IMU

70 Articles

Sit Up Straight!: Open Source Bluetooth Posture Sensing

December 16, 2020 by 4 Comments

As more and more people spend their working hours behind a computer, bad posture and the accompanying back pain and back problems become a growing epidemic. To combat this in his own daily life, [ImageryEel] made PosturePack, a wearable Bluetooth-enabled posture sensor.

The PosturePack is designed to fit into a small pocket sewn into the pack of an undershirt, between the shoulder blades. It consists of a custom PCB with an ATmega32U4, BNO055 IMU, Bluetooth module,  small LiPo and power circuitry. Based on the orientation data from the IMU, a notification is sent over Bluetooth to a smartphone whenever the user hunches forward.

[ImageryEel] says although the mobile notifications worked, haptic feedback integrated into the unit would be a better option. This could also be used to remind the user to stand up and take a break now and then, and provide an alternative to a smartwatch for activity monitoring without sending every movement to someone else’s servers. Software will always be the hardest part for projects like these, especially as the device become “smarter”. Learning to recognize activity and postures is actually a good place for tiny machine learning models.

Compared The posture sensors we covered before had to be installed and set up at a specific workstation, like an ultrasound-based version attached to a chair, and a webcam-based version.

Peripheral Doesn’t Need Deskspace

September 11, 2020 by 9 Comments

Some of us are suckers for new hardware. There’s absolutely nothing shameful about a drawer overflowing with gamepads, roll-up keyboards, and those funny-shaped ergonomic mice. MyTeleTouch won’t sate your itch for new hardware because [Dimitar Danailov] didn’t design hardware you hold, because it uses your phone as a catch-all Human Interface Device, HID. A dongle plugs into a standard USB port, and your Android phone can emulate a USB keyboard, mouse, or gamepad over Bluetooth.

Chances are high that you already set up your primary computer with your favorite hardware, but we think we’ve found a practical slant for a minimalist accessory. Remember the last time you booted an obsolete Windows desktop and dug out an old mouse with a questionable USB plug? How long have you poked around the bottom of a moving box trying to find a proprietary wireless keyboard dongle, when you just wanted to type a password on your smart TV? What about RetroPi and a game controller? MyTeleTouch isn’t going to transform your daily experience, but it’ll be there when you don’t want to carry a full-size keyboard down three flights of stairs to press {ENTER} on a machine that spontaneously forgot it has a touch screen. If you don’t have opportunities to play the hero very often, you can choose to play the villain. Hide this in a coworker’s USB port, and while they think you’re sending a text message, you could be fiddling with their cursor.

We enjoy a good prank that everyone can laugh off, and we love little keyboards and this one raises the (space) bar.

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Bike Computer Powers On Long After Your Legs Give Out

August 20, 2020 by 13 Comments

A typical bicycle computer from the store rack will show your speed, trip distance, odometer, and maybe the time. We can derive all this data from a magnet sensor and a clock, but we live in a world with all kinds of sensors at our disposal. [Matias N.] has the drive to put some of them into a tidy yet competent bike computer that has a compass, temperature, and barometric pressure.

The brains are an STM32L476 low-power controller, and there is a Sharp Memory LCD display as it is a nice compromise between fast refresh rate and low power. E-paper would be a nice choice for outdoor readability (and obviously low power as well) but nothing worse than a laggy speedometer or compass.

In a show of self-restraint, he didn’t try to replace his mobile phone, so there is no GPS, WiFi, or streaming music. Unlike his trusty phone, you measure the battery life in weeks, plural. He implemented EEPROM memory for persistent data through power cycles, and the water-resistant board includes a battery charging circuit for easy topping off between rides.

When you toss the power of a mobile phone at a bike computer, someone will unveil the Android or you can measure a different kind of power from your pedals.

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Travel Globe Spins You Around Memory Lane

July 4, 2020 by 2 Comments

We all have our own preferences when it comes to travel souvenirs — that little something that brings back the memories and feelings of a past holiday every time we look at it, whether it’s the cliché fridge magnet, some local speciality, or just the collection of photos we took. But then there are those journeys that can’t be summarized into a single item and may require a bit more creativity. For [Jonathan], it was last year’s trip around the world that took him and [Maria] to locations all over Europe, Asia, and Oceania, and he found a great way to remember it: an interactive, laser-cut travel globe displaying all the places they went to.

Building a sphere is of course a bit tricky with a laser cutter, so [Jonathan] went for the icosahedron shaped Dymaxion map projection (think of a large d20 dice) and burnt the world onto it. Inside the globe is an ESP8266, an MPU-6050 IMU, and a bunch of LEDs to light up the travel locations using the WLED library. Taking the data from the IMU, he customized the WLED library to determine which way the globe is positioned, and highlights the top-facing location in a different color.

