Save Cells From The Landfill, Get A Power Bank For Your Troubles

April 27, 2025 by Donald Papp 34 Comments

A hefty portable power bank is a handy thing to DIY, but one needs to get their hands on a number of matching lithium-ion cells to make it happen. [Chris Doel] points out an easy solution: salvage them from disposable vapes and build a solid 35-cell power bank. Single use devices? Not on his watch!

[Chris] has made it his mission to build useful things like power banks out of cells harvested from disposable vapes. He finds them — hundreds of them — on the ground or in bins (especially after events like music festivals) but has also found that vape shops are more than happy to hand them over if asked. Extracting usable cells is most of the work, and [Chris] has refined safely doing so into an art.

Disposable vapes are in all shapes and sizes, but cells inside are fairly similar.

Many different vapes use the same cell types on the inside, and once one has 35 identical cells in healthy condition it’s just a matter of using a compatible 3D-printed enclosure with two PCBs to connect the cells, and a pre-made board handles the power bank functionality, including recharging.

We’d like to highlight a few design features that strike us as interesting. One is the three little bendy “wings” that cradle each cell, ensuring cells are centered and held snugly even if they aren’t exactly the right size. Another is the use of spring terminals to avoid the need to solder to individual cells. The PCBs themselves also double as cell balancers, providing a way to passively balance all 35 cells and ensure they are at the same voltage level during initial construction. After the cells are confirmed to be balanced, a solder jumper near each terminal is closed to bypass that functionality for final assembly.

The result is a hefty power bank that can power just about anything, and maybe the best part is that it can be opened and individual cells swapped out as they reach the end of their useful life. With an estimated 260 million disposable vapes thrown in the trash every year in the UK alone, each one containing a rechargeable lithium-ion cell, there’s no shortage of cells for an enterprising hacker willing to put in a bit of work.

Power banks not your thing? [Chris] has also created a DIY e-bike battery using salvaged cells, and that’s a money saver right there.

Learn all about it in the video, embedded below. And if you find yourself curious about what exactly goes on in a lithium-ion battery, let our own Arya Voronova tell you all about it.

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DIY AI Butler Is Simpler And More Useful Than Siri

April 15, 2025 by Donald Papp 8 Comments

[Geoffrey Litt] shows that getting an effective digital assistant that’s tailored to one’s own needs just needs a little DIY, and thanks to the kinds of tools that are available today, it doesn’t even have to be particularly complex. Meet Stevens, the AI assistant who provides the family with useful daily briefs. The back end? Little more than one SQLite table and a few cron jobs.

A sample of Stevens’ notebook entries, both events and things to simply remember.

Every day, Stevens sends a daily brief via Telegram that includes calendar events, appointments, weather notes, reminders, and even a fun fact for the day. Stevens isn’t just send-only, either. Users can add new entries or ask questions about items through Telegram.

It’s rudimentary, but [Geoffrey] already finds it far more useful than Siri. This is unsurprising, as it has been astutely observed that big tech’s digital assistants are designed to serve their makers rather than their users. Besides, it’s also fun to have the freedom to give an assistant its own personality, something existing offerings sorely lack.

Architecture-wise, the assistant has a notebook (the single SQLite table) that gets populated with entries. These entries come from things like reading family members’ Google calendars, pulling data from a public weather API, processing delivery notices from the post office, and Telegram conversations. With a notebook of such entries (along with a date the entry is expected to be relevant), generating a daily brief is simple. After all, LLMs (Large Language Models) are amazingly good at handling and formatting natural language. That’s something even a locally-installed LLM can do with ease.

[Geoffrey] says that even this simple architecture is super useful, and it’s not even a particularly complex system. He encourages anyone who’s interested to check out his project, and see for themselves how useful even a minimally-informed assistant can be when it’s designed with ones’ own needs in mind.

DIY Soldering Tweezers, Extra Thrifty

April 12, 2025 by Donald Papp 11 Comments

It started when [Mitxela] was faced with about a hundred incorrectly-placed 0603 parts. Given that he already owned two TS101 soldering irons, a 3D printer, and knows how to use FreeCAD (he had just finished designing a custom TS101 holder) it didn’t take long to create cost-effective DIY soldering tweezers.

Two screws allow adjusting the irons to ensure the tips line up perfectly.

The result works great! The TS101 irons are a friction-fit and the hinge (designed using the that-looks-about-right method) worked out just fine on the first try. Considering two TS101 irons are still cheaper than any soldering tweezer he could find, and one can simply undock the TS101s as needed, we call this a solid win.

One feature we really like is being able to precisely adjust the depth of each iron relative to each other, so that the tips can be made to line up perfectly. A small screw and nut at the bottom end of each holder takes care of that. It’s a small but very thoughtful design feature.

Want to give it a try? The FreeCAD design file (and .stl model) is available from [Mitxela]’s project page. Just head to the bottom to find the links.

We’ve seen DIY soldering tweezers using USB soldering irons from eBay but the TS101 has a form factor that seems like a particularly good fit.

Biting Off More Than I Can Chew

April 12, 2025 by Elliot Williams 39 Comments

Earlier this year, I bought one of those K40-style laser machines that was listed at a ridiculously low price, and it arrived broken. Well, let me qualify that: the laser tube and the power supply work perfectly, but that’s about the best you can say about it.

