This post is a slight departure from my normal posts which are usually about wireless. But since I'm technically part of the wireless sensor networking world, I figured a fun, little post about sensing might be appropriate.

I actually put this together about six months ago to show to the Tokyo Hackerspace back when we didn't have a space. We were meeting in restaurants and would show off our latest weird designs over there. It was really a horrible place with a lot of loud drunks and people shouting at each other. And that was just inside our booth :)

Anyways, I showed them that if you used capacitive touch sensors, you would actually be able to draw your own buttons and be able to sense touch events on them. Incidentally, if you tweak the sensitivity high enough, you can also sense touch events through insulators like wood and plastic which I always thought was kind of cool. Perhaps I'm going to play with that some other time.

I've been super busy lately with the MJ concert lighting, putting together classes for the Tokyo Hackerspace, the part-time consulting job, and trying to open a webshop and I felt like I wanted to blow off some steam. I finished teaching the class yesterday and I got a lot of the busy parts of the consulting finished last week. Since I had some extra time, I thought I'd pull out my old board and put the original demo together. I just had to tweak the driver a bit to accomodate the Chibi board and I hooked it into the breadboard peripheral. In case you're wondering, I'm using the Atmel QT1106 touch sensing IC which has inputs for 7 buttons and 1 wheel/slider.

The main part of the video is that you can draw your own touch sensitive buttons as long as you use some type of conductive material. In this case, I used the graphite from pencil lead to draw the touch sensitive electrode. Unfortunately, my drawing skills really suck so I'm posting the tutorial and the driver so that someone with more artistic skill might be able to take it and do something beautiful with it. Another point that I didn't make very clear is that after you change the geometry of any capacitive touch buttons, you need to recalibrate the system. This sets the touch threshold which is the value that the IC will consider a non-touch. When this value changes and crosses the threshold, then it will register a touch event and issue an interrupt.

In the video, it's kind of hard to see the LED because of the background light, but you can kind of see it. Well, here's the video. Hope you enjoy it:

And here's the link to the driver. I've included the actual touch sensor driver as well as the main file which shows how the driver is used.

Driver Link

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