Concrete USB Hub Isn’t Going Anywhere

When starting a new project, the choice of material can have a big effect on the character of the finished product. Wood is stylish and has a certain elegance to it, while polished or brushed aluminium is great for a more futuristic feel. Sometimes though, you just want big, cheap and heavy – in which case, concrete is your friend!

[BALES] was short on USB ports, and needed a hub with plenty of connectivity. Concrete had the benefits of being solid and heavy, and also impervious to beverages. Thus, a melamine form was produced, chosen as its surface doesn’t give the concrete anything to grab on to. A foam skull was cut out and added to create an inlay for decoration, and the 7-port octopus-style hub was placed inside.

With careful attention paid to the mixture consistency, the concrete was poured into the mold and allowed to set. Care was taken to avoid air bubbles and to ensure the mixture flowed completely into the mold, without leaving air pockets behind the inserted components. After allowing it to set for a few days, the part was demolded, with care taken to minimise edge crumbling. The foam skull was removed, and infilled with black epoxy, with a little more used to coat the top and sides of the hub. As a finishing touch, a foam pad was fitted to the base to allow it to sit on a desk without scratching everything up.

In the end, [BALES] has ended up with a hefty hub that won’t skitter around when plugging and unplugging devices. It should also serve admirably as a sturdy drink coaster on those cold winter nights. If you’re trying a similar project yourself, note that sometimes concrete can be surprisingly conductive. Video after the break.

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Printable Filament Spool Hub Skips the Bearings

When you really start fine-tuning your 3D printer, you might start to notice that even the smallest things can have a noticeable impact on your prints. An open window can cause enough of a draft to make your print peel up from the bed, and the slightly askew diameter of that bargain basement filament can mess up your extrusion rate. It can be a deep rabbit hole to fall down if you’re not careful.

One element that’s often overlooked is the filament spool; if it’s not rotating smoothly, the drag it puts on both the extruder and movement of the print head can cause difficult to diagnose issues. For his custom built printer, [Marius Taciuc] developed a very clever printable gadget that helps the filament roll spin using nothing but the properties of the PLA itself. While the design might need a bit of tweaking to work on your own printer, the files he’s shared should get you most of the way there.

All you need to do is print out the hubs which fit your particular filament spools (naturally, they aren’t all a standard size), and snap them on. The four “claws” of the hub lightly contact a piece of 8 mm rod enough to support the spool while limiting the surface area as much as possible. The natural elasticity of PLA helps dampen the moment that would result if you just hung the hub-less spool on the rod.

The STL files [Marius] has provided for his low-friction hubs should work fine for anyone who’s interested in trying out his design, but you’ll need to come up with your own method of mounting the 8 mm rod in a convenient place. The arms he’s included are specifically designed for his customized Prusa Mendel, which is pretty far removed from contemporary desktop 3D printer design. Something to consider might be a piece of 8 mm rod suspended over the printer, with enough space that you could put a couple spools on for quick access to different colors or materials.

Hackers have been trying to solve the spool friction issue for years, and as you might expect we’ve seen some very clever designs in the past. But we especially like how simple [Marius] has made this design, and the fact that you don’t need to source bearings to build it. If you’re thinking of giving this new design a shot, be sure to leave a comment so we know how it worked out for you.

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Unicycle Given a Hand Crafted Gear Box

Being able to coast on a bicycle is a feature that is often taken for granted. The use of a freewheel was an improvement made early in the bicycle’s history, for obvious reasons. This also unlocked the ability to build bikes with multiple gears, allowing higher speeds to be easily reached. On a unicycle, however, there’s no chain and the pedals are permanently fixed to the wheel’s axle, meaning that there is (usually) no freewheel and no gearing. [johnybondo] wanted to get some more speed out of his unicycle, though, and realized he could do this with his own homemade internal geared hub for his unicycle.

The internal hub gear was machined and welded by hand as a one-off prototype. There are commercial offerings, but at $1700 it’s almost best to fund your own machine shop. It uses a planet gearset which is more compact than a standard gear, allowing it to fit in the axle. Once all the machining was done, it was time to assemble all of the gears into the hub, lace it to the wheel with spokes, and start pedaling away. Since it was so successful, he plans to build another and lace it to a larger wheel which will allow him to reach even higher speeds. If this isn’t fast enough for you, personally, there are other options available for ludicrous speed.

