Add Scroll Wheels And Buttons To Smartphones With 3D-Printed Widgets Read By Accelerometer

The first LED digital wristwatches hit the market in the 1970s. They required a button push to turn the display on, prompting one comedian to quip that giving one to a one-armed man would be in poor taste. While the UIs of watches and other wearables have improved since then, smartphones still present some usability challenges. Some of the touch screen gestures needed to operate a phone, like pinching, are nigh impossible when one-handing the phone, and woe unto those with stubby thumbs when trying to take a selfie.

You’d think that the fleet of sensors and the raw computing power on board would afford better ways to control phones. And you’d be right, if the modular mechanical input widgets described in a paper from Columbia University catch on. Dubbed “Vidgets” by [Chang Xiao] et al, the haptic devices are designed to create characteristic acceleration profiles on a phone’s inertial measurement unit (IMU) when actuated. Vidgets take various forms, from push buttons to scroll wheels, each of a similar size and shape and designed to dock into one of eight positions on the back of a 3D-printed phone case. Once trained, the algorithm watches for the acceleration signature caused by actuating a Vidget, and sends commands to the phone to mimic the corresponding gestures. The video below demonstrates a couple of use cases, of which the virtual saxophone is our favorite.

This is really clever stuff, and ventures deep into “Why didn’t I think of that?” territory. Need to get ahead of the curve on IMUs to capitalize on what they can do? You could start with [Al Williams]’ primer on micro-electromechanical systems, or MEMS.

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Door Springs And Neopixels Demonstrate Quantum Computing Principles

They may be out of style now, and something of a choking hazard for toddlers, but there’s no denying that spring doorstops make a great sound when they’re “plucked” by a foot as you walk by. Sure, maybe not on a 2:00 AM bathroom break when the rest of the house is sleeping, but certainly when used as sensors in this interactive light show.

The idea behind [Robin Baumgarten]’s “Quantum Garden” is clear from the first video below: engaging people through touch, sound, and light. Each of the 228 springs, surrounded by a Neopixel ring, is connected to one of the 12 inputs on an MPR121 capacitive touch sensor. The touch sensors and an accelerometer in the base detect which spring is sproinging and send that information to a pair of Teensies. A PC then runs the simulations that determine how the lights will react. The display is actually capable of some pretty complex responses, including full-on games. But the most interesting modes demonstrate principles of quantum computing, specifically stimulated Raman adiabatic passage (STIRAP), which describes transfers between quantum states. While the kids in the first video were a great stress test, the second video shows the display under less stimulation and gives a better idea of how it works.

We like this because it uses a simple mechanism of springs to demonstrate difficult quantum concepts in an engaging way. If you need more background on quantum computing, [Al Williams] has been covering the field for a while. Need the basics? Check out [Will Sweatman]’s primer.

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A Coin Cell Powers This Tiny ESP32 Dev Board

Just for the challenge, just for fun, just for bragging rights, and just to do a little showing off – all perfectly valid reasons to take on a project. It seems like one or more of those are behind this tiny ESP32 board that’s barely larger than the coin cell that powers it.

From the video below, [Mike Rankin] has been working down the scale in terms of powering and sizing his ESP32 builds. He recently completed a project with an ESP32 Pico D4 and an OLED display that fits exactly on an AA battery holder, which he populated with a rechargeable 14550. Not satisfied with that form factor, he designed another board, this time barely larger than the LIR2450 rechargeable coin cell in its battery holder. In addition to the Pico D4, the board sports a USB charging and programming socket, a low drop-out (LDO) voltage regulator, an accelerometer, a tiny RGB LED, and a 96×16 OLED display. Rather than claim real estate for switches, [Mike] chose to add a pair of pads to the back of the board and use them as capacitive touch sensors. We found that bit very clever.

Sadly, the board doesn’t do much – yet – but that doesn’t mean we’re not impressed. And [Mike]’s no stranger to miniaturization projects, of course; last year’s Open Hardware Summit badge was his brainchild.

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Anti-Lock Brakes For Bike Might Make Rides A Little Safer

Crashing one’s bike is a childhood rite of passage, one that can teach valuable lessons in applied physics. Assuming the kid is properly protected and the crash is fairly tame, scrapes and bruises are exchanged for the wisdom to avoid sand and gravel patches, and how to avoid a ballistic dismount by not applying the front brakes harder than or before the rear brakes.

But for many of us, those lessons were learned long ago using a body far more flexible than the version we’re currently in, and the stakes are higher for a bike ride that includes braking mistakes. To help with that, [Tom Stanton] has been working on anti-lock brakes for bicycles, and in the process he’s learned a lot about the physics and engineering of controlled deceleration.

