A man and a woman stand at opposite ends of a wooden-framed bicycle. It has 20" tires and a long, black seat. A rack extends over the front tire for carrying small items.

Plywood Bicycle Makes Frame Building More Accessible

Bike frames are simple on the surface, but can quickly become complicated if you want to fabricate one yourself. Brazing and welding tend to be less common skills than knowing how to bolt things together, so [Arquimaña] has brought us the OpenBike to make the process accessible to more people.

An open-source set of files designed for CNCs and 3D printers, the OpenBike uses readily available materials like sheet plywood to make a sturdy, if unconventional-looking, bicycle. Like many other consumer goods, most bike frames are currently built in Asia. This allows for economies of scale, but removes locals from the design process. By using simpler tools, OpenBike allows for more local direction of what features might be needed for a particular region.

Shifting even a small portion of trips to more active forms of transport is an important part of lowering carbon emissions, so making bikes a more attractive means of transportation is always welcome. What might be important in one region might be superfluous and expensive in another (multiple gears in a hilly region, for example). OpenBike could be especially useful as a way to rapid-prototype different feature sets for a particular region before committing to a more traditional frame-building technique for larger batches of bikes.

If you want to see some other bike hacks, why not check out this extending bicycle, this steampunk recumbent trike, or these bike hacks from around the world?

 

via Yanko Design

Breakers for the system on a DIN rail, with markings like 48V and 24V and 12V and so on on the bottom, and two hefty devices of some kind on the bottom, probably MPTT controllers, with hefty wires running from them.

Low-Voltage DC Network Build Incited By Solar Panels

Nowadays, some people in Europe worry about energy prices climbing, and even if all the related problems disappear overnight, we’ll no doubt be seeing some amounts of price increase. As a hacker, you’re in a good position to evaluate the energy consuming devices at your home, and maybe even do something about them. Well, [Peter] put some solar panels on his roof, but couldn’t quite figure out a decent way to legally tie them into the public grid or at least his flat’s 220V network. Naturally, a good solution was to create an independent low-voltage DC network in parallel and put a bunch of devices on it instead!

He went with 48V, since it’s a voltage that’s high enough to be efficient, easy to get equipment like DC-DCs for, safe when it comes to legal matters concerned, and overall compatible with his solar panel setup. Since then, he’s been putting devices like laptops, chargers and lamps onto the DC rail instead of having them be plugged in, and his home infrastructure, which includes a rack full of Raspberry Pi boards, has been quite content running 24/7 from the 48V rail. There’s a backup PSU from regular AC in case of overcast weather, and in case of grid power failures, two hefty LiFePO4 accumulators will run all the 48V-connected appliances for up to two and a half days.

The setup has produced and consumed 115kWh within the first two months – a hefty contribution to a hacker’s energy independence project, and there’s enough specifics in the blog post for all your inspiration needs. This project is a reminder that low-voltage DC network projects are a decent choice on a local scale – we’ve seen quite viable proof-of-concept projects done at hackercamps, but you can just build a small DC UPS if you’re only looking to dip your feet in. Perhaps, soon we’ll figure out a wall socket for such networks, too.

The project's wrist-worn heartrate sensor shown on someone's hand, Caption: Our device has three main components: watch electronics (arrow to watch display), organism enclosure (arrow to the 3D-printed case of the watch) and our living organism physarum polycephalum a.k.a slime mold.

What If Your Day-To-Day Devices Were Alive?

We take advantage of a variety of devices in our day-to-day life, and we might treat them as just pieces of hardware, elements fulfilling a certain purpose — forgotten about until it’s time to use them. [Jasmine Lu] and [Pedro Lopes] believe that these relationships could work differently, and their recent paper describes a wearable device that depends on you as much as you depend on it. Specifically, they built wrist-worn heart rate sensors and designed a living organism into these, in a way that it became vital to the sensor’s functioning.

