Just How Dodgy Are Cheap USB Chargers Anyway?

November 3, 2023 by Dan Maloney 49 Comments

Aside from apparently having both the ability to reproduce on their own and simultaneously never being around when you need one, USB chargers seem innocuous enough. The specs are simple: convert mains voltage to 5 volts, and don’t kill anyone while doing it. Both specs are typically met by most designs, but judging by [DiodeGoneWild]’s latest USB charger teardown, the latter only just barely, and with a whole lot of luck.

The sad state of plug-in USB power supplies is one of [DiodeGoneWild]’s pet gripes, and deservedly so. Most USB chargers cram a lot of electronics into a mighty small volume, and are built to a price point, meaning that something has to give in the design. In the case of the two units he tears apart in the video below, it’s pretty clear where the compromises are. Neither unit met the specs on the label in terms of current supplied and voltage regulation, even the apparently more capable quick charger, which is the first to go under the knife. The PCB within holds some alarming surprises, like the minimal physical isolation between the mains part of the circuit and the low-voltage section, but the real treat is the Schottky diode that gets up to 170°C under full load. Safety tip: when you smell plastic burning, throw the thing out.

The second charger didn’t fare any better; although it didn’t overheat, that’s mainly because it shut itself off before it could deliver a fraction of its rated 1 amp output. The PCB construction was shoddy in the extreme, with a squiggly trace standing in for a proper fuse and a fraction of a millimeter separation between primary and secondary traces. The flyback transformer was a treat, too; who doesn’t want to rely on a whisper-thin layer of cheap lacquer to keep mains voltage out of your phone?

All in all, these designs are horrible, and we have to thank [DiodeGoneWild] for the nightmares we’ll have whenever we plug into one of these things from now on. On the other hand, this was a great introduction to switch-mode power supply designs, and what not to do with our own builds. Continue reading “Just How Dodgy Are Cheap USB Chargers Anyway?” →

Custom Fume Hood For Safe Electroless Plating

October 22, 2023 by Bryan Cockfield 10 Comments

There are plenty of chemical processes that happen commonly around the house that, if we’re really following safety protocols to the letter, should be done in a fume hood. Most of us will have had that experience with soldering various electronics, especially if we’re not exactly sure where the solder came from or how old it is. For [John]’s electroless plating process, though, he definitely can’t straddle that line and went about building a fume hood to vent some of the more harmful gasses out of a window.

This fume hood is pretty straightforward and doesn’t have a few of the bells and whistles found in commercial offerings, but this process doesn’t really require things like scrubbing or filtering the exhaust air so he opted to omit these pricier and more elaborate options. What it does have, though, is an adjustable-height sash, a small form factor that allows it to easily move around his shop, and a waterproof, spill-collecting area in the bottom. The enclosure is built with plywood, allowing for openings for an air inlet, the exhaust ducting, and a cable pass-through, and then finished with a heavy-duty paint. He also included built-in lighting and when complete, looks indistinguishable from something we might buy from a lab equipment supplier.

While [John] does admit that the exhaust fan isn’t anything special and might need to be replaced more often than if he had gone with one that was corrosion-resistant, he’s decided that the cost of this maintenance doesn’t outweigh the cost of a specialized fan. He also notes it’s not fire- or bomb-proof, but nothing he’s doing is prone to thermal anomalies of that sort. For fume hoods of all sorts, we might also recommend adding some automation to them so they are used any time they’re needed.

Continue reading “Custom Fume Hood For Safe Electroless Plating” →

Hackaday Links: August 27, 2023

August 27, 2023 by Dan Maloney 26 Comments

We mentioned last week how robotaxi provider Cruise was having a no-good, very bad week, after one of their driverless taxis picked a fight with a semi, and it was revealed that amorous San Franciscans were taking advantage of the privacy afforded by not having a driver in the front seat. It appears that we weren’t the only ones to notice all the bad news, since California’s Department of Motor Vehicles issued an order to the company to cut its robotaxi fleet in half. The regulatory move comes after a recent Cruise collision with a fire truck, which injured a passenger in the taxi. Curiously, the DMV order stipulates that Cruise can only operate 50 vehicles during the day, while allowing 150 vehicles at night. We’d have thought the opposite would make more sense, since driving at night is generally more difficult than during daylight hours. But perhaps the logic is that the streets are less crowded at night, whereas daytime is a more target-rich environment.

Continue reading “Hackaday Links: August 27, 2023” →

3D Printing Safety (According To The UL)

June 4, 2023 by Al Williams 17 Comments

If you want to start a heated discussion in 3D printing circles, ask people about the requirements to print safely. Is ABS safe to print without ventilation? Can you drink out of a PLA cup? How nasty is that photo resin if you spill it on yourself? If you are at home, it’s more or less up to you. But if you are building a shared hackerspace, a corporate workstation, or a classroom, these questions might come up, and now, the UL has your answer. The UL200B document is aimed at 3D printers in “institutions of higher education,” but we imagine what’s good for the university is good for us, too.

