Fail Of The Week: Can An Ultrasonic Cleaner Remove Bubbles From Resin?

April 16, 2024 by Donald Papp 23 Comments

[Wendy] asked a very good question. Could putting liquid resin into an ultrasonic cleaner help degas it? Would it help remove bubbles, resulting in a cleaner pour and nicer end product? What we love is that she tried it out and shared her results. She purchased an ultrasonic cleaner and proceeded to mix two batches of clear resin, giving one an ultrasonic treatment and leaving the other untouched as a control.

Sadly, the test piece had considerably *more* surface bubbles than the untreated control, as well as a slight discoloration.

The results were interesting and unexpected. Initially, the resin in the ultrasonic bath showed visible bubbles rising to the surface which seemed promising. Unfortunately, this did not lead to fewer bubbles in the end product.

[Wendy]’s measurements suggest that the main result of putting resin in an ultrasonic bath was an increase in its temperature. Overheating the resin appears to have led to increased off-gassing and bubble formation prior to and during curing, which made for poor end results. The untreated resin by contrast cured with better color and much higher clarity. If you would like to skip directly to the results of the two batches, it’s right here at 9:15 in.

Does this mean it’s a total dead end? Maybe, but even if the initial results weren’t promising, it’s a pretty interesting experiment and we’re delighted to see [Wendy] walk through it. Do you think there’s any way to use the ultrasonic cleaner in a better or different way? If so, let us know in the comments.

This isn’t the first time people have tried to degas epoxy resin by thinking outside the box. We’ve covered a very cheap method that offered surprising results, as well as a way use a modified paint tank in lieu of purpose-made hardware.

Fail Of The Week: A Potentially Lethal Tattoo Removal Laser Power Supply

March 24, 2024 by Dan Maloney 7 Comments

Caveat emptor is good advice in general, but in the wilds of eBay, being careful with what you buy could be life-saving. To wit, we present [Les Wright]’s teardown and very ginger power-up of an eBay tattoo-removal laser power supply.

Given that [Les] spent all of around $100 on this widowmaker, we’re pretty sure he knew what he was getting himself into. But he likely wasn’t quite prepared for the scale of the sketchiness this thing would exhibit. The deficiencies are almost too many to number, starting with the enclosure, which is not only made completely of plastic but assembled from individual sheets of flat plastic stock that show signs of being glued together by hand. Even the cooling water tank inside the case is pieced together this way, which probably led to the leaks that corroded the PCBs. Another assembly gem is the pair of screws the big energy storage capacitor is jammed under, presumably to hold it in place — because nothing says quality like a BOM that can’t spring for a couple of cable ties. Click through the break to read more and see the video.

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Fail Of The Week: The Little Remote-Controlled Snowblower That Couldn’t

March 3, 2024 by Dan Maloney 17 Comments

[Punxatawny Phil]’s prognostications aside, winter isn’t over up here in the Northern Hemisphere, and the snow keeps falling. If you’re sick of shoveling the driveway and the walk and you don’t have a kid handy to rope into the job, relax — this rapidly assembled junkyard RC snowblower will do just as crappy a job while you stay nice and warm inside.

This build seemed to have a lot of potential at the start, based as it was on a second-hand track-drive snowblower, something that was presumably purpose-built for the job at hand. [Lucas] quickly got to work on it; he left the original gasoline engine to power the auger but took most of the transmission off so that each track could be driven separately with a wheelchair motor. That seemed like a solid idea as far as steering goes, but the fact that he chose to drive the 24 volt motors with a single 12 volt deep-cycle battery worked against him out in the snow.

With a battery upgrade for better traction, the snowblower actually got around in the snow pretty well. [Lucas] also added some nice features, like a linear actuator to remotely engage the auger — a nice safety touch when kids and pets are around — and a motor to control the direction of the chute. Even these improvements weren’t enough, though; it worked insofar as it moved snow from where it was to where it wasn’t, but didn’t really move it very far. To the casual observer, it seems like there’s just not enough weight to the machine, allowing it to ride up over the snow rather than scraping the driveway clean. Check out the video below and see what you think.

Now, we’re not picking on [Lucas] here. Far from it — we enjoyed this build as much as some of his other stuff, like his scratch-built CO2 laser tube and his potty-mouthed approach to Kaizen tool organization. We still think this one has a lot of potential, and we’re glad he vowed to continue working on it for next winter.

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Fail Of The Week: PCB LED Cube Fails Successfully

February 5, 2024 by Dan Maloney 24 Comments

Remember LED cubes? We sure do — they were all the rage for a while, and then it seemed like everyone just sort of lost interest in them. There are probably a lot of reasons for that, not least of which is likely the amount of work it takes to put one together from discrete LEDs and separate pieces of wire. Could there be a better way?

Of course there could, and [Sasa Karanovic] thought he had it all figured out with this PCB-based LED cube. At first glance, it seems to make perfect sense; after all, weren’t PCBs invented to take the place of all that pesky point-to-point wiring in the early days of electronics? The boards [Sasa] designed are pretty cool, actually. They’ve each got room for 16 addressable WS2812 LEDs in 5 mm packages, with every possible bit of substrate removed to block the minimum amount of light. That left very little room for traces on the 2-mm-wide arms, so the PCBs had to have four layers, which raised eyebrows at the PCB house when [Sasa] submitted the design.

Such an airy and open design obviously has the potential for mechanical issues, which [Sasa] addressed by adding pads at three corners of each board; a vertical PCB connects to each LED board to provide mechanical support and distribute signals to the LEDs. The cube seems solid enough as a result, and even when handled the LED boards don’t really flop around too much. See the cube in action in the video below.

