Author: Lewin Day

3316 Articles

Building A Trash Can Reverb

August 11, 2025 by 6 Comments

These days, if you want a reverb effect, you just dial up whatever software plugin most appeals to you and turn the dials to taste. However, [Something Physical] specialises in… physical things… and thus built a reverb the old fashioned way. Using a trashcan, of course.

The concept is simple enough—the method of operation is exactly the same as any old plate reverb. Audio is played through a speaker connected to the plate (or trashcan), causing it to vibrate. The sound is then picked up at another point on the plate (or trashcan) with some kind of microphonic pickups, amplified, and there you have your reverb signal.

Given it’s built around a piece of street furniture, [Something Physical] has dubbed this the Street-Verb. It uses a class D amp to drive a speaker with a bolt stuck to it. The bolt is then put in contact with the trashcan itself to transfer the vibration. A pair of piezo elements are used as the pickups, run through a preamps built with a humble BC109C transistor. Since there are two pickups, the Street-Verb is effectively a stereo reverb unit, though the input is only mono. [Something Physical] set up the speaker driver and pickups to be easily movable, and was able to test the device with all kinds of street furniture, like gates and street signs, but the trashcan ‘verb setup is by far the most compelling.

We’ve featured other plate reverb builds before, too, albeit less garbage-themed. Video after the break.

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The Trials Of Trying To Build An Automatic Filament Changer

August 11, 2025 by 16 Comments

Running out of filament mid-print is a surefire way to ruin your parts and waste a lot of time. [LayerLab] was sick of having this problem, and so sought to find a proper solution. Unfortunately, between off-the-shelf solutions and homebrew attempts, he was unable to solve the problem to his satisfaction.

[LayerLab] had a simple desire. He wanted his printer to swap to a second spool of filament when the first one runs out, without ruining or otherwise marring the print. It sounds simple, but the reality is more complicated. As an Australian, he couldn’t access anything from InfinityFlow, so he first attempted to use the “auto refill” features included on the Bambu Labs AMS 2. However, it would routinely make filament changes in outside wall areas of a print, leaving unsightly marks and producing poorer quality parts.

His next effort was to use the Wisepro Auto Refill Filament Buffer. It’s a feeder device that takes filament from two spools, and starts feeding the backup spool in to your printer when the primary spool runs out. Unfortunately, [LayerLab] had a cavalcade of issues with the device. It would routinely feed from the secondary spool when there was still primary filament available, jamming the device, and it didn’t come with a proper mounting solution to work with consumer printers. It also had bearings popping out the top of the housing. Attempts to rework the device into a larger twin-spool rig helped somewhat, but ultimately the unreliability of the Wisepro when changing from one spool to another meant it wasn’t fit for purpose. Its feeder motors were also to trigger the filament snag cutters that [LayerLab] had included in his design.

Ultimately, the problem remains unsolved for [LayerLab]. They learned a lot along the way, mostly about what not to do, but they’re still hunting for a viable automatic filament changer solution that suits their needs. Filament sensors help, but can only do so much. If you reckon you know the answer, or a good way forward, share your thoughts in the comments. Video after the break.

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2025 One Hertz Challenge: Using Industrial Relays To Make A Flasher

August 10, 2025 by 8 Comments

These days, if you want to flash some LEDs, you’d probably grab a microcontroller. Maybe you’d go a little more old-school, and grab a 555. However, [Jacob] is even more hardcore than that, as evidenced by this chunky electromechanical flasher build.

[Jacob] goes into great detail on his ancillary write-up, describing how the simple building blocks used by industrial control engineers can be used to make a flasher circuit that cycles once per second. Basically, two relays are paired with two 0.5-second delay timers. The two relays tag each other on and off on delay as their timers start and expire, with the lamp turned on and off in turn.

We’ve had lots of other great entries to our One Hertz Challenge, too — from clocks to not-clocks. There’s still time to get an entry in — the deadline for submission is Tuesday, August 19 at 9:00AM Pacific time. Good luck out there!

2025 Hackaday One Hertz Challenge

Building A 7-Segment Shadow Clock

August 10, 2025 by 6 Comments

There are plenty of conventional timepieces out there in the world; we’ve also featured a great many that are aesthetically beautiful while being unreadably esoteric. This neat “shadow clock” from [Smart Solutions for Home] is not conventional, but it’s still a clock you could use every day.

The display is made of four seven-segment digits, which have a subtle appearance. Each segment uses a solenoid to extend it forward out of the display, or to retract it flush with the faceplate. This creates a numerical display in all one color, with the physical protrusion doing the job of making the numbers visible. This is perhaps where the “shadow clock” name comes from, though you notice the protruding segments moreso than the shadows they cast on the faceplate.

