Here is another interesting Arduino-based project that we're surprised hasn't been already published sooner - converting the gear change system on a bike from the cable-pull system to completely electronic. However Nabil rose to the challenge and made it happen with an Arduino, some electronics and a strong servo. The control buttons for the gears are mounted on the side of the handlebar as such:
with the servo neatly mounted on the derailleur:
The circuitry is contained in a box over the centre of the handlebars. This project offers a lot of scope for improvement over time, including storing data in the EEPROM for gear position data or even data logging over time.
When reproducing this project you can reduce the size of the electronics component by using our Arduino-compatible Leostick and matching ProtoStick for the external electronics:
For construction information visit the website, and you can download the code and design data from Nabil's github page.