Tired Of Fruit Ninja? Try Vegetable Assassin Using An ESP32 Sword

April 25, 2020 by Sharon Lin 2 Comments

In a world where ninjas no longer rule the social hierarchy, where can a ninja-wannabe practice their sword fighting skills? In the popular Introduction to Embedded Systems class at the Massachusetts Institute of Technology, a team of students made their own version of the popular mobile game Fruit Ninja with a twist – you’re fighting your true nemesis, vegetables.

Vegetable Assassin allows single or multi-player mode, with players slicing vegetables on a screen using fake swords with sensors to detect the players’ motion. The web-based game allows swords to communicate their orientation to the game session with a WebSocket connection to a server, with the game generated and rendered using a 3D client JavaScript library. Rather than using MQTT, which also uses a persistent TCP connection as well as lower overhead, WebSocket provided maximum browser support.

An onboard ESP32 microcontroller and IMU track the sword movements. The game begins by calibrating the sword movements within the play area. Information is generated using the Madgwick algorithm, a 9-degrees-of-freedom algorithm that uses 3-axis data from the sword’s gyroscope, accelerometer, and magnetometer and outputs the absolute orientation of the sword.

The sword and browser both connect to the same channel on the server through a WebSocket connection, identified by a session ID similar to how web chat rooms are implemented. A statistics server manages the allocation of session IDs and other persistent game data to track high scores.

As for the graphics, a Three.js WebGL library creates the scene and camera, loading the game into the browser’s animation frame. Other scripts load the 3D models for the fruits and vegetables in the game, update their positions based on the physics engine provided by Cannon.js, and render UI elements within the game.

Curious? The project site has the microcontroller code to build your own sword that you can use to play the demo. If you don’t have an ESP32 and accelerometer handy you can play Vegetable Assassin in your browser instead.

Homemade Masks In A Time Of Shortage

March 18, 2020 by Sharon Lin 528 Comments

Due to the worldwide pandemic of COVID-19, there has been a huge shortage of ~~N95~~ masks. [Paddy Robertson] from Smart Air has been working on designs for a DIY mask that may be able to protect those who haven’t been able to secure their own masks. While there may be an abundance of memes around the various material people have been able to use to substitute for the filters, there is some very real science behind the sorts of materials that can effectively protect us from the virus.

According to a studied performed at Cambridge University during the 2009 H1N1 flu pandemic, while surgical masks perform the best at capturing Bacillus atrophaeus bacteria (0.93-1.25 microns) and Bacteriophage MS virus (0.023 microns), vacuum cleaner bags, and tea towels~~, and cotton T-shirts~~ were not too far behind. The coronavirus is 0.1-0.2 microns, well within the range for the results of the tests.

As it turns out, cotton homemade masks may be quite effective as alternatives – not to mention reusable. They also found out that double layering the masks didn’t help with improving the protection against viruses. On the other hand, one significant design choice was the breathability of the material. While vacuum cleaner bags may be quite effective at keeping out small particles, they aren’t as comfortable or easy to breathe in as cotton masks.

Have you tried making your own cotton masks? In a time when hospitals are running low on surgical masks, it’s possibly the best option for helping to keep much-needed medical supplies in the hands of those helping at the front line.

[Thanks to pie for the tip!]

Drones Can Undertake Excavations Without Human Intervention

March 16, 2020 by Sharon Lin 4 Comments

Researchers from Denmark’s Aarhus University have developed a method for autonomous drone scanning and measurement of terrains, allowing drones to independently navigate themselves over excavation grounds. The only human input is a starting location and the desired cliff face for scanning.

For researchers studying quarries, capturing data about gravel, walls, and other natural and man-made formations is important for understanding the properties of the terrain. Controlling the drones can be expensive though, since there’s considerable skill involved in manually flying the drone and keeping its camera steady and perpendicular to the wall it is capturing.

The process designed is a Gaussian model that predicts the wind encountered near the wall, estimating the strength based on the inputs it receives as it moves. It uses both nonlinear model predictive control (NMPC) and a PID controller in its feedback control system, which calculate the values to send to the drone’s motor controller. A long short-term memory (LSTM) model is used for calculating the predictions. It’s been successfully tested in a chalk quarry in Denmark and will continue to be tested as its algorithms are improved.

Getting a drone to hover and move between GPS waypoints is easy enough, but once they need to maneuver around obstacles it starts getting tricky. Research like this will be invaluable for developing systems that help drones navigate in areas where their human operators can’t reach.

[Thanks to Qes for the tip!]

Using IR LEDs To Hide In Plain Sight

February 28, 2020 by Sharon Lin 83 Comments

Getting by without falling under the gaze of surveillance cameras doesn’t seem possible nowadays – from malls to street corners, it’s getting more common for organizations to use surveillance cameras to keep patrons in check. While the freedom of assembly is considered a basic human right in documents such as the US Condition and the Universal Declaration of Human Rights, it is not a right that is respected everywhere in the world. Often times, governments enforcing order will identify individuals using image recognition programs, preventing them from assembling or demonstrating against their government.

Freedom Shield built by engineer [Nick Bild] is an attempt at breaking away from the status quo and giving people a choice on whether they want to be seen or not. The spectrum of radiation visible to humans maxes out around 740nm, allowing the IR waves to remain undetected by normal observers.