On first power-up, it made a horrible noise, the Y-axis was jammed, the X-axis was so off-square that it was visibly apparent, and it turned out that as I fixed one of these problems after the other, that it was just the tip of the iceberg. The Y-axis was jammed because the belts were so tight that they made the motor bind. Replacing them, because they were simply too short, got the stage moving, but it didn’t engage the endstops. Fixing those revealed that the motor was stepped wrong, and flipping the pins in the connector finally got it homing in the right direction. Full disassembly and reassembly steps required at each stage here.

The X-axis just needed adjustment, but the opto on its endstop had been completely crushed by a previous failed homing, and I had to desolder and resolder in a new one. (Keep your junkbox well stocked!) With the machine working, it became obvious that the driver board was barely usable. It accelerates horribly jerkily, which makes the motors skip and stall. It had to be run artificially slowly because it couldn’t make the corners. So I put in a new motor controller board that handles Gcode and does legitimate acceleration ramps.

Movement mostly fixed, it was time to align the laser. Of course, the optical path is all messed up, they forgot the o-ring that holds the focusing lens in place, and the thing keeps powering down randomly. This turns out to be because of the aiming red laser pointer, which has a positive case, which is shorting through the single wrap of electrical tape that “insulates” it from the machine’s frame. When this shorts, the motor driver board browns out. Lovely!

Once I was finally able to start aligning the beam, I discovered that the frame is warped out of plane. The simple solution is to take it all apart again and shim it until it’s flat, but I just haven’t had the time yet. I’m not beaten, but it’s been eating up hours after hours on the weekends, and that time is scarce.

I love DIY, and I love taking a machine apart in order to understand it. Once. But I’m now on my tenth or twelfth unmounting of the motion stage, and frankly, it’s no fun any more. It would have been quicker, if maybe not cheaper, to have built this machine entirely from scratch. At least for the moment, I’ve bitten off more than I have time to chew.

Reviving A Maplin 4600 DIY Synthesizer From The 1970s

March 19, 2025 by Donald Papp 16 Comments

A piece of musical history is the Maplin 4600, a DIY electronic music synthesizer from the 1970s. The design was published in an Australian electronics magazine and sold as a DIY kit, and [LOOK MUM NO COMPUTER] got his hands on an original Maplin 4600 that he refurbishes and puts through its paces.

Inserting conductive pegs is how the operator connects different inputs and outputs.

The Maplin 4600 is a (mostly) analog device with a slightly intimidating-looking layout. It features multiple oscillators, mixers, envelope generators, filters, and a complex-looking patch bay on the right hand side that is reminiscent of a breadboard. By inserting conductive pins, one can make connections between various inputs and outputs.

Internally the different features and circuits are mostly unconnected from one another by default, so the patch board is how the instrument is “programmed” and the connections made can be quite complex. The 4600 is one of a few synthesizer designs by [Trevor Marshall], who has some additional details about on his website.

The video (embedded below) is a complete walk-through of the unit, including its history, quirks, and design features. If you’d like to skip directly to a hands-on demonstrating how it works, that begins around the 10:15 mark.

Synthesizers have a rich DIY history and it’s fascinating to see an in-depth look at this one. And hey, if you like your synths complex and intimidating, do yourself a favor and check out the Starship One.

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DIY Open-Source Star Tracker Gets You Those Great Night Shots

February 25, 2025 by Donald Papp 15 Comments

What does one do when frustrated at the lack of affordable, open source portable trackers? If you’re [OG-star-tech], you design your own and give it modular features that rival commercial offerings while you’re at it.

What’s a star tracker? It’s a method of determining position based on visible stars, but when it comes to astrophotography the term refers to a sort of hardware-assisted camera holder that helps one capture stable long-exposure images. This is done by moving the camera in such a way as to cancel out the effects of the Earth’s rotation. The result is long-exposure photographs without the stars smearing themselves across the image.

Interested? Learn more about the design by casting an eye over the bill of materials at the GitHub repository, browsing the 3D-printable parts, and maybe check out the assembly guide. If you like what you see, [OG-star-tech] says you should be able to build your own very affordably if you don’t mind 3D printing parts in ASA or ABS. Prefer to buy a kit or an assembled unit? [OG-star-tech] offers them for sale.

Frustration with commercial offerings (or lack thereof) is a powerful motive to design something or contribute to an existing project, and if it leads to more people enjoying taking photos of the night sky and all the wonderful things in it, so much the better.

MIT Demonstrates Fully 3D Printed, Active Electronic Components

February 19, 2025 by Donald Papp 26 Comments

One can 3D print with conductive filament, and therefore plausibly create passive components like resistors. But what about active components, which typically require semiconductors? Researchers at MIT demonstrate working concepts for a resettable fuse and logic gates, completely 3D printed and semiconductor-free.

Now just to be absolutely clear — these are still just proofs of concept. To say they are big and perform poorly compared to their semiconductor equivalents would be an understatement. But they do work, and they are 100% 3D printed active electronic components, using commercially-available filament.

How does one make a working resettable fuse and transistor out of such stuff? By harnessing thermal expansion, essentially.

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