The main goal of this research was to design and implement a simple power meter for cycling. The designed power meter had to be affordable, so we chose to use the crank arm solution. In order to achieve the objectives, we had to measure the tangential force applied on the crank arm using tensometric stamps. Also, we had to measure the cadence based on zero-crossing of the applied force, and to transmit data to external applications using Bluetooth Low Energy (BLE). The hardware implementation is based on BF350-3AA tensometric stamps, HX711 amplifier and Seeed XIAO nRF52840 Sense microcontroller, while the software implementation is based on the HX711_MP.h and bluefruit.h libraries. Experiments prove that the proposed solution (cost approx. 29€) meets the requirements. After calibration, our system achieved a deviation of ~10% compared to Tacx virtual power data, confirming its feasibility for amateur training applications.