What’s nice about this design is the perfect spacing between the LEDs in all three dimensions, and the way everything lines up nice and straight. That would be really hard to do with wire, even for the most practiced of circuit sculptors. [Sasa] seems to agree, but still deems the build a failure because the PCBs block too much of the view. We suppose he’s got a point, and we’re not sure how well this would scale to an 8×8 cube. We’re not sure how we’d feel about paying for PCBs that are mostly air either, but as failures go, this one still manages to be pretty successful. Continue reading “Fail Of The Week: PCB LED Cube Fails Successfully” →

Fail Of The Week: This Flash Drive Will NOT Self-Destruct In Five Seconds

November 25, 2023 by Dan Maloney 49 Comments

How hard can it be to kill a flash drive? Judging by the look of defeat on [Walker]’s face in the video below, pretty darn hard.

To bring you up to speed, and to give the “Mission: Impossible” reference in the title some context, it might be a good idea to look over our earlier coverage of [Walker]’s Ovrdrive project. It started way back in 2022 with the idea that some people might benefit from a flash drive that could rapidly and covertly render the data stored on it, err, “forensically unavailable.” This would require more than just erasing the data, of course, so [Walker] began looking at ways to physically kill a memory chip. First up was a voltage doubler to apply voltage much greater than the absolute maximum rating of 4.6 V for any pin on the chip. That corrupted some files on the flash chip, enough of a win to proceed to a prototype that actually succeeded in releasing the Magic Smoke.

But sadly, that puff of smoke ended up being a fluke. [Walker] couldn’t repeat the result, at least not with the reliability required by people for whom data privacy is literally a life-or-death matter. To increase the odds of a kill, he came up with an H-bridge circuit to reverse the polarity of the memory chip’s supply. Surely that would kill the chip, and from the thermal camera images, it sure looked promising. But apparently, even 167°C isn’t enough to forensically disable the chip, which kind of makes sense from the point of view of reflow survivability.

What’s next for [Walker]? He says he’s going to team up his overvoltage and reverse-polarity methods for one last shot, but after that, he’s about out of reasonable options. Sure, a thermite charge or a vial of superacid would do the trick, but neither is terribly covert. If you’re going to go that way, you might as well just buy a standard flash drive and throw it in the microwave or a blender. And we need to remember that this may be something the drive’s owner needs to do with jack-booted thugs kicking in the door, or possibly at gunpoint. It wouldn’t do to be too conspicuous under such circumstances. That’s why we like the “rapid power cycling” method of triggering the drive’s self-destruct sequence; it could easily be disguised as shaking hands in a stressful situation.

Who knew that memory chips were this robust? Kudos to [Walker] for getting the project as far as he did, and we’re still rooting for him to make it work somehow.

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Fail Of The Week: Car Starter Motors Aren’t The Best Fit For EBikes

April 14, 2023 by Dan Maloney 40 Comments

A lot of what real engineering is all about is designing to the limits of your materials, with a healthy margin for error. On the other hand, seat-of-the-pants engineering often takes the opposite tack — working with the materials you have and finding their limits after the fact. While the former is more rigorous and better suited to anything where life and limb are on the line, there’s something to be said for the flexibility that informal engineering offers.

[Austin Blake]’s latest eBike is a case study in informal engineering. [Austin] started out wondering if a starter motor from a car engine would make a decent electric bike motor. Our first instinct before watching the video below was to answer that question with a resounding “No!” Yes, starter motors seem like a natural for the job, delivering high torque in a compact package. But starting a car engine is the very definition of a low-duty-cycle application, since it should only take a second or two of cranking to get an engine started. Pressing a motor designed for such a task into continuous duty seems like, well, a non-starter.

And to be fair, [Austin] fully acknowledges this from the start. He even retrofits the motor, wisely replacing the shaft bushings with proper bearings in an attempt to get a better duty cycle. And it works, at least for a while — with the motor, a homebrew battery, and an ESC mounted to a bike frame, the bike was actually pretty peppy. But bearings aren’t the only thing limiting a starter motor to intermittent duty operation. The short drive really heated up the motor, and even with a few ventilation holes knocked in the motor housing, it eventually released the Magic Smoke. The video has all the gory details.

As always, we like to stress that “Fail of the Week” is not necessarily a badge of shame. We appreciate it whenever someone shows us the way not to go, as [Austin] did here. And let’s keep in mind that he’s had success with this approach before, albeit with a much, much bigger starter motor.

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Fail Of The Week: Epic 312 Weeks Of Fixing A Broken Project

February 17, 2023 by Anool Mahidharia 7 Comments

If a hacker guardian angel exists, then we’re sure he or she was definitely AWOL for six long years from [Aaron Eiche]’s life as he worked on perfecting and making his Christmas Countdown clock. [Aaron] started this binary clock project in 2016, and only managed to make it work as expected in 2022 after a string of failures.

In case you’d like to check out his completed project first, then cut the chase and head over to his Github repository for his final, working version. The hardware is pretty straightforward, and not different from many similar projects that we’ve seen before. A microcontroller drives a set of LED’s to show the time remaining until Christmas Day in binary format. The LEDs show the number of days, hours, minutes and seconds until Christmas and it uses two buttons for adjustments and modes. An RTC section wasn’t included in the first version, but it appeared and disappeared along the six year journey, before finding a spot in the final version.

The value of this project doesn’t lie in the final version, but rather in the lessons other hackers, specially those still in the shallow end of the pool, can learn from [Aaron]’s mistakes. Thankfully, the clock ornament is not very expensive to build, so [Aaron] could persevere in improving it despite his annual facepalm moments.

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