Testing A Cheap Bench Power Supply Sold On Amazon

May 3, 2025 by Maya Posch 2 Comments

We’ve all seen those cheap bench power supply units (PSUs) for sale online, promising specifications that would cost at least a hundred dollars or more if it were a name brand model. Just how much of a compromise are these (usually rebranded) PSUs, and should you trust them with your electronics? Recently [Denki Otaku] purchased a cheap unit off Amazon Japan for a closer look, and found it to be rather lacking.

Internals of the cheap bench PSU reviewed by Denki Otaku on YouTube.

Major compromises include the lack of an output power switch, no way to check the set current limit without shorting the output, very slow drop in output voltage while adjusting due to the lack of a discharge circuit, and other usability concerns. That’s when the electrical performance of the PSU got tested.

Right off the bat a major issue in this cheap switching mode PSU is clear, as it has 200 mV peak-to-peak noise on its output, meaning very little output filtering. The maximum power output rating was also far too optimistic, with a large voltage drop observed. Despite this, it generally worked well, and the internals – with a big aluminium plate as heatsink – look pretty clean with an interesting architecture.

The general advice is to get a bench PSU that has features like an output power button and an easy way to set the voltage and current limits. Also do not connect it to anything that cares about noise and ripple unless you know that it produces clean, filtered output voltages.

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Peeking At Poking Health Tech: The G7 And The Libre 3

April 29, 2025 by Heidi Ulrich 8 Comments

Continuous glucose meters (CGMs) aren’t just widgets for the wellness crowd. For many, CGMs are real-time feedback machines for the body, offering glucose trendlines that help people rethink how they eat. They allow diabetics to continue their daily life without stabbing their fingertips several times a day, in the most inconvenient places. This video by [Becky Stern] is all about comparing two of the most popular continuous glucose monitors (CGMs): the Abbott Libre 3 and the Dexcom G7.

Both the Libre 3 and the G7 come with spring-loaded applicators and stick to the upper arm. At first glance they seem similar, but the differences run deep. The Libre 3 is the minimalist of both: two plastic discs sandwiching the electronics. The G7, in contrast, features an over-molded shell that suggests a higher production cost, and perhaps, greater robustness. The G7 needs a button push to engage, which users describe as slightly clumsy compared to the Libre’s simpler poke-and-go design. The nuance: G7’s ten-day lifespan means more waste than the fourteen-day Libre, yet the former allows for longer submersion in water, if that’s your passion.

While these devices are primarily intended for people with diabetes, they’ve quietly been adopted by a growing tribe of biohackers and curious minds who are eager to explore their own metabolic quirks. In February, we featured a dissection of the Stelo CGM, cracking open its secrets layer by layer.

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British wartime periscope on a workbench

British Wartime Periscope: A Peek Into The Past

April 22, 2025 by Heidi Ulrich 4 Comments

We all know periscopes serve for observation where there’s no direct line-of-sight, but did you know they can allow you to peer through history? That’s what [msylvain59] documented when he picked up a British military night vision periscope, snagged from a German surplus shop for just 49 euros. Despite its Cold War vintage and questionable condition, the unit begged for a teardown.

The periscope is a 15-kilo beast: industrial metal, cryptic shutter controls, and twin optics that haven’t seen action since flares were fashionable. One photo amplifier tube flickers to greenish life, the other’s deader than a disco ball in 1993. With no documentation, unclear symbols, and adjustment dials from hell, the teardown feels more like deciphering a British MoD fever dream than a Sunday project. And of course, everything’s imperial.

Despite corrosion, mysterious bulbs, and non-functional shutters, [msylvian59] uncovers a fascinating mix of precision engineering and Cold War paranoia. There’s a thrill in tracing light paths through mil-spec lenses (the number of graticules seen that are etched on the optics) and wondering what secrets they once guarded. This relic might not see well anymore, but it sure makes us look deeper. Let us know your thoughts in the comments or share your unusual wartime relics below.

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Hacking A Cheap Rechargeable Lamp With Non-Standard USB-C Connector

April 12, 2025 by Maya Posch 40 Comments

The "USB C" cable that comes with the Inaya Portable Rechargeable Lamp. (Credit: The Stock Pot, YouTube) — The “USB C” cable that comes with the Inaya Portable Rechargeable Lamp. (Credit: The Stock Pot, YouTube)

Recently [Dillan Stock] over at The Stock Pot YouTube channel bought a $17 ‘mushroom’ lamp from his local Kmart that listed ‘USB-C rechargeable’ as one of its features, the only problem being that although this is technically true, there’s a major asterisk. This Inaya-branded lamp namely comes with a USB-C cable with a rather prominent label attached to it that tells you that this lamp requires that specific cable. After trying with a regular USB-C cable, [Dillan] indeed confirmed that the lamp does not charge from a standard USB-C cable. So he did what any reasonable person would do: he bought a second unit and set about to hacking it.

[Dillan] also dug more into what’s so unusual about this cable and the connector inside the lamp. As it turns out, while GND & Vcc are connected as normal, the two data lines (D+, D-) are also connected to Vcc. Presumably on the lamp side this is the expected configuration, while using a regular USB-C cable causes issues. Vice versa, this cable’s configuration may actually be harmful to compliant USB-C devices, though [Dillan] did not try this.