It seems a simple concept – use a sensor to detect when a wheel is slipping due to decreased friction between the tire and the roadway, and release braking force repeatedly through an actuator to allow the driver or rider to maintain control while stopping. But that abstracts away a ton of detail, which [Tom] quickly got bogged down in. With a photosensor on the front wheel and a stepper motor to override brake lever inputs, he was able to modulate the braking force, but not with the responsiveness needed to maintain control. Several iterations later, [Tom] hit on the right combination of sensors, actuators, and algorithms to make a decent bike ABS system. The video below has all the details of the build and testing.

[Tom] admits bike ABS isn’t much of an innovation. We even covered an Arduino-instrumented bike that was to be an ABS testbed a few years back. But it’s still cool to see how much goes into anti-lock systems.

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Rifle-Mounted Sensor Shows What Happens During Shot

People unfamiliar with shooting sports sometimes fail to realize the physicality of getting a bullet to go where you want it to. In the brief but finite amount of time that the bullet is accelerating down the barrel, the tiniest movement of the gun can produce enormous changes in its trajectory, and the farther away your target is, the bigger the potential error introduced by anticipating recoil or jerking the trigger.

Like many problems this one is much easier to fix with what you can quantify, which is where this DIY rifle accelerometer can come in handy. There are commercial units designed to do the same thing that [Eric Higgins]’ device does but most are priced pretty dearly, so with 3-axis accelerometer boards going for $3, rolling his own was a good investment. Version 1, using an Arduino Uno and an accelerometer board for data capture with a Raspberry Pi for analysis, proved too unwieldy to be practical. The next version had a much-reduced footprint, with a Feather and the sensor mounted in a 3D-printed tray for mounting solidly on the rifle. The sensor captures data at about 140 Hz, which is enough to visualize any unintended movements imparted on the rifle while taking a shot. [Eric] was able to use the data to find at least one instance where he appeared to flinch.

We like real-world data logging applications like this, whether it’s grabbing ODB-II data from an autocross car or logging what happens to a football. We’ll be watching [Eric]’s planned improvements to this build, which should make it even more useful.

A Low Cost VR Headset

Virtual reality systems have been at the forefront of development for several decades. While there are  commercial offerings now, it’s interesting to go back in time to when the systems were much more limited. [Colin Ord] recently completed his own VR system, modeled on available systems from 20-30 years ago, which gives us a look inside what those systems would have been like, as well as being built for a very low cost using today’s technology.

The core of this project is a head tracker, which uses two BBC Microbits as they have both the accelerometer and compass needed to achieve the project goals. It is also capable of tracking an item and its position in the virtual space. For this project, [Colin] built everything himself including the electronics and the programming. It also makes use of Google Cardboard to hold the screen, lenses, and sensors all in the headset. All of this keeps the costs down, unlike similar systems when they were first unveiled years ago.

The ground-up approach that this project takes is indeed commendable. Hopefully we can see the code released, and others can build upon this excellent work. You could even use it to take a virtual reality cycling tour of the UK.

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Building An Electric Scooter That’s Street Legal, Even In Germany

Sometimes a successful project isn’t only about making sure all the electrons are in the right place at the right time, or building something that won’t collapse under its own weight. A lot of projects involve a fair amount of social engineering to be counted as a success, especially those that might result in arrest and incarceration if built as originally planned. Such projects are often referred to as “the fun ones.”

For the past few months, we’ve been following [Bitluni]’s DIY electric scooter build, which had been following the usual trajectory for these things – take a stock unpowered scooter, replace the rear wheel with a 250 W hub motor, add an ESC, battery, and throttle, and away you go. Things took a very interesting turn, however, when his street testing ran afoul of German law, which limits small electric vehicles to a yawn-inducing 6 kph. Unwilling to bore himself to death thus, [Bitluni] found a workaround: vehicles that are only assisted by an electric motor have a much more reasonable speed limit of 25 kph. So he added an Arduino with a gyro and accelerometer module and wrote a program to only power the wheel after the rider has kicked the scooter along a few times – no throttle needed. The motor stops after a bit, needing another push or two to kick it back on. A brake lever kills the motor, as does laying the scooter on its side. It’s quite a clever design, and while it might not keep the Polizei at bay, you can’t say he didn’t try.

[Bitluni] has quite a range of builds, from software-defined television to bad 3D-scanners to precision wine glass whacking. You should check out his stuff. Continue reading “Building An Electric Scooter That’s Street Legal, Even In Germany”