Now, this gear is still “fixed” in the sense that it’s a permanent gear ratio for his unicycle and it doesn’t allow him to shift gears or coast. There’s no freewheel mechanism so the unicycle can still be pedaled forward and backwards like a traditional unicycle. The advantage of this setup is that the wheel spins 1.5 times for every one revolution of the pedals, allowing him to more easily reach higher speeds.

Wireless Doorbell Hacked Into Hands-on MQTT Tutorial

The project itself is very simple: getting push notifications via MQTT when a wireless doorbell sounds. But as [Robin Reiter] points out, as the “Hello, world!” program is a time-honored tradition for coders new to a language, so too is his project very much the hardware embodiment of the same tradition. And the accompanying video build log below is a whirlwind tour that will get the first-timer off the ground and on the way to MQTT glory.

The hardware [Robin] chose for this primer is pretty basic – a wireless doorbell consisting of a battery-powered button and a plug-in receiver that tootles melodiously when you’ve got a visitor. [Robin] engages in a teardown of the receiver with attempted reverse engineering, but he wisely chose the path of least resistance and settled on monitoring the LEDs that flash when the button is pushed. An RFduino was selected from [Robin]’s ridiculously well-organized parts bin and wired up for the job. The ‘duino-fied doorbell talks Bluetooth to an MQTT broker on a Raspberry Pi, which also handles push notifications to his phone.

The meat of the build log, though, is the details of setting up MQTT. We’ve posted a lot about MQTT, including [Elliot Williams]’ great series on the subject. But this tutorial is very nuts and bolts, the kind of thing you can just follow along with, pause the video once in a while, and have a working system up and running quickly. There’s a lot here for the beginner, and even the old hands will pick up a tip or two.

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Scratch-Built EV From Hoverboards

Electric vehicles are everywhere now. Even though battery technology hasn’t had the breakthrough that we need to get everyone out driving an electric car, the price for batteries has dropped enough that almost anything else is possible. The hoverboard was proof of this: an inexpensive electric vehicle of sorts that anyone who was anyone in 2015 had. Taking his cue from there, [Harris] used off-the-shelf parts normally used for hoverboards to build his own battery-powered trike.

The trike is homemade from the ground up, too. The H-frame was bolted together using steel and lots and lots of bolts. Propulsion comes from a set of hub motors that are integrated into the wheels like a hoverboard or electric bicycle would have. Commonly available plug-and-play lithium batteries make up the power unit and are notably small. In fact, the entire build looks like little more than a frame and a seat, thanks to the inconspicuous batteries and hub motors.

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Modular Multicopter Core Flies in Multiple Orientations

[Ioannis Kedros] claims to be rather new to the game of building multi-rotor drones. You’d never know it looking at his latest creation. Yes, we’re talking about the quadcopter seen here, but it’s the core of the machine that’s so interesting. He came up with a PCB hub that allows multiple orientations to be used with the same board. These include tri-copter, and quadcopter with different strut angles for different applications.

multicopter-hub-pcbThe silk screen of the PCB has dotted lines showing the different angles possible for one pair of motor supports. One set makes a perfect “X” for traditional quadcopter flight. Another reduces the angle between front and back struts for higher-performance quad flight, while the last set is intended for a tricopter setup.

We’d recommend taking a look at [Ioannis’] project writeup whether this particular application interests you or not. His design techniques go through all possible manner of checks before placing the PCB order. There is no substitute for this process if you want to avoid getting burnt by silly mistakes.

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Add external power to any USB hub

[Andrew] was getting some poor performance from a couple of USB devices he had connected through an unpowered hub. This is a problem because the hub prevents devices from negotiating with the host controller for more current. He fixed it by adding an external power supply to his USB hub.

In this case the PCB already had a footprint for a power connector. The manufacturer uses one board for several different models and just leaves the supply components unpopulated. [Andrew] managed to find a barrel jack in his parts bin that matched the footprint.

One important thing to do before hooking up the source is to disconnect the 5v wire from the incoming cable from the computer. The other tip we can give you is to use a good regulated 5v source to ensure you don’t damage the stuff you’re trying to power. That means avoiding deals that are too good to be true.