Category: Interfaces
Date: Fall/Winter, 2013/2014
Press: Idx.net, REform, Dep. of Computer Science at Aarhus University
Publication: Kinetic wave: raising awareness of the electromagnetic spectrum
Kinetic Wave is a shape-changing interactive installation that reacts to radio waves from nearby devices, such as smartphones, tablets or similar. People interact with the installation simply by answering a phone call, browsing the internet or using other radio equipment in close proximity, which will initiate a series of movements. The design consists of twelve glowing rings suspended from the ceiling, each moving independently and collectively forming the shape of a wave when enough signals from devices are present in the area.
In brief, the prototype is controlled by a combination of an Arduino Yún and Arduino Mega. The Mega has twelve stepper motors attached, one for each glowing ring. The motors move the rings up and down, coordinated in such a way that the rings will collectively resemble waves. The responsibility of the Yún is to stream data and receive instructions from the internet, making awesome things such as the live representation on the kinetic wave website possible(note: when the system is active) and bringing it into the internet-of-things paradigm.
Furthermore, the ambient amount of radio communication is sensed with an RF power detector, which measures signal intensity on different frequencies, including the bands of typical Wi-Fi and cellular networks. The last aspect is the glowing light. We wanted it to be smooth with no visible bulbs or LEDs, so we ended up illuminating the rings with electroluminescent wires, which are attached to the inner and outer edges of each individual ring. Below, I will account for the different technological aspects of the design and how we build it with the purpose of showcasing it at TEI’14 in Munich.
A major component of the kinetic wave installation include the twelve rings that are suspended from the base construction and controlled by a stepper motor each. The rings were designed in Adobe Illustrator and we had it lasercut in diffused acrylic afterwards at Aarhus School of Architecture. The base of the construction is made out of aluminium and is designed to hold the stepper motors and electronic. The base is made by hand at the Metal Works-workshop at Godsbanen, Aarhus.
Kinetic Wave is fully connected to the Internet through Arduino Yún. What that essentially means is that we can have a lot of the logics placed on a server instead of locally on the Arduino boards, where it would be much harder to continuously adjust. Therefore, the only thing the Arduino boards know how to do is to control the stepper motors to make the basic ring movements and to collect raw RF measurements. Determining which movements to make and when is fully controlled by a Node.js server, pushing the instructions over Websockets and Spacebrew to the Yún, which then redirects that information to the Mega over serial communication. The Yún simply streams the RF signal strength values to the Node server, which then – based on pre-set parameters – calculates live dBm values and determines which of the currently six different wave intensities to instruct the installation to make. Of course, a lot of additional benefits arise from having it all internet connected, such as the live view on this website and a remote control written in JavaScript that we use for demonstration purposes.
Kinetic Wave reacts to wireless communication around it, so we needed a way to detect this in an anonymous way. An RF power detector proved to be the solution, since it is a very generalized way of detecting the amount of radio communication. We got the LT5534 chip from LINEAR Technology, and they were really kind to send us a couple of free samples. Our only challenge was to solder the chip onto a breakout board, since it is tiny.
The chip is an RF power detector that works in the 50MHz to 3GHz frequency range. Our primary aim was to measure Wi-Fi and 3G / 4G networks – around 1.8 GHz or 2.6 GHz for 4G in Denmark, and typically 2.4 GHz for most 802.11n networks. We can roughly adjust which frequency bands the detector should be most sensitive to by the length of the antenna. We went with a simple 12 cm wire antenna, which should be good at those frequencies.
Every ring is connected to two wires which are rolled up and down by custom-made pullies driven by stepper motors. In addition, each stepper motor is controlled by a seperate AutoDriver board, which is based on the L6470 Stepper Driver. In other words, every ring has its own pully system, stepper motor and AutoDriver board. The motors we used are bought from Sparkfun, and the Sparkfun AutoDriver board makes controlling them precisely with Arduino a breeze.
Visit KINETICWAVE.SPACE for a more information.