For this week's project, I wanted to try a different tangible interface.
I browsed the different Arduino libraries to get a sense of whats out there and found the Capacitive Sensor library. The possibility of creating a touch sensor out of many different materials seemed extremely interesting, so I decided to give it a shot.
I read about capacitive sensing here and also followed the libraries example to make a few tests for myself.
Very promising results were found:
Changing the resistor value between the pins allows you to calibrate a threshold or sensitivity for the sensor.
Having your laptop connected to the power outlet changes the results.
Touching two sensors at the same time reduces the sensed capacity to approximately half.
You can sense capacitance through different materials.
You can measure the distance from your finger to the sensor's connection to use it as a linear sensor.
Two pads connected through a 10MOhm resistor
Preliminary testing of the fabric and resistor values. As the article suggested, 1MOhm seams reasonable.
I was very happy with these results but I must confess that I was having a hard time thinking of a use for this. After commenting this with a few people, the idea for a touch sensor for a bicycle handrail that turns the headlight on automatically came to be.
So, fabrication time.
The simple Arduino sketch can be found here
Video demo of the finalized prototype
Conclusions
I am focusing my efforts into making things with user in mind. I have to admit that while the technical aspect of it was straightforward, my definite challenge is finding things that have a real meaning to them and create them. This handlebar prototype was extremely satisfying to build, and I gathered very valuable fabrication skills that I'm sure I'll be able to carry with me through the rest of the program.