Weed Eater String Made From Plastic Bottles

For those who don’t mind constantly adding tiny but measurable amounts of microplastics to their landscaping, string trimmers are an excellent way of maintaining edging around garden beds, trimming weeds, or maintaining ground covers on a steep hill. One problem with them, though, is that not only is the string consumable but it can be expensive. Plus, if you have a trimmer with a proprietary spool you need to hope the company never goes out of business. Or, you can simply refill your string spool with this handy tool.

The build uses plastic bottles to create the string from what would likely become garbage anyway. First, a sharp roller-style knife slices the plastic into a long thin strip. Once cut, it is fed through a heater similar to a hot end on a 3D printer which allows the plastic to be deformed or forged into a cylinder. From there the plastic is added onto a spool, which also has the motor in it that drives the entire mechanism. In this case it is using an old variable-speed drill.

From the comments on the video, there is some discussion about the economics of using this string in a weed eater. It’s likely the plastic won’t last as long as specialty string trimmer string, and the time and expense of making the plastic may never save much money. But we have to give credit to the ingenuity nonetheless. And, if you’re really into recycling plastic just for the sake of keeping it out of the landfill, there are plenty of other ways to go about accomplishing that goal.

I will NEVER buy weed whip line again! from landscaping

Pocket Radio Powered By Tiny Microcontroller

Before the days of MP3 players and smartphones, and even before portable CD players, those of us of a certain age remember that our cassette players were about the only way to take music on-the-go. If we were lucky, they also had a built-in radio for when the single tape exhausted both of its sides. Compared to then, it’s much easier to build a portable radio even though cassettes are largely forgotten, as [wagiminator] shows us with this radio design based on an ATtiny.

The build is about as compact as possible, with the aforementioned ATtiny 402/412 as its core, it also makes use of an integrated circuit FM tuner,  an integrated audio amplifier with its own single speaker, and a small OLED display. The unit also boasts its own lithium-polymer battery charger and its user interface consists of only three buttons, plenty for browsing radio stations and controlling volume.

The entire build fits easily in the palm of a hand and is quite capable for a mobile radio, plus all of the schematics and code is available on the project page. While it doesn’t include AM capability, just the fact that FM is this accessible nowadays when a few decades ago it was cutting-edge technology is quite remarkable. If you’re looking for an even smaller FM receiver without some of the bells and whistles of this one, take a look at this project too.

Computer Vision Extracts Lightning From Footage

Lightning is one of the more mysterious and fascinating phenomenon on the planet. Extremely powerful, but each strike on average only has enough energy to power an incandescent bulb for an hour. The exact mechanism that starts a lightning strike is still not well understood. Yet it happens 45 times per second somewhere on the planet. While we may not gain a deeper scientific appreciation of lightning anytime soon, but we can capture it in various photography thanks to this project which leverages computer vision machine learning to pull out the best frames of lightning.

The project’s creator, [Liam], built this as a tool for stormchasers and photographers so that they can film large amounts of time and not have to go back through their footage manually to pull out the frames with lightning strikes. The project borrows from a similar project, but this one adds Python 3 capabilities and runs on a tiny netbook for more easy field deployment. It uses OpenCV for object recognition, using video files as the source data, and features different modes to recognize different types of lightning.

The software is free and open source, and releases are supported for both Windows and Linux. So far, [Liam] has been able to capture all kinds of electrical atmospheric phenomenon with it including lightning, red sprites, and elves. We don’t see too many projects involving lightning around here, partly because humans can only generate a fraction of the voltage potential needed for the average lightning strike.

DIY Airless Tires Work Surprisingly Well

Airless tires have been “a few years away” from production for decades now. They’re one of the automotive version of vaporware (at least those meant for passenger vehicles), always on the cusp of being produced but somehow never materializing. They have a number of perks over traditional air-filled tires in that they are immune to flats and punctures, and since there aren’t any airless tires available at the local tire shop, [Driven Media] decided to make and test their own.