While that would already make a nice souvenir on its own, [Jonathan] didn’t stop here. Using Google’s My Maps service, which lets you create custom maps with own points of interest and have for example photos attached to them, the ESP8266 hosts the travel map also as a web page. Feeding the IMU data to the JavaScript code that’s handling the map API, the globe itself now doubles as an input device to control the virtual map. So whenever the globe is physically rotated to highlight a certain location, the web page’s map is focused to that same location and shows randomly the pictures they have taken there. Check out the video below to see it all in action.

This is a great way to reminisce about a memorable journey even years down the road, and while it may not be flexible to extend, it seems like the kind of trip that deserves a standalone device anyway. Plus, the Dymaxion map is definitely an interesting projection — so here’a a foldable one, just because. And If you like tracking things on a globe, here’s one that shows the location of the ISS.

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A Robotic Golf Club To (Possibly) Boost Your Game

June 11, 2020 by 8 Comments

Golf can be incredibly frustrating even for the well practiced player, and probably one of the leading causes for swearing on Saturday mornings. In effort to solve this global problem [Shane Wighton], is creating the ultimate cheat device robotic golf club, that can eliminate all the clubs in one, and adjust for the desired distance mid-swing.

Different golf clubs are mostly defined by their loft angle, or the angle at which the club face is designed to strike the ball in relation to the ground, with the purpose of changing the takeoff angle and therefor the distance traveled. To eliminate the need for different clubs, [Shane] made a head for which the loft angle can be set using a rotary encoder and display on the shaft. However building a tilting a mechanism that can survive the ±4000 lbs of force generated during impact requires some clever engineering. The first iteration was a rather impressive hydraulic design, but it required a large hydraulic power source and the pressure waves generated in the system caused the pistons in the head to blow out every time. The second iteration uses a hobby servo with a combination of machined and SLA printed parts, but in such a way that no force is transmitted to the servo at impact, similar to how a lead screw works. [Shane] actually managed to play a full 18 holes with no problems.

The second feature on the club is to adjust the loft angle mid-swing for the speed of the club to hit the ball a specified distance. A high precision IMU is used to measure the speed and angle of the club. The servo can’t move instantaneously, so it has to predict the impact velocity based on past data. Unfortunately no two swings are ever exactly the same, which introduces some error into the system. Continue reading “A Robotic Golf Club To (Possibly) Boost Your Game” →

Flexible PCB Earrings Put The Art In Art Deco

May 24, 2020 by 5 Comments

Earrings have been a hackers’ target for electronic attachment for quite a while, but combining the needed components into a package small enough to wear in that finicky location is quite a challenge. If [Sawaiz Syed]’s Art Deco Earrings are anything to go by, ear computers have a bright future ahead of them!

This is a project unusually well described by its name. It is in fact an earring, with art deco styling. But that sells it way too short. This sliver of a flex circuit board is double sided to host an ATtiny, accelerometer, LDO, and eight 2020 formfactor controller-integrated LEDs. Of course it’s motion sensitive, reacting to the wearer’s movement via LED pattern. [Sawaiz] makes reference to wearing it while dancing, and we can’t help but imagine an entire ballroom all aglow with tiny points of LED light.

The Art Deco Earrings are also set apart by the thoroughness of their documentation (have we mentioned how much we love detailed documentation?). [Sawaiz] not only drops the source in your lap, but the README in the Github repo linked at the top walks the reader through each component of the design in detail. Plus the PCBA render is so complete it includes a model of the wire loop to fit through the wearer’s ear; how cool is that? The single piece that’s still in progress is the battery. The earring itself hosts an LDO, so all that is required is stashing a battery somewhere discrete, perhaps in the user’s hair? We’re looking forward to seeing what [Sawaiz] works out.

For the full effect, check out the gif of an assembled unit in action after the break.

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From Zero To LED Cube In Less Than Seven Months

May 22, 2020 by 17 Comments

We know that LED video cubes are so last year, but that doesn’t mean we don’t still love to see them. Any project that incorporates over 24,000 LEDs is bound to be impressive, after all. But the more interesting bit about [Mike Cann]’s self-contained LED cube has more to do with the process he chose to get to the finished product.

There are two ways to approach a new project, especially when you’re new to hardware hacking like [Mike] is. One is to jump in with both feet and just see what happens, for good or for ill. The other is is to ease into it with a starter project, to find out where your limitations lay and work around them gradually. [Mike Cann] wisely chose the latter approach with his LED cube project, starting with an LED sand toy. The single 64 x 64 LED panel was a bit easier to work with, and got him up to speed on the care and feeding of such hardware, as well as the code needed to drive it. The video below tells the tale of scaling that project up by a factor of six to make the cube, a process that had its share of speedbumps. Everything ended up fitting together great, though, letting [Mike] get on to the software side. That’s where this project really shines — the smartphone app running the cube is really slick, and the animations are great.

There’s clearly room for new features on [Mike]’s cube, so here’s hoping he can carve out some time to make a great build even better. For inspiration he might want to check out this side-scrolling Castlevania cube, or perhaps read up on the finer points of OpenGL for LED cubes.

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