Running the show is an ESP32, paired with H-bridges to drive the solenoids that make up the 7-segment displays. The H-bridges are driven via shift registers to reduce the number of GPIO pins needed. Unlike many other ESP32 clock builds, this one uses a DS3231 real-time clock module to keep accurate time, rather than solely relying on Internet-based NTP time servers. Configuring the clock can be done via a web interface. Design files are available online.

If you think you’ve seen this recently, maybe you’re thinkig of this prototype for a very similar display by [indoorgeek]. And that’s not the only way to make shadow clocks either. After all, the term is not enforced or defined by any global horological organization. Maybe that’s a good thing! Video after the break.

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2025 One Hertz Challenge: Estimating Pi With An Arduino Nano R4

August 9, 2025 by 10 Comments

Humanity pretty much has Pi figured out at this point. We’ve calculated it many times over and are confident about what it is down to many, many decimal places. However, if you fancy estimating it with some electronic assistance, you might find this project from [Roni Bandini] interesting.

[Roni] programmed an Arduino Nano R4 to estimate Pi using the Monte Carlo method. For this specific case, it involves drawing a circle inscribed inside a square. Points are then randomly scattered inside the square, and checked to see if they lie inside or outside the circle based on their position and distance of the circle’s outline from the center point of the square. By taking the ratio of the points inside the circle to the total number of points, you get an approximation of the ratio of the square and circle’s areas, which is equal to Pi/4. Thus, multiply the ratio by 4, and you’ve got your approximation of Pi.

[Roni] coded a program to run the Monte Carlo simulation on the Arduino Nano R4, taking advantage of the mathematical benefits of its onboard Floating Point Unit. It generates 100 new samples for the Monte Carlo approximation every second, improving the estimation of pi as it goes. It then displays the result on a 7-segment display, and beeps as it goes. [Roni] readily admits the project is a little too close in appearance to a classic Hollywood bomb.

We’ve seen some other neat Pi-calculating projects before, too.

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3D Printing A Giant Beyblade Arena

August 9, 2025 by 4 Comments

Beyblade spinning tops are pretty easy to find at toy shops, department stores, and even some supermarkets. However, the arenas in which the tops do battle? They’re much harder to come by, and the ones on sale in any given market often leave a lot to be desired. [LeftBurst] got around this problem by printing a grandiose Beyblade arena.

[LeftBurst]’s desire was to score a Beyblade stadium more similar to those featured in the anime, which are much larger than those sold as part of the official toy line. [Buddha] was enlisted to model the massive arena, but it then needed to be printed. Given its size, printing it in one piece wasn’t very practical. Instead, [LeftBurst] decided to print it in segments which would then have to be assembled. Super glue was used to put all the parts together, but there was more left to do. The surface finish and joins between the parts would cause issues for tops trying to move across the surface. Thus ensued a great deal of post-processing with primer, putty, and a power sander.

The final result is a massive stadium that plays well, and is ideal for larger multi-Beyblade battles that are more akin to what you’d see in the anime. If you’re playing at this scale, you might appreciate some upgraded launcher technology, too.

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One File, Six Formats: Just Change The Extension

August 8, 2025 by 39 Comments

Normally, if you change a file’s extension in Windows, it doesn’t do anything positive. It just makes the file open in the wrong programs that can’t decode what’s inside. However, [PortalRunner] has crafted a file that can behave as six different filetypes, simply by swapping out the extension at the end of the filename.

The basic concept is simple enough. [PortalRunner] simply found a bunch of different file formats that could feasibly be crammed in together into a single file without corrupting each other or confusing software that loads these files.

It all comes down to how file formats work. File extensions are mostly meaningless to the content of a file—they’re just a shorthand guide so an operating system can figure out which program should load them. In fact, most files have headers inside that indicate to software what they are and how their content is formatted. For this reason, you can often rename a .PNG file to .JPEG and it will still load—because the operating system will still fire up an image viewer app, and that app will use headers to understand that it’s actually a PNG and not a JPEG at heart, and process it in the proper way.

[PortalRunner] found a way to merge the headers of various formats, creating a file that could be many different types. The single file contains data for a PNG image, an MP4 video, a PDF document, a ZIP archive, a Powerpoint presentation, and an HTML webpage. The data chunks for each format are lumped into one big file, with the combined headers at the very top. The hijinx required to pull this off put some limitations on what the file can contain, and the files won’t work with all software… but it’s still one file that has six formats inside.

This doesn’t work for every format. You can’t really combine GIF or PNG for example, as each format requires a different initial set of characters that have to be at the very beginning of the file. Other formats aren’t so persnickety, though, and you can combine their headers in a way that mostly works if you do it just right.

If you love diving into the binary specifics of how file formats work, this is a great project to dive into. We’ve seen similarly mind-bending antics from [PortalRunner] before, like when they turned Portal 2 into a webserver. Video after the break.

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