The 45-page document isn’t an easy read. It does cover both “material extrusion” and “vat photopolymerization” technology. In fact, they identify seven “most common” processes ranging from powder bed fusion, energy deposition, and more. The work results from a UL task force with participants from Harvard, Princeton, and Carnegie-Mellon. We were surprised there didn’t seem to be any industry representation, but maybe that was on purpose.

With extrusion printing — what we’d call FDM — the focus seems to be on ultra-fine particles and volatile organic compounds (VOCs). However, the level of VOCs rose up to six times with resin printers when compared to FDM. Filters helped with ABS, nylon, and ASA, and polycarbonate/ABS. The paper does acknowledge that PLA is probably safer, although it is quick to point out that PLA with additives may not be as safe as plain PLA. If you want a quick summary, check out Table 2, starting on page 23.

The rest of the document is about creating a safety plan for all the printers that might be on a college campus — that might not be as interesting. However, you’ll want to skip forward to the appendix section. It has some data about relevant industrial standards and other data.

This is a great step in analyzing the risks of 3D printing. Of course, laser printers and copiers also spew micro-particles, and we seem to have survived those for a number of decades. Still, more data is good — you should be informed to make decisions about your health and safety. We didn’t see much in the document that covered food safety, something we’ve talked about before. If you want to monitor your VOC exposure, we got you.

High Voltage Power Supply From USB

April 30, 2023 by Bryan Cockfield 14 Comments

Those who work in different spaces may have different definitions of the term “high voltage”. For someone working on the GPIO pins of a Raspberry Pi it might be as little as 5 volts, someone working on a Tesla coil might consider that to be around 20 kV, and an electrical line worker might not reference something as HV until 115 kV. What we could perhaps all agree on, though, is that getting 300 volts out of a USB power supply is certainly a “high voltage” we wouldn’t normally expect to see in that kind of context, but [Aylo6061] needed just such a power supply and was eventually able to create one.

In this case, the high voltages will eventually be used for electrophoresis or electrowetting. But before getting there, [Aylo6061] has built one of the safest looking circuits we’ve seen in recent memory. Every high voltage part is hidden behind double insulation, and there is complete isolation between the high and low voltage sides thanks to a flyback converter. This has the benefit of a floating ground which reduces the risk of accidental shock. This does cause some challenges though, as voltage sensing on the high side is difficult while maintaining isolation, so some clever tricks were implemented to maintain the correct target output voltage.

The control circuitry is based around an RP2040 chip and is impressive in its own right, with USB isolation for the data lines as well. Additionally the project code can be found at its GitHub page. Thanks to a part shortage, [Aylo6061] dedicated an entire core of the microprocessor to decoding digital data from the high voltage sensor circuitry. For something with a little less refinement, less safety, and a much higher voltage output, though, take a look at this power supply which tops its output voltage around 30 kV.

Ski Season Sees Apple’s Crash Detection System Fire Deluge Of False Positives

February 9, 2023 by Lewin Day 39 Comments

Smartphone features used to come thick and fast. Cameras proliferated, navigation got added, and then Apple changed the game by finally making touch computing just work. Since then, truly new features have slowed to a trickle, but Apple’s innovative crash detection system has been a big deal where safety is concerned.

The problem? It’s got a penchant for throwing false positives when iPhone and Apple Watch users are in no real danger at all. We first covered this problem last year, but since then, the wintery season has brought yet more issues for already-strained emergency responders.

Continue reading “Ski Season Sees Apple’s Crash Detection System Fire Deluge Of False Positives” →

LED Driver Circuit For Safety Hat Sucks Single AAA Cell Dry

January 19, 2023 by Donald Papp 21 Comments

[Petteri Aimonen] created an omnidirectional LED safety light to cling to his child’s winter hat in an effort to increase visibility during the dark winter months, but the design is also great example of how to use the Microchip MCP1640 — a regulated DC-DC step-up power supply that can run the LEDs off a single AAA cell. The chip also provides a few neat tricks, like single-button on/off functionality that fully disconnects the load, consuming only 1 µA in standby.

[Petteri]’s design delivers 3 mA to each of eight surface-mount LEDs (which he says is actually a bit too bright) for a total of about 20 hours from one alkaline AAA cell. The single-layer PCB is encased in a clear acrylic and polycarbonate enclosure to resist moisture. A transistor and a few passives allow a SPST switch to act as an on/off switch: a short press turns the unit on, and a long press of about a second turns it back off.

One side effect is that the “off” functionality will no longer work once the AAA cell drained too badly, but [Petteri] optimistically points out that this could be considered a feature: when the unit can no longer be turned off, it’s time to replace the battery!

The usual way to suck a battery dry is to use a Joule Thief, and while this design also lights LEDs, it offers more features and could be adapted for other uses easily. Interested? [Petteri] offers the schematic, KiCAD file for the PCB, and SVG drawing of the enclosure for download near the bottom of the project page.