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A Safer Bicycle Handrail

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.

Laser cutting the handrail segments

Final product. A prototype for a bike handrail that turns the light on automatically when you touch either of the sides

The simple Arduino sketch can be found here

Video demo of the finalized prototype


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.


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