fotw

19 Articles

Fail Of The Week: How Not To Die Of Boredom During Isolation

April 1, 2020 by 26 Comments

They say you can’t actually die from boredom, but put a billion or so people into self-isolation, and someone is bound to say, “Hold my beer and watch this.” [Daniel Reardon]’s brush with failure, in the form of getting magnets stuck up his nose while trying to invent a facial touch reminder, probably wasn’t directly life-threatening, but it does underscore the need to be especially careful these days.

The story begins with good intentions and a small stack of neodymium magnets. [Daniel]’s idea for a sensor to warn one of impending face touches was solid: a necklace with magnetic sensors and wristbands studded with magnets. Sounds reasonable enough; one can easily see a compact system that sounds an alarm when a hand subconsciously crosses into the Danger Zone while going in for a scratch. Lacking any experience in circuits, though, [Daniel] was unable to get the thing working, so he started playing with the magnets instead. One thing led to another, and magnets were soon adorning his earlobes, and then his nostrils. Unfortunately, two magnets became locked on either side of his septum, as did two others meant to neutralize the pull of the first pair. So off [Daniel] went to the emergency department for a magnetectomy.

Of course it’s easy to laugh at someone’s misfortune, especially when self-inflicted. And the now-degaussed [Daniel] seems to be a good sport about the whole thing. But the important thing here is that we all do dumb things, and hackers need to be especially careful these days. We often work with sharp, pointy, sparky, toxic, or flammable things, and if we don’t keep our wits about us, we could easily end up in an ER somewhere. Not only does that risk unnecessary exposure to COVID-19, but it also takes medical resources away from people who need it more than you do.

By all means, we should be hacking away these idle hours. Even if it’s not in support of COVID-19 solutions, continuing to do what we do is key to our mental health and well-being. But we also need to be careful, to not stretch dangerously beyond our abilities, and to remember that the safety net that’s normally there to catch us is full of holes now.

Thanks to [gir.st] for the tip — you actually were the only one to send this in.

Fail Of The Week: Padlock Purports To Provide Protection, Proves Pathetic

January 21, 2020 by 49 Comments

Anyone in the know about IoT security is likely to steer clear of a physical security product that’s got some sort of wireless control. The list of exploits for such devices is a long, sad statement on security as an afterthought, if at all. So it’s understandable if you think a Bluetooth-enabled lock is best attacked via its wireless stack.

As it turns out, the Master 5440D Bluetooth Key Safe can be defeated in a few minutes with just a screwdriver. The key safe is the type a realtor or AirBnB host would use to allow access to a property’s keys. [Bosnianbill] embarked on an inspection of the $120 unit, looking for weaknesses. When physical attacks with a hammer and spoofing the solenoids with a magnet didn’t pay off, he decided to strip off the resilient skin that Master so thoughtfully provided to prevent the box from marring the finish of a door or gate. The denuded device thus revealed its awful secret: two Phillips screws, each securing a locking shackle to the cover. Once those are loose, a little prying with a screwdriver is all that’s need to get the keys to the kingdom.

In a follow-up video posted later, [Bill] took a closer look at another key safe and found that Master had made an anemic effort to fix this vulnerability with a squirt of epoxy in each screw head. It’s weak, at best, since a tap with a hammer compresses the gunk enough to get a grip on the screw.

We really thought [Bosnianbill]’s attack would be electronic, like that time [Dave Jones] cracked a safe with an oscilloscope. Who’d have thought a screwdriver would be the best way past the wireless stack?

Continue reading “Fail Of The Week: Padlock Purports To Provide Protection, Proves Pathetic” →

Fail Of The Week: Thermostat Almost Causes A House Fire

January 8, 2020 by 63 Comments

Fair warning: any homeowners who have thermostats similar to the one that nearly burned down [Kerry Wong]’s house might be in store for a sleepless night or two, at least until they inspect and perhaps replace any units that are even remotely as sketchy as what he found when he did the postmortem analysis in the brief video below.

