Tiny Motion Detection Alarm Does The Trick

If you have mischievous children or forgetful elderly in your life, you might want to build a couple of these tiny motion detection alarms to help keep them out of harm’s way. Maybe you want to keep yourself out of the cookie jar. We say good for you.

But you could always put one of these alarms on a window, a drawer, or anything else you don’t want opened or moved. The MPU6050 3-axis IMU makes sure that any way the chosen item gets jostled, that alarm is going off.

As you may have guessed, there isn’t much more to this build — the brain is a Seeed Xiao ESP32-C3, and there’s a buzzer, a battery, a switch, and a push button to program it.

The cool thing about using an ESP32-C3 is that [gokux] can use these for other things, like performing a task when motion is detected. If you do want to build yourself a couple of these, here are step-by-step instructions.

If you’d rather detect motion in the vicinity, here’s a PIR-based solution.

Fancy Gyroscopes Are Key To Radio-Free Navigation

Back in the old days, finding out your location on Earth was a pretty involved endeavor. You had to look at stars, use fancy gimballed equipment to track your motion, or simply be able to track your steps really really well. Eventually, GPS would come along and make all that a bit redundant for a lot of use cases. That was all well and good, until it started getting jammed all over the place to frustrate militaries using super-accurate satellite-guided weapons.

Today, there’s a great desire for more accurate navigational methods that don’t require outside communications that can easily be jammed. High-tech gyroscopes have long been a big part of that effort, allowing the construction of inertial navigation systems with greater accuracy than ever before.

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Behold The Mega-Wheelie, A Huge One-Wheeled Electric Skateboard

DIY electric personal vehicles are a field where even hobbyists can meaningfully innovate, and that’s demonstrated by the Mega-Wheelie, a self-balancing one-wheeled skateboard constructed as an experiment in traversing off-road conditions.

[John Dingley] and [Nick Thatcher] have been building and testing self-balancing electric vehicles since 2008, with a beach being a common testing ground. They suspected that a larger wheel was the key to working better on rough ground and dry sand and tested this idea by creating a skateboard with a single wheel. A very big, very wide wheel, in fact.

The Mega-Wheelie houses a 24V LiFePO4 battery pack, 450 W gearmotor with chain and sprocket drive, SyRen motor controller from Dimension Engineering, Arduino microcontroller, and an inertial measurement unit to enable the self-balancing function. Steering is done by leaning, and the handheld controller is just a dead man’s switch that disables the vehicle if the person piloting it lets go.

Design-wise, a device like this has a few challenging constraints. A big wheel is essential for performance but takes up space that could otherwise be used for things like batteries. Also, the platform upon which the pilot stands needs to be as low to the ground as possible for maximum stability. Otherwise, it’s too easy to fall sideways. On the other hand, one must balance this against the need for sufficient ground clearance.

Beaches are rarely covered in perfectly smooth and firm sand, making them a good test area.

In the end, how well did it work? Well enough to warrant a future version, says [John]. We can’t wait to see what that looks like, considering their past 3000 W unicycle’s only limitation was “personal courage” and featured a slick mechanism that shifted the pilot’s weight subtly to aid steering. A video of the Mega-Wheelie (and a more recent unicycle design) is embedded just below the page break.

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An Electric Unicycle, In Minimalist Form

When self balancing scooters hit the market a few years ago they brought alongside them a range of machines, from the hoverboard kids toys which have provided so many useful parts, to the stand-astride electric unicycles. These last machines have a bulky battery and controller box atop the wheel, and [Dycus] set his sights on this by transferring it to a backpack with the vehicle’s IMU sensor relocated to one of the pedals.

Such a job is not merely a simple case of rewiring with some longer cables, as a first challenge the IMU communicates via I2C which isn’t suitable for longer distances. This is solved by a chipset which places the I2C on a differential pair, but even then it’s not quite a case of stepping on and zipping about. The PID parameters of the balancing algorithm on a stock machine are tuned for the extra weight of the battery on top, and these needed to be modified. Fortunately there have been enough people hacking the STM microcontroller and firmware involved for this task to be achievable, but we’d rate it as still something not for the faint-hearted.

The final result can be seen in the video below, and the quality of the physical work shows as very high. The former battery box is repurposed into a stylish backpack, and though the newly minimalist foot pedals and wheel are a little less easy to get going he zips around with ease.