The tires are surprisingly inexpensive to make. A few pieces of drainage tubing of varying diameters, cut to short lengths, and then bolted together with off-the-shelf hardware is all it takes, although they note that there was a tremendous amount of hardware needed to fasten all the pipe lengths together. With the structure in place they simply cut a tread off of a traditional tire and wrapped it around each of the four assemblies, then bolted them up to their Caterham street-legal race car for testing.

While the ride quality was notoriously (and unsurprisingly) rough and bumpy, the tires perform admirably under the circumstances and survive being driven fairly aggressively on a closed-circuit race course. For such a low price and simple parts list it’s shocking that a major tire manufacturer like Michelin hasn’t figured out how to successfully bring one to a light passenger car yet.

Thanks to [Itay] for the tip!

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Performing Magic With A Little High-Tech Help

Doing magic with cards involves a lot of precise dexterity to know which card is where. For plenty of tricks, this is often knowledge and control of a single card or a small number of cards. But knowing the exact position of every single card in the deck could certainly be helpful, so the Nettle Magic Project was created to allow magicians to easily identify the location of cards in the deck.

The system works through the use of computer vision to identify a series of marks on the short edge of a stack of cards. The marks can be printed in IR- or UV-sensitive ink to make them virtually invisible, but for demonstration these use regular black ink. Each card has landmarks printed on either side of a set of bit markers which identify the cards. A computer is able to quickly read the marks and identify each card in order while the deck is still stacked, aiding the magician in whichever trick they need to perform.

The software only runs on various Apple devices right now, including iPhones and iPads, but the software is readily available fore experimentation if you are a magician looking to try something like this out. Honestly, we don’t see too many builds focusing on magic, sleight-of-hand or otherwise, and we had to go back over a decade to find a couple of custom magical builds from a magician named [Mario].

Thanks to [Tim] for the tip!

Gym Equipment Converted To Generator

Energy cannot be created or destroyed, but the most likely eventual conclusion of changing it from one form or another will be relatively useless heat. For those that workout with certain gym equipment, the change from chemical energy to heat is direct and completely wasted for anything other than keeping in shape. [Oliver] wanted to add a step in the middle to recover some of this energy, though, and built some gym equipment with a built-in generator.

Right now he has started with the obvious exercise bike stand, which lends itself to being converted to a generator quite easily. It already had a fairly rudimentary motor-like apparatus in it in order to provide mechanical resistance, so at first glance it seems like simply adding some wires in the right spots would net some energy output. This didn’t turn out to be quite so easy, but after a couple of attempts [Oliver] was able to get a trickle of energy out to charge a phone, and with some more in-depth tinkering on the motor he finally was able to get a more usable amount of energy to even charge a laptop.

He estimates around 30 watts of power can be produced with this setup, which is not bad for a motor that was never designed for anything other than mechanical resistance. We look forward to seeing some other equipment converted to produce energy too, like a rowing machine or treadmill. Or, maybe take a different route and tie the exercise equipment into the Internet connection instead.

Arduino Drum Platform Is Fast

Drums are an exciting instrument to learn to play, but often prohibitive if there are housemates or close neighbors involved. For that problem there are still electronic drums which can be played much more quietly, but then the problem becomes one of price. To solve at least part of that one, [Jeremy] turned to using an Arduino to build a drum module on his own, but he still had to solve yet a third problem: how to make the Arduino fast enough for the drums to sound natural.

Playing music in real life requires precise timing, so the choice of C++ as a language poses some problems as it’s not typically as fast as lower-level languages. It is much easier to work with though, and [Jeremy] explains this in great detail over a series of blog posts detailing his drum kit’s design. Some of the solutions to the software timing are made up for with the hardware on the specific Arduino he chose to use, including an even system, a speedy EEPROM, hardware timers, and an ADC that can sample at 150k samples per second.

With that being said, the hardware isn’t the only thing standing out on this build. [Jeremy] has released the source code on his GitHub page for those curious about the build, and is planning on releasing several more blog posts about the drum kit build in the near future as well. This isn’t the only path to electronic drums, though, as we’ve seen with this build which converts an analog drumset into a digital one.

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