The organism in question is Physarum polycephalum, a slime mold that needs water to stay alive and remain conductive — if you don’t add water on a regular basis, it eventually dries out and hibernates, and adding water then will revive it. The heart rate sensor’s power rail is controlled by the mold, meaning the sensor functions only as long as you keep the mold alive and healthy. In their study, participants were asked to wear this device for one-two weeks, and the results go way beyond what we would expect from, say, a Tamagotchi — with the later pages describing participant reactions and observations being especially impressive.

For one, the researchers found that the study participants developed a unique sense of connection towards the slime mold-powered device, feeling senses of responsibility and reciprocity, and a range of other feelings you wouldn’t associate with a wearable. Page 9 of the paper tells us how one participant got sick, but still continued caring for the organism out of worry for its well-being, another participant brought her “little pet mold friend” on a long drive; most participants called the slime a “friend” or a “pet”. A participant put it this way:

[…] it’s always good to be accompanied by some living creature, I really like different, animals or plants. […] carrying this little friend also made me feel happy and peaceful.

There’s way more in the paper, but we wouldn’t want to recite it in full — you should absolutely check it out for vivid examples of experiences that you’d never have when interacting with, say, your smartphone, as well as researchers’ analysis and insights.

With such day-to-day use devices, developing a nurturing relationship could bring pleasant unexpected consequences – perhaps, countering the “kept on a shelf since purchase” factor, or encouraging repairability, both things to be cherished. If you’ve ever overheard someone talking about their car or laptop as if it were alive, you too might have a feeling such ideas are worth exploring. Of course, not every device could use a novel aspect like this, but if you wanted to go above and beyond, you could even build a lamp that needs to be fed to function.

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A Single-Watt Hydroponic Lighting System

Hydroponic systems are an increasingly popular way to grow plants indoors using a minimum of resources. Even some commercial farming operations are coming online using hydroponic growing techniques, as these methods consume much less water, land area, and other resources than traditional agricultural methods. The downside is that the required lighting systems often take an incredible amount of energy. That’s why [ColdDayApril] set up a challenge to grow a plant hydroponically using no more than a single watt.

The system is set up to grow a single pepper plant in what is known as a deep-water culture, where the plant is suspended in a nutrient solution which has everything it needs to grow. The lightning system is based around the Samsung LM301B which comes close to the physical limits for converting electricity into white light and can manage around 220 lumens. A special power supply is needed for these low-power diodes, and the light is efficiently directed towards the plant using a purpose-built reflective housing. By placing this assembly very close to the plant and adjusting it as it grows, [ColdDayApril] was able to take the pepper plant from seed to flowering in 92 days.

It’s worth noting that the rest of the system uses a little bit of energy too. A two watt fan helps circulate some air in the hydroponic enclosure, and deep-water systems usually require an air pump to oxygenate the water which uses another two watts. This is still an impressive accomplishment as most hobbyist builds use lighting systems rated in the hundreds of watts and use orders of magnitude more energy. But, if you’re willing to add some fish into the system you can mitigate some of the energy requirements needed for managing the water system even further.

A Solar Supercap Power Supply To Keep Your Projects Running

Solar garden lights and many other similar trinkets typically rely on cheap rechargeable batteries as a power source when the sun isn’t shining. [Darryl] figured that a supercapacitor could do the job instead, and set about building a solar supercap power supply that could run various projects. 

The power supply is built to use a small 60 x 40mm solar panel that provides approximately 500 mW at max output. This charges two supercapacitors which feed their output into a TPS61200 boost converter, specifically designed for working with ultra-low input voltages down to 0.3 V. The boost convert can then be configured to output 3.3 V or 5 V depending on the desired voltage for the device to be powered. A special MOSFET array part is used to charge the dual supercaps in series, ensuring they stay balanced and don’t get overcharged by the sun.

The design has worked well in practice. [Darryl] reports that it has successfully powered a LoRa device reporting every 10 minutes for over two years without issue.

Solar power is a magical thing, capable of providing energy for free if you can get out there and capture it. If you’re working on your own solar-powered projects, don’t hesitate to drop us a line!

