In power generation systems the synchronization of an alternator with the electrical network are an important and critical task. This paper presents the design and building of an automatic three-phase alternator synchronizer based on a low-cost open-hardware Arduino platform. The synchronization is performed by means of measuring a phase voltage of both the synchronous generator and the electrical grid; then the measured voltages are conditioned and sent to the Arduino board, which is programmed to determine the correct moment to connect the alternator to the grid. To validate the prototype, a laboratory setup has been built with the alternator driven by a commercial dc drive. The design and practical implementation of the system is proposed as a project-based learning (PBL) activity for undergraduate final year students at the University of Bío-Bío, Chile. A description of the constructed prototype and the results obtained are presented and discussed.