With the second unit in hand, he then started hacking it, with the full plans and schematic available on his website.

The changes include a regular USB-C port for charging, an ESP32 board with integrated battery charger for the 18650 Li-ion cell of the lamp, and an N-channel MOSFET to switch the power to the lamp’s LED. With all of the raw power from the ESP32 available, the two lamps got integrated into the Home Assistant network which enables features such as turning the lamps on when the alarm goes off in the morning. All of this took about $7 in parts and a few hours of work.

Although we can commend [Dillan] on this creative hack rather than returning the item, it’s worrying that apparently there’s now a flood of ‘USB C-powered’ devices out there that come with non-compliant cables that are somehow worse than ‘power-only’ USB cables. It brings back fond memories of hunting down proprietary charging cables, which was the issue that USB power was supposed to fix.

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The Lowly Wall Wart Laid Bare

April 2, 2025 by Tom Nardi 18 Comments

Getting a look at the internals of a garden variety “wall wart” isn’t the sort of thing that’s likely to excite the average Hackaday reader. You’ve probably cracked one open yourself, and even if you haven’t, you’ve likely got a pretty good idea of what’s inside that sealed up brick of plastic. But sometimes a teardown can be just as much about the journey as it is the end result.

Truth be told, we’re not 100% sure if this teardown from [Brian Dipert] over at EDN was meant as an April Fool’s joke or not. Certainly it was posted on the right day, but the style is close enough to some of his previous work that it’s hard to say. In any event, he’s created a visual feast — never in history has an AC/DC adapter been photographed so completely and tastefully.

[Brian] even goes so far as to include images of the 2.5 lb sledgehammer and paint scraper that he uses to brutally break open the ultrasonic-welded enclosure. The dichotomy between the thoughtful imagery and the savage way [Brian] breaks the device open only adds to the surreal nature of the piece. Truly, the whole thing seems like it should be part of some avant garde installation in SoHo.

After he’s presented more than 20 images of the exterior of the broken wall wart, [Brian] finally gets to looking at the internals. There’s really not much to look at, there’s a few circuit diagrams and an explanation of the theory behind these unregulated power supplies, and then the write-up comes to a close as abruptly as it started.

So does it raise the simple teardown to an art form? We’re not sure, but we know that we’ll never look at a power adapter in quite the same way again.

Tiny Bubbles In The Memory

March 31, 2025 by Al Williams 15 Comments

We are always fascinated by bubble memory. In the late 1970s, this was the “Next Big Thing” that, as you may have guessed, was, in fact, not the next big thing at all. But there were a number of products that used it as non-volatile memory at a time when the alternative was tape or disk. [Smbakeryt] has a cool word processor with an acoustic coupler modem made by Teleram. Inside is — you guessed it — bubble memory.

The keyboard was nonfunctional, but fixable. Although we wouldn’t have guessed the problem. Bubble memory was quite high tech. It used magnetic domains circulating on a thin film of magnetic material. Under the influence of a driving field, the bubbles would march past a read-write head that could create, destroy, or read the state of the bubble.

Why didn’t it succeed? Well, hard drives got cheap and fairly rugged. The technology couldn’t compete with the high-density hard drives that could be reached with improved heads and recording strategies. Bubble memory did find use in high-vibration items, but also wound up in things like this terminal, at least one oscilloscope, and a video game.

Bubble memory evolved from twistor memory, one of several pre-disk technologies. While they are hard to come by today, you can find the occasional project that either uses some surplus or steals a part off of a device like this one.

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Inside A Fake WiFi Repeater

March 27, 2025 by Maya Posch 29 Comments

Fake WiFi repeater with a cheap real one behind it. (Credit: Big Clive, YouTube)

Over the years we have seen a lot of fake electronics, ranging from fake power saving devices that you plug into an outlet, to fake car ECU optimizers that you stick into the OBD port. These are all similar in that they fake functionality while happily lighting up a LED or two to indicate that they’re doing ‘something’. Less expected here was that we’d be seeing fake WiFi repeaters, but recently [Big Clive] got his hands on one and undertook the arduous task of reverse-engineering it.

The simple cardboard box which it comes in claims that it’s a 2.4 GHz unit that operates at 300 Mbps, which would be quite expected for the price. [Clive] obtained a real working WiFi repeater previously that did boast similar specifications and did indeed work. The dead giveaway that it is a fake are the clearly fake antennae, along with the fact that once you plug it in, no new WiFi network pops up or anything else.

Inside the case – which looks very similar to the genuine repeater – there is just a small PCB attached to the USB connector. On the PCB are a 20 Ohm resistor and a blue LED, which means that the LED is being completely overdriven as well and is likely to die quite rapidly. Considering that a WiFi repeater is supposed to require a setup procedure, it’s possible that these fake repeaters target an audience which does not quite understand what these devices are supposed to do, but they can also catch more informed buyers unaware who thought they were buying some of the cheap real ones. Caveat emptor, indeed.

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