| Bicycling is a sport that has various benefits and purposes. One of the innovation in bicycling world as the technology advances is on its transmission. A good bicycle transmission must able to keep the cadence of its rider at ideal value. For this writing, there will be a study of designing and building a bicycle gear shifter which is able to keep the cadence at ideal value. The design of mechatronics system includes the mechanical, electrical, and informatics system. The design of mechanical system that will be done includes the design of brackets, mounting, and servo motor choice. The design of program is using Arduino IDE software. The system is able to shift the gear ratio to lower or higher position automatically as the cadence of the rider changes dynamically. From the results of designing and building phase, an automatic gear shifter based on cadence input that uses Hall effect sensor as its input, arduino microcontroller as its computer, and servo motor as its actuator has been made and is working well |