve learned by exploring space, and it seems to apply here as well.

Images: AdobeStock, Tandem Diabetes

Ask Hackaday: Do You Calibrate Your Instruments?

May 9, 2024 by Jenny List 54 Comments

Like many of you, I have a bench full of electronic instruments. The newest is my Rigol oscilloscope, only a few years old, while the oldest is probably my RF signal generator that dates from some time in the early 1950s. Some of those instruments have been with me for decades, and have been crucial in the gestation of countless projects.

If I follow the manufacturer’s recommendations then just like that PAT tester I should have them calibrated frequently. This process involves sending them off to a specialised lab where their readings are compared to a standard and they are adjusted accordingly, and when they return I know I can trust their readings. It’s important if you work in an industry where everything must be verified, for example I’m certain the folks down the road at Airbus use meticulously calibrated instruments when making assemblies for their aircraft, because there is no room for error in a safety critical application at 20000 feet.

But on my bench? Not so much, nobody is likely to face danger if my frequency counter has drifted by a few Hz. Continue reading “Ask Hackaday: Do You Calibrate Your Instruments?” →

ArdEEG Lowers The Cost Of Brain-Computer Interfaces

May 8, 2024 by Tom Nardi 22 Comments

Considering the incredible potential offered by brain-computer interfaces (BCIs), it’s no wonder there are so many companies scrambling to make their mark in the field. Some see it as an assistive technology, while others imagine it as the future of interactive entertainment. Regardless of the application, the technology has yet to make much inroads with the DIY crowd — largely due to the complexity and cost of the hardware involved.

But that might change in the near future thanks to projects like ardEEG from [Ildar Rakhmatulin]. This open source shield mounts to the top of the Arduino UNO R4 WiFi and features eight channels for collecting electroencephalogram (EEG) data, such as from a dry electrode cap. The signals can then be processed on the computer using the provided Python example code. From there, the raw data can be visualized or plugged into whatever application you have in mind.

Why target the relatively uncommon WiFi version of the Uno? It’s probably obvious for those with experience with this kind of hardware, but for safety, the system needs complete electrical isolation. The Arduino and shield are powered by a common USB battery bank, and all communication is done over WiFi. Even still, the documentation is clear that the ardEEG is not a medical device, and hasn’t been certified by any regulatory agency — its use is entirely at your own risk.

[Ildar] tells us the hardware will be available soon and should cost under $250, making it one of the most affordable BCI development platforms out there. As with his earlier PiEEG project, the hope is that basing the system around a common device in the hacker and maker scene will help democratize access to BCI research.

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This Week In Security: XZ, ATT, And Letters Of Marque

April 5, 2024 by Jonathan Bennett 11 Comments

The xz backdoor is naturally still the top story of the week. If you need a refresher, see our previous coverage. As expected, some very talented reverse engineers have gone to work on the code, and we have a much better idea of what the injected payload does.

One of the first findings to note is that the backdoor doesn’t allow a user to log in over SSH. Instead, when an SSH request is signed with the right authentication key, one of the certificate fields is decoded and executed via a system() call. And this makes perfect sense. An SSH login leaves an audit trail, while this backdoor is obviously intended to be silent and secret.

It’s interesting to note that this code made use of both autotools macros, and the GNU ifunc, or Indirect FUNCtions. That’s the nifty feature where a binary can include different versions of a function, each optimized for a different processor instruction set. The right version of the function gets called at runtime. Or in this case, the malicious version of that function gets hooked in to execution by a malicious library. Continue reading “This Week In Security: XZ, ATT, And Letters Of Marque” →

Hackaday Links: March 31, 2024

March 31, 2024 by Dan Maloney 5 Comments

Battlelines are being drawn in Canada over the lowly Flipper Zero, a device seen by some as an existential threat to motor vehicle owners across the Great White North. The story started a month or so ago, when someone in the government floated the idea of banning devices that could be “used to steal vehicles by copying the wireless signals for remote keyless entry.” The Flipper Zero was singled out as an example of such a nefarious device, even though relatively few vehicles on the road today can be boosted using the simple replay attack that a Flipper is capable of, and the ones that are vulnerable to this attack aren’t all that desirable — apologies to the 1993 Camry, of course. With that threat hanging in the air, the folks over at Flipper Devices started a Change.org petition to educate people about the misperceptions surrounding the Flipper Zero’s capabilities, and to urge the Canadian government to reconsider their position on devices intended to explore the RF spectrum. That last bit is important, since transmit-capable SDR devices like the HackRF could fall afoul of a broad interpretation of the proposed ban; heck, even a receive-only SDR dongle might be construed as a restricted device. We’re generally not much for petitions, but this case might represent an exception. “First they came for the Flipper Zero, but I did nothing because I don’t have a Flipper Zero…”

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