Hungry for more? This ain’t the first we’ve shown you.

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Hackaday Links: August 20, 2023

In some ways, we’ve become a little jaded when it comes to news from Mars, which almost always has to do with the Ingenuity helicopter completing yet another successful flight. And so it was with the report of flight number 54 — almost. It turns out that the previous flight, which was conducted on July 22, suffered a glitch that cut the flight short by forcing an immediate landing. We had either completely missed that in the news, or NASA wasn’t forthcoming with the news, perhaps until they knew more. But the details of the error are interesting and appear related to a glitch that happened 46 flights before, way back in May of 2021, that involves dropped frames from the video coming from the helicopter’s down-facing navigational camera. When this first cropped up back on flight six, it was only a couple of missed frames that nearly crashed the craft, thanks to confusion between the video stream and the inertial data. Flight engineers updated the aircraft’s software to allow for a little more flexibility with dropped frames, which worked perfectly up until the aborted flight 53.

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Alpakka: A Creative Commons Game Controller

Input Labs’ mission is to produce open-source Creative Commons hardware and software for creating gaming controllers that can be adapted to anyone. Alpakka is their current take on a generic controller, looking similar to a modern Xbox or PlayStation controller but with quite a few differences. The 3D printed casing has a low-poly count, angular feel to it, but if you don’t like that you can tweak that in blender to just how you want it. Alpakka emulates a standard USB-attached keyboard, mouse, and Xinput gamepad in parallel so should just work out of the box for both Linux and Windows PC platforms. The firmware includes some built-in game profiles, which can be selected on the controller.

No special parts here, just 3D prints, a PCB and some nuts and bolts

The dual D-pads, augmented with an analog stick, is not an unusual arrangement, but what is a bit special is the inventive dual-gyro sensor arrangement –which when used in conjunction with a touch-sensitive pad — emulates a mouse input. Rest your thumb on the right-hand directional pad and the mouse moves, or else it stays fixed, kind of like lifting a mouse off the pad to re-center it.

The wired-only controller is based around a Raspberry Pi Pico, which has plenty of resources for this type of application giving a fast 250 Hz update rate. But to handle no fewer than nineteen button inputs, as well as a scroll wheel, directional switch, and that analog stick, the Pico doesn’t have enough I/O, needing a pair of NXP PCAL6416A I2C IO expanders to deal with it.

The PCB design is done with KiCAD, using a simple 3D printed stand to hold the PCB flat and the through-hole components in place while soldering. Other than a few QFN packages which might be a problem for some people, there is nothing tricky about hand-soldering this design.

We’ve been seeing custom game controllers as long as we’ve been hacking, here’s an interesting take on the mouse-integration theme. If you’re comfortable rolling the hardware side of things, but the firmware is a sticking point, then perhaps look no further than this neat RP2040 firmware project.

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Digital Light Pipes Clock various view of seven-segment display using illuminated light-pipes

LED Clock Has Its Pipes On Display

For most hackers and makers, building a clock is a rite of passage. Few, though, will be as unusual and engaging as this design by [TerraG2].

By combining addressable LEDs, light pipes and 7-segment displays, [TerraG2] has built a timepiece that looks great and will surely be a great conversation starter as well. It’s packed full of features such as automatic brightness control, an accelerometer controlled user interface, and WiFi to make sure it’s always accurate.

partial rear view of the clock showing illuminated light pipes
Partial rear view of the clock showing illuminated light pipes

The decision to leave the light pipes visible behind the main display really makes the project stand out from other clock builds, and the methods [TerraG2] has used to achieve this look will no doubt be transferable to a host of other projects.

The LEDs are courtesy of a standard 8×8 RGB matrix, with a custom 3D-printed shroud to hold the light pipes in place and a clever connector at the other end to illuminate the segments. With two LEDs per segment, seven segments per digit, and four digits, there’s even room for some extra features down the line if you can think of a use for those eight spare LEDs.

The brain of the project is an ESP8266 D1 with an MPU6050 inertial measurement unit (IMU) to detect when it’s flipped over to change the color scheme.

Full documentation is on Github, and a video of the clock in use is after the break.

Light pipes have been used to great effect in some other clock projects we’ve seen, such as this modern Nixie clock and this “clock of clocks”, as well as in this light organ that we showed recently.

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