The project uses 940nm infrared (IR) LEDs embedded in clothes to overwhelm photo diodes in IR-sensitive cameras used for surveillance. Since the wavelength of the lights are not visible to humans, they don’t obstruct normal behavior, making it an ideal way to hide in plain sight. Of course, using SMD LEDs rather than the larger sizes would also help with making the lights even less visible to the naked eye.

The result doesn’t perfectly obscure your face from cameras, but for a proof-of-concept it’s certainly a example of how to avoid being tracked.

Continue reading “Using IR LEDs To Hide In Plain Sight” →

Printing Liquid Concrete

February 24, 2020 by Sharon Lin 9 Comments

In the world of additive manufacturing, there’s always need materials being added to the list of potential filaments to use for printing objects. A method of rapid liquid printing of concrete designed by [Anatoly Berezkin] of Stoneflower 3D makes it possible to print a large variety of shapes from concrete while avoiding the negative effects of fast dehydration. The technique is based on an approach to printing polyurethanes, developed by MIT in 2017. This technique requires physically drawing a 3D object within a gel suspension using a chemical curing process. The gel allows gravity to not affect the printing process, as well as helping out with the curinng. Berezkin, an engineer and hobbyist working out of his garage, has published other work including print heads, ceramic printing, and micro printing sets.

One might be skeptical of whether the weight of the material could cause potential collapse during the printing process, or whether it is simply unrealistic to print objects given the time needed for the concrete to dry. Their demo shows the process being done in household items – bowls and tupperware – combining affordable items such as clay, concrete, and sand for the matrix and mortar. The viscous clay is strong enough to act as a good scaffold for keeping the concrete structure in place as it is being printed. As their video demonstrates, at least for simply objects, the process seems relatively fast.

RLPC doesn’t require toxic chemicals or proprietary components such as gels and suspensions. Its immersion of the final printed object in a humid environment is also superior to the standard process of liquid deposition for hardening concrete. Moreover, the process simply requires clay or retarded mortar for the matrix and mortar paste for turning into concrete. It’s advertised as eco-friendly, but just the simplicity of the materials needed for the matrix and mortar make this a promising technique.

Continue reading “Printing Liquid Concrete” →

Advanced Timber Architecture Gives New Life To Wooden Structures

January 25, 2020 by Sharon Lin 62 Comments

When it comes to building materials, wood doesn’t always draw the most attention as the strongest in the bunch. That honor usually goes to concrete and steel – steel embedded in concrete provides support and a foundation for tall buildings, while concrete increases tensile strength and can be formed into a variety of shapes with the help of rebar. Wood, on the other hand, decays and is vulnerable to moisture damage and fire.

That’s not necessarily the case anymore, thanks to the development of advanced timber. New materials like glulam, or sheets of timber bonded with moisture-resistant structural adhesives, can be produced using two to three times less energy than steel, making them environmentally-friendly alternatives to other building materials. Granted, this requires the beams to be burned at the end of their lifespan, but glulam still has an equivalent or better environmental profile compared to steel, not to mention a lower cost.

Among engineered wood, there are some varieties more commonly used among hobbyists – MDF, plywood, or particle board for instance. Others, like Cross-Laminated Timber (CLT) are more common among building materials. While CLT buildings have existed for decades, recently major cities like Stockholm and Vancouver have seen a resurgence of timber construction. Since wood can theoretically store carbon for the entire length of its lifespan, up to 0.8 tons in a cubic meter of spruce, some architecture firms like Oslotre are building houses with a negative carbon footprint.

Projects like Sidewalk Labs and Masthamnen are proposing entire neighborhoods and skyscrapers built from advanced timber. Compared to International Style architecture, characterized by gray concrete, shiny metal, and glass, this movement could be a step towards returning to natural architectural forms. Given the stress reducing effects of green spaces in cities, engineered wood buildings could bridge the gap between modern architectural styles and natural woodlands.

A Commmand Center For Children With Sensory Needs

January 25, 2020 by Sharon Lin 4 Comments

Toys for children are meant to be fun and interactive, but they’re even better if they’re educational as well. For [carrola1], a parent of a 4-year-old suffering from from medical disabilities, sensory needs, and autism, a more personalized approach seemed best. The electrical engineer built a wall-mounted command center with plenty of switches, buttons, and knobs to trigger to keep any child happy.

Apart from basic inputs, the device also has a color sensor – the command center can ask the child for an object of a particular color and congratulate them with a song when they’ve successfully acquired one.

The software for the audio and light controls was written in C for a STM32L0 series MCU, with CMSIS as the hardware abstraction layer and STM32CubeIDE as the IDE. The design uses SPI and I2C for serial communication and I2S for communicating between the digital audio devices. Physical inputs include toggle switches, rotary switches, and key switches to provide variety, with all physical hardware connected to the MCU on a custom PCB.

The audio output, sourced from a library of wav files, seems like the most challenging part of the build: the amps needed to be changed from left channel mono configuration to stereo, the output had to be LC filtered, and the code for had to be optimized for size to allow the audio files to play.

You can check out a video of the command center in action on the Reddit post.