The story begins back in the 1980s, when the Southern New England area where [Kerry] lives enjoyed a housing boom. Contractors rushed to turn rural farmland into subdivisions, and new suburbs crawled across the landscape. Corners were inevitably cut during construction, and one common place to save money was the home’s heating system. Rather than engage an HVAC subcontractor to install a complicated heating system, many builders opted instead to have the electricians install electric baseboards. They were already on the job anyway, and at the time, both copper and electricity were cheap.

Fast forward 40 years or so, and [Kerry] finds himself living in one such house. The other night, upon catching the acrid scent of burning insulation, he followed his nose to the source: a wall-mounted thermostat for his electric baseboard. His teardown revealed burned insulation, bare conductors, and scorched plastic on the not-so-old unit; bearing a 2008 date code, the thermostat must have replaced one of the originals. [Kerry] poked at the nearly combusted unit and found the root cause: the spot welds holding the wires to the thermostat terminal had become loose, increasing the resistance of the connection. As [Kerry] points out, even a tenth of an ohm increase in resistance in a 15 amp circuit would dissipate 20 watts of heat, and from the toasty look of the thermostat it had been a lot more than that.

The corner-cutting of the 1980s was nothing new, of course – remember the aluminum wiring debacle? Electrical fires are no joke, and we’re glad [Kerry] was quick to locate the problem and prevent it from spreading.

Continue reading “Fail Of The Week: Thermostat Almost Causes A House Fire” →

Fail Of The Week: Ambitious Vector Network Analyzer Fails To Deliver

December 31, 2019 by 18 Comments

If you’re going to fail, you might as well fail ambitiously. A complex project with a lot of subsystems has a greater chance of at least partial success, as well as providing valuable lessons in what not to do next time. At least that’s the lemonade [Josh Johnson] made from his lemon of a low-cost vector network analyzer.

For the uninitiated, a VNA is a versatile test instrument for RF work that allows you to measure both the amplitude and the phase of a signal, and it can be used for everything from antenna and filter design to characterizing transmission lines. [Josh] decided to port a lot of functionality for his low-cost VNA to a host computer and concentrate on the various RF stages of the design. Unfortunately, [Josh] found the performance of the completed VNA to be wanting, especially in the phase measurement department. He has a complete analysis of the failure modes in his thesis, but the short story is poor filtering of harmonics from the local oscillator, unexpected behavior by the AD8302 chip at the heart of his design, and calibration issues. Confounding these issues was the time constraint; [Josh] might well have gotten the issues sorted out had the clock not run out on the school year.

After reading through [Josh]’s description of his project, which was a final-year project and part of his thesis, we feel like his rating of the build as a failure is a bit harsh. Ambitious, perhaps, but with a spate of low-cost VNAs coming on the market, we can see where he got the inspiration. We understand [Josh]’s disappointment, but there were a lot of wins here, from the excellent build quality to the top-notch documentation.

Fail Of The Week: Z-Tape Is No Substitute For Solder

November 26, 2019 by 36 Comments

Here at Hackaday, we see all kinds of mechanical construction methods. Some are impressively solid and permanent, while others are obviously temporary in nature. The latter group is dominated by adhesives – sticky stuff like cyanoacrylate glue, Kapton tape, and the ever-popular hot glue. They’ve all got their uses in assembling enclosures or fixing components together mechanically, but surely they have no place in making solid electrical connections, right?

Maybe, maybe not. As [Tom Verbeure] relates, so-called Z-tape just might be an adhesive that can stand in for solder under certain circumstances. Trouble is, he couldn’t find the right conditions to make the tape work. Z-tape, more properly called “Electrically Conductive Adhesive Transfer Tape 9703”,  derives its nickname from the fact that it’s electrically conductive, but only in the Z-axis. [Tom] learned about Z-tape in [Joe FitzPatrick]’s malicious hardware prototyping workshop at the 2019 Hackaday Superconference, and decided to put it to the test.

