Planet Arduino

You likely use touchscreens every day when interacting with your phone — perhaps even to read this article — but prototyping your own capacitive matrix is unfortunately out of reach for most makers and electronics novices. As seen here, researchers have devised a new technique that will allow for easier prototyping of this type of interface, which can function on both flat and curved surfaces, over a variety of materials.

To accomplish this, the team developed an Arduino library, as well as one for Processing, and used OpenCV to track multiple finger positions. Interactions have been tested with an Uno, Mega and LilyPad, and would presumably work with almost any other Arduino board as needed!

We introduce Multi-Touch Kit, a low-cost do­ it-yourself technique to enable interaction designers, makers, and electronics novices alike to rapidly create and experiment with high-resolution multi-touch sensors of custom sizes, ge­ ometries, and materials. 

In contrast to existing solutions, the Multi-Touch Kit is the first technique that works with a commodity microcontroller (our implementation uses a standard Arduino) and does not require any specialized hardware. As a technical enabler, we contribute a modified multi-touch sensing scheme that lever­ ages the human body as a transmission channel of MHz range signals through a capacitive near-field coupling mechanism. This leads to a clean signal that can be readily processed with the Arduino’s built-in analog-to-digital converter, resulting in a sensing accuracy comparable to industrial multi-touch con­ trollers. Only a standard multiplexer and resistors are required alongside the Arduino to drive and read out a touch sensor matrix. 

The technique is versatile and compatible with many types of multi-touch sensor matrices, including flexible sensor films on paper or PET, sensors on textiles, and sensors on 3D printed objects. Furthermore, the technique is compatible with sensors of various scale, curvature, and electrode materials (silver, copper, conductive yarn) fabricated using conductive printing, hand-drawing with a conductive pen, cutting, or stitching. 

Today when you get a text, you can respond with message via an on-screen keyboard. Looking into the future, however, how would you interact unobtrusively with a device that’s integrated into eyeglasses, contacts, or perhaps even something else?

TipText is one solution envisioned by researchers at Dartmouth College, which uses a MPR121 capacitive touch sensor wrapped around one’s index finger as a tiny 2×3 grid QWERTY keyboard.

The setup incorporates an Arduino to process inputs on the grid and propose a number of possible words on a wrist-mounted display that the user can select by swiping right with the thumb. A new word is automatically started when the next text entry tap is received, allowing for a typing speed of around 12-13 words per minute.

If you’d like to integrate touch functionality to your LED matrix project, then tuenhidiy may have just the thing for you. 

The setup uses 16 pairs of IR emitter and receivers arranged down the length of the bi-color 16×32 matrix to tell when one has inserted a finger or other object into an area. When sensed, it changes the corresponding column on the display from red to green or back again.

An Arduino Mega is used for overall control of the device, along with shift registers and multiplexers/demultiplexers to account for the massive amount of IO needed. 

Code for the build is available on GitHub, and you can see it demonstrated in the video below.

Amanda Ghassaei (previously featured on Arduino Blog with Glitchbox and Vocal Effect box ) published the instructions to build an Arduino-powered infrared touchscreen / coffee-table interface that she’s been using to control various music and graphics applications on her computer.

Although the project was done a while ago, she considers it special because it was her first Arduino/electronics project and recently she’s taken it apart to refinish the wood and fix a few things and then published detailed documentation on Instructables:

The touchscreen uses infrared (IR) sensing to detect fingers and other objects on the screen. An IR laser at each corner shines IR light across the surface of the screen. When a finger or other object touches the surface, it causes the IR light to scatter in many directions. Some of this light is directed down into the screen, towards an array of 64 IR sensors. By scanning through the sensors, you can determine the x and y position of the touch event(s) and use this to control a variety of apps.