ERRF 22: Recreator 3D Turns Trash Into Filament

In Back to the Future, Doc Brown returns to 1985 with a version of his DeLorean time machine that has been modified with technology from the future. After telling Marty they need to go on yet another adventure, Doc recharges the DeLorean’s flux capacitor and time circuits by tossing pieces of garbage into the slick Mr. Fusion unit mounted to the rear of the vehicle. The joke being that, in the future, you could simply head over to the local big box store and pick up a kitchen appliance that’s capable of converting waste matter into energy.

Unfortunately, we’re nowhere near powering our homes with banana peels and beer cans. But if the Recreator 3D is any indication, the technology required to turn plastic bottles rescued from the trash into viable PET filament for your 3D printer is all but upon us. While there are still some aspects of the process that could stand to be streamlined, such as fusing multiple runs of filament together into one continuous roll, the core concepts all seem to be in place.

The MK5Kit Mini is currently in development with LDO Motors.

Creator [Josh Taylor] made the trip out to the 2022 East Coast RepRap Festival to not only show off the Recreator 3D, a project he’s been working on now for over a year, but to get people excited about the idea of turning waste plastic into filament. It’s not necessarily a new concept, and in fact [Josh] says earlier efforts such as the PETBOT are what inspired him to create his own open source take on the “pultrusion” concept.

According to [Josh], actually printing with the recycled filament isn’t that different from using commercial PETG, though it’s recommended you lower your speeds. A nozzle temperature of around 260 °C seems to work best, with the bed at 70 °C. Interestingly, the filament produced by the process is actually hollow inside, so the most critical change to make is increasing your extrusion rate to about 130% of normal to compensate for the internal void.

The current revision of the Recreator 3D, known as the MK5Kit, can be assembled using several core components salvaged from a low-cost Ender 3 printer in addition to a number of parts that the user will need to print themselves. For those who’d rather not source the parts, [Josh] says he hopes to get formal kits put together sometime next year, thanks to a partnership with LDO Motors.

But ultimately, [Josh] says the most important thing to him is that the plastic is recycled instead of getting sent to a landfill or incinerator. So whether you build a Recreator 3D or come up with your own design, all are welcome to the PET Pultruders United Facebook group he’s created to discuss the finer points of turning plastic trash into treasure.

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A solar inverter that asks for a password on its display

Decompiling Software To Fix An Old Solar Inverter

It’s a fact of life that electronic devices become obsolete after a few years. Sometimes this is because technology has moved on, but it can also happen that a perfectly functional device becomes near-useless simply because the original manufacturer no longer supports it. When [Buy It Fix It] found a pair of second-hand Power-One Aurora solar inverters, he ran into an issue for which he needed access to the service menu, which happened to be password-protected. The original manufacturer had ceased to exist, and the current owner of the brand name was unable to help, so [Buy It Fix It] had to resort to reverse engineering to find the password.

Thanks to the Wayback Machine over at the Internet Archive, [Buy It Fix It] was able to download the PC software bundle that originally came with the inverters. But in order to access all features, a password was required that could only be obtained by registering the unit with the manufacturer. That wasn’t going to happen, so [Buy It Fix It] fired up dnSpy, a decompiler and debugger for .NET programs. After a bit of searching he found the section that checked the password, and by simply copying that section into a new program he was able to make his own key generator.

With the service password now available, [Buy It Fix It] was able to set the inverter to the correct voltage setting and hook it up to his solar panels. Interestingly, the program code also had references to “PONG”, “Tetris” and “tiramisu” at various places; these turned out to be Easter eggs in the code, containing simple versions of those two games as well as a photo of the Italian dessert.

Inside the software archive was also another program that enabled the programming of low-level functions within the inverter, things that few users would ever need to touch. This program was not written in .NET but in C or something similar, so it required the use of x32dbg to look at the machine code. Again, this program was password-protected, but the master password was simply stored as the unencrypted string “91951” — the last five digits of the manufacturer’s old phone number.

The inverter was not actually working when [Buy It Fix It] first got it, and his repair video (also embedded below) is also well worth watching if you’re into power electronics repair. Hacking solar inverters to enable more features is often possible, but of course it’s much easier if the entire design is open source.

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