A card from a Cisco router served as a testbed thanks to an unpopulated chip footprint. The 0.5-mm pin spacing on the TSOP-48 chip was within spec for the Z-tape, but the area of each pin was 30 times smaller than the recommended minimum bonding area. While the chip was held down mechanically by the Z-tape, only five of the 48 pins were electrically connected to the pads. Emboldened by the partial success, [Tom] tried a 28-pin SOIC chip next. The larger pins and pads were still six times smaller than the minimum, and while more of the pins ended up connected by the tape, he was unable to make all 28 connections.

Reading the datasheet for the adhesive revealed that constant pressure from a clamp or clip might be necessary for reliable connections, which suggests that gluing down SMD chips is probably not the best application for the stuff. Still, we appreciate the effort, and the fine photomicrographs [Tom] made showing the particles within the Z-tape that make it work – at least in some applications.

Fail Of The Week: Electromigration Nearly Killed This Xerox Alto

February 3, 2019 by 51 Comments

The Living Computers museum in Seattle has a Xerox Alto, the machine famous for being the first to sport a mouse-based windowing graphical user interface. They received it in working condition and put it in their exhibit, but were dismayed when a year later it ceased to operate. Some detective work revealed that the power supply was failing to reach parts of the machine, and further investigation revealed an unlikely culprit. Electromigration had degraded the contacts between the supply pins and the backplane traces.

If electromigration is new to you, don’t feel ashamed, it was a new one to us too. It’s “the transport of material caused by the gradual movement of the ions in a conductor due to the momentum transfer between conducting electrons and diffusing metal atoms“, got it? Okay, that’s just a long way to say that passing a sufficiently high current through a conductor for a long time can physically move the metal of that conductor.

This one just doesn’t pop up very often. But in the case of the Alto, an under-specified power distribution system caused a lot of current to flow through too few solder joints. Those joints were left without enough metal to make a decent connection, so they failed.

The fix came with a set of sturdy busbars freshly soldered to the pins, but the interest in this piece comes more from the unusual phenomenon that caused it. That soldered joints can seemingly flow away defies belief. It’s still something most of us will never encounter, but like tales of ball lightning it’s one for the “Fancy that!” collection.

We’ve covered the Alto before, most notably [Ken Shirriff]’s work in restoring the Computer History Museum’s example.

Fail Of The Week: Did My Laser Cutter Tube Really Burn Out?

November 23, 2018 by 28 Comments

All the cool kids are doing it these days, or more like for many years now: you can get a laser cutter for a song if you don’t mind doing your own repairs and upgrades — you know, being a hacker. The downside is that some failures can really ruin your day. This is what [Erich Styger] encountered with his cutter that is just a bit more than a year old. This Fail of the Week looks at the mysterious death of a CO2 laser tube.

This is the infamous K40 laser cutter. Our own [Adam Fabio] just took one on a couple of months back and [Erich] even references Hackaday coverage of the K40 Whisperer project as what pushed him over the edge to make the purchase. We’ve followed his blog as he acquired the cutter and made upgrades along the way, but after an estimated 500 hours of use, a horrible teeth-gnashing screech sprung forth from the machine. [Erich’s] reaction was to hit the e-stop; that’s certainly why it’s there.

Chasing down the problem is a story well-told, but as is often the case with these FotW articles, in the end what caused the failure is not entirely known. We’d love to hear what you think about it in the comments below.

The investigation began at the power supply for the laser, but that didn’t yield any answers. Next he moved to the tube itself, noticing that the wire connection to the tube’s anode wasn’t soldered. The anode is an unknown material he suspects to be graphite and he found a video showing the “soldering” process for connecting a wire. (We added quotes to that as the video he linked doesn’t actually solder anything but the wrapped wire strands themselves.) The solution he found is a great tip to take away from the story. It’s a socket by TE Connectivity to which he soldered the wire. Assuming it’s power rated for the task, and won’t fall off during normal operation, this is a great way to do it.

But we digress. Even with the connection made, the old tube had to be replaced with a new one. It’s also notable that the portion of that anode inside the bad tube is orange in color when a new tube would be black like the part on the outside. Does this hint at why that tube died, and could this have been avoided? If you have insight, help us learn from this failure by leaving a comment below.