DIY: Use Any Surface as a Touch Interface 1


Wouldn’t it be useful to be able to turn any surface, liquid or solid, into a touch interface? With a recently published Instructable, you can learn how to use an Arduino board to detect – for example – a single touch, multiple fingers and a grasp on almost any surface. Meet Touché for Arduino!

Touché for Arduino from Mads Hobye on Vimeo.

At CHI 2012, Medea’s Mads Hobye was introduced to the Touché interface. Touché is a new sensing technology that can not only detect a touch event, but simultaneously recognize complex configurations of the human hands and body during touch interaction. Developed by Disney Research Lab, Touché significantly enhances touch interaction in a broad range of applications, from enhancing conventional touchscreens to designing interaction scenarios for unique use contexts and materials. For example, you can add complex touch and gesture sensitivity not only to computing devices and everyday objects, but also to the human body and liquids.

Naturally, Touché caught Mads Hobye’s attention because of his general interest in creating novel embodied touch interfaces for playful interaction. He wondered if it would be possible to convert the technology into something that could be explored using off-the-shelf components and an Arduino board. Mads had the honor to meet the Disney researchers and discussed with them whether it would be possible to convert their system into the Arduino platform. Their immediate reaction was that the Arduino would not be able to generate good enough frequencies. Mads asked DZL if he could solve this problem and this was his solution (written in Geek):

The Touché hardware uses a really fancy Direct Digital Synthesizer IC from Analog Devices. It generates a really pure sine wave signal with frequencies between 1kHz and 3.5MHz with high resolution. While the Arduino is capable of generating frequencies in this range the signal is a square wave with lots of harmonic frequency components and really low frequency resolution.

Simply using this signal with the circuit described in the Touché paper would result in a really messy frequency graph due to the harmonics from the square wave. The solution is to use the filtering properties of the LC circuit to our advantage. By measuring the signal after the inductor (coil) rather than before we only see a nice sine wave shaped signal, free of all the unwanted frequency components. As a result, we now see a peak in signal at resonance rather than a notch but the signal contains the same information.

Solution published as an Instructable for others to use and explore
With DZL’s permission, the solution has been packaged as an instructable that can be found here. Hobye have made a simple graphing sketch that enables you to see the data and also do simple gesture recognition. Further, the instructable contains a step-by-step guide on how to build the circuit and upload the code. The only special components is a coil that can be made out of wire wrapped around a toilet paper roll.

Possibilities
What kind of interfaces it can be used for can we only speculate on, but by making an instructable we enable a vast amount of people to come up with new ideas and possibilities. In the context of Medea, the system will probably result in new versions of the Mediated Body, with richer and more dynamic possibilities for interpersonal touch interaction.

Related articles
- Touchbox: Intriguing touch between strangers
- Three contributions from Medea to the CHI 2012 conference in Austin
- Mediated Body: Designing social and playful embodied interaction