LED wristbands are now a common feature of large arena concerts and events, with a variety of capabilities and technical implementations. In the video after the break, Wall Street Journal does a fascinating deep dive into these wearable light shows.
The three main control technologies are IR light, RF radios, and Bluetooth. The IR-controlled ones are the simplest, and we’ve covered a teardown, a reverse engineering effort and reflash of the Pixmob IR armbands.
Finally, we get a good behind-the-scenes look at how they are controlled. Using pan-tilt IR emitters mounted on lighting towers, the operators can sweep across the audience controlling color and light levels or activating pre-programmed sequences.
RF armbands have the simplest control setup, only requiring a single portable transmitter connected to a computer running the control software. It does however require some pre-planning for more complex light displays, to ensure each section of the audience is individually addressable.
The most advanced and expensive versions are handheld light sticks controlled via Bluetooth from an app on the users smartphone, and are popular at K-Pop concerts. Each device is linked to the users seat number, making them individually addressable and allowing the lighting operators to produce complex patterns, and even text, in the crowd.
While each of these devices is simple and underwhelming on its own, tens of thousands working together produce impressive effects and probably hide some hard-earned engineering experience.
[Nathan] needed an autonomous mower to help on the farm, so he built his own without breaking the bank. It might not be the prettiest machine, but it’s been keeping his roads, fences and yard clear for over a year. In the video after the break, he gives a detailed breakdown of its build and function.
It’s built around a around a simple angle-iron frame with a normal internal combustion push mower at it’s core. 18″ bicycle-type wheels are mounted at each corner, each side driven by an e-bike motors via long bicycle chains. Nathan had to add some guards around his wheel sprockets to prevent the chains slipping of due to debris.
Al the electronics and the battery is simply mounted on top of the frame, away from the motors to avoid magnetic interference with the compass. The brain of the system is a Pixhawk autopilot with a GPS module running ArduPilot, a staple for most of the autonomous rovers, boats and aircraft we’ve seen. The control station is just a Windows laptop running Mission Planner, with a 900 MHz radio link for comms with the mower. [Nathan] also gives a overview of how he uses a spreadsheet to set up waypoints.
This lawnmower’s straightforward design and use of easy-to-find components make it an excellent source of inspiration for anyone looking to build their own functional machine.
Characterizing the aerodynamic performance of a vehicle usually requires a wind tunnel since it’s difficult to control all variables when actually driving. Unless you had some kind of perfectly straight, environmentally controlled, and precision-graded section of road, anyway. Turns out the Catesby Tunnel in the UK meets those requirements exactly, and [Tom Scott] recently got to take a tour of it.
The 2.7 kilometer (1.7 mile) long tunnel was constructed as a railway tunnel between 1895 and 1897, thanks to the estate owner objecting to the idea of “unsightly trains” crossing his property. The tunnel’s construction was precise even by modern standards, deviating only 3 mm from being perfectly straight along its entire length. It lay abandoned for many years until it was paved and converted into a test facility, opening in 2021.
To measure the speed without the luxury of GPS reception, a high-speed camera mounted inside a vehicle detects reflective tags mounted every 5 m along the tunnel’s wall. This provides accurate speed measurement down to 0.001 km/h. A pair of turntables are installed at the ends of the tunnel to avoid an Austin Powers multi-point turn (apparently that’s the technical term) when turning around inside the confined space.
Due to the overhead soil and sealed ends, the temperature in the tunnel only varies by 1 – 2 °C year round. This controlled environment makes the tunnel perfect for coastdown tests, where a vehicle accelerates to a designated speed and then is put into neutral and allowed to coast. By measuring the loss of speed across multiple runs, it’s possible to calculate the aerodynamic drag and friction on the wheels. Thanks to the repeatable nature of the tests, it was even possible to calculate the aerodynamic losses caused by [Tom]’s cameras mounted to the outside of the vehicle.
When one thinks of art, a birdbath may not be the first thing that comes to mind. However, there is no denying that the La Fontaine aux Oiseaux (The Bird Fountain) is a true work of art. This automaton, created by automaton maker [François Junod] in collaboration with 20 different workshops and craftsmen, represents thousands of hours of work and boasts a complex beauty that is both visible and hidden.
Commissioned by the Van Cleef & Arpels jewelry company, this purely mechanical display piece features a pair of jewel-encrusted birds that perform a little routine around the edge of the bath every hour. All the birds’ appendages move while bird song is added with the help of a whistle and bellows. The “water” is also mechanized, with a series of metal plates moving together to create ripple effects, while a water lily opens and closes and a dragonfly flutters above the surface.
The overall effect of this ridiculously over-the-top mechanical art piece is absolutely mesmerizing. Even if the bejeweled exterior isn’t quite your style, you can still appreciate its intricate workings thanks the video after the break giving us a peek at the development.
With the availability of precision controllable actuators, it’s easy to overlook the simple but versatile mechanisms that got us here. In the video after the break, [Teaching Tech] explores the basics of cams and how to use them in your projects.
Cams are used to convert rotation into linear motion, and are probably best known for their use in engines and locking mechanisms. [Teaching Tech] first goes over the basic design and terminology in CAD, and demonstrates it’s use with a cam follower, locking mechanism, cam plate, and a knob that snaps to predefined positions. Of course a cam shape is not limited to a single lobe, but can have multiple lobes of various heights to create different motion patterns.
The limited availability of texts transcribed to Braille and the required embossing equipment is a challenge world wide, but especially in poorer countries. To alleviate this problem, a team makers from in Cameroon have been developing BrailleRAP, an open source Braille embosser.
BrailleRAP is built built using commonly available 3D printer components, printed parts, and a laser-cut acrylic or wood frame. Paper is fed between a pair of carriages, the bottom one punching dots with a solenoid while the other acts as the anvil. Sheets of paper are fed in one or two at a time with stepper controlled rollers to control the position. At a cost of about $250, it is about a tenth of the price of the cheapest commercial solution, and the team have created excellent documentation so anyone can build it.
Measuring local rainfall has real practical uses, especially in agriculture, but most of us will have to admit that it’s at least partly about drawing cool graphs on a screen. Whatever your motivation, you can build this open source electronic rain gauge designed by [Sebastian] of Smart Solutions for Home, and integrate it with Home Assistant.
This 3D printed rain gauge is of the ubiquitous tipping bucket type and uses a magnet and hall effect sensor to detect every time the bucket tips out. The sensor is soldered to a custom PCB with ESP32 configured using ESP Home. By keeping it in deep sleep most of the time and only waking up when the tip of the bucket, [Sebastian] estimates it can run about a year on four AA batteries, depending on rainfall. The hinge mechanism is adjustable to ensure that both buckets will tip with the same volume of water.
FDM 3D printed enclosures are not known for being waterproof, so [Sebastian] coated the PCB with varnish to protect it from moisture. This worked well enough that he could leave it running in a bowl of water for a few hours without any ill effects. The end result looks good and should be able to handle the outdoors for a long time.