Circuit Secrets: Exploring A $5 Emergency Light

December 28, 2024 by Heidi Ulrich 2 Comments

Who would’ve thought a cheap AliExpress emergency light could be packed with such crafty design choices? Found for about $5, this unit uses simple components yet achieves surprisingly sophisticated behaviors. Its self-latching feature and decisive illumination shut-off are just the beginning. A detailed analysis by [BigCliveDotCom] reveals a smart circuit that defies its humble price.

The circuit operates via a capacitive dropper, a cost-effective way to power low-current devices. What stands out, though, is its self-latching behavior. During a power failure, transistors manage to keep the LEDs illuminated until the battery voltage drops below a precise threshold, avoiding the dreaded fade-to-black. Equally clever is the automatic shut-off when the voltage dips too low, sparing the battery from a full drain.

Modifications are possible, too. For regions with 220V+ mains, swapping the dropper capacitor with a 470nF one can reduce heat dissipation. Replacing the discharge resistor (220k) with a higher value improves longevity by running cooler. What remarkable reverse engineering marvels have you come across? Share it in the comments! After all, it is fun to hack into consumer stuff. Even if it is just a software hack.

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A Twenty-Segment Display, Artistically

December 24, 2024 by Elliot Williams 21 Comments

We all know and love the humble seven-segment display, right? And if you want to make characters as well as numbers, you can do an okay job with sixteen segments off the shelf. But if you want something more art-deco, you’ll probably want to roll your own. Or at least, [Ben] did, and you can find his designs up on GitHub.

Taking inspiration from [Posy]’s epic investigation of segmented displays, [Ben] sat down with a sketchpad and created his own 20-segment font that displays numbers and letters with some strange, but frankly lovely, segment shapes. There is no center line, so letters like “T” and numbers like “1” are a little skewed, but we think it’s charming.

We’ve seen about a bazillion takes on the seven-segment idea over the years here. Most recently, we fell in love with this 21-segment beauty, but honestly the original eight(!) segment patent version is charming as well. Anyway, picking a favorite segmented display at Hackaday is like picking your favorite child, if you have a few hundred children. We love them all.

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Vintage Audio Amp Gets LED Lighting Upgrade

December 22, 2024 by Lewin Day 22 Comments

Vintage hi-fi gear can be very attractive, particularly compared to modern stuff. However, when this stuff starts getting into its third or fourth decade after production, things start to wear out. Chief among them—the little incandescent bulbs that light up the dials with such a beautiful glow. [Piffpaffpoltrie] was suffering just this problem on an old Technics amp, and decided to go for a more modern upgrade.

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Building The Spectacular Fibonacci128 Simple Add-On

December 16, 2024 by Tom Nardi No comments

This year, we not only challenged Supercon attendees to come up with their own Simple Add-Ons (SAOs) for the badge, but to push the envelope on how the modular bits of flair work. Historically, most SAOs were little more than artistically arranged LEDs, but we wanted to see what folks could do if they embraced the largely unused I2C capability of the spec.

[Squidgeefish] clearly understood the assignment. This first-time attendee arrived in Pasadena with an SAO that was hard to miss…literally. Looking directly at the shockingly bright 128 RGB LED array packed onto the one-inch diameter PCB was an experience that would stay with you for quite some time (ask us how we know). With the “artistically arranged LEDs” aspect of the nominal SAO handled nicely, the extra work was put into the design so that the CPU could control the LED array via simple I2C commands.

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Tis The Season

December 7, 2024 by Elliot Williams 16 Comments

’Tis the season for soldering! At least at my house. My son and I made some fairly LED-laden gifts for the immediate relatives last year, and he’s got the blinky bug. We were brainstorming what we could make this year, and his response was “I don’t care, but it needs to have lots of LEDs”.

It’s also the season for reverse engineering, apparently, because we’re using a string of WS2812-alike “fairy lights”. These are actually really neat, they look good and are relatively cheap. It’s a string of RGB LEDs with drivers, each dipped in epoxy, and run on a common three-enameled-wire bus. Unlike WS2812s, which pass the data on to the next unit in the line and then display them with a latching pulse at the end of a sequence, these LED drivers seem to count how many RGB packets have been sent down the wire, and only respond to their own number.

This means that if you cut up a string of 200 LEDs, it behaves like a string of 200 WS2812s. But if you cut say 10 LEDs off the string, where you cut them matters. If you cut it off the front of the string, you only have to send 10 color packets. If you cut them off the other end, you need to send 290 dummy packets before they even start listening. Bizarre, but ’tis the season for bizarre hacks.

And finally, ’tis the season for first steps into “software architecture”. Which is to say that my son is appreciating functions for the first time in his life. Controlling one LED is easy, but making a light show is about two more abstraction layers on top of that. We’ve been having fun making them dim, twinkle, and chase so far. We only have two more weekends, though, and we don’t have a final light show figured out yet, but after all, ’tis the season for last minute present hacking.

Homebrew Phosphorescence Detector Looks For The Glow In Everyday Objects

November 28, 2024 by Dan Maloney 8 Comments

Spoiler alert: almond butter isn’t phosphorescent. But powdered milk is, at least to the limit of detection of this homebrew phosphorescence detector.

Why spend a bunch of time and money on such a thing? The obvious answer is “Why not?”, but more specifically, when [lcamtuf]’s son took a shine (lol) to making phosphorescent compounds, it just seemed natural for dad to tag along in his own way. The basic concept of the detector is to build a light-tight test chamber that can be periodically and briefly flooded with UV light, charging up the putatively phosphorescent compounds within. A high-speed photodiode is then used to detect the afterglow, which can be quantified and displayed.

The analog end of the circuit was the far fussier end of the design, with a high-speed transimpedance amplifier to provide the needed current gain. Another scaling amp and a low-pass filter boosts and cleans up the signal for a 14-bit ADC. [lcamtuf] went to great lengths to make the front end as low-noise as possible, including ferrite beads and short leads to prevent picking up RF interference. The digital side has an AVR microcontroller that talks to the ADC and runs an LCD panel, plus switches the 340 nm LEDs on and off rapidly via a low gate capacitance MOSFET.

Unfortunately, not many things found randomly around the average home are all that phosphorescent. We’re not sure what [lcamtuf] tried other than the aforementioned foodstuffs, but we’d have thought something like table salt would do the trick, at least the iodized stuff. But no matter, the lessons learned along the way were worth the trip.

Building A Pi-Powered LED Chess Board

November 25, 2024 by Lewin Day 12 Comments

If you live near Central Park or some other local chess hub, you’re likely never short of opponents for a good game. If you find yourself looking for a computer opponent, or you just prefer playing online, you might like this LED chessboard from [DIY Machines] instead.

At heart, it’s basically a regular chessboard with addressable LEDs of the WS2812B variety under each square. The lights are under the command of an Arduino Nano, which is also tasked with reading button inputs from the board’s side panel. The Nano is interfaced with a Raspberry Pi, which is the true brains of the operation. The Pi handles chess tasks—checking the validity of moves, acting as a computer opponent, and connecting online for games against other humans if so desired. Everything is wrapped up with 3D printed parts, making this an easy project to build for the average DIY maker.

The video tutorial does a great job of covering the design. It’s a relatively simple project at heart, but the presentation is great and it looks awfully fun to play with. We’ve featured some other great builds from [DIY Machines] before, too. Video after the break. Continue reading “Building A Pi-Powered LED Chess Board” →