Development of a powermeter for bicycle II

• Main Author: Leong, Eric Jia-le.
• Other Authors: Yap Fook Fah
• Format: Final Year Project
• Language: English
• Published: 2010
• Subjects: DRNTU::Engineering::Mechanical engineering::Prototyping
• Online Access: http://hdl.handle.net/10356/40632
• Institution: Nanyang Technological University

For most serious cyclists, knowing one’s current performance is paramount to training more effectively (Friel, 2003). A powermeter, which measures a cyclist power output, is by far the most accurate and effective tool in a cyclist or coach’s arsenal. Currently, powermeters that are commercially available are high in cost and are usually require a high price to use proprietary software and interfaces (Allan & Coggan, 2006, p.33). As the sport of cycling continues to grow, the aim of this project is to avail this training tool to a greater audience, by providing an economical means of purchasing such a technology, while providing accurate and user-friendly features found on commercially available items. In this project, power output from a rider is measured across 8 strain gauges in a Wheatstone bridge set up. The voltage difference across the bridge will then be amplified and fed wirelessly to the receiver. Much development has been made to streamline the circuit used to minimize power usage. All redundant electronics in previous designs has been removed. Furthermore, three AAA batteries are used to provide greater mAH and battery life, while the input voltage is regulated at 3.3V for stable input. The wireless transmission is made possible with the usage of two Xbee Wireless Chips. On the receiver end, development has been made to allow a housing to protect and encompass the receiver. It has an Ingress Protection, IP65 rating, which ensures sufficient protection against wear and tear (Barnes, 2004, p.36-6). The receiver takes in data through the wireless Xbee chips and input this information to the PIC Microcontroller for calculation. The PIC acts as a microcontroller that processes the information and outputs them into a screen for the rider to understand. Another key importance of this project is the utilization of free and open source software to program the entire system. The X-CTU software used by the wireless chips is free, and the APIs allow customization for different applications. Similarly, the PIC on the receiver side makes use PIC Assembly Language, a free and open source language as well. To compete with commercially available powermeters, aesthetics have been improved to provide greater fit and functionality to the end user. The crank arms fit tighter to the dynamic plate due to alterations of the mounting points, as well as a tapering hole for the spindle. The mountings have foam padding to provide some form of shock proofing to the circuit boards, and to prevent any items from becoming loose. Lastly, all items are sealed up using either Poron Gaskets or RTV Silicone Gaskets. This is to prevent water seepages and lengthen the lifespan of usage.