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.

Sega controller houses auto-launch emulator

[Joe’s] wife grew up playing Sega games and he wanted to help her unwind by reliving the experience. Since the work computer she uses when travelling isn’t a good place to install emulators he built this plug-and-play emulator inside of a Sega controller.

We’ve seen this type of thing a few times before (even with XBMC in a SNES controller) but there is one thing we hadn’t thought of lately. Newer versions of Windows have auto-launch disabled for USB drives. But [Joe] knew that there were still some USB sticks that manage to auto-launch anyway so he researched how those work. It turns out that they have two partitions, one is formatted as a CDFS which looks like a CD-ROM to Windows and allows auto-launch. He used this method of partitioning a USB stick, storing the ROMs on the mass storage partition and the emulator and the CDFS partition. To finish the hack he cracked open the controller and found room for a USB hub and the PCB from the thumb drive.

If you still have cartridges lying around you can pull the ROMs off of them over USB.

Archaeopteryx: a large, colorful MIDI controller

This is [Robert Jarvis’] new MIDI controller which he has christened the Archaeopteryx. It makes its home (quite nicely might we add) in a discarded wooden cutlery case. This provides a strong and stable base for the controls while keeping the electrical connections close at hand for any rewiring or repair work.

The interface is made up of several different input devices. The guts from two Korg Nanokontrols donated the sliders and pots. These are both USB devices and they join with a USB keyboard which has been rewired to work with the colorful push buttons. All three devices connect to a hub inside which makes the device work using just one cable connection to the computer.

There’s a lot of wiring shoved into that shallow case. But if he keeps the keyboard mapping straight we think it won’t be too hard to configure the device. We like it that [Robert] included a snapshot of the back-of-the-envelope prototyping plans he made. This kind of ‘how I got there’ information is what we’re looking for when choosing projects to feature.

Bicycle hub hydropower

[Niklas Roy] wanted to create electricity from moving water so he came up with this hyrdopower generator. It is part of his grand scheme to rent out small personal fountains made from buckets. They need electricity to run so he hooked up the generator to the water jet of a public fountain. It should be possible to use this setup with falling water in a similar way that other generators do.

To build the device he cut fins out of PVC pipe to use as the scoops. They are attached to a Shimano hub generator, meant for producing power while you pedal. The hub is mounted in the front for from a bicycle, which can then be mounted anywhere moving water is available. The only thing that worries us about the setup is [Niklas’] comment that being showered with water didn’t destroy the hub right away.

See the hub and the smaller fountains